Niño Alejandre Relos, Sharon Juliet M. Arruejo, Carlomagno P. Ancheta, Jr.
The impact of climate variability on insect pest occurrence was studied to establish information beneficial to agricultural pest management by monitoring the rates of pest invasion using light trap equipment and ascertain benchmarks of climate changes that influence distribution of the species of brown plant hopper, green leaf hopper, stem borer and parasitic wasp.
Correlation and graphical analysis were employed to determine the significant relationship between the two years monthly totals of the pests and three climatic variables: temperature, rainfall and relative humidity. Lag variables up to five months were also included.
The result showed high significant correlation with brown plant hopper and temperature lag 4 months (r2 = 0.630915), the green leaf hopper and temperature lag 4 months (r2 = 0.7620), the stem borer and temperature lag 5 months (r2 = 0.62171). Unusual result however was obtained where the total of parasitic wasp for the current month is highly significant with rainfall and relative humidity for next month.
Based on the observed facts, the following conclusion was drawn: (1) Climate variability affect insect pest behavior and dynamics although the impact vary with species; (2) The behavior of wasp confirms folklore meteorology; and (3) The impact of climate variability on insect pests occurrences are good inputs to farm weather forecasting.
Further monitoring of the insect dynamics and climate variability is recommended for future comprehensive study in relation to climate change.
Adelaida T. Castillo
A case study has been made to describe the synoptic and sub-synoptic conditions of an extreme example of rainy season wet spell that occurred in Central Luzon on July 2002 using both observations and a numerical model. Heavy monsoon rains inundated Central luzon starting 5 July. Observations showed that an unusual disturbance developed over the southwestern section of Luzon which extends from northern Palawan to eastern Mindoro. This convective cell moved northwestward and developed into a deep convection producing heavy rainfall over the coast and near the mountains. Strong convergence of Indian Southwesterlies and South Pacific Trades is evident. The mesoscale systems actively interacted with large scale conditions providing a favorable environment for the development of heavy rainfall during this particular rainy season wet spell. The simulated convection using NCAR MM5 shows consistency with observations near coastal areas although there is a notable difference from observations near the mountains. Simulated results suggest two types of band formation: one initiated by convergence of large scale flows and another by convective cell existing in a strong southwesterly air stream.
Nikos Viktor B. Peñaranda
This paper is an initial exploration of cloud-to-ground (CG) lightning occurrences in the Philippines using the untapped lightning data generated by the subset of the WSI Global Lightning Network® operating in the Southeast Asian region. Using thunderstorm (PAGASA) and CG lightning (WSI) data, the use of lightning detection network as an alternative or supplemental tool in detecting and analyzing thunderstorms events has been examined by analyzing the seasonal pattern of thunderstorms activity as revealed by Cloud-to-Ground (CG) lightning strokes occurring in the Philippine domain. Results reveal the profile of thunderstorm activity during the study period that includes information on spatio-temporal hazard related to CG lightning and indirectly, to thunderstorm severity. Additionally, the use of lightning data refined the analyses of thunderstorm events by providing information that relate thunderstorm dynamics and microphysical structure, which is unavailable in the traditional thunderstorm data.
Ariel R. Zamudio
The diurnal variation of rainfall in Northern Luzon is described by discussing the role of topography and local wind systems during three different monsoon periods in three different years using observation data from PAGASA-DOST. Baguio, which is a mountainous area, is found to experience maximum rainfall activity during the day in all the different monsoon seasons of three different years. This is attributed to the upslope winds. The daytime and nightime maximum in coastal areas is caused by the convergence between sea/land breeze and prevailing flow of by sea breeze and land breeze itself. During the northeast monsoon period, coastal stations in the eastern part of the region received more rainfall compared to the coastal stations in the western part. While during southwest monsoon period, coastal stations in the western part received more rainfall than coastal stations in the eastern part. Furthermore, this study will evaluate if the numerical model PSA/NCAR MM5 can simulate the diurnal variation of rainfall in Northern Luzon by adapting parameterization scheme from previous numerical studies. The result shows that although the model captured the accumulated rainfall pattern at some coastal stations, it did not capture the pattern in the mountainous and valley areas. In general, the model results do not capture the observed diurnal variation of rainfall. This shows that simulating diurnal variation of rainfall is sensitive in terms of topography since topography has a significant effect on the daily variation of rainfall.
Julie M. Nimes
The inaccurate prediction of storm surge accounts for the uncertainty of the landfall point forecast. This study describes the method for providing relatively accurate prediction of storm surges using numerical modelling techniques. Two cases of landfalling tropical cyclones were examined focusing on the storm surge response of the basin, using observational and numerical modelling techniques. Observational data analyses include the study area, meteorological and synoptic weather features of two cyclones affecting the area, observed surges and astronomical tide height. For modelling studies, the depth integrated hydro-dynamical storm surge model for shallow water was employed. Maximum sustained wind was used as the atmospheric driving force to generate storm surges. Other input parameters are the radius of maximum winds, the forward speeds, the angles of approach to the basin and the initial cyclone position. Fourteen datasets of simulated and observed surge heights were used in the calibration and validation of the model. The calibration involves the selection of the best surface wind coefficient for the basin of Dingalan and adjacent coast of San Luis. The selection was done by conducting sensitivity tests. The results showed that the model with a 0.000658 surface wind coefficient and with 0.00005 constant bottom coefficient was found to be the best values. The calibrated storm surge model performed satisfactorily. The calibrated model was used in the generation of the maximum envelope of water (MEOW). Three model runs were performed from three different landfall points of TY Kading (1978) along the coast of Dingalan and adjacent coast of San Luis. The resulting composite of peak surges make up a map of MEOW. The developed technique of the composite of pre-computed MEOW from the equally spaced distance of parallel points of landfall can provides a summary of the worst case surge scenario given the uncertain in the current forecast situation. Compilation of historical pre-computed MEOWs has been found by other countries as a practical warning tool in the formulation of advisories for disaster mitigation.
Landrico U. Dalida, Jr.
A Regional Climate Model Version 3 (RegCM3) was used to simulate the seasonal rainfall (June, July, August and September 2001). The model performance was assessed on a smaller domain covering the Philippines using subjective analysis of rainfall pattern and computation of skill scores. The model was tested by shifting the domain 10 degrees to the left of the Control run, ShL, and to the right ShR. ShL covers more landmass than bodies of water while ShR include more ocean than the control run. ShL and ShR were used to determine the effect of changing the boundary position. The model was then tested using different cumulus parameterization schemes: Grell with Fritsch Chappel closure (FC), Grell with Arakawa-Schubert closure (AS) and Kuo. Assessment of the model performance was first based on subjective analyses of the maps in order to determine how well the rainfall patterns were simulated.The model was then assessed according to bias or anomaly, root mean square error and measures of forecast skills: Bias, % Bias Score and Hit rate. The bases for comparison were the monthly rainfall observations of 44 PAGASA stations and Tropical Rainfall Measuring Mission (TRMM). The contingency table used to determine the skill scores were grouped into four threshold levels: 0-100 mm, 100-300 mm, 300-500 mm and >500 mm. Subjective analyses of the rainfall maps reveal that the domain shifted 100 to the left performs better than Con and ShR with ShR a close second. Using areal rainfall instead of point rainfall, shifting the domain reveals that ShL estimates better the rainfall. On the other hand, the choice of cumulus parameterization schemes affects greatly the model's performance. Subjective analyses show that FC generally overpredicts while AS underpredicts. Nevertheless, it is not distinct whether FC and AS have an edge over the other. Regarding the determination of rainfall contribution of convective and non-convective or stable rainfall produced by RegCM to the total rainfall (TPR), the study was able to show that cumulus convection contributed much to the TPR except for some occasion wherein stable rainfall is greater than convective rains. The use of RegCM for simulating seasonal rainfall is promising. The rainfall pattern and the rain-causing synoptic weather systems were simulated or captured in more cases. However, the rainfall amount was found to be highly sensitive to cumulus parameterization. Kuo gives consistently poor performance and is not recommended for further use in RegCM3. More studies using other cumulus parameterization schemes is recommended and compared with FC. To further improve the model performance, other options such as changing some parameters in the biosphere-atmosphere transfer scheme should be investigated.
Esperanza O. Cayanan
Intense southwest monsoon (SWM) rainfall events causing massive landslides and flash floods along the western sections of the Philippines were studied through conduct of observational and numerical analysis. The heavy rainfall during the southwest monsoon season is hypothesized as caused by strong convective activity generated by monsoon westerlies and enhanced by the presence tropical cyclone (TC) in the vicinity of northeastern Luzon. The strong westerlies upon interaction with the mountain ranges along the west coast of Luzon produce strong vertical motion and consequently generate heavy rainfall. Scientific investigation of four SWM rainfall cases were undertaken to prove this hypothesis. The heavy rainfall cases selected are of varying condition in terms of the presence and position of tropical cyclones. The first case involved two TCs within the Philippine area of responsibility (PAR), the second case has a TC crossing Luzon Island, the third case involves a strong typhoon that passed to the NE of Luzon and the fourth case has no tropical cyclone in the PAR. Five year (2002 - 2006) time series of five-day moving average rainfall from eleven western Luzon stations was utilized in the selection of events. Observational analysis revealed that during the rainfall events, a trough is present over the northeastern portion of the Philippines between the islands of Luzon and Taiwan from the surface to 850 hPa level. Heavy rains in the amount of 20 mm/day and greater the recorded for duration of 5 days or longer over the western sections of Luzon from southern station (Sangley) to northern station (Laoag). Due to exposure and topography, the SWM rainfall distribution is maximum over the western part and decreases eastward except for the case of crossing tropical cyclone where maximum rainfall occurred along its path. It was also noted that heavier and longer duration rainfall occurred when tropical cyclones are embedded within the trough. In this situation, the weather condition is characterized by strong southwesterlies/westerlies of more than 20 meters/sec over the South China Sea and western sections of the Philippines from the surface to 850 hPa levels. The trough migrates northward from an initial NW-SE orientation with the axis rotating counterclockwise until it attains a SW-NE orientation with the upper end over southern Japan. As shown in the 850 hPa latitude-time cross section of zonal wind, the migration of the trough is modulated by the 30-60 day northward and 12-24 day westward oscillations. The position of the trough over Luzon Island up to Luzon Strait between Taiwan and Philippines and the strength of the westerlies of 20 meters/sec from the surface to 850 hPa level could serve as indicators of the occurrence of SWM heavy rainfall events. Through the aid of Fouries analysis, the hypothesis on the cause of heavy rainfall during the southwest monsoon has been presented and explained scientifically through the investigation of four selected cases of heavy rainfall events. With the use of Fourier transforms, the total streamflow is decomposed into monsoon basic flow (Wave Number 0 and 1) and tropical cyclone perturbation flow (Wave Numbers 2-23). The procedure was done to isolate the TC and study its effect or contribution to the monsoon rainfall activity. It was shown that the combined westerlies from the basic flow and westerlies generated by the tropical cyclone interact with the Cordillera Mountain ranges along the west coast of Luzon whose peaks are above 2,000 meters. The strong westerlies are forced to rise above the mountains resulting to strong vertical motion that brings about heavy rainfall. The rising motion is enhanced by the convergence of the northwesterlies from the tropical cyclone and the southwesterlies from the basic monsoon flow over the western Luzon. The numerical analysis involved simulation of the four cases of heavy rainfall events using the Fifth Generation Mesoscale Model (MM5) of the National Center for Atmospheric Research (NCAR)/Penn State University (PSU). In the simulation, four convective parameterization schemes (CPS) are tested to see which is best applicable to the local setting. The CPSs tested include Grell, Betts-Miller (BM), Anthes-Kuo (AK) and Kain Fritsch (KF). Generally, MM5 model did not perform well in the daily simulation of the SWM rainfall. The positions of the troughs and the vortices are displaced. However, the 5-day average of windfields and the total rainfall distribution are close to the observed analysis. In the skill test, the threat score and bias score at the heavy rain intensity threshold showed that the MM5 model fairly simulated the total volume of 5-day rainfall. But in terms of quantity of intense events, the rainfall amount is under-estimated. The skill of the model decreases as the rainfall intensity increases which means that the model performed better for less intense rainfall. The model had some difficulty in simulating the intense convection which is also the findings of other studies using MM5. On the most appropriate CPS, Grell was able to capture the major features of the rainfall distribution of the 5-day SWM rainfall events as well as the track of the tropical cyclone that crossed Luzon Island. It performed better than the other schemes as shown by the least mean error and the root-mean square error (RMSE). The diagnostic analysis of the model simulations did not yield encouraging results. The daily simulations of the model are not good enough. It is noted that the isolation of the cyclone waves is not completely accomplished because vortices are still present in the basic flow. The small model output domain could only preserve the cyclone wave vortices but not the large-scale long wave background flow unlike the NCEP analysis which covers the entire globe. Further studies on this regard shall be undertaken in the future.
Marcelino Q. Villafuerte II
This study aims to investigate possible impact of future global warming on rainfall brought by southwest monsoon season in the Philippines. The Climate Type 1 region as classified by Modified Coronas, where the monsoon is well pronounced, served as the pilot area of the study. First, rainfall is investigated historically in terms of its annual and decadal variations. Then, a "nested" modeling is applied to determine if key characteristics can be simulated and find out if these will be altered in the future. The latest version of Abdus Salam International Center for Theoretical Physics (ICPT) Regional Climate Model Version 3 (RegCM3) nested in a coupled atmosphere-ocean General Circulation Model, ECHAM5/MPI-OM, is used. It was run at 40 km horizontal grid spacing covering the entire Philippines. Two periods were analyzed; first 1961-1990 which served as the baseline period and subjected for validation; second, 2010-2039, as the future projection period. Observational datasets which includes surface observation performed by PAGASA; gridded datasets from APHRODITE, Climatic Research Unit (CRU) and ERA 40 were utilized to validate historical model generated rainfall and surface wind. The model performed well in simulating seasonal cycle of rainfall, daily rainfall magnitude/intensity and prevailing surface wind. Spatial details of rainfall were also produced. Projections for the next thirty years revealed an increase in the mean southwest monsoon rainfall by up to 20% primarily during the peak of rainy season. Increase in the mean rainfall might be attributed to more frequent occurrences of days with heavy rain (>50mm) as projected in the future.
Sonny N. Pajarilla
An observational and theoretical study of sea breeze over Samar Island for the month of May 2009, was conducted. The surface observations of PAGASA weather stations in Catarman, Borongan, Guiuan and Catbalogan were utilized in the observational phase of the study. Through surface observations of wind direction and speed, temperature and relative humidity (RH) coupled with FY2D satellite pictures, three characteristic sea breezes have been examined with different prevailing flow, that is southeast, southwest and a variable direction from southeast to southwest. The northern side of the island (Catarman station) consistently manifested the sea breeze characteristics in all three cases. However, a more intense sea breeze was observed with the southeast prevailing flow. The consistent manifestation of sea breeze over Catarman is due to the fact that either southeasterly or southwesterly flow prevailing over the island, the northern side would have an offshore flow of winds which causes the formation of a strong sea breeze circulation. The offshore prevailing wind advects warmer air over land towards the sea which tends to produce a strong horizontal temperature gradient within a thick layer of the atmosphere and a corresponding strong pressure gradient in the surface layers. Contrarily, on the windward side, the prevailing onshore wind advects the colder air over the sea which inhibits the rise in temperature over land. Consequently, the horizontal pressure gradient is weaker and a weaker circulation is developed, yet stronger winds are measured on the windward coast because of the combined effect of the prevailing flow and the weak sea breeze circulation. Hence, Catarman is the most affected area over Samar island of the sea breeze circulation during the month of May where the large scale prevailing flow is southeasterly to southwesterly. The theoretical phase of the study has utilized the fifth-generation PSU/NCAR Mesoscale Model (MM5) a limited-area, nonhydrostatic, terrain-following sigma-coordinate model. Cumulus parameterization sensitivity test has been conducted which resulted to the integration of Kain-Fritsch (KF) into the model runs of MM5. KF had the highest correlation coefficients in terms of temperature and humidity. The model and the observed winds were not in agreement with each other. The model had an over estimated value of wind speed and the direction was not precise. The large error could have been caused by the coarse model domain and human error in conducting manual observations. The modeling results had been consistent with the observed sea breeze characteristics. It was found that the region of positive vertical motion forms first on the leeward coast and moves inland at a rate slower than the total wind. Strong vertical velocities at about 2 mps were observed at 900 mb (~ 1 km) level. The simulated pattern of vertical motion qualitatively agrees with the development of clouds observed by satellites. The depth of the simulated sea breezes agrees with the 2 km sea breeze characteristic of previous studies over tropical regions. It was manifested by the return flow of the model output to be about 850 - 800 mb level or roughly 1.5 - 2 km in height. From a good set of observations and a localized model configuration, the observed sea breezes over Samar island in May 2009 were very well described and simulated. Since the simulations were good, sea breeze characteristics and its associated weather over the area can therefore be forecasted. Higher temporal and spatial resolution of surface observations was recommended to improve observational analyses. Likewise, to reduce the degree of error in the model simulations and future forecasting, a finer resolution and more physics option was also recommended to be integrated in the model runs utilizing high speed computers.
Nievares C. Nivagine
Metro Manila has evidently gone through a transformation from an urban to a highly urbanized region in the country. The interaction of complex wind flow patterns and the effects of urbanization have lead to the changes in mesoscale circulation and, consequently, the time and location of rainfall. A numerical experiment was conducted using MM5 to describe the effects of urbanization on the mesoscale circulation and its associated rainfall. The study of urban effects includes the impact on the heat energy balance, thermodynamic process and circulation. A comparison between observed and simulated temperature, winds and rainfall shows that MM5 is capable to simulated the mesoscale circulation and its associated rainfall. Urban effects are shown to increase temperature over the urbanized area, which is more notable on the boundaries of the urbanized and rural area, including the coastal area, which enhances sea and lake breezes and produces strong convergence zones. The corresponding vertical velocity distribution of convergence zones and occurrence of rain mixing ratio at different atmospheric level shows an increase of rainfall over the northern section of the urbanized area, which is clearly described by the 24 hour accumulated rainfall. In addition, the location of rainfall occurrence is also consistent with the decrease in temperature, sensible and latent heat fluxes.
Sheila S. Schneider
An observational and modeling study of typhoon Reming is conducted. Reming developed from a tropical depression south of Guam. During the next three days, Durian moved westward and intensified rapidly into a super typhoon near the southern tip of Catanduanes Island. Subsequently, Durian continued to move westward through the central Philippines. During this time, the cyclone weakened rapidly. The observational study includes a detailed analysis of the rainfall variations during the passage of the typhoon over the Bicol regions. Rainfall observations from TRMM and rain gauges are used in the analysis. During the time of maximum intensity, the rainfall distribution is characterized primarily by an axially symmetric pattern, with a minimum over the center. A departure from this symmetry consists of a rainfall maximum of about 25mm/hr, which is located southeast of the center. The symmetrical pattern becomes disorganized during the subsequent westward movement of the typhoon. In addition, there is a decrease in the rainfall intensity. The corresponding raingauge observations are generally not consistent with the TRMM observations. This lack of consistency is presumbly due to the highly variable characteristic of natural rainfall variations. In general, the MM5 model simulations of rainfall are not entirely satisfactory, except for the simulations of the 24 hour accumulated rainfall. The relatively poor performance of the MM5 model suggest that further studies should be conducted in order to improve the accuracy of the model.
Ninio Alejandre Relox, Sharon Juliet M. Arruejoa
Initial study towards the development of nowcasting scheme of rainfall in Metro Manila was conducted using rainfall observation in three weather stations located South to Southwest of the study area, namely: Iloilo, Puerto Princesa and Coron. The procedure which was adapted is similar to the Early Warning System (EWS) for flood although this initiative was based on the assumption that the amount of rain observed at three stations will be equal to the rain rate in Port Area.
Analysis show that real time rainfall in Iloilo, Coron and Puerto Princesa, gave similar pattern with Port Area rainfall which is lag 24-, 96-, and 72-hours, respectively although with deviations in some cases. The amount, however, are not equal. Correlation coefficients of the test data also confirm the graphical result. Despite the fact that the rainfall observation in three identified stations is not reliable for nowcasting rainfall in Metro Manila the method used still shows great potential and can be improved by establishing a rainfall station close to and in front of where the monsoon wind is passing before it reaches Metro Manila.
It is therefore recommended that a follow-up study be conducted by establishing a rainfall observation station at the Southwest of Lubang Island which will serve as Early Warning Site of rainfall for Metro Manila.
Roy A. Badilla
The Metropolitan Manila has been experiencing recurrent flooding especially in the low lying areas along the Pasig-Marikina River. Because of this problem, the Philippine government has implemented several projects to achieve effective flood control operations in the area. The first project to be completed was the construction of Mangahan floodway. However, after the completion of the project, informal settles have stated building their houses in the side slope of the floodway making it risky to operate the Rosario Weir. Rosario Weir is the structure that controls the inflow to the Mangahan Floodway. This study focuses on the development of a HBV model and a DUFLOW model to study the flood wave behaviour in the study area and to come up with calibrated models which could be used as basis for the operation of Rosario Weir and Napindan Hydraulic Control Structure for effective flood control and early warning in Mangahan Floodway. The HBV-96 model was applied to stimulate the runoff from Pasig-Marikina River Basin using hourly hydrometeorological data. Four rainfall stations and one water level station for a period of three years were used for the calibration and validation of the model. The catchment was extracted from SRTM elevation data and was divided into six sub-basins. Land cover classes applied for this study were field and forest. Other land cover classes that can be specified in the HBV model do not apply to the study area. Two modules of the DUFLOW model were used for his study; the water quantity module and the RAM module. The DUFLOW water quantity module was setup using twelve river cross sections along the upper Marikina River with a river length of 20.10 kilometers. However, the distances between river cross sections along the river length is not uniform. Water level data from Montalban water level station was used as the upstream boundary condition and the data from Mangahan water level station was used as the downstream boundary condition. The calibration of the DUFLOW water quantity module was done at Marikina water level station. Inflow from the intermediate area between the upstream boundary node and the calibration node was handled by RAM module. However, no calibration was done in RAM module because of unavailability of in-situ data although model parameters were specified based on a priori knowledge about the site characteristics. After the DUFLOW calibration, the hydrograph from the HBV model simulation was used as the upstream boundary condition while the downstream boundary condition remains the same. The purpose of integrating the results of the HBV model to the DUFLOW model is to increase the flood lead time which could be beneficial for flooded control and early warning purposes. The results obtained from this research were satisfactory giving a Nash-Sutcliffe efficiency coefficient (R2) of 0.79 and 0.76 for the HBV model calibration and validation data set, respectively. The DUFLOW model was more accurate with R2 of 0.91 for the model that used in the Montalban observed water level data and 0.90 for the model that used the simulated HBV hydrograph. Hence, the calibrated models can be applied for the flood control and early warning system in Mangahan Floodway.
This study attempts to determine the dominant influence on the motion of tropical cyclone (TC) Muifa (2004) using the expanded potential vorticity tendency (PVT) framework to explain TC motion. The framework suggests that a TC is likely to move towards the region of maximum asymmetric PVT which is mainly contributed by the asymmetric components of potential vorticity (PV) advection and diabatic heating (DH). To diagnose the process first, the limited area grid-point Eta model is used to generate the analysis data to obtain air temperature, zonal and meridional components of wind. Cloud top temperature from the Geostationary Observing Environmental Satellite (GOES-9) infrared (IR) images in the wavelength range of 10.2-11.2µm and 11.5-12.5µm were also used. Here, the results are illustrated on a circular grid using radar plot. The circulation of TC Muifa and its environment is illustrated by the typical distribution of sea-level pressure, wind vectors, GOES-9 IR derived temperature, vorticity, and potential temperature. As Muifa intensifies the vertical structure of potential vorticity (PV) becomes more symmetric as this is distributed horizontally and vertically. The role of the individual physical processes of PV advection and diabatic heating (DH) is to generate heat to contribute to the overall process of PVT. Each individual contribution is apparently indicated by the azimuthal asymmetric structure where the maximum magnitude of DH dominates over the PV advection terms. DH maximum occurred at 12 GMT 18 November during which Muifa reaches its peak wind speed at 115 knots. On the average, DH is not maximum during the day which implies that much of the latent heat release occurred during the night. The positive correlation of DH with maximum wind decreases towards the TC center. On the other hand, the negative correlation of PV advection terms with maximum wind increases towards the TC center. The maximum in PV advection terms rotates ahead or is aligned to the direction ahead of the turning motion. But, in instantaneous motion, the maximum in the PV advection terms points to the direction of motion. In one section of the track where the recurving direction is opposite to the direction of turning motion: the magnitude of the SAAPV term to the left of the direction of motion, increases clockwise while the magnitude in the AASPV infront of the direction of motion decreases clockwise. In terms of magnitude, DH is a dominant influence modifying the PVT structure and hence, the motion of TC Muifa while in terms of pattern, the PV advection terms are dominant indicators of the steering flow and the direction of motion.
Susan R. Espinueva
A study on the effects of rainfall and soil moisture to compute water yield over the Angat multi-purpose reservoir have been carried out. Simulations experiments were done using the Blockwise Topography Model with Muskingum-Cunge Routing (BTOPMC), a continuous, semi-distributed rainfall run-off model which is based on the continuity equation and Darcy's law. By employing a 250-meter grid scale on the digital elevation model (DEM) of Angat, the BTOPMC was used to explore the effects of antecedent rainfall and soil moisture in the determination of water yield over the Angat reservoir. The study will also investigate the following: 1) effects of land cover and soil type in the computation of inflow, 2) effects of having no trees in the watershed; 3) seasonal effect of rainfall in the watershed; 4) the potential of the model in forecasting the water yield. The hydrographs generated during the wet (high flow) and dry (low flow) months were likewise investigated in this study. Finally, the versatility of the model in inflow forecasting was tested using three years of independent data series. Results of the different experiments show that the soil parameters classified in terms of lateral transmissivities of the soil texture such as clay, sand and silt and the decay factor of the soil transmissivity are the more sensitive parameters affecting the simulated hydrograph or inflow. Based on the correlation between the observed and simulated inflows, the model performs better during the high flow months than during the dry months. Rainfall along the eastern portions of the watershed increases the inflow of the Angat reservoir by as much as 63%. Using a separate series of data and the best fit parameters derived, results show that the BTOPMC model has good potential for application in forecasting the inflow of Angat reservoir.
Meriem R. Carbone
This research dealt on the understanding and extent in the practices of the responses to typhoon Warning Signals 1, 2, 3, and 4 in the coastal areas of the First Congressional District of Albay, in order to help the people understand each signal and determine the suitable responses. Specifically it answered the ff. sub-problems: 1. What is the level of understanding of people to Public Storm Warning Signals 1, 2, 3, and 4 in the coastal areas of the towns of the First Congressional District of Albay as perceived by Fishermen, School Officials, Barangay Officials? 2.) What is the extent of the responses practiced by the people in the coastal areas of the towns of First Congressional District of Albay as perceived by Fishermen, School Officials? 3.) Is there a significant difference in the level of understanding of the people in the coastal areas in the towns of the First Congressional District of Albay to Public Storm Warning Signals 1, 2, 3, and 4 as perceived by Fishermen, School Officials, Barangay Officials? 4.) Is there a significant difference in the rank order in the extent of the responses to Public Storm Warning Signals 1, 2, 3, and 4 as practiced by people in the coastal areas in the town of the First Congressional District of Albay as perceived by Fishermen, School Officials, Barangay Officials? 5.) Is there a significant difference in the rank order in the extent of practice of the response to Public Storm Warning Signals 1, 2, 3, and 4 among the perceptions of fishermen, school officials and barangay officials? This research covered the period for the year 2004. To answer the problems the descriptive method was used with a questionnaire checklist to collect the data from fishermen, school officials and barangay officials. Findings of this study revealed that: 1.) Indicators in Public Storm Warning Signals 1,2,3, and 4 were "much understood" except for Public Storm Warning Signal 4, Indicator 1, which was "very much understood" as perceived by the fishermen, School officials and barangay officials also revealed that the people of the coastal barangay "much understood" Public Storm Warning Signals 1,2,3, and 4 except Public Storm Warning Signal No. 1, Indicator 2 "winds of 30 to 60 kph maybe expected in at least 36 hour," which was only "understood," with a weighted mean of 3.43. 2.) The extent of the responses to Public Storm Warning Signals 1, 2, 3, and 4 were "always" or "often" in Tiwi, Malinao, Tabaco, Malilipot, and Bacacay except in Sto. Domingo, where "advertising the people to take necessary precaution" was "sometimes." Public Storm Warning Signal 1 was "sometimes" as stated by the fishermen. School officials also perceived that the extent on the practice of the responses were "always" or "often" in the coastal areas of the different town but in Malinao it was only "sometimes" for the extent of the responses for Public Storm Warning Signals 3 and 4. Extent in the practice of the responses as perceived by barangay officials was "always" or "often." However, in Bacacay, it was "sometimes" for all responses to Public Storm Warning Signal 1. 3.) Fishermen, school officials and barangay officials did not differ in their perceptions on the level of understanding of the people to Public Storm Warning Signals 1, 2, 3, and 4 in the coastal areas of the towns in the First Congressional District of Albay. 4.) The rank order in the Extent of the responses to Public Storm Warning Signals 1, 2, 3, and 4 as practiced by the people in the coastal areas of the towns in the First Congressional District of Albay did not differ significantly as perceived by the fishermen. However, school and barangay officials perceived that the responses to Public Storm Warning Signals 1, 2, 3, and 4 as practiced by the people in the coastal areas differed significantly. 5.) Looking into the rank order in the extent of the responses as practiced by the people in the coastal areas the perception of fishermen, school officials and barangay officials were not significantly different for Public Storm Warning Signals 1, 2, 3, and 4 but were significantly different for Public Storm Warning Signal No. 3. Based upon the findings, the ff. conclusions were drawn: 1.) People in the coastal areas of the towns of the First Congressional District of Albay, generally "much understood" Public Storm Warning Signals 1,2,3, and 4 as perceived by fishermen, school officials and barangay officials. 2.) The responses of people in the coastal barangays of the towns in the First Congressional District to Public Storm Warning Signals 1,2,3, and 4 were generally "always" if not "often" as perceived by fishermen, school officials and barangay officials. 3.) The perceptions of fishermen, school officials and barangay officials on the level of understanding of the people in the coastal areas of the barangays in the towns of the First Congressional District were nearly the same. 4.) To the fishermen, the rank order on the extent of the responses as practiced by the people in the coastal areas to Public Storm Warning Signals 1, 2, 3, and 4 do not differ. While schools and barangay officials perceived that the responses of people to Public Storm Warning Signals 1, 2, 3, and 4 differed significantly. 5.) The fishermen, school officials and barangay officials did not differ significantly in their perceptions in the rank order of the extent of the responses as practiced to Public Storm Warning Signals 1, 2, and 4 but differ significantly in Public Storm Warning Signal 3. The study recommended the ff.: 1.) Encourage people in the coastal areas to continuously monitor the development of the typhoon through the radio. 2.) Encourage a higher degree of service among barangay officials in the preparation of evacuation centers. 3.) PAGASA should provide materials like PAGASA Bicol comics to the three groups of respondents and other members in the barangay about Public Storm Warning Signals. 4.) Provincial Disaster Coordinating Council (PDCC) and PAGASA should regularly conduct trainings and seminars about disaster preparedness with emphasis on important details about Public Storm Warning Signals 1,2,3, and 4. 5.) Schools should include in their Social Sciences and Science and Technology subjects lessons about typhoon warnings and how to plot in the weather map. 6.) A research study on understanding and response to Typhoon Warning in inland areas of other towns of Albay.
Vivien S. Esquivel
The reliability of our water resources is of today’s great concern. An assessment would be of great help to water resources managers and policy makers in that it would show the changes in the efficiency of the present water resource systems under extreme climate events like El Niño and La Niña.
A statistical analysis was undertaken in this study, relating the behavior of inflows of Angat and Magat water reservoirs with the corresponding El Niño indices i.e., sea surface temperature anomalies (SSTA) and Southern Oscillation Index (SOI).
Standardized monthly inflow anomalies from April to March of the following year to concide with the rain-year were averaged and plotted in a time series to show the general relationship between inflow and the corresponding sea surface temperature anomalies and Southern Oscillation Index. With Angat water reservoir, four (4) negative anomalies were experienced out of the six (6) El Niño episodes and two (2) positive anomalies. On the other hand, five (5) out of six (6) La Niña episodes exhibited positive anomalies and one (1) negative anomaly. Magat water reservoir experienced four (4) negative anomalies during the six (6) El Niño events and four (4) positive anomalies during the six (6) La Niña events.
To examine further the effects of ENSO, continuous monthly-standardized inflow anomaly data from 1970 to 2002 observed in Angat and Magat water reservoirs were also assembled in a time series. These data were lag correlated from 0 to 12 months with the corresponding SSTA and SOI averages and found to have consistent negative values with SSTA and the opposite with SOI. SSTA’s strongest relationship with inflow is on the 4th month lag time and SOI’s strongest relationship with inflow is on the 3rd month lag time. These relationships refer to both reservoirs. Magat exhibited higher correlation values than Angat.
Composites for a 36-month period of each El Niño and La Niña events were also presented to show the magnitude of inflow anomalies during these extreme climate events. El Niño composites were centered at the peak of SST positive anomaly, while La Niña composites were centered at the peak of SOI positive anomaly. Negative inflow anomalies on both reservoirs are significant during El Niño years. La Niña years did not cause much impact on inflow anomalies and their effects are comparable to normal years.
Cynthia P. Celebre
Terrain-induced meso-scale circulations such as sea and mountain breezes occurring over Metro Manila were examined. The study involved observational as well as theoretical phases.
The observation stage that was undertaken on 14-16 May 2002 aimed to use the gathered data to initialize and validate the model as well as determine the variations of the structure of the lower atmosphere during the daytime. During the study period, NAIA, Port Area, and Science Garden synoptic stations were used. The PAGASA Astronomical Observatory was temporarily employed by installing instruments that observed relative humidity, dry bulb temperature and wind speed and direction. The radiosonde mobile van of the Natural Disaster and Research Branch (NDRB) of PAGASA was also employed. A simultaneous three-hourly release of pilot balloons was also made at the PAGASA Astronomical Observatory and the Planetarium in Rizal Park in Manila. A vehicle moving every hour from 8AM to 5PM from Quirino Grandstand towards inland was also part of the observation program.
Analyses of specific humidity, temperature and wind speed and direction showed that Port Area was frequently affected by sea breeze although the circulation penetrated inward up to the vicinity of the PAGASA Astronomical Observatory. Onset of sea breeze in NAIA was difficult to determine due to the effect of Manila Bay and Laguna de Bay on the area.
The second segment applied the Advanced Regional Prediction System (ARPS) numerical model that was developed by the Center for Analysis and Prediction of Storms (CAPS) of the University of Oklahoma, U.S.A. It was utilized to simulate the meso-scale circulations occurring over the domain during the day.
The ARPS Version 4.0 was implemented for the entire Metro Manila Area including the Manila Bay and Laguna de Bay. With a 2-km grid spacing, the horizontal domain had 55 x 55 grid points spanning about 110 km x 110 km (1° latitude x 1° longitude). The study made use of the three-dimensional Cartesian geometry (X, Y, Z) with 80-grid points and 200 m grid distance in the vertical.
Six experiments were designed to determine the effects of various factors such as wind speed, wind direction and land use on a flat or with terrain domain, in the development of terrain-induced meso-scale circulations. The results of these experiments showed that for a flat domain, rainfall occurred near the urban area for low wind speed. Increasing the wind speed caused the rainfall to move farther from the urban area but no rainfall was observed for the maximum wind speed used. The amount of accumulated rainfall, was greatest for the lowest wind speed. It was also observed that changes in the wind direction caused changes in the location of cloud and rainfall formation.
For a domain with terrain, it was observed that the urbanization effect with respect to temperature was not evident in all simulations since cloud and rainfall were observed near the mountain. Accumulated rainfall increased for the 2 m/s wind but no rainfall was also noticed for the 5 m/s wind speed.
A late formation of cloud was observed when only rural and water surfaces were utilized instead of also including an urban area as land use. Results also displayed that cloud and rainfall occurrences were located at the eastern most section of the domain.
Nestor B. Nimes
Series of experiments are conducted to demonstrate the effect of moving storm rainfall over a catchment such as the Angat basin. Four (4) years of hourly rainfall accumulation from three (3) gaging locations in the study area comprise the dataset used in the study. First and second order moments (mean, variance, auto-covariance and cross-covariance) are evaluated and used to establish the different parameters of the Neyman-Scott stochastic, space-time rainfall model. The model is based on clustering principle in storms and the random characteristics of storm rainfall. The parameters are established by the application of the Newton-Raphson Iterative Non-Linear Least Squares and the Fletcher-Reeves Conjugate Gradient methods for optimization.
Rainfall fields are generated with specified storm direction of movement and at different speeds. Eight (8) cardinal directions and five (5) storm speeds are applied and produced seventy two (72) hours of rainfall traces in various amounts and spatial distribution over the basin.
The effect of moving storm rainfall is investigated by the application of the National Weather Service-PC version model (NWS-PC) in the simulated runoff hydrographs based on the stochastically generated rainfall data, soil data and basin characteristics as input. Corresponding inflows are investigated in terms of times to peak, peak discharges and total volumes.
Results show that most of the maximums of the rainfall fields generated are located at the exit of the storms except the one coming from the south, where the maximum of the rainfall field is located in the east side instead in the north. This finding shows a notable variability in the location of maximums in the rainfall field at different directions. The variation in the total maximum generated rainfall at different directions is range from 195 mm. to 240 mm. This variation at different directions of storm may be small, but cannot be disregarded. Apparently, the variation in the pattern of minimum and maximum values in the rainfall field is significant on the distribution of the rainfall field, in its location and its spatial distribution. The findings mentioned above, indicate that at different storm directions influence the spatial rainfall distribution, while different speeds affect considerably the magnitude of rainfall over the basin.
The investigation shows that the variations on the times to peak both in the direction and speed are quite considerable at the 50% CDF but not at the 90% CDF. There are significant variations in the times to peak in the 10 kph and 20 kph speeds based on different directions, while other speeds have no indication of variations. The slower storms generated large amount of rainfall than the faster storms in all directions. In slower storms, the peak discharges and the corresponding total volumes are higher than the faster storms in all directions. Hence, the storm movements have significant effect on inflow in the Angat reservoir and cannot be neglected in proper evaluation and assessment for dam operation.
The Neyman-Scott stochastic, space-time rainfall model is recommended for hydrologic simulation studies because of its capability to capture the rainfall physical structure and characteristics, and its ability to capture the space-time structure of the rainfall process. Likewise, the National Weather Service PC version model for runoff simulation is also recommended because it can run fast on desktop computers both in calibration and simulation mode. Moreover, it is flexible in its input, parameterization and output operation and can be applied in any type of basin.
Shirley J. David
The study made use of the first-order three-state Markov chain process to characterize rainfall occurrences. The three states were defined as light, when rainfall amount ranges from <60mm/24 24="" 60="" 180="" when="" rainfall="" amount="" ranges="" from="" hr="" and="" is="">180mm/24 hr. To derive the transition probability matrices the method of maximum likelihood was used in the estimation of the transition probabilities. Data on daily rainfall from nine (9) synoptic weather stations were considered. Factors such as month, station and Sea Surface Temperature anomalies (Ssta) were considered to analyze the estimated transition probabilities. To understand and explain the variability that might be present in the estimated transition probabilities the analysis of variance using the Generalized Linear Models (GLM) procedure were performed.
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The analysis of variance approach was used to determine the significant factors that might explain the estimated transition probabilities. Based on the results of the analysis of variance using the GLM procedure of the Statistical Analysis System (SAS), it was noted that for light-to-light transition no factors were found to significantly affect its occurrence. For the light-to-moderate, light-to-heavy, moderate-to-light, moderate-to-moderate, moderate-to-heavy, heavy-to-light, heavy-to-moderate and heavy-to-heavy the factor SSTa was found to have significant contribution in their variability. Aside from SSTa, month and station appear to be significant factors to consider in explaining the variations in the following transitions light-to-moderate, light-to-heavy, moderate-to-light, moderate-to-moderate and heavy-to-light. For the transition moderate-to-heavy the factor station, aside from Ssta, was found to significantly affect its variability. For heavy rainfall occurrences preceded by moderate rainfall occurrences the factor month was also found to be significant.
Roberto T. Rivera
The sensitivity of the characteristic features of the sea breeze to model parameters were not thoroughly documented in the past as these were largely conducted within the context of a much broader study. This is in sharp contrast to past sea breeze studies which are functions of the environmental parameters. Two model parameters which are quite sensitive in the mesoscale are surface friction and ice microphysics. Their greatest impacts are manifest on the systems intensity. A two-dimensional, nonhydrostatic and compressible formulation of the ARPS (Advanced Regional Prediction System) model is developed to examine the net effect on sea breeze intensities of an ice microphysics and surface friction. A control simulation is first done to serve as benchmark and is followed by two sets of experiments. The first set includes ice in its microphysics parameterization and the second set includes a series of simulations in which the surface momentum drag coefficient is varied from 0.08, 0.04, 0.02, and 0.005. The results of these experiments are compared to that of control simulation. The characteristic features which are compared are the distribution of the horizontal and vertical velocities as well as the horizontal divergence. The inclusion of ice, as expected, strengthened the entire sea breeze circulation but rather than occur in most of the semi-diurnal cycle, this intensification was cut short. The resulting sea breeze layers towards the end of the integration period are comparatively weaker. Increasing the surface friction also increases the negation of surface convergence due to relatively weak flows. Decreasing this value enhances the surface convergence due to relatively strong flows. By simulating some additional friction experiments, it was found that when this is decreased further, there is a certain lower range of values in which the convergence peaks and decline. This suggests that there is an optimum value for friction which maximizes the intensity of the sea breeze circulation. These auxiliary values, however, are far from being too realistic.
Nancy T. Lance
The geographical delineation of flood prone areas in the City Camp Lagoon was discussed. The study area is located at the western portion of Baguio City one (1) kilometer from the City proper and when inundated, eight (8) barangays were affected. The techniques of defining the flood hazard were based directly from recorded inundation areas and actual interviews with the affected communities. The assessment was done by relating the flooding to the primary physical characteristics of City Camp Lagoon utilizing topographical, climatological, geomorphological and geological information of the area. Results showed that the extent and severity of the flooding were aggravated by the geomorphology, surface-water run-off, topography, lack of urban planning, improper drainage and human intervention such as uncontrolled garbage disposal.
Jori J. Loiz
The variations of tropical cyclone activity in the Northwest Pacific, particularly in the Philippine Area of Responsibility (PAR), are greatly influenced by an atmospheric and oceanographic phenomenon called El Niño-Southern Oscillation (ENSO), which occurs every 2 to 9 years. This phenomenon affects the Philippine economy since it is mainly agriculturally-based. Agriculture is dependent on rainfall which is contributed largely by tropical cyclones that enter or originate in the PAR.
This study is an attempt to determine the effects of El Niño, particularly the 1997/1998 event, on the tropical cyclone activity in the PAR. NCEP/NCAR reanalyzed charts of mid-tropospheric humidity, upper-level divergence, outgoing longwave radiation (OLR) anomaly, sea surface temperature (SST) anomaly and wind vectors in 850- and 200-hpa are used in the study. These parameters are mentioned by Gray (1977) as essential factors in tropical cyclone formation.
Reduction of tropical cyclone formation and activity is observed at the height of the occurrence of ENSO. Also, the opposite is observed when the cold episode, which is called La Niña, starts to affect the region.
Vicente B. Malano
A numerical/spectral wave model for the prediction of waves over shallow water has been developed. It is based on the balance equation of energy spectrum in spherical coordinate system applied over a rectangular basin. The effects of varying the grid spacing, bathymetry as well as the wave frequency are examined by neglecting the source and sink functions. The wave heights generated by the different wind intensities and directions are likewise investigated in this study. Results of the different experimentations show that the wave heights generated are found reasonable. The waves are well distributed. Predicted Significant Wave Heights Over Manila Bay are sufficiently realistic.
Francis A. Araniador
This study aims to use the National Center for Atmospheric Research (NCAR) 5th Generation Mesoscale Model (MM5) in the prediction of rainfall associated with tropical cyclones in the Philippines, using a reasonably powerful SGI Origin 2000 supercomputer. The models extracted 24-hr accumulated rainfall forecast data are compared with the observed 24-hr accumulated rainfall recorded from the synoptic stations. MM5 product in graphical form is also compared with satellite pictures of the cloud field. Using contingency tables, the individual scores such as skill score, threat score, bias, Probability of Detection (POD), the number hits are computed in categorical classes. The preliminary evaluation showed that the threat Score (TS) for No Rainfall category ranges from 0.12-0.6, 0.12-0.6 for Light Rainfall category and 0.13-0.35 for Moderate category which is an indication of better forecast compared to the work of Junker, NW et al. (1995) whose threat score values range from 0.07-0.14. There was a high Threat Score and probability of Detection for rainfall occurrence category compare with Non-rainfall Occurrence category. An average skill score of 0.11 using 2x2 contingency table was high enough compared with an average skill score of 0.07 for a 16 category frequency distribution contingency table. Using all the cases involved the overall skill score is 0.18. Rainfall occurrence for Non-tropical cyclone related events has a high probability of detection, threat score, bias and skill score compared with the rainfall occurrence for tropical cyclone related events. The difference between predicted and observed rainfall was analyzed and resulted into a more negative rainfall value in most cases with an indication of under prediction while positive RR values for the rest of the cases. In general, the model has the ability to forecast rainfall associated with tropical cyclone in categorical classes so that there is better Skill Score for light RR category compared with other categories.
Salvador S. Olinares
An assessment of mitigation program activities for natural disasters of PAGASA-DOST in the Cordillera Administrative Region for the year 2001.
Herman L. Ngohayon
Remotely sensed data and observations were obtained from the low-altitude satellites and from the readily available high-altitude geostationary satellites. The capabilities of the Tropical Rain Measuring Mission-Microwave Imager (TRMM-TMI) and the Defense Meteorological Satellite Program-Special Sensor Microwave Imager (DMSP-SSMI) were assessed. Imageries generated by these sensors were utilized. Reliability of these imageries are of paramount importance to data-sparse Northwestern Pacific Ocean, Philippine Sea and the South China Sea where most of the tropical cyclones that caused enormous damages and casualties to the Philippines have originated. The imageries were mostly taken from the Naval Research Laboratory, Monterey through their website via Internet. Brightness temperature values were obtained from the composited satellite imageries of intense tropical cyclones that had entered the Philippine Area from 1998 to 2001. The brightness temperature corresponds to cold cloud tops where deep and intense convection was observed. Similarly, these imageries easily depicted the tropical cyclone eye or center and delineated the location of the eyewall and the spiral cloud bands that correspond to the location of strong winds experienced at the Earth's surface. Likewise, the sea surface temperature observed at the surface, elevation and latitude-longitude was taken and labeled as synoptic predictors. Excellent results were obtained when remotely sensed data and synoptic observations were correlated with the maximum winds (VMAX) and the minimum sea level pressure (MSLP). It revealed high potentials of the low altitude polar orbiting satellites. When utilizing a single independent variable that is from the TMI 85H Tbano (0-2), the root mean square error (RMSE) was 13.21 kph. By employing a number of related predictors with the multiple linear regression analysis, the RMSE was pegged at 12.14 kms. a reduction of 8.8%. When test measures were applied, the TMI 85H Tb ano(0-2) emerged to be more superior from among the other satellite sensors. Finally, when combining remotely sensed (satellite) data and synoptic observations results were found to be comparable and even better. The coefficients, error characteristics and tests performances when applied to MSLP as a measure of TC intensity has a RMSE of 6.13 hPa better than 8.34 hPa which was obtained by Velden in his 1997 study.
Shirley J. David
The study made use of the first-order three-state Markov chain process to characterize rainfall occurrences. Light rainfall occurs when rainfall amount ranges from 0 - 2.5 mm, moderate rainfall with amount from 2.6 - 15 mm and 15.1 mm or more as heavy rainfall. Data on daily rainfall from seven synoptic stations considered. Factors such as year, month, station and episode (El Niño and La Niña events) were considered to analyze the estimated transition probabilities. To understand and explain the variability that might be inherent to the estimated transition probabilities analysis of variance, variance component analysis and the lag-correlation analysis were used.
The analysis of variance was used for the purpose of determining the significant factors that might explain the estimated transition probabilities. Significant factors were further subjected to variance component analysis. Lag correlation analysis was used to determine if there is a significant relationship between the estimated transition probabilities and the Lagged-Southern Oscillation Index, which was lagged up to eighteen months.
Based on the results of the analysis of variance using the generalized linear models (GLM) procedure of Statistical Analysis Software (SAS), it was noted that for light-to-light and heavy-to-heavy transitions the significant factors were month, station and episode whereas for the other transitions such as light-to-moderate, light-to-heavy, moderate-to-light, moderate-to-moderate, moderate-to-heavy, heavy-to-light, and heavy-to-moderate, month and station were found to be significant.
The estimates of the variance components revealed that the variance associated with the experimental errors are cosiderably larger than the estimated variances of the significant factors considered to have influenced the estimated transition probabilities.
The relationship between the Lagged-Southern Oscillation Index (SOI) and the estimated transition probabilities were determined using the Lag-correlation analysis. The results showed a weak correlation between the estimated transition probabilities and SOI of preceding years nor same year.
Gilda C. Borja, Jocelyn B. Balacuit
The general objective of this study is to combine the salient hydrologic and meteorological variables to derive new variables that would be useful in examining surface water supplies. It also aims to develop a climatology of water variability and demand to examine these for possible critical periods, when a deficit (demand is greater than storage) is expected to occur. Specifically, this study aims to predict long-range seasonal variation of rainfall and surface water supply in the Bicol Region.
The surface water supply in the Bicol Region, particularly the Bicol River Basin was examined for 36 years, 1960-1996. A hydrologic accounting system, using rainfall and temperature as inputs was used to derive variables such as Potential Evapotranspiration (PET), soil moisture and runoff. These were combined with the basic hydrologic variables (stream discharge and lake contents).
Annual and monthly rainfall during normal wet and dry years were calculated and plotted to derive the geographical rainfall variations in the study area. It was also used to combine with other basic variables to derive additional variables such as Delta, storage and demand.
Complete time-series climatologies for all variables were presented.
Venus R. Valdemoro
Rationale: Public weather forecasts and warnings are of no use unless they reach the public. The PAGASA is mandated to "mitigate or reduce the losses to life, property and the economy of the nation occasioned by typhoons, floods, droughts and other destructive weather disturbances". Weather and climate affect people's safety, livelihood and leisure activities. Timely and up-dated weather information can protect people, dictate what they wear, how, when and where they travel and help them decide what activities to pursue. The cooperation of all media partners is fundamental to the success of the weather public information and communication activities of PAGASA. Statement of the Problem: This study analyzed the PAGASA weather information dissemination system vis-a-vis issues and problems. Specifically, it sought answers to the ff. questions: 1.) What is the status of PAGASA's warning and forecasting system in terms of objective; organizational structure; personnel and facilities? 2.) To what extent do media personnel understand and use information on weather conditions and forecasts? 3.) How do the general public perceive PAGASA's weather information dissemination system in terms of: a.) Source of information on weather forecasts and warnings; b.) Types of media used in weather information dissemination; c.) Updatedness as to the time of dissemination; d.) Frequency of updates made on weather information dissemination 4.) Are there significant differences in the perception of PAGASA weather information dissemination by the general public grouped according to regions they represent? Research Design: The descriptive method was used in this study by gathering facts through survey questionnaire with the present situation, the prevailing condition, current practices, contemporary events, the characteristics of the groups of individual, their behavioral paterns, attributes and opinions. It is means to find out qualitatively and quantitatively existing condition or relationship practices that prevail, beliefs, processes that are going on effects that are being felt, or trends that are developing. Its goal is to predict and identify relationships among and between variables. It provides information that will serve as basis for improving the warning system and messages being issued by the PAGASA. Treatment of Data: The data were analyzed and treated statistically. The statistical measures used in the study were percentage, weighted, mean, ranking and chi-square. Findings: a.) The status of weather information dissemination system of PAGASA in terms objectives are clearly defined in the stated functions to attain the mandated functions. The organizational structure of PAGASA suggest that there are specific positions and levels with defined functions and job responsibilities. On personnel, both in training and educational attainment (technical and non-technical) PAGASA could boast of a very strong man component as revealed of their educational qualifications and the continuous in-house training and foreign assisted trainings. While, PAGASA is well equipped with the state-of-the-art equipment as attested by its admission for membership to the WMO, also it is continuously maintaining and upgrading its equipment. b.) The extend of understanding of media personnel reveals a "moderate" to a "Great Extent" of understanding and use of weather Information Dissemination system of PAGASA by the Media Personnel of that the Mediamen are able to carry on weather information dissemination of PAGASA. Perceptions of the General Public on PAGASA's Information Dissemination System. Three indicators of weather conditions were used namely fair weather, fine weather and stormy weather. Data show that media personnel have good grasp of information relating to weather conditions. Media personnel are not quite at home with information relating to weather systems. This is so because not all media practitioners were able to attend media seminar-workshop conducted by PAGASA where all of these weather systems affecting the country are discussed thoroughly. It appears that media personnel understand the meaning of public storm signals. Based on findings it would seem that the Media Personnel would need to further on their basic knowledge on the Weather Information Dissemination system. While their knowledge is interpreted as "great extent" from the following indicators like Public Storm Signals, Weather Conditions Stages of Tropical Cyclone, Weather Forecasts and Effects of the Typhoon and Parts of the Typhoon and Weather Systems is only moderate. As perceived by the respondents from Regions 2, 3, and 5 information about a typhoon are disseminated by PAGASA two days before the start of bad weather. On the other hand, they claimed that information is disseminated three days or more before the start of bad weather. Some said the information is disseminated only one day before the start of bad weather. Nobody claimed that they received information about a typhoon right on the day bad weather occurs. Data show that the respondents from Region 2, 3 and 5 get information about weather conditions from the radio, television, newspapers, from the local PAGASA Station, neighbors and friends and from local officials. The radio is the number one medium also because should there is power failure due to strong winds and other factors during the occurrence of strong typhoons radio could be battery-operated. Updatedness as to the time of dissemination. As to how early forecast about an approaching typhoon are disseminated to the public and how frequently updates about an on-going storm shows that the respondents from Region 2 generally receive information about an approaching tropical cyclone two days before the start of bad weather. The Differences in the Perceptions of Respondents on PAGASA's Weather Information Dissemination System When Grouped by Regions shows that statistically no significant differences were found in the perceptions of the respondents from Regions 2,3, and 5 on how early information about a typhoon is disseminated by PAGASA as revealed by the obtained chi square value 5.584. Significant differences were found among the perceptions of the respondents from the three regions with respect to the frequency of updates on the typhoon as revealed by the computed chi square value of 10.50 which exceeds the critical value of 9.488 at .05 level of significance.. Data show that people from Region 3 and 5 tend to get updates on the typhoon more frequently than those in Region 2 and this could be attributed to the distance from the main forecasting center which is located in Quezon City. Conclusions: a.) PAGASA recognized the role of media men in the realization of its stated objective and function. Through an accurate and timely weather information dissemination system, which could be interpreted in terms of efficiency and effectiveness, could create a positive image for PAGASA. Media personnel are generally well versed with information relating to weather conditions, forecasts, tropical cyclones, effects of the typhoons and public storm signals but they are less familiar with weather systems and parts of a typhoon. b.) It could be expected that PAGASA could be able to function effectively thus realizing its mandate. c.) It is within the capacity of PAGASA to attain the mandated functions since its personnel are generally equipped with the knowledge required in their jobs through their educational attainment, local and foreign trainings. d.) PAGASA is equipped with state of the art equipment and therefore PAGASA is capable of locating, tracking and forecasting any weather disturbance. e.) The general public are forewarned as revealed in this study and are familiar with the weather information dissemination system, and it is because even if the tropical cyclone is outside the Philippine Area of Responsibility, the PAGASA could properly locate the weather disturbance through the satellite receiving facilities. f.) There are no significant differences in the perceptions of the general public on the weather information dissemination system. Recommendations: a.) More up-to-date equipment for weather forecasting should be utilized by PAGASA and push for the implementation of the 6-year modernization plan of the agency. b.) Modification of PAGASA weather forecasting and warning system as to effectively counter the adverse effect of tropical cyclone and other disturbances; c.) Media people engaged in weather information dissemination must meet certain qualifications set by PAGASA itself in addition to requirements of attending in-service training and seminar done periodically. d.) Issuance/Release of updates on the development of tropical cyclone as the case may warrant giving importance to the threatened areas. e.) Observance of formal and professional coordination among agencies in weather information dissemination (both governmental and non-governmental organizations). f.) A possible evaluation of existing laws (P.D. 78 and R.A. 1190) and practices, to determine a more systematic and accurate weather information dissemination system is a must. g.) Further study on OCD and PIIAS (PAGASA) could be undertaken to clearly delineate functions and duties on weather information dissemination system of the country.
Edino Nonato Leonardo Nolasco
Precipitation information is critical to understanding the hydrologic balance on the global scale and in understanding the complex interactions among the components within the hydrologic cycle. Past researches concentrate mostly on the mean precipitation amount on an hourly, daily, monthly and even yearly basis. In this research our main objective is to know the rainfall distribution structure of a tropical cyclone using satellite data. This paper involves the investigations of rainfall structures of the two tropical cyclone systems that have made landfall over the Island of Okinawa not too long ago, tropical cyclones Jelawat (August 2000) and Saomai (September 2000), using the Geostationary Meteorological Satellite (GMS) data and the Tropical Rainfall Measuring Mission (TRMM) data. GMS data have cloud temperatures in a wide area but have no information about rainfall amount. As for the TRMM data, it has information of rainfall amount but only in restricted regions and time. We succeeded to obtain coarse rainfall structures in a wide area and finally we show the evolution of the total rainfall amount of the tropical cyclones.
Gilda C. Borja
The effects of El Niño/La Niña on Philippine rainfall were studied. The study focused on determining the regional variations of these effects as well as their dependence on the intensity and magnitude of El Niño and La Niña. Rainfall stations all over the country were classified into climate types. Correlation analysis showed that except for type I climate, not all stations belonging to the same climate type have the same rainfall characteristics. It was therefore necessary to sub-group Type III and Type IV climate into two.
Results of lag-correlation analysis between sea surface temperature anomalies and rainfall anomalies show that a tendency of increasing sea surface temperature anomaly (SSTa) is likely to be followed or preceded by a decreasing rainfall anomaly. This was observed for all climate types except for Type I which showed an increasing rainfall after a lag of four months. This could mean that some other factor or system is affecting the areas with Type I climate.
Time series analysis was presented to show the general relationship between rainfall variations and the corresponding sea surface temperature anomalies covering the period 1961-1997. For purposes of smoothing and filtering the rainfall anomaly, running mean or moving average was employed.
In order to determine the general characteristics of rainfall variations, composites were constructed for seven warm episodes (El Niño) and six cold episodes (La Niña) during the period 1961-1997. A composite shows the time variations of the rainfall anomaly curve, with the corresponding curve of SSTa for a three-year period centered at the El Niño or La Niña year. For more intense El Niño, the duration of negative rainfall anomalies was found to be longer and the magnitude is bigger, and positive rainfall anomalies occurred mostly on the last quarter of the La Niña year until the second quarter of the following year for a strong La Niña.
Maps showing geographical variations of rainfall anomalies, both for El Niño and La Niña episodes, show that each episode or event behaves differently in their effects, intensity and magnitude and likewise the areas affected.
Differential maps were constructed to compare events with very similar SSTa, viz; 1979 and 1976 El Niño and 1970 and 1964 La Niña. The rainfall variation during El Niño may be due to cyclone passage over Luzon areas, and the Intertropical Convergence Zone, ITCZ for the lower latitudes. During La Niña differences occur mostly along climate type. Areas of Type I climate are drier, while the rest of the country is wetter, due to weaker southwest monsoon activity and longer period of occurrence of the northeast monsoon or trades.
Martin F. Rellin, Jr.
With the country’s exposure to weather-related natural disasters, due to the nature of its geographic setting, the effectiveness of the agency to provide timely and accurate weather forecasts and tropical cyclone warnings is of paramount importance. This undertaking seeks to further improve PAGASA’s delivery of public weather services and contribute in providing solutions to the problems besetting the organization by identifying its strengths and weaknesses through internal scanning of the organization’s environment.
This study analyzes PAGASA’s human, physical and financial resources. The area on human resource shows that the weather forecasters are adequate and/or competent enough to provide timely and accurate weather forecasts and warnings, while the weather observers and Engineering and Maintenance Division (EMD) engineers/technicians are somehow adequate and/or competent, meaning they are neither adequate and/or competent nor inadequate and/or incompetent. The area on physical resources indicates that the weather forecasting instruments/equipment of PAGASA are somehow adequate. Among the five weather forecasting instruments/equipment, weather-satellite receiving equipment and basic weather instruments are effective and efficient, while telecommunications equipment, weather radar and upper-air equipment are somehow effective and efficient, meaning these equipment are neither effective and efficient nor ineffective and inefficient. Supplies and materials of PAGASA are inadequate, and the weather forecasting methods/techniques are adequate and effective. The area on financial resource also indicates that the PAGASA has inadequate annual budgetary allocations.
This investigation concludes with discussions about the importance of an adequate and/or competent human resources, and adequate, effective and efficient physical resources as well as adequate financial resources to ensure timely and accurate weather forecasts and tropical cyclone warnings of PAGASA. It also discusses the causes and solutions to the inaccuracy of the organization’s weather forecasts and warnings. The results of this study can be used by both DOST and PAGASA officials as a reference to further improve the services of PAGASA. Educators and students can also use the results to serve as an excellent material for future studies. Finally, the results can be used by the employees of PAGASA to take steps in improving the weaknesses of the organization.
Vicente B. Malano, Bernardo M. Soriano, Jr., Marino L. Mendoza
A numerical/spectral model is adapted over the eastern coast of Luzon and the Bicol Region to predict its state. The model is formulated based on the energy balance equation for deep water. The forcing function of the model consists of surface wind generated by the cyclone model of Holland with inflow angle of 25 degrees. The model domain is divided into 17 x 17 grids with 1 degree spacing. There are five typhoon cases that are investigated in this project. Validations of the model output are investigated using the TOPEX/Poseidon data.
Esperanza O. Cayanan, Bernardo M. Soriano, Jr.
Statistical rainfall forecasting models for the Visayas, Mindanao and Bicol Regions are developed using stepwise regression analysis. For Visayas and Mindanao, a set of 16-year rainfall observations, which are lagged for three hours, was utilized as developmental data and two to three-year independent data for testing. The predictors for the Visayas Region are weather parameters observed at Mactan, Iloilo and Tacloban. Results indicate appreciable performance of the January and February equations while further independent testing is recommended for the May, June and September equations.
For the Mindanao Region, the predictors are from Cagayan de Oro, Davao and Zamboanga. Evaluation of forecasts showed good performance for the June equation, but a longer period of test data is recommended to add more confidence in the forecast. More test data are also recommended for the December, January and February equations to check their real performance. Based on the observed rainfall pattern, it is suggested that Mindanao be divided into eastern and western forecast areas which means that two sets of forecast equations have to be developed.
In the Bicol Region, the predictor data, lagged for one day, from Daet, Legaspi and Virac were used in the regression. Insignificant correlation was obtained, hence a statistical model of shorter time lag and forecast range is proposed.
Julie M. Nimes, Fredolina D. Baldonado
Eleven occasions of tropical cyclone occurrences in three categories of depression (winds up to 64 kph), storm (winds > 64 < 119 kph) and typhoon (winds greater than or equal to 119 kph) that made landfall in Albay Gulf were studied including the water level responses due to associated cyclone surges. The time series of water level observations (observed, surge and astronomical tide levels) and the different cyclone parameters (wind and pressure) were examined and other parameters such as radius of maximum winds, landfall point and cyclone angle of approach were investigated. Other physical factors affecting surge levels such as the bathymetry, topography and coastal configuration of the Gulf were likewise described. Eventually, notable surges at the Gulf were compared with those at San Miguel Bay.
The study was supplemented by a statistical dynamical surge model, which gave considerable insight into the expected peak water level at cyclone landfall.
Results show that the different cyclone intensities induce different water level responses. Reasons are proposed for the observed differences.
Vicente P. Palcon, Jr.
The aim of this study is to assess the PAGASA Telecommunication Systems in the collection and dissemination of Meteorological Information. More specifically, this study answered the ff. questions: a.) How does the Telecommunication Systems perform in terms of collection and dissemination of Meteorological Information? b.) What is the status of the Telecommunication Systems in terms of equipment in place? The descriptive method of research was used in this study. A survey questionnaire was used with some unstructured follow-up interview. Documents and records of PAGASA was also utilized as secondary data. The study will attempted to determine the prevailing condition or situation of the meteorological telecommunication system in the country linked at PAGASA. Respondents of the study: The Chief Meteorological Officer of the 53 weather stations were the respondents of the study. The selection of the participating stations were taken from the records of the PAGASA wherein these stations are connected to Meteorological Telecommunication System as well as the Main Communication Center for a total of 54 stations. Instrumentation: The questionnaire was the main research instrument of the study which was divided into three parts, namely: 1. Collection of Meteorological Information, 2.) Dissemination of Meteorological Information and 3.) Equipment in Place. Data Gathering Procedure: The study made sure of both secondary and primary data as the source of information. The secondary data was taken from the records of the PAGASA on maintenance records submitted by the participating stations. While the primary data was gathered through the survey questionnaire floated to 53 weather stations and MCC. Statistical Treatment: The data collected were computed, tabulated, analyzed and interpreted using statistics like frequency counts and percentages to show the relationship of a part to the whole. Summary of findings: The collection of meteorological information by each collection centers when totalled came up with the equivalent of 93%. The 7% non-performance of the collection of meteorological information is mostly located in Tuguegarao Area. The dissemination of meteorological information performed by weather stations under each particular collection centers when totalled came up with the equivalent of 70%. The 30% non-performance of the dissemination of meteorological information was concentrated more in MCC where 37% of the stations under MCC were prominent. The equipment for the data exchange system of MTS were mostly functioning with the percentage of 91 to 100. The preference on using MTS system in sending and receiving meteorological information was more prominent with the equivalent of 76% who preferred to use it. Conclusions: Based on the findings in this study, the researcher came up with the ff. conclusions: 1.) As a whole, the 93% of collection of meteorological information is still efficient, although the target must be 100%. 2.) The performance of the PAGASA Telecommunication System in terms of dissemination of meteorological information is poor in terms of efficiency as shown by the percentage obtained. 3.) The status of the PAGASA Telecommunication System in terms of equipment in place were mostly functional although the preference in the use of MTS system in sending and receiving meteorological information was also poor due to the ff. reasons: a) Defective data exchange system equipment; b) Difficulty in establishing communication link due to interference; c) The attitude of the Observer on Duty to use or not to use MTS system Recommendations: Based on the conclusions reached, the ff. recommendations are hereby advanced: 1.) The dissemination of meteorological information has something to do with the time allotted, hence, a higher speed modem or protocol is required in order to surpass the noise and interference blocking the signal. 2.) Coordinate with some specialized Agencies of the DOST to develop a message handling system locally which include PC-based software to perform the same function of I/O terminal on which WMO format data can also be forwarded to Global Telecommunication System (GTS). 3. Implement a stringent policy regarding the dissemination of meteorological information to avoid the lack of apathy of the Observer on Duty in using the MTS system. 4.) Conduct an actual size observation and propagation of usable frequencies to determine the cause of the radio interference. 5.) Finally, there is a need to follow-up the present study utilizing a much more comprehensive survey on respondent's perception.
Edwin F. Manresa
This study aims to determine trends in key climatic elements in Laoag, Ilocos Norte, suggest possible causes and how these trends may relate to global warming. Time series of daytime and night time data of the principal climate elements (temperature, relative humidity, cloudiness and rainfall) were analyzed by means of a simple regression analysis and by computation of signal to noise ratio (S/N). The following periods and seasons were used: 30 year, decadal (1962-1971, 1972-1982 and 1983-1992), Non-El Nino years, El Nino years, northeast monsoon, southwest monsoon and north pacific trades. Based on regression analysis of the 30-year series, temperature and relative humidity trends increased by 0.55°C (daytime), 0.77°C (night time) and 4.58% (daytime), 3.50% (night time) while cloudiness and rainfall trends decreased by -0.41 okta (daytime), -0-61 okta (night time) and -0.24 mm, (daytime), -0.24mm (night time) respectively. The increase in temperature despite the decrease in cloudiness indicates that greenhouse gases may have increased. In addition, the relative increase in night time over daytime temperature further shows that greenhouse gases may have increased which effect is dominant during night time. In the decadal trends, the first decade gave positive trends in all the elements. The second decade showed negative trends for both cloudiness and rainfall, positive trend for relative humidity and varying trend for temperature. In the third decade, cloudiness and rainfall exhibited negative trend while temperature and relative humidity gave varying trends. The initial warming in the first decade is similar to the results of 2 X CO2 climate models of Manabe and Wetherald (1980), Hansen et al. (1984) and to the historical warm analogue model of Sellers (1986). In the second decade, daytime temperature decreased probably due to the series of volcanic eruptions from 1980 to 1982. In the third decade, although decreasing very slightly at -0.02°C, night time temperature is above normal. In general, temperature is increasing throughout the periods. The trends of the climatic elements could not be attributed to the recurring El Niño phenomenon as the same trends were also obtained when El Niño years were removed from the series (non-El Niño years), except for rainfall. Rainfall data showed increasing trend in the non-El Niño years opposite to that with El Niño years. This signifies that rainfall is related to the recurring El Niño phenomena. This result is supported by other climate studies in the tropics, which showed that rainfall and convection are related to the recurrence of the El Niño phenomenon (Chu et al. 1996). Signal to noise ratio gave values greater than one for all seasons except for rainfall during the north Pacific trades and northeast monsoon. This result is similar to the study of Hegerl et al. (1996). This is indicative of the changing external conditions. In general, the results of this study suggest that the trends in climate are indicative of a climate signal due to external forcing such as increase in greenhouse gas concentration. This suggests that the climatic trends in Laoag, Ilocos Norte may possibly be related to global warming.
Ninio A. Relox
Statement of the problem: the evaluation was able to resolve the following problems: (1) How does the forecast compare with the actual in terms of: wind and time frame? Geographical position? (2) How did the residents affected by the typhoon respond to PAGASA warning in terms of acceptability and action? Research Design - The study utilized a descriptive method of evaluation. The weather advisories and bulletins issued by PAGASA including weather observation reports from field stations during the passage of typhoon Gading were the bases of the evaluation of the forecast. The impact of which is assessed based on the human response interview result. Respondents of the study - Human response survey was conducted in the area affected by typhoon "Gading". Initially, a total of 90% respondents in the human response interview were targeted in the affected area. The final total number of response obtained was 113. Instrumentation - Human response questionnaire was the instrument used in this study. The investigation dealt with four main subjects namely; 1) Socio-economic information of the respondent, 2) Warning comprehension, 3) Warning acceptance, and 4) Action taken based on the warning received. For forecast evaluation, analysis of variance and streamline analysis were employed. Data Gathering Procedure - The study made use of all meteorological data obtained from the Weather Branch of PAGASA. In the case of human response, thirty respondents aging 12 years old and above regardless of social standing were interviewed in the area situated North of the "eye", thirty in the area where the "eye" crossed, and thirty in the area South of the "eye" track. Data Analysis - The forecast maximum sustained wind and positions were compared against the observed in the areas affected by the cyclone. Aside from geographical positions (latitude and longitude) of the cyclone, which were subjected to statistical analysis, other meteorological parameters were evaluated by using meteorologically accepted evaluation method. Human response on the other hand was assessed in terms of total response in relation to the warning level raised. Summary of findings - Forecast evaluation results show that prior to disaster impact, advance information about typhoon Gading was given out warning the public for possible typhoon danger. There were confusing statements indicated in the warning pertaining the validity of the information and the time of issuance for the next bulletin, and the predicted time of occurrence of maximum sustained wind in the warned areas and the meaning of the typhoon signals raised. Although these discrepancies can be considered minor problems in the warning statements, concerned institution should try to find ways for improvement. There were cases where intensification of the cyclone was observed and in fact tropical depression Gading was upgraded to tropical storm, but still the warning signal was not increased. The warning was upgraded only 3-hours before the typhoon unleased its fury in the forecast areas. Considering forecast accuracy of the predicted geographical position, statistical result shows that there was no evidence that the forecast and the observed have significant difference at 5% level of significance. When the observed data, however, was subjected to streamline analysis, a very large forecast position discrepancy was observed except when the cyclone was already overland. It is revealed by streamline analysis that beginning 2:00 am of September 18, the center of Gading was already in the vicinity of Lingayen Gulf that remained almost stationary until 2:00 pm of the same date after which, it healed in the East-Northeast direction toward the vicinity of Japan. This method, however, may not be possible during cyclone occurrence because data influx during bad weather is hampered by destruction of communication systems. Another significant fact unearth in the evaluation is the intensification of Gading during its landfall. Normally, tropical cyclone starts to weaken during landfall due to the effect of irregular terrain. This case is exceptional. Short term predictions, according to Hamilton (1998), cannot be done with any useful reliability or consistency due to the heterogeneous nature of the atmosphere and the uncertain stress with it. Typhoon hazards are fundamentally complex in nature due to the uncertain state of the forces that trigger the events. Generally, the forecast can be considered accurate and comparable with the works conducted in advanced countries especially for maximum sustained wind. In the United States, out of 480 tornado warnings released with the use of Doppler radar, only 237 of 0.49 were false alarm. In typhoon Gading case, out of 9 predictions, (excluding those that cannot be verified), 7 were correct for 6-hr forecast, 6 for 12-hr and 5 for 24-hr. In the case of human response, result showed that out of 113 respondents, 46 said that the forecast was accurate, 13 said it is partially correct, 39 said it is not, and 15 were not sure of its accuracy. As regard to warning comprehension, 84 respondents claimed full comprehension of the warning message, 19 claimed partial comprehension, and 10 did not understand. Verification, however, shows that nobody fully understood except for the 43 respondents who partially understood. Analyzing the influence of the three variables (perception about warning accuracy, warning comprehension and even the verified comprehension, these all have only minimal influence for positive response. Majority opted to have no response. It was found that increasing the signal level has great influence for positive response-the information that was not fully considered in the case of typhoon Gading. Conclusions - Based on the presented facts, it is concluded that: 1.) Timely and sufficient disaster information about typhoon Gading was given out by PAGASA. There were inconsistencies and in some occasion inaccuracies, but the forecast of geographical positions and wind in terms of time frame and intensity can still be considered correct and the primary purpose for issuing the warning was served. 2.) Forecast accuracy is not the only factor affecting mobilization of the people for the conduct of precautionary measures. Other variables may be considered like disaster education and human behavior or attitude toward the disaster information received. It is risk perception factor toward the issued warning that highly contributed to people's positive action. 3.) The success in the implementation of disaster mitigation plan is dependent on the concerted effort exerted by all concerned. Consequently, its failure may be the result of the negative attitude of just one component of the whole process. - Recommendations -Having been able to synthesize the weaknesses and strengths of the warning and human response, the ff. recommendations are hereby promulgated: 1.) The weather service should device means to simplify disaster warning that will be equally understandable to all users. This work may be possible by the collaborative work of the scientists, sociologists including verbal communication experts. 2.) Innovative disaster information education such as movie ads in movie houses, disaster education caravan in the rural areas, film showing using the developed typhoon disaster movie, etc. be conducted. 3.) Research aimed at reviewing typhoon disaster mitigation programs and program implementation such as typhoon disaster information dissemination should be conducted to ensure that all components (i.e. media, local government, non-government organizations, etc. role) have positively contributed to the efficiency in disaster information campaign. It is further recommended that the evaluation of disaster mitigation policies be conducted in order to obtain guidance in revising or developing appropriate disaster implements.
Esperanza O. Cayanan, Bernardo M. Soriano, Jr.
Short range objective techniques of forecasting rainfall probability and visibility at three airport stations in the Philippines (Cagayan de Oro City, Roxas City and Dumaguete City) were developed using stepwise regression analysis. A 15-year data set (1978-1992) was used as developmental data and a three-year data set (1993-1995) was utilized for forecast skill verification. Both rainfall probability and visibility forecast equations for January, February and December (northeast monsoon months) for Cagayan de Oro City Airport can be used operationally at a significant level of accuracy. The forecast equations developed for Roxas City Airport gave insignificant results for most of the months. For Dumaguete City Airport, rainfall probability equations for April and November and visibility forecast equations for March and April attained good results.
Vicente B. Malano, Bernardo M. Soriano, Jr., Marino L. Mendoza
A numerical model is developed for storm surge prediction incorporating overland surges over the Gulf of Leyte. The model is formulated using the depth-integrated form of the transport equations applicable for storm surges. Movement of land/sea boundary is one dimensional. The forcing function of the model consists of surface wind generated by a symmetric cyclone model of Jelesnianski with inflow angle of 15 degrees. The model domain is divided into 30 x 41 grids with 1 km spacing. At each grid point, the maximum water height is computed during the 24-hour model time.
Results reveal that the maps of mean envelope of water can be used to predict storm surge over the Gulf of Leyte. With the aid of these maps, improvement of the model can be achieved by incorporating more theoretical typhoons with different characteristics, e.g. radius of maximum winds and typhoon intensity and movement. A similar study can be replicated in other surge-prone areas of the country.
Shirley J. David, Gaspar B. Salaguste
The study relates the behavior of rainfall intensity and water level during the passage of the tropical cyclone. The observation of 3-hourly rainfall data from the Science Garden Synoptic Station and the water level from the San Juan River Basin in Quezon City is considered from the time the tropical cyclone entered the Philippine Area of Responsibility (PAR) in order to have a longer series available for the estimation procedures.
The study made use of the regression technique, the Linear Regression with Autocorrelated Errors, to account for the serial correlation that is present in the data. The performance of the developed model is accounted for by using the Mean Absolute Percentage Error (MAPE).
Contrary to most hydrological literatures, rainfall intensity in this particular study was found to be an insignificant parameter to explain the water level in a river. This was attributed to the possibility of non-representativeness of the rainfall data considered in the development of the model. The results showed that lags 1 and 6 are the significant time that have bearing on the consequent behavior of water level.
It is suggested that more cases should be studied to come up with more conclusive results.
Nathaniel T. Servando
The behavior of two tropical cyclones (TC) due to mutual interaction are investigated through observational analysis and a series of numerical experiments using a non-divergent barotropic model. The basis of the observational analysis is the 45-year northwestern Pacific (NWP) TC data from 1952-1966. From these records, the so-called binary TC are picked based on the following criteria: TC which co-existed for at least 48 hours with separation distance of not more than 13 degrees lat. (1400 km) and attained at least storm intensity. Results indicate that the total number of binary TC reached 91 out of the 1,200 recorded number of storms or typhoons during the period or a percentage of 7.6 with an average of 2.02 cases per year. The orientation of the binary TC at the initial stage of interaction are generally E-W and NE-SW. Furthermore, decreasing separation distance with time was noted in about 50% of the total binary TC. Only four cases (4.4%) of the approaching binary TC were observed to have merged into one single TC. Results from the numerical experiments indicated that the relative motion of the cyclonic vortices are sensitive to the separation of the binary vortices. There is a critical separation distance at which a distinct bifurcation between merging and non-merging occurs. Below the critical separation distance merger takes place and above which, repulsion occurs. The critical separation distance varies with size of the binary vortex system and in particular, not affected by intensity changes if the initial separation distance is below 700 km. At larger separation distance, variations in intensity alter the critical separation distance, with the weaker binary systems merging at relatively higher separation distance than the stronger binary systems. On the interaction of two unequal vortices in terms of intensity, the stronger vortex dominates. The weaker vortex is destroyed by the strong tangential wind of the stronger vortex as they move closer. The presence of shear in the environmental flow has significant impact on the relative motion and attraction of the pair vortex. A cyclonic shear enhances the relative cyclonic rotation and favors merger. An anticyclonic shear reduces the relative cyclonic rotation and inhibits merger.
Felicidad V. Villareal
A model for simulating the radial distribution of tropical cyclone rainfall is developed. The model is primitive equation model in cylindrical coordinates with axial symmetry; a sigma coordinate is used. It incorporates microphysical cloud processes for explicit prediction of cloud water and rain water; these processes are evaluated by using the formulation of Kessler (1969). The sensitivity of the rainfall predictions of the model to the microphysical parameters involving autoconversion and accretion is examined. It is found that the model is fairly sensitive to the collection efficiency. On the other hand, the model is relatively insensitive to the auto conversion threshold value and autoconversion factor. The sensitivity of the model to the formulation of the drag coefficient is also examined. It is found that the model is quite sensitive to values of the drag coefficient. A constant value of drag coefficient equal to 0.003 is found to be a good alternative to using a variable drag coefficient, especially for stronger intensities of tropical cyclones (typhoon). On the basis of the results of the above-mentioned sensitivity tests, together with observational verification, the optimum values of the model parameters are determined. After determining these, the model is utilized to study the dependence of the rainfall distribution on the intensity and size of the cyclonic circulation. This is done by conducting a series of numerical simulations or numerical experiments with the model. Various sizes and intensities of tropical cyclone are specified by prescribing the appropriate value of horizontal diffusion coefficient. A total of fifteen (15) experiments have been made. The experiments show that, in general, the radial profile of rainfall rate is similar in shape to the corresponding radial profile of wind speed. In all intensity of tropical cyclones, the rainfall maximum is always located slightly closer to the cyclone center relative to the location of the wind maximum. Expressions which describe the radial profile of the simulated rainfall rate are formulated. These are based on equations which describe the radial wind profile of tropical cyclones. The equations has been used by Holland (1980). The two important parameters which are incorporated in the radial rainfall rate profile are the maximum rainfall rate and the radius where the maximum rate is located. If these two parameters are known, then one can determine the rainfall rate at any radius. An attempt is done to develop empirical equations or regression equations for determining these two parameters in terms of the wind profile. One regression equation specifies the maximum rainfall rate in terms of the maximum wind. The other regression equation specifies the radius of maximum rainfall rate in terms of radius of maximum wind. One can use these expressions for predicting the rainfall rate at any distance from the cyclone center from a forecast of the intensity and the size of the cyclone.
Bonifacio G. Pajuelas
The long period variations of rainfall in the Philippines are studied. This is done by first classifying the rainfall stations into climate types and then constructing time series of rainfall anomalies called rainfall anomaly indices (RAI) for each of the defined climate type. The RAI is the composite of standardized rainfall anomaly for a group of stations representing a region of quasi-homogeneous climate. An F-test suggests that the geographical variations of standardized rainfall anomaly is insignificant as compared to the temporal variations within each climate type, which mean that the RAI's are representative of each climatic region and can be used with confidence. In order to determine the longer period variations of the RAI time series, the shorter period variations are eliminated by very low frequency filter. Firstly, the rainfall stations were classified into climate types based on interstation correlations, the time averaged monthly standard deviations (SD), and maximum rainfall. five climate types emerged: the first two which is opposite to each other describe the dominant rain period and the remaining three types are intermediate between the first two. These intermediate types are further delineated into : (a) SD range < 100 (b) SD range from 100 to 147 (c) and SD range > 147. The minimum correlation coefficient within each climate type is 0.75. Secondly, the standardized rainfall anomaly (SRA) for every station in each climate type are compared, and the variance structure of the geographical and temporal variations of the standardized anomaly were computed to determine the significance of the RAI. In each 4-month period, plots of individual stations SRA generally respond to the prevailing climatic condition that influence the region. There are some inconsistencies in the sensitivity of the individual stations' SRA as shown in the time series of graphs. However, the geographical variations of these SRA's are statistically insignificant compared with the temporal variations, which imply high confidence on these RAI's. Thirdly, RAI graphs and statistical characteristics of each time series are analyzed. The time series graphs of RAI reveal the wet and dry periods in each climatic region which suggest the dominant phase of the Southern Oscillation. Chi-square test suggests that all unfiltered RAI samples do not significantly differ from the normal (Gaussian) distribution, except in western Luzon where samples have skewness and kurtosis which differ significantly from normal. The Von Neumann ratio showed that non-random elements are significantly present in all RAI samples. However, Mann-Kendall rank statistics indicated these trends are not significant in the unfiltered RAI series. On the other hand, 10-year moving average (10Y-MA) filtered RAI series trends are significant particularly over eastern Philippines, Mindanao region, and Central Visayas during the 4-month period of February, March, April and May (FMAM). The trend is further accentuated by the 30Y-MA filtered RAI's. Student's t-test suggested a significant decrease in the mean unfiltered RAI values of FMAM 1973-1996 series of type 3 climate. In the 10Y-MA filtred RAI, climate types 2, 4 and 5 display also significant change in the mean RAI values of FMAM 1973-1996.
Nathaniel A. Cruz
Early, normal and late onset of rainfall associated with the southwest monsoon are analyzed by compositing pentad (five-day) values of selected meteorological parameters. Results showed that the early onset of rainy season (May 2, 1984) was primarily due to the passage of a tail of a cold front over the northern part of the country. Although, there was an early start of the rains, the rainy condition was not sustained due to weak southwest flow. On the case of the normal start (May 28, 1988), the onset can be clearly attributed to the prevalence of the southwest monsoon. Associated with this condition is the normal northward migration of the Intertropical Convergence Zone as well as the northward movement of the ridge of the North Pacific high pressure area. One distinct characteristic of this type of onset is the continuous rainfall over the western part of the country for several pentads after the onset. The persistence of the ridge of the NPHPA over the country was the main reason for the late onset of the rains (June 23, 1993). Analysis showed that the unseasonal position of the ridge has a significance influence in the movement of the ITCZ as well as the monsoon trough. Rainfall conditions, like the case of the early start, experienced a significant decrease after the onset. Significant wind shift (associated with the start of the southwest monsoon) is likewise related to rainfall onset. Investigation showed that a significant change in wind direction (from easterlies to southwesterlies) at selected synoptic stations occurs before the onset of the rains except on instances when the onset was brought about by other systems like cold fronts. An index was developed to assist in the forecasting of monsoon and possibly rainfall onset in the future. Called the Brunei-Hongkong index, the average pressure gradient between the two stations several pentads before the onset, could serve as an indicator of possible start of the southwest monsoon as well as the rainy season.
Carina G. Lao
Philippine summer rainfall, which contributes to 60 percent of the annual rainfall over most parts of the country, is very vital to the national economy. In the light of the importance of this parameter, this study investigated the variability and characteristics of summer rainfall and its relationship with other parameters. The results were used to formulate equations for the prediction of 5-day total rainfall in Luzon and Manila 5 days in advance.
Linear regression equations were developed for predicting 5-day total rainfall in the summer month of June for 5 areas lying mainly in Northern Luzon, Central Luzon and Manila. The potential predictors considered were 5-day mean surface pressure, 850-, 700-, and 500-hPa pressure heights of stations surrounding the Philippines (Nanning, Ponape and Marianas), and 5-day mean station pressure, rainfall, relative humidity, dew point depression and cloud cover of 11 selected stations in the Philippines. The selection of predictors was done by considering three basic principles, namely, physical relationship with the predictand, availability and predictability. Also, previously observed averaged rainfall (5-day lag) was used as additional predictor. These were preliminarily screened by correlation and then by stepwise regression. A 7-year period of data (1984-1990) was used in the study.
The results of the preliminary investigation showed that rainfall tends to occur concurrently in the 5 areas of the study. The rain episodes are common to all stations that were selected for the study based on a 14-year period (1981-1994).
The relationship between area-averaged rainfall and average surface pressures was determined using time series analysis. Results show that the surface pressures in Marianas, Nanning and Ponape have good relationship with rainfall in the 5 areas of study. If the pressure in Marianas is high (low), rainfall in each area of study is high (low). The opposite results were obtained between rainfall in each area and pressures in Nanning and Ponape.
Prior to the regression analysis, the possible predictors 5 to 12 days before the period to be predicted were correlated with rainfall in the 5 areas of study. Also, 10 sets of data for the predictand/predictors for the 5 areas and for 5-day lag period were also correlated and regressed to determine their relationships with rainfall. Results show that 2 (Area 1 total rainfall and Baguio relative humidity), 2 (Area 2 total rainfall and Baguio rainfall), 10 (Area 3 total rainfall, Ponape and Nanning surface pressures, heights of 850- and 500-hPa level pressure in Nanning, heights of 700- and 500-hPa level pressure in Marianas, pressures of Dumaguete and Dagupan, and Baguio rainfall), 8 (Area 4 total rainfall, heights of 700- and 500-hPa level pressure in Marianas, surface pressures of Dumaguete, Baguio, Catarman and Ambulong, and Baguio rainfall), and 8 (Area 5 total rainfall, Nanning surface pressure, heights of 850- and 700-hPa level pressure in Nanning, height of 850-hPa level pressure in Marianas, surface pressures of Dumaguete and Tacloban and Baguio rainfall) predictors are highly correlated with the rainfall of Areas 1, 2, 3, 4 and 5, respectively, for the month of June, 5 days in advance.
Utilizing the 7-year period of 210 cases on dependent data, results of the verification show that the performance efficiency for each of the 5 areas is more than 80%. Using 4-year independent data (1992-1995), the overall performance efficiency of the regression scheme conducted on 120 cases for each of the 5 areas which is more than 83% is also considered remarkable and promising.
Salvador S. Olinares
To determine the level of attainment of the objectives of the disaster program, the level of implementation of activities of the program, their level of effectiveness, the degree of seriousness of the problems encountered relative to the implementation of the activities of the disaster program and the frequency of adaption of remedial measures to minimize the problems relative to the implementation of the activities of the disaster program. The investigation was conducted in the City of Baguio and the Province of Benguet. The respondents were 300 residents of Baguio City and another 300 residents of the province. The descriptive was the method used in the study. The main data gathering tool was the questionnaire supplemented by interview and observation. The t-test statistical method was used to test the null hypotheses. The ff.: are the salient findings of the study: 1.) There was a significant difference between the perceptions of the residents of the City of Baguio and the Province of Benguet on the level of attainment of the objectives of the disaster program of PAGASA. 2.) There was a significant difference between the resident of the City of Baguio and the Province of Benguet on the level of implementation of the activities of the disaster program of PAGASA. 3.) There was no significant difference between the residents of Baguio City and Benguet Province on the level of effectiveness of the disaster program of PAGASA. 4.) There was a significant difference between the perception of the residents of Baguio City and Benguet Province on the degree of seriousness of the problems encountered relative to the implementation of the activities of the disaster program of PAGASA. 5.) There were six remedial measures to minimize the problems encountered in the implementation of the disaster program in the City of Baguio and the Province of Benguet. CONCLUSIONS: 1.) The objectives of the disaster program of PAGASA were moderately attained. 2.) The activities of the disaster program of PAGASA were moderately implemented. 3.) The disaster program of the PAGASA was moderately effective. 4.) The problems encountered relative to the implementation of the activities of the disaster program of PAGASA were very serious. RECOMMENDATIONS: 1.) PAGASA should exert more effort in order that they will fully attained their objectives for the welfare and benefit of the residents of Baguio City and Province of Benguet. 1a. PAGASA should regularly disseminate that there is a Disaster Program being implemented and undertaken in the locality. 2.) Disaster Program activities should be better implemented. 2a. Adequate information campaign materials and strategies should be implemented by PAGASA with regard to the effects of natural weather hazards/disturbances. 2b. Trainings, seminars and drills related to the Disaster Program should be implemented by the PAGASA in order to minimize/lessen the loss of lives, properties and human sufferings and others. 2c. There should be a regular meeting with local officials, government organizations and non-government organizations in coordination with PAGASA regarding natural hazards disturbances and natural disasters, especially in relation to tropical cyclones. 3.) The effectiveness of the Disaster Program should be further improved. 3a. Continuous monitoring of various activities of the Disaster Program should be implemented by the PAGASA in order to evaluate if the program is effective or not. 4.) The identified problems should be threshed out. 4a. Communication equipment, vehicles, sirens and other logistics should be provided and procured. 4b. Residents should actively involved themselves for the success of the Disaster Program. 4c. Concerned officials should consistently support financially and morally the objectives of the Disaster Program. 5.) Remedial measures should be adapted in order to minimize the problems encountered in the implementation of the Disaster Program. 5a. There should be a continuity in the implementation of all Disaster Program activities in order to seek for further improvements, developments and to minimize/lessen previous mistakes and shortcomings committed by both the implementors and beneficiaries. 5b. Concerned PAGASA personnel should enhance their commitment and actively participate for the attainment of the objectives/goals of the Disaster Program. 6.) A similar study should be conducted after 5 years.
Teodoro F. Ambas
This study attempted to investigate the factors associated with the level of performance of PAGASA field observers in data reporting for calendar year 1997. Specifically, the study sought answers to the following subproblems: (1) What is the level of performance of PAGASA day field observers based on the weather elements as follows: 1.1 skills and related knowledge 1.2 altitude toward work, peers and superiors and 1.3 advancement / promotion / recognition (2) What is the level of performance of PAGASA night field observers based on the weather elements as follows: (same as in no. 1) (3) Are there significant differences between the level of performance of the two groups of respondents on the three major variables? (4) What are the factors associated with the differences in their level of performance? (5) What modernization plan may be proposed to enhance the level of performance of PAGASA field observers? The descriptive research method through the validated survey questionnaire and documentary analysis technique were employed in this study to obtain data from the respondents. The respondents of the study were the 236 out of 279 personnel assigned in the fifty six (56) PAGASA Weather Stations in the Philippines. FINDINGS: From the analysis of data, the findings were as follows: 1. The field observers assigned in the regional Stations of PAGASA during the day shift considered skills and related knowledge, altitudes towards work, peers and superiors and advancement/promotion and recognition as factors highly associated to the very satisfactory and outstanding level of performance as weather observers. There were supported by the obtained overall mean of 3.91, 4.38 and 3.80 respectively. The field observers of PAGASA with night shift assigned in the regional station also indicated that skills and related knowledge, attitude towards work, peer and superior and advancement, promotion and recognition were factors considered as highly to very highly associated with the level of performance among the employees of PAGASA particularly those assigned in the night shift. 3. No significant differences were found between the level of performance and the factors of skills and related knowledge, attitudes toward work, peer and superiors, and the advancement/promotion/recognition among the two groups of respondents as supported by the obtained t-test values which were much lower than the tabular value of 1.95 at .05 significant level. The hypotheses therefore were accepted. 4. There were factors that were very much associated with the level of performance which the respondents considered these as the problems in the performance of their duties. 5. A Proposed modernization plan to enhance the level of performance of weather observers in particular and the efficient and effective delivery system of PAGASA in general was undertaken considering foremost the salient findings of the study. CONCLUSIONS: In the light of the findings, the ff.: conclusions are drawn: 1. The scientific, technical and technological know-how, skills in the operations of instruments, human relation and human behavior at work and the recognition derived from work were factors identified by the employee of PAGASA that greatly influenced their performance. 2. Inadequate on-the-job training on the operations of meteorological communication system, delay in the repairs of defective MTSDP facilities, breakdown of relay stations, outmodelled facilities were factors that influenced the inefficient and ineffective delivery system of the employees. Considering the problems encountered and the factors associated to work among the employees and the inadequate and outmodeled instruments, PAGASA's vision, mission and mandated functions of excellence in its distinctive competency in meteorology, operational hydrology, astronomy, climatology and other allied sciences and to provide world class capability in monitoring, analysis, forecasting and warning of tropical weather system might not be attained. 4. The proposed modernization plan for the PAGASA may serve as the take-off point to enhance the level of performance of employee for an effective and efficient delivery system to the Filipino people. RECOMMEMDATIONS: 1. Since the day and night shift field observers of PAGASA revealed that there were factors associated with the level of performance, the agency head through the HRMS should immediately organized and implemented the staff development programs to enhance these factors and to include foremost an on-the-job training of the participants. 2. Organizational climate and reward system which have strong psychological impact on the employees must be emphasized by PAGASA managers. Aside from the annual budget of PAGASA, the head of the agency or the immediate person concerned should tap NGO's and other GO's for probable financial assistance regarding the problems on adequate of instruments, delay in the release of budgetary allocations and the outmodel facilities and equipment. 4. The proposed modernization plan be implemented to the fullest through appropriate representation of the legislative branches of the government. 5. Similar researches be continuously conducted to generate data on the performance of the employees of PAGASA, their problems and solutions. 6. Lastly, the results of this study are recommended to be published, disseminated and discussed with all concerned for information and feedback.
Flaviana D. L. Hilario
Point estimates of hourly, 3-hr. 6-hr, 12-hr and 24-hr rainfall from tropical cyclones were computed using 3-hr interval of infrared and visible images from the Geostationary Meteorological Satellite (GMS) of Japan. Multiple regression models involving IR, VIS and combination of the two parameters were developed to estimate short duration rainfall Independent data were used to validate the models.
For very short duration rainfall estimation (hourly and 3-hr), the correlation between the observed and the estimated rainfall from IR only models is very low. However, it was observed that high rainfall values are always associated with high IR brightness value but high IR brightness value is not always associated with high rainfall values. On the other hand, the visible parameters were found to be highly correlated with very short duration rainfall. This could be attributed to the presence of cirrus anvil which is more sensitive to the infrared than the visible measurements.
The total time period of the rainfall estimation appears to be an important factor in the accuracy of the calculations particularly with models involving infrared parameters only. The scatter of hourly and 3-hr rainfall estimates are relatively large, however, the scatter decreases as estimates are accumulated over longer period of time. For models with visible parameters, the scatter also decreases as the period of accumulation increases.
In general, the estimated rainfall for the periods hourly, 3-hr, 6-hr, 12-hr and 24-hr showed overestimation for lower rainfall values and underestimation for higher rainfall values. The results also showed that as the period of accumulation of rainfall increased, the correlation between the observed and the estimated rainfall also increased.
Validation of the five models (with IR parameters only) using independent data sets (T.C. Akang) yielded slightly lower correlation coefficients for 3-hr to 12- hr rainfall estimation. The 24-hr estimated rainfall has much lower correlation coefficient which can attribute to the limited number of samples used in the model development. Models with visible brightness as parameter adequately estimated 3-hr, 6-hr and 9-hr rainfall of T.C. Akang. Validation of the 3rd order polynomial of IR for 6-hr and 12-hr rainfall showed relatively poor performance of the model. The observed rainfall from the synoptic stations are much higher than the rainfall used in model development which could account for the low skill of the model.
Fredolina D. Baldonado
The approach to the determination of radar reflectivity - rainfall intensity (Z-R) relationship is discussed. Calculations of the simultaneous reflectivity factors and rain rates in a volume of air are performed based on the solution to the radar equations by infusion of the different radar parameters and the measurement of return power of the electromagnetic wave. Linear regressions are applied to the transformed data sets and constants and coefficients in the relations that take the form Z=ARb are determined. A set of empirical Z-R relations for different locations in a river basin as well as for particular storms are obtained. The experimental average relation, Z = 66.8R2.61 is likewise determined.
The relationships show differences in excess of 50% in rainfall rate at the same reflectivity. These differences may be associated with differences in synoptic conditions affecting rain types, geographic location and to variations in precipitation with height.
Juan D. Cordeta
This study was primarily conducted to determine the status of the integrated lessons on natural hazards in the immediate grades science curriculum in the Division of Quezon City in terms of the Objectives, Curriculum Content, Time Allotment, and Teaching Methods Devices. Specifically, it sought to answer the following problems: (1) What is the profile of the Teachers of Science in the Public Elementary School as to? (1.1) Sex, (1.2) Age, (1.3) Educational attainment (1.4) Teaching experience and (1.5) Training/seminar workshop on natural hazards. (2) What is the status of the integrated materials on natural hazards in science curriculum as perceived by the teacher-respondents in the intermediate grades in terms of: Objectives, curriculum content, time allotment, teaching methods/devices? (3) Are there significance differences between the perceptions of Grades V and VI teacher-respondents on the lessons integrating natural hazards in the intermediate grades science curriculum when grouped according to their professional variables and their perceptions in general on the Objectives, Content, Time allotment, and Teaching Methods/Devices? Methodology: The descriptive method of research was used to achieve the objectives of this study which was to determine the status of the integrated materials on natural hazards in the intermediate grades science curriculum in terms of objectives, content, time allotment and teaching methods/devices. The respondents of the study were 165 teachers of science from the Division of Quezon City for the School Year 1995-1996. The statistical tools utilized were frequency, simple percentage, weighted means and simple ranking. To test the hypotheses, the T-test of mean difference was utilized. The questionnaire was the main instrument used in gathering the data needed in the study. Interviews were also resorted to in case responses were not conclusive or if question was not fully answered.
Salvador G. Quirimit
It is becoming clear day by day that humankind is causing major changes in the compositions of earth's environment on local, regional and global scales. These changes are caused by fossil fuel combustion, land used changes, biomas burning, deforestation, agricultural practices and industrial processes. scientists do not yet have a good understanding of the Earth system and its processes. Out of many uncertainties in the system one important uncertainty is the degree of nonlinearity of many Earth system processes. Therefore, to study and monitor the climatic changes in detail observations of various processes should be undertaken starting from short time scale of monthly variations to decade variations. In the present study, we have studied the monthly variation of sea surface temperature, water vapour and wind speed distribution over oceans. The SST images describe the movement of ocean currents, thermal equator etc. the water vapour images follow the sea surface temperature distribution to good extent. The wind speed pattern over the globe provides very good information about the monthly variations around the latitudes. The discontinuities in the global pattern of the above parameters can be identified from the images. Therefore, year to year variations can be monitored using the data from the satellites to update and generate new global environmental maps. In this study, the relationships between SST and WV are investigated in two climatic regions. Ocean wise analysis indicates that the SST and WV correlation are found to be better in Indian and Pacific ocean in comparison to Atlantic ocean region. However, this study should be extended to the other years to draw any valid conclusion. However, monthly relationships derived from the study will be useful to predict WV concentration from SST images. The GIS package used in this study is IDRISI for Windows. It is felt that the image analysis package is having only limited statistical procedures. Therefore, it is suggested here to expand the statistical package to accommodate at least the non-linear equations and curve fitting techniques, etc.
Prisco D. Nilo
A two-dimensional storm surge model with non-uniform grid system is developed and used to simulate four local storm surge occurrences and one well documented storm surge event in South Carolina, USA. The hydrodynamic equations are vertically integrated and the model considers the effects of surface stress, gradient in atmospheric and water pressure, bottom stress and coriolis acceleration. A Rankine-vortex typhoon model is used to generate the cyclonic wind field. In the computation of surface stress the bulk-aerodynamic parameterization is utilized. While the bottom stress is assumed to vary directly with the depth-averaged current and inversely with the depth of the fluid. The model also have provision for overland flooding and coastal drying. The movement of the coastal boundary is governed by the difference between the surge height and the elevation of the adjacent grid inland. A number of theoretical experiments are conducted to test the response of the model to changes in grid resolution and basin characteristics. Results show that the model is sensitive to grid resolution and that storm surge predominantly occurs in shallow continental shelves. It is also shown that bay-shaped basins attain higher surges compared to straight coastlines. Further, it is shown that inland slope controls the extent of inland flooding. Actual simulations were performed which include the 1912 storm surge in Sogod Bay, the 1975 storm surge in Tandag, the 1981 storm surge in Baler Bay, the 1994 case of Katring which generated an insignificant surge height in Lamon Bay, and the 1989 storm surge in South Carolina. The results of the simulations demonstrate that the model has shown modest skill to simulate the depth-averaged current driven by the intense tangential winds of typhoons and to predict reasonable surge heights. An operational procedure for storm surge forecasting is also presented in this study for future consideration.
Herman L. Ngohayon
Upper tropospheric temperature anomalies (T250) and the horizontal Laplacian to the upper tropospheric temperature field (2T250) were determined from the radiances remotely sensed by the TIROS Operational Vertical Sounder (TOVS) on board a NOAA series (11 and 12) of polar orbiting satellite. A total of 88 cases from 18 tropical cyclones passing over the Philippine Region were monitored and surface pressure anomalies at 6-and 12-degree radius (P6 and P12) and maximum surface wind speed (Vmax) were obtained. Relating these data, a statistical model was developed to estimate the tropical cyclone intensity. Results showed excellent correlation with about 80% of the variations in Vmax was accounted for by T. No significant improvement in the coefficient of determination (r²) was achieved when ²T was regressed in linear form, exponentially and when both T and ²T were combined as predictors. The same trend is observed in the predictive equations for the pressure anomalies P6 and P12. The dependent samples indicate standard errors of 10 kts and 8 hPa for maximum winds and surface pressure, respectively, which is comparable with the results obtained by Le Marshall et al. (1994) and Velden et al. (1991) for Western North Pacific tropical cyclones. The accuracy of the intensity estimates suggest that this method could be adopted operationally to supplement the Dvorak method of intensity estimation.
Esperanza O. Cayanan
A long duration rainfall episode which happened during the last two weeks of August 1990 was investigated in order to establish some indicators to predict the future occurrence of a similar phenomenon. The synoptic situations before, during and after the rainfall episode were studied and described. The investigation involved analyses of surface pressure charts, wind profile from surface to 200 hPa levels, important weather systems like tropical cyclones and satellite imageries. Composite maps of surface pressure and geopotential heights at 850 hPa level were preparted. Results showed that the rain episode was caused by the Intertropical Convergence Zone (ITCZ) which passed thru the islands of Batanes connecting with the monsoon trough over China Mainland. The passage of three tropical cyclones during the period activated the ITCZ and enhanced the southwest monsoon flow over the western sections of Luzon, thereby increasing the intensity of rainfall over the area.
The distribution of rainfall in time and space was also examined. It was noted that the long duration rainfall episode started over Southwestern Luzon (Palawan) moving northward and westward. The intensity of rainfall also increases in the same direction. A preliminary criterion for defining a rainfall episode as a SW wet spell was proposed after the investigation.
Vicente B. Malano
A numerical model is developed for storm surge prediction incorporating overland surges. The model is formulated using the depth-integrated form of the transport equations applicable for storm surges and is applied over an idealized basin with straight coast. Movement of land/sea boundary is one dimensional. The local water elevation and the sea surface slope are examined first to regulate the movement of the boundary. The forcing function of the model consists of surface wind generated by a symmetric cyclone model of Jelesnianski with inflow angle of 15 degrees. The effects of inland inundation of sea water are investigated by varying the slope of inland elevation as well as the basin size and shape. The model is simulated with observed surges in the Bay of Baler and Tandag, Surigao del Sur Basin with considerable success.
Nathaniel T. Servando
A set of idealized experiments using a nondivergent barotrophic model are used to investigate the influence of different environmental conditions, vortex characteristics and beta effect on tropical cyclone motion. The environmental flow is found to be essential in moving the cyclone along the direction of the flow by advecting the vorticity of the vortex along. The differential advection of earth vorticity by the cyclone circulation or B-effect distorts the cyclone which causes deviation poleward and westward from the imposed flow. The imposition of a more complicated environmental flow and distinctive change in motion is explained by the local changes of relative vorticity brought about by the interaction between the vortex and the environmental flow with their associated vorticity. The sensitivity of tropical cyclone motion to changes on the characteristics of the vortex with respect to maximum wind, radius of maximum wind, decay parameter of the vortex and asymmetry is discussed. Results show that increasing the maximum wind speed and radius of maximum wind increases the poleward component of motion while no significant change in motion when the decay parameter is changed. The initially prescribed asymmetry on the vortex found to have small effect on motion except when the flow is relatively calm. Experiments on the sensitivity of vortex motion on model resolution reveal the importance of better resolution in modelling the tropical cyclone motion in order to better resolve the maximum wind and the inner wind profile and to determine the vortex center properly.
Susan R. Espinueva
The need for a timely and accurate flood forecast has always been the primary concern of the hydrologist or flood forecaster. This need has been evident during the past decades up to the present due to frequent flooding resulting from environmental and geomorphological factors. One (1) crucial factor in the preparation of a flood forecast is the availability of an objective tool i.e. flood forecasting model to aid in finding out the relation between rainfall and runoff to minimize the time required in the formulation of the forecast. The need to augment the forecasting scheme of the Flood Forecasting Branch prompted the study to tackle application of an existing model (HEC-1) to one (1) of the monitored river basins in the Philippines. HEC-I was developed by the US Army Corps of Engineering Hydrologic Engineering Center (HEC). HEC-I is an event based model capable of simulating multiple floods for multiple basin development plans (Flood Hydrograph Package User's Manual, 1990). The model performs various computations in one single storm analysis because there is no provision for recovery of precipitation loss rate during periods of little or no precipitation. The input is the basin hyetograph and the output is the streamflow hydrograph at desired locations. The model wa applied in the Sipocot river basin using four (4) flood events for simulation and two (2) independent events for verification. Sensitivity of parameters was conducted and the forecasting capability of the model was tested.
Eugenio M. Aquino
In this study, the quantitative calculations of heat, moisture, momentum and kinetic energy budgets are pursued over the South China Sea during the prevailing northeast monsoon. These terms are expressed as fluxes. The calculations are carried out using thermodynamic and moisture equations as well as momentum equations averaged over space and time with the radiational heating values taken from climatological results of Dopplick (1970). The distribution of these terms yield pattern of the apparent heat source and apparent heat sink together with kinetic and momentum fluxes. As a result of this study, a noticeable trend of the calculated values of the budgets and fluxes is similar to the results of other experiments carried during Northern winter periods and almost within the same area of concern. It may be added too that since the atmosphere is a large and uncontrollable laboratory, reasonable estimate of the quantified parameters are conclusive enough to merit this study.
Cynthia P. Celebre
The occurrence and characteristics of the 40- to 50-day oscillation in the Philippines is studied. Station pressure, rainfall and wind data from different stations located in the country were filtered and subjected to spectral and cross-spectral analyses.
Results of the spectra of station pressure indicate that the oscillation extends from the southernmost (Zamboanga) to the northernmost (Basco) station and from the extreme western (Pto. Princesa) to the easternmost (Guiuan) station. Spectra of wind data showed that the phenomenon seems to be present at all levels of the atmosphere, while spectral peaks at the periods of interest are also present for rainfall. Cross-spectral results of station pressure also indicate that the oscillations in one station are also present in other stations. The phase angle distribution suggests that most oscillations in the area of study propagate westward near the equator, then northwestward to north northwestward in the higher latitudes. Some disturbances that originate from the west travel northeastward to northward. One possible application of the results of this study is the determination of the probable preferred seasonal tracks of tropical cyclones in the Philippines.
Maribel G. Enriquez
The concentrations of carbon monoxide, hydrocarbon, nitric oxide, nitrogen dioxide, sulfur dioxide, oxidant and dust at Manila and Quezon City were studied in relation to the volume of rainfall (mm) and temperature readings (degree celsius). The concentrations of these pollutants were quite high during the months when rainfall profiles were at minimum from October to June in Manila and from October to April in Quezon City and temperature profiles at its maximum (March to June). Moreover, the study showed promising relationship between the weather elements and atmospheric pollutants profiles based on correlation coefficient which demonstrated a five-percent (5%) level of significance and regression equations. Also, a lesson guide for this study was prepared that may be useful as a tool for science teaching particularly in air pollution.
Shirley V. Almazan
A numerical model for studying the development of sea breeze rainfall in the vicinity of a straight coastline is described. The model is based on the time dependent primitive equations which is able to describe explicitly the formation of rain and its subsequent space and time variations. The description is done by incorporating a prediction equation for rain water which is derived through a parameterization of cloud microphysical processes. Integration of the model has been made to simulate the development of a sea breeze over a flat terrain. The large scale prevailing conditions used in the simulation correspond to cases with no prevailing flow, with onshore (sea to land) prevailing flow and with offshore (land to sea) prevailing flow during the rainy season. Experiments on vertical stability, relative humidity, vertical windshear and surface heating in relation to the characteristics of sea breeze rainfall are also made. The experiments show that the model is able to simulate the sea breeze rainfall reasonably well.
Bernardo M. Soriano, Jr.
The dependence of the structure and intensity of tropical waves on the vertical profiles of the basic state is studied. A two-dimensional version of the primitive equations in cartesian (x, z) coordinates is integrated to determine the effect of the vertical profiles of the basic zonal wind, the initial temperature and the initial humidity. Microphysical processes are included by use of conservation equations for cloud water, water vapor and rain water. In general, the numerical model is initialized by prescribing a perturbation in the temperature field of 1°K over a horizontal distance of about 60 km from the center and from the surface up to the 900 m ( ~ 900 hPa) level.
Results of experiments without the prevailing zonal wind indicate that the structure and intensity of the wave are influenced more by the vertical profile of the initial perturbation temperature. The depth of the trough and the strength of the winds around the upper level ridge during the early periods are found to be directly proportional to the position of the perturbation temperature. The intensity of the winds around the trough seems to depend on the magnitude of the perturbation temperature and the humidity of the troposphere during these periods. The wind patterns at these times may be the result of the approximate geostrophic balance condition that is assumed at the initial time. When the other forces become significant, the structure of the wave becomes more or less similar in all cases while the intensity of the winds is still a function of the initial perturbation temperature and initial humidity.
The wave structure and intensity are greatly influenced by the vertical profile of the mean zonal wind also during the early periods, i.e. the trough and ridge axes tend to lean towards the direction of the vertical shear of the zonal wind component. However, in the latter periods, the axes incline toward the direction of the prevailing zonal wind which likewise determine the rate and direction of propagation of the wave. The prevailing zonal flow reduces the intensity of the winds around the wave throughout the integration period. The winds seem to intensify near the lateral boundaries possibly due to the increased horizontal diffusion, which is specified at four grid points near it, and to the no-gradient boundary condition there and zero vertical advection at the top boundary. In general, however, the simulations seem to agree with the results of Kurihara and Kawase (1985) and the observations of Reed and Recker (1971) and Thompson et al, (1979).
Esperanza O. Cayanan, Lourdes V. Tibig, Carina G. Lao
A short-term statistical model to predict rainfall probability was developed for seven airport stations namely Ninoy Aquino International Airport (NAIA), Mactan International Airport, Laoag, Legaspi, Iloilo, Davao and Zamboanga Domestic Airports based on Markov chain technique. To determine the probability of rainfall, multiple linear least squares regression was applied on 14 covariates using a 16-year data set. The performance of the model was verified using the Half-Brier score and actual testing was undertaken by employing a 3-year independent data set. Most of the monthly forecast equations attained a high percentage accuracy of forecast. However, it is recommended that the use of the model should be supported by subjective analysis.
Teodora B. Domingo
In support of the self-reliance program of the government, a project on the fabrication and development of 100-gm. and 350-gm. meteorological balloons to conform with the quality and standard set by the World Meteorological Organization was initiated in the PAGASA in 1979.
Meteorological balloons appear a deceptively very simple device but its fabrication requires accurate instruments and engineering design and elaborate care in compounding. The latex emulsion is compounded with vulcanizing agents, accelerators and antioxidants.
Services to the public through reliable forecast, a factor affecting commerce and industry, shipping and agriculture, is dependent on intensive vertical analysis of the upper atmosphere. Accurate weather forecasting demands availability of upper air data, obtained with the aid of meteorological balloons and production of these balloons is the core of this study.
Rolu P. Encarnacion
A numerical model of the cold surge is developed to simulate cloudiness and rainfall over a warm ocean surface and a land mass with prominent topographic features. The model atmosphere consists of 3 layers: a) surface layer b) mixed layer and c) stable layer. The set of primitive equations is averaged in the mixed layer to yield prediction equations for the horizontal components of the wind, potential temperature and mixing ratio in the layer, and the height of the base of the overlying stable layer. Parameterizations of the interactions between the well-mixed convective layer with both the underlying and overlying layers are employed so that time dependent calculations could be limited to the well-mixed layer.
The model is used to study the dependence of cloudiness and rainfall associated with a cold surge on the prevailing synoptic conditions. A radiosonde observation representing inland conditions is utilized to define the initial state of the atmosphere for a control run. The control run and other numerical integrations (experiments) were used to analyze the cloudiness and rainfall patterns. Two groups of experiments were performed in this study: a) cold surge flow from land mass to warmer ocean surface and b) cold surge flow from the ocean to a warmer land mass with topography.
The results show that the model is capable of simulating the behavior of the atmosphere during cold surge episodes. The predicted variables are found to be reasonable and physically realistic.
Carina G. Lao, Rafael P. Lao, Benjamin R. Ofina
This study attempts to improve the first paper of Lao (1989). The relationship between the variations of tropical cyclones in the Western North Pacific, in terms of cyclone days, and the rainfall and pressure of selected stations in Thailand and Hongkong, in addition to the previous data have been studied. The resulting relationships have been used to develop statistical methods for seasonal prediction.
The relationship between these cyclone days and the different variables are studied by the same methods used in the paper of Lao (1989).
Significant correlations are found between the Ubon Ratchathani (Thailand) rainfall and cyclone days. Years with relatively many tropical cyclones are preceded by high rainfall values in this area.
The regression equations which have been developed in this study are verified using one dependent data set and two independent data sets.
The results show that the most accurate prediction is one which predicts the number of cyclone days for the first half of the cyclone season (MAUG). This study suggests that the Western North Pacific tropical cyclone activity is predictable some months prior to the start of the cyclone season.
Flaviana D. Hilario
Two methods (maximum likelihood and parallelepiped) of classifying clouds types and terrestial surfaces at daytime using three channels of the Advanced Very High Resolution Radiometer (AVHRR) are presented. Using spectral information, five cloud types (low, cumulus, cirrus over land, high and combination of high and low), land, sea, and snow were identified. Both methods were able to classify land, sea, low, cirrus over land and high clouds fairly well. The use of the ratio of Channel 2 to Channel 1 helped in recognizing sunglint and snow as well as providing a very clear distinction between land and water surfaces which is not possible with the use of two-channel (visible and infrared) classification. However, difficulties were encountered by both techniques in identifying cumulus clouds and combination of high and low clouds. A visual comparison with the manual nephanalysis done by the Royal Meteorological Society showed that the maximum likehood was found to give better classified images than the parallelepiped but the latter is much faster. For better visual analysis, a majority filter was applied to the classified images. The smoothing technique resulted in less unclassified pixels for the parallelepiped classification and bigger cloud type areas for both methods.
Shirley V. Almazan
A numerical model for studying sea breeze rainfall is described. The model uses two-dimensional, time-dependent primitive equations and includes equations for predicting rain and cloud amounts explicitly. Integration of the model has been made to simulate the development of a sea breeze over flat terrain. The large scale prevailing conditions used in the simulation correspond to cases with no prevailing flow, with onshore prevailing flow and with offshore prevailing flow during the rainy season. Experiments on the effect of vertical stability on the characteristics of sea breeze rainfall were also made. The results show that the model is able to simulate the sea breeze circulation reasonably well. In addition, the results also show the development of rainfall in the early afternoon, its intensification with time and its subsequent weakening.
Aida M. Jose
Semestral and 12-month rainfall anomalies subjected to power spectrum analysis using the approach of Blackman and Tukey. Analysis revealed 2 significant quasi-periodicities with wavelengths equivalent to 2 to 2.5 years and 4 to 5 years. These quasi-periodicities which possibly represent certain pulsation in the general atmospheric circulation were considered in the choice of plausible predictors of seasonal rainfall performance. Empirical equations to predict seasonal rainfall performance were then developed for various stations in the Philippines using multiple linear regression. The choice of plausible predictors were based on diagnostics of the physical mechanisms of abnormalities in the seasonal evolution of large-scale circulation patterns affecting the climate of the Philippines. Five categories of potential predictors used in the regression are composed of (a) pressure tendency (b) seasonal pressure (c) pressure gradient (d) monthly pressure (e) surface air temperature and (f) upper-air mean zonal wind. The results of the regression analysis indicated that rainfall anomalies at 37 stations in the Philippines responded significantly and selectively to particular predictors. There are certain areas in which the seasonal rainfall are more predictable in a particular semester than the other. Comparison of the predicted values based on independent data sets, with the observed values for 3 sample stations showed that the predicted and the observed values are positively and closely related to each other. Because of the diversity of seasonal rainfall variation and its responses to various predictors from station to station, comparisons of the spatial distribution of the predicted and observed values for 1960 and 1980 were made. Specific areas of predicted categories of seasonal rainfall anomalies were identifiable in the spatial distribution patterns for the observed values. Scatter diagrams comparing the predicted and observed values at various points of observations during the 2 semesters of both years showed remarkable goodness of fit. Examination of the yearly values of the regression coefficients for 3 sample stations indicated certain degree of stability. However, for operational purposes, updating of such coefficients should be made as a component of the scheme to assure that the behaviour of the predictors be within the atmospheric mode of the most recent past. Isolated discrepancies in the prediction results could be attributed mainly to either too slow or abrupt change in the seasonal evolution of the general circulation patterns which can not be captured by the regression scheme. In addition to this limitation, is the inherent disadvantage in the use of regression which tends to underestimate predicted values from that of the observed.
Raquel V. Francisco
A two-dimensional, slab-symmetric cloud model with detailed microphysics is presented. Drops were classified into 37 size classes representing a droplet spectrum from 1 um to 4 mm radius. Each class of droplet is subjected to condensation and collection processes. New droplets were formed by the nucleation process. The sensitivity of the model to changes in the eddy diffusion coefficients is discussed. The effect of the magnitude of initial perturbation, environmental winds, and cloud interactions on cloud growth are also investigated. Results show that the model is capable of simulating the life history of a warm cloud from initiation to dissipation stage. Comparison with actual observations based on day 261 of GATE reveal some realistic features of the model. Numerical experiments on simultaneous clouds show that the upshear cloud grows stronger than its downshear counterpart. Experiments on non-simultaneous clouds reveal that the younger cell grows at the expense of the older cell.
Prisco D. Nilo
Meteorological variables which are likely associated with Zamboanga wet season rainfall and onset date are examined in a stepwise regression analysis. Consequently, a long-range forecasting scheme for Zamboanga wet reason rainfall and onset date anomaly is developed. The regression equations involved two predictors each for rainfall and onset date. Three predictors include Darwin sea level pressure and Jakarta rainfall. The forecast experiments for the period 1947-83 show that the regression models for Zamboanga wet season rainfall and onset date have a considerable accuracy in predicting extreme anomalies. However, the results also show that the forecasts for normal conditions as well as the overall accuracy is not good. The statistical method using geographical technique was also examined, and the results of the tests show that graphical approach is inferior to the use of regression models. The various aspects of regression and graphical forecasting scheme are discussed.
Imelda I. Valeroso
A method for predicting the movement of tropical cyclones based on Model Output Statistics is presented. Tropical cyclones which entered the Philippine Area of Responsibility (PAR) for the period covering 1978-1986 consisting of 557 forecast cases were utilized as the development data set for the experiment. Latitude-longitude positions of tropical cyclones at initial time, and the forecasts of the latest modified, operational Barotropic Model of PAGASA using a 2x2 grid system, were taken as predictors and the predictands included the 12-hourly forecasts. The simple linear and the multi-linear regression equations from both the unstratified and the stratified data, were utilized as predictive equations and were the bases of the new Model Output Statistics forecast. Seven (7) tropical cyclones consisting of 57 forecast cases which occurred in 1987 and 1988 were used as the independent data for forecast verification. Results show the usefullness of statistical correction in improving the forecast of the operational Barotropic Model. The latitude forecast improvement of the operational Barotropic Model forecast by the use of the "direct" MOS scheme, whereby the regression equations obtained from the forecasts of the model were utilized at the predictive equations is remarkable. The over-all latitude forecast improved by 40.70% at the 24-hr forecast period, and by 41.95% for the entire 72-hr forecast, period, by the application of the multilinear quarterly regression equation. This is followed by the multi-linear monthly (32.13% over-all 24-hr forecast), and the simple linear quarterly (36.52% entire 72-hr forecast).
Shirley V. Almazan, Catalino P. Arafiles, Bernardo M. Soriano, Jr.
The Manila Bay is one of the Philippines' important bodies of water which is being subjected to tremendous stresses due to the burgeoning population of the Metropolitan Manila Area. Several human activities such as reclamation and wastewater disposal have greatly affected the features of the Bay. These activities and their impacts on the coastal environment are presented in this paper.
Carina G. Lao
The long period variations of tropical cyclone occurrence (both frequency and tracks) have been studied. These variations of tropical cyclone have been related with rainfall, pressure, El Niño and the Quasi-Biennial Oscillation. The resulting relationships have been used to develop statistical methods for seasonal prediction.
The frequency of the tropical cyclone occurrence is specified in terms of cyclone days. The relationship between these cyclone days and the different variables mentioned earlier are studied by the ranking method, correlation analysis, compositing and spectral analysis. Prediction equations are developed to predict the total annual number of cyclone days, as well as the corresponding number for selected periods of the typhoon season.
The significant periods which are revealed by the analysis of the long period variations of the cyclone days correspond to periodicities of 36, 24 and 14 months. These periods are also found in the time series of rainfall and pressure. The periodicity at 24 months could be related to the Quasi-Biennial Oscillation.
The study also indicates that the most important relationship is between the frequency of tropical cyclone occurrence and rainfall in Nauru and Galapagos; and pressure in Darwin, which occur a few months before the typhoon season.
With respect to El Niño, there are more tropical cyclones during periods of moderate to strong El Niño. On the otherhand, with respect to Quasi-Biennial Oscillation, more tropical cyclones occur when the 30 mb. zonal wind has easterly component.
The regression equations which have been developed in this study are tested using dependent and independent data sets. The results show that the most accurate prediction equation is the one which predicts the number of cyclone days for the second half of the cyclone season (SEPD).
Eugenio M. Aquino, Esperanza O. Cayanan, Cynthia P. Celebre
A graphical method of forecasting rainfall over northeastern Mindanao was developed. Eighteen weather elements observed at NAHA (Japan) at 0000Z for a period of 20 years for the months of December, January and February were considered. Four out of these elements were used as predictors. Rainfall data from three stations in the Philippines were utilized as the dependent variable in the study. The method showed encouraging results.
Melba P. Cristobal, Hernando O. Pantoja, Jr., Rolu P. Encarnacion
An earthquake swarm occured in Siquijor Island which lasted for 4 months from December 1980 to March 1981 and was felt intensively in Lazi where epicentral locations were confined. The b value for this type of seismic activity was obtained applying the least squares method with the frequency of events and amplitude as the parameters.
The b defines its relation to a seismotectonic parameter which varies among regions of different geotectonic structures. It also follows a certain pattern to what kind of characteristic the earthquakes fall.
The computed b value in this group of earthquake study is 0.6, a low value belonging to the range when the activity is tectonic in origin. This study further suggests that faulting is a major contributory factor to the continuous generation of ground tremors increasing then decreasing for some period after enough energy has been released.
Esperanza O. Cayanan, Cynthia P. Celebre
Thirty weather elements observed at 0000Z covering the months of March, April and May for a period of 25 years (1961-1985), were chosen as predictors in this study. By using the stepwise regression analysis, three equations for thunderstorm forecasting were derived. The first forecast equation is applicable for March-May period and was formulated using only the first twenty-five predictors. The second equation is adopted for the month of May, using the same predictors. The last equation is adopted for the March-May period and was formulated using all the thirty predictors. Results showed that Equation 3 could be a good tool in forecasting thunderstorms if further testing and refinement is undertaken.
Claro S. Doctor and Priscilla P. Duque
The Philippines, due to its geographical location, shall continue to contend with a great variety of possible disasters---typhoons, floods, volcanic eruptions, earthquakes, landslides, etc. These disasters have caused enormous sufferings to our people in terms of loss of life and property. Damage to typhoons and floods alone from 1965 to 1986 ranged from P 27.7 million to P 2,164.6 millions which constituted to about 0.07 to 4.3 percent of the GNP at 1972 price level. According to government planners from NEDA, one or two strong typhoons could roll back our economic progress by three to five years. It is only imperative, therefore, that the government should take a serious look into the plight of the country's disaster preparedness and prevention program and consider it as a support strategy to national development. A National Calamities and Disaster Preparedness Plan had been prepared by the OCD in 1976 after a strong earthquake hit South Western Mindanao on August 17, 1976. The Plan is now the subject of this study to test its effectiveness based on the selected factors as composition/organization, communication, test exercises, damage assessment and feedback mechanism vis-a-vis damage mitigation and people's responses before, during and after an emergency. The study also determined, based on the above-factors, whether or not amendments or revision of the Plan is necessary. Based on the foregoing problems, we have hypothesized and tested the following: (1) that the Plan is effective in terms of the selected factors; and (2) that the Plan does not need any amendments nor revision. To assist these researchers in their nationwide survey, a questionnaire was prepared for the general public and for Disaster Coordinating Council (DCC) officials at all levels to test their perception towards the selected factors. Also, analysis of typhoon/ flood damage from 1965 to1986 vis-a-vis the GNP and typhoon/flood damage table and the GNP against damage curves were used to determine the effects of typhoons and floods on the economy. Interviews, documentary analysis, synectics and other related research tools were used to arrive at reasonable conclusions and recommendations. The findings of the study were the following: (1) That the Disaster Coordinating Council (DCCs) at all levels were not much organized; ill-equipped, especially in terms of funding and communications facilities, lack of training and exercises, and therefore, they can not respond effectively before, during and after an emergency. (2) That the NDCC has not been actively involved in disaster management and operation except through an Action Group which has been quite active but was disregarded several times in the past with the creation of Task Forces or Ad Hoc Committee to oversee to the on-going disaster operations. This could be an indication of lack of awareness of the NDCC or its Action Group. (3) That public awareness/information campaign on disaster preparedness is gaining foothold in the countryside due to the immediate and appropriate reactions of the people towards disaster warnings/information; and (4) That typhoons/floods remain as the most destructive disasters in the country but damages attributed thereto tend to decrease everytime that the government enhances its disaster preparedness and prevention activities although this finding is not conclusive as other factors have not been considered. Based on the above findings, we have recommended the ff.: (1) There is a need to enhance the organization of disaster coordinating councils at the local levels and strengthen their response capabilities in all the 3 disaster phases --pre disaster, during disaster and post-disaster phase. (2) The NDCC, as the highest policy-making body for disasters, should be restructured with the chairmanship to be lodged with a key individual in the Office of the President (OP) since the council assumes a staff function within OP. (3) Intensity public awareness campaign on the nature and threats of disasters and counter measures against them thru the use of the broadcast media, which are the most reliable and effective sources of disaster warnings/information. (4) Congress should pass a single legislation, a Disaster Counter measures Act or a Disaster Preparedness and Prevention Law, something to that effect, incorporating primary elements as national disaster organization, national disaster plan, finding, declaration of a state of calamity, and such other measures as monitoring of natural phenomena like typhoons, issuance of warnings and the precautionary measures that the public should do; conduct emergency measures such as flood fighting and evacuation; measures on rescue, relief rehabilitation measures for the education and information of the population, including school children; measures for the restoration of school buildings, etc; and (5) While awaiting for Congress to act on recommendation No. 4, the Office of the President should issue an Executive Order soonest possible to incorporate the aspects and factors cited in recommendation Nos. 1 to 4 and all other aspects of disaster preparedness and prevention in the country, following the legislative requirement of a national disaster plan given on pages 51 and 52 of this study. (6) A more detailed studies on the disaster coordinating councils, communications and public information, feedback mechanism and damage assessment aspects of disaster preparedness and prevention may be undertaken by concerned government agencies and/or private organizations or persons to serve as a basis for future and/or current disaster planning by the government.
Santiago T. Martin
A storm surge numerical model was developed to compute storm surges induced by a typhoon crossing Manila Bay. The linearized form of the vertically integrated equations of motion for shallow water were used. Five experiments were performed for each of the four cases of typhoon track. Results showed that for a typhoon crossing any point of the bay at any direction from the eastern side, the peak surge occurs at the northern portion of the bay. The highest value is generated by a typhoon moving westward and crosses the center of the bay.
Rolu P. Encarnacion
The Philippines, having the highest annual frequency of tropical cyclones in the world, is considered as a naturally surge-prone area. However, operational application of storm surge prediction schemes in the country are still in the formulative stages of development. This study is a modest contribution to these efforts. A one-dimensional numerical storm surge prediction model is formulated and developed in this paper.
The domain of the model is oriented perpendicular to the coast over a model basin in which the bottom slopes can be varied. The forcing function consists of surface wind generated by model typhoons. Experiments were performed with various formulations of the bottom stress. Several conceivable behaviors of the model typhoons were simulated in the experiments.
The results indicated that the model had performed well in simulating the observed storm surges in Baler, Aurora in 1981. This paper attempted to explain the prediction results with established theories and concepts regarding the behavior and movements of the sea under the actions of the driving and forcing effects of tropical cyclones particularly in the generation of the surges at the coast.
Jaime F. Bucoy
The present study is an initial attempt to apply objective analysis techniques in the interpolation of wind data from observation stations to equally spaced grid points for the purpose of assimilating data as input numerical prediction models using a variation of weighted average method. The programme was executed in the Nova mini-computer adapting a 17x23 grid points in a region from 20 degrees S to 44 degrees N and from 92 degrees E to the international dateline. The streamline and isotach patterns obtained by objective analysis of 4 cases are compared against conventional analyses. The result of comparison produced promising outputs. The average root mean square geographical distributions of errors are 5.42 mps and 4.84 mps for u and v wind components, respectively. The first guess wind pattern used in this study was the past 12-hr. ago analysis.
Ana B. De la Cruz
The study is an attempt to improve the performance of the operational barotropic model presently used in PAGASA. Three methodologies are considered together with the operational one. The main revisions consist of the improvement of the interpolation scheme and the computational scheme of the forecast position. Of these revisions, regression analysis was applied to the result of the method with the best forecast as shown from a verification. The forecast using the best method was correlated with the actual track to formulate a regression equation which is expected to give an improved forecast. This is done to improve further the forecast position if the deviation from the actual track is proven to be linearly correlated. Revision 2, the combination of improvement in the interpolation and computational scheme of the forecast position, shows to have improved the operational barotropic model though not significantly.
Alan L. Pineda
Starting from the continuity equation and equation describing the behavior of the lake during floods is derived. The "quasi-linear storage type" was utilized as input to the model to accommodate the time of concentration. A computer program for HP-9845 was created for semi-automatic parameter calibration. The model went through a normal routine of application and parameter optimation in two lakes in Bicol River Basin namely: Lake Bato and Lake Buhi. The results are satisfactory according to the criteria for flood forecasting. The model then is integrated into an operation flood forecasting in Bicol River Basin.
Flaviana de Leon Hilario
The water balance was computed for four weather stations in the Bicol Region over a period of ten days or a decade. The parameters used were crop evapotranspiration, effective rainfall and change in soil water content. The Penman equation was used to get the potential evapotranspiration and by multiplying it by the appropriate crop coefficient, the crop evapotranspiration was computed. The relation between the average rainfall was used to get the effective rainfall. Computing the water balance for different growing periods for each station shows that in general, there is adequate water supply in the region. The optimum planting dates for rice production are December 1 for Legaspi and Virac, December 21 for Virac for the 2nd cropping and June 1 for Daet and Virac, July 1 for Legaspi for the 1st cropping. However, Masbate was found to be suitable for rice based on crop water requirement. Corn production is highly suitable in Masbate where 3 croppings are possible. The optimum planting date is anytime during the month of December and May 1. Other places in the Region can be planted with corn one or two times a year. The main problem in the Region are typhoons, rains for long duration of time, floods and lack of water, when and where it is needed.
Ellaquim A. Adug
Typhoons and floods are natural phenomena that have become part of the way of life of the people not only in the Philippines but also in many other countries of the world. The disastrous effects of these phenomena on the lives and livelihoods of the people and on properties have caused increasing concerns of many developing countries. Its great impact on the economy and people has led specialized agencies of the United Nations to conduct studies in order to provide guidelines for the prevention and mitigation of such natural disaster.
Rolu P. Encarnacion
The study of the seismicity of a certain locality has always been the obsession of many earthquake scientists, since seismicity is the general view of the frequency of earthquakes in a certain place during a certain period. This research paper deals with the Philippine seismic activities for the period 1901 to 1974. With the aid of the basic equation of the Gutenberg-Richter's statistical relation and a modification of this relation by Peter Welkner, 6-value had been determined and subsequently, a-value, which is regarded as the index of the mean annual seismic activity, was also computed for the area of study correspondingly.
Nevertheless, the highlight of this report is on the estimation of expected maximum earthquake motions, that is; the particle velocity at the base rock and the acceleration on the ground at their extreme values for some return periods. For the maximum velocity calculations, Kanai's attenuation model was used and for the maximum acceleration, the average of McGuire and Oliveira's attenuation models were considered. In this aspect, the author utilized computer programs in the analysis and calculation schemes. There were 19 selected sites of the country which were run through the computer program and yielded results favorably in accordance with Philippine seismicity. The importance of these results lies on the fact that it projects a probability of occurrence of at least some destructive tremors during a specific time interval. In seismological point of view, this probability is better known as the earthquake risk over a specified location and on a certain period of time. Furthermore, the probability value will be very useful in the field of Earthquake Engineering.
Bernardo M. Soriano, Jr.
In this study, the technique of determining a statistical relationship between a desired meteorological element and parameters from a dynamical model at some projection time was applied to predict precipitation amounts associated with large-scale atmospheric phenomena at three forecast intervals. The 500-mb vorticity advection, which is one of the output parameters of the Barotropic Model developed by the Department of Meteorology and Oceanography, University of the Philippines, was used as predictor in this technique called Model Output Statistics (MOS).
Regional and general simple regression equations were derived on two different grid networks over the Philippines after intermediate preparation of limited available data. This indicated a higher correlation between the variables in the finer grid mesh where curvilinear equations were then obtained. Tests of significance on correlation coefficients favored the non-linear formulas. However, generalized equations of both sets of formula did not have significant difference.
Experiments on ten independent tropical cyclone cases revealed that the curvilinear equations yield generally closer regional estimates over the three forecast intervals. However, predictions were underestimated. The discrepancy of the estimates was attributed to the preponderance of less significant vorticity advection values in the curvilinear formulas. In view of the small diference between the predictions of the two sets of equation and due to the higher significance of the correlation in the curvilinear equations, the use of the last set of formulas was preferred.
Emma A. Vergara, Araceli L. Fontano, Cynthia A. Pajadan
The study aimed to monitor the weather conditions in the open oceans within the Philippine area of responsibility, with particular interest on the state of the sea. The variables ranging from 24 to 27 were used in a stepwise-regression analysis. The technique had offered a fairly reasonable forecasting tool as an alternative due to the lack of any study on parameters like wind waves and swells. In cases where only the wind speed value (FF) would be available, the height of the swell (SHGT) could be roughly expressed as:
The height of the wind waves (WHGT) at a given day (YY) and wind speed (FF) could be estimated in the form:
Beyond these preliminary findings, no clear-cut conclusions could be made due to the constraints imposed by the limited observations. It would be worthwhile to consider extending the data input in terms of time and area coverage, in future studies.
Rodolfo A. de Guzman
The development and structure of the axisymmetric tropical cyclone is investigated using theoretical and numerical approaches. The relationship of the distribution of the diabatic heating to the growth of the system is a focal concern of this study. Firstly, an axisymmetric model of the free atmospheric circulation of a tropical cyclone in steady state is developed. The sensitivity of the transverse circulation and heating distribution to the specification of the spatial distribution of the prescribed vortex flow and the vertical velocity at the top of the boundary layer is discussed. Using a momentum integral boundary layer treatment, the model response to specified tangential wind distributions is evaluated as well. Also, the scale selection role of the amplitude and vertical partitioning of the diabatic heating within a CISK framework is demonstrated. In particular, the development of a disturbance with typhoon-like characteristics is shown analytically and numerically to be possible when the heating profile has a low-level maximum. In the numerical model, this development occurs without using a balanced vortex as initial condition. The effects of the differences between the treatments using an analytical Ekman-CISK model and a primitive equation numerical model is elaborated upon. Comparison with pertinent observational studies reveals some of the realistic features of our model results.
Rodito D. Buan
An attempt was made to understand how the amount/intensity and distribution pattern of the weather parameters at different stages of growth affect the sugarcane yield. The mathematical model and system used appear to be sufficiently for practical purposes, giving an objective information which is far better than subjective guesses made in the past about the effects of weather on sugarcane yield. The second degree multiple regression equation was employed in an attempt to quantify the relationship between sugarcane yield and meteorological parameters. The results showed that sugarcane reacts differently to climatic parameters during different stages of development. The resultant response is manifested in the final yield. Above average weekly total rainfall had a favorable effect on yield during emergence, but a markedly reduced effect during tillering to maturity. Above average maximum temperature depressed yield during the emergence and in the last part of the ripening stage to harvest; however, a markedly favorable effect during the three-fourths to full canopy or during the later part of tillering through elongation stages. Above average minimum temperature had a favorable effect of the growth stages of sugarcane except, during the later part of ripening to harvest. Above average weekly total sunshine duration had varying degrees of favorable effects on the growth of sugarcane from emergence to maturity. Beneficial effects of a low magnitude was observed during early emergence and late maturity, while maximum favorable effect was observed during the elongation period. This is because the elongation period coincides with the peak monsoon period whereby cloudiness reduces sunlight-an element very much needed by the crop at this stage; while low magnitude effect of sunshine during early emergence and late maturity might be due to too high sunshine intensities during this period. Above average weekly total solar radiation depressed yield during emergence period while favorable effect was observed for the subsequent stage. The peak beneficial effect was observed during the elongation stage which coincides with the effect of sunshine duration. Generally, sugarcane was observed to be more sensitive to climatic variables used in this study during emergence, elongation and ripening stages. The use of the "Selected Development Stages" method to predict sugarcane yield gave relatively better results as compared to the second degree multiple regression equation model. The reason for this may attributed to the consideration given to the effects of the interaction among variables. Nevertheless, the multiple correlation coefficients cannot be considered significant owing to the limited period of data utilized. Its performance is, however, better than the first model in predicting the final yield of sugarcane. The "selected development stages" method will be very useful in predicting yield of sugarcane, with a lead time of about two to three months before harvest. The results of this study show that a reliable scheme for forecasting sugarcane yield well in advance of harvest is feasible, using selected weather parameters as predictors.
Teresita S. Laudet
This study aimed to determine the growth and development response of winged bean and its microclimate; as monoculture and as intercropped with corn and with ampalaya. The methodology involved planting of winged bean under simulated conditions of short (11 hours), normal (12 hours) and long (13 hours) day length and as monocrop and intercrop with corn and with ampalaya. As intercrop, the microclimate of winged bean is modified. The statistical analysis made use of strip-plot in randomized complete block design. Comparison of treatment means was made during the least significant differences (LSD) test.
Catalino P. Arafiles, Catalino P. Alcances, Jr.
A historical review of storm surges in the Philippines for the period 1897-1975 reveals certain areas inundated by storm surges. To identify storm surge potentials of Philippine basins, peak storm surges were estimated with the use of a simple empirical relation requiring only the knowledge of three meteorological parameters and the basin shoaling factor. The shoaling factor for each basin was computed by the use of a set of regression equations. Comparisons of actual observed storm tide and computed storm surge shows that the effect of coastal configuration and astronomical tide significantly affect the magnitude of the total storm tide.
Marilyn C. De Guzman
This paper is an attempt to simulate the development of typhoons by solving the hydrodynamic equations of the atmosphere using numerical methods. The essential features of the study involve the use of cylindrical pressure coordinate system under the assumption of symmetry, and use of primitive equations. The effect of cumulus clouds is parametized as proposed by Ooyama (1964) where the latent heat released in a vertical column of air is specified by the horizontal mass convergence in the friction layer. Further, the distribution of heat in the vertical is proportional to the temperature difference between cumulus clouds and the large-scale field (Kuo, 1968).
Renato R. Abcede
The results show that:
- During the Northeast Monsoon, pollution concentrates in the Guadalupe (Makati), Bagong Ilog (Pasig), Ermita and Pandacan (Manila) and Baclaran (Rizal) areas.
- During the Southwest Monsoon, pollution concentration concentrate in the Guadalupe, Bagong Ilog, Ermita and Pandacan, Baclaran and also in the Cubao and Balintawak (Quezon City) areas.
- During the transition period from the Northeast to the Southwest monsoon seasons, pollutants were noted to be concentrated in the Guadalupe, Mandaluyong, Cubao and Quiapo areas.
- Maximum concentration at the ground and at 15-meter level were observed to be relatively closer to the source in an unstable condition and relatively far downwind of the source in a stable condition.
Juan F. Asuncion
Mean monthly streamlines and isotachs for selected pressure levels (850-700-500-300 and 200 mb) over Southeast Asia and neighboring areas have been analyzed with variable (non-hemogeneous) periods of record. The horizontal and vertical, month to month and season to season behavior and characteristics of the different flow patterns and the more salient features of the atmosphere, viz., the intertropical convergence zone (ITCZ) with the associated vortices, convergence and equatorial troughs; the sub-tropical centers of outflows and their associated latitudinal axes; the seasonal monsoon flow; the low and high level equatorial easterlies; the Bengal Bay trough and the northern hemisphere westerly (short wave) trough; the northern hemisphere upper level westerlies; the northern hemisphere sub-tropical jet stream and the equatorial easterly jet stream, at these levels and from one level to another, as depicted by the charts are also discussed. There was no attempt made whatsoever, to explain dynamically the causes behind these changes. The adequacy and availability of these charts and what they have depicted will be invaluable to Philippine requirements as well as to new and non-tropical meteorologists. To meteorological analysts, a more thorough analysis of the upper air flow can be made by referring to these charts and will be a necessary tools for operational forecasters in their prognostic techniques.
Cipriano C. Ferraris, Bernardo M. Soriano, Jr.
This paper represents an attempt to elaborate the generalized charts of maximum rainfall for different durations and return periods required for the design of small hydraulic structures. In this study, the generalized charts are given for one-day and two-day rainfall and return periods of 2, 5, 10, 15, 25 and 50 years. The results should be applied in a precautionary manner taking into consideration that some of the stations have rainfall data for a continuous period of only 8 years.
Emma P. Amores-Vergara
Different mathematical models for assessing the effects of weather on crop development were considered and reviewed. Three popularly used in linear models - the average span, the Reaumur's degree-day equation and the Nuttonson's photothermal equation - and the non-linear equation called the triquadratic model as postulated by Robertson (1968) were tested using meteorological and astronomical data from the Science Garden and the Radiation Center, Philippine Weather Bureau, in Diliman, Quezon City. However, evidences gathered from a year's experiment in the Science Garden consisting of twelve (12) monthly plantings of sweet corn of the H801 variety and also from other investigations along this area pointed to the triquadratic model as postulated by Robertson in 1968 to be the best mathematical expression for calculating the effects of the thermal and solar radiation environment on crop development among the models employed.
Leoncio A. Amadore
Some important facts about tropical cyclones in general, and typhoons in the Philippine Area of Responsibility (PAR), in particular, are mentioned. A brief summary of different objective techniques of forecasting tropical cyclone movement is presented. It has been found out by meteorologists that these forecast techniques gave a variety of forecast positions even when applied to the same cyclone. It is therefore, one of the purposes of this study to evaluate the accuracy of seven different forecasting techniques in the PAR in order to determine which of these forecast techniques could help best the typhoon forecaster in the area. Using the best-track cyclone positions and post-analysed weather charts, 24-hr forecast positions of 28 tropical cyclones of 1968 to 1970, in the area bounded by 5°N - 25°N and 115°E-145°E, were made. The techniques tested are: Persistence, Climatology, (P+C)/2, Arakawa, Miller-Moore, Wang and Tse. The arithmetic mean and standard deviation of latitude and longitude forecast errors and the mean resultant errors of each technique were computed. The results showed that: 1) there is positive bias in Arakawa's latitude and longitude forecasts. 2) there is positive bias in the latitude forecast and negative bias in the longitude forecast of the Miller-Moore technique. 3) Persistence technique got the lowest mean resultant error followed by (P + C)/2, Miller-Moore, and Arakawa technique. 4) Climatology technique has the largest mean resultant error. 5) the results of this investigation are generally in good agreement with the results of other researchers. Some differences are noted in the arithmetic mean and standard deviation of errors of the 1969 sample and the 1968 and 1970 samples of Climatology and Persistence techniques. This is due to the fact that most of the cyclones of 1969 recurved east of the Philippines while the 1968 and 1970 cyclones moved westward or northwestward. A certain degree of subjectivity entered into the calculation of Wang's and Tse's techniques, hence the large forecast errors obtained. If the Arakawa and Miller-Moore techniques are corrected for their bias, the mean resultant errors are expected to reduce. Giving equal weightage to Persistence and Climatology techniques in combination is only based on general experience that the two methods are complementary. A more rational way of combining the two forecasts is presented. Using the standard deviation of forecast errors obtained for Persistence and Climatology forecasts and knowing the correlation between the two, a new forecast combination is derived for the area under study: For latitude: F3=0.6 P + 0.4 C For Longitude: F3=0.8 P + 0.2 C. The standard deviation of errors of the new forecast combination is less than the standard deviation of errors of either Persistence or Climatology or the (P+C)/2 forecast. This new combination obtained the least mean resultant forecast error during the 1971 tropical cyclone season as against Persistence, Climatology, (P+C)/2 techniques and the Weather Bureau official forecasts.
Cipriano C. Ferraris
This is a study of rainfall and flood parameters for the period 1946 to 1966 over the Pampanga River Basin to find relationships between rainfall amount and flood height, weather systems and flood occurrence, flood magnitude and frequency of recurrence and between maximum flood flow and drainage area. Also analyzed are the annual variation of peak flood stages.
Aida M. Jose
Statistical parameters of Manila rainfall data are computed and examined using 105 years of record (1865-1969). Variability of the rainfall is high and the distribution is positively skewed. It is shown also that long periods of Manila rainfall records are necessary to stabilize the values of mean and standard deviations for both dry and wet months. Analysis of the variation of 5-term binomially weighted averages of twelve months rainfall indicates long period oscillations of 33 to 43 years irregular shorter period oscillations of 5 to 11 years.
Mariano T. Asuncion
Different techniques for estimating potential evapotranspiration or evaporation plus actual evapotranspiration have been reviewed and some were tested using readily available meteorological and astronomical data at the College Weather Station, University of the Philippines, College of Agriculture, Los Baños, Laguna. Experimental evidence lends the most support to the Penman formula as the best empirical method for calculating potential evapotranspiration which has also has a more sound physical basis than most others.
Gaudioso R. Tabamo
The intertropical convergence zone is defined by different writers in different ways and it has been discussed under many different names. There is also difference of opinion as to whether rainfall occurs in separate patches or as a continuous belt along the major wind discontinuity or whether it is dispersed over a narrow zone or a wider zone in the general vicinity of the wind discontinuity. In general, it is implied from the literature that the more prominent wind discontinuity at some level or levels in the tropical atmosphere is sometimes associated with close or distant precipitation.
The association of precipitation with wind discontinuity has been implicitly accepted without proof, and the lines or zones which have been drawn on published synoptic charts appear to be a composite representation of rainfall and wind-field. To determine whether the major wind discontinuity is associated in some way with areas of rainfall and whether there is a zone of rainfall along the wind discontinuity or whether rainfall is dispersed over a wide zone, completely separate analyses of wind-fields and of the rainfall charts over the Philippines have been made in the present study and these have been related graphically. For determination of the wind field there are 11 pilot balloon stations and 46 synoptic observing stations, approximately 70 miles apart, which regularly report the direction of movement of the lowest and middle clouds at various levels. The scarcity of observations of wind-speed make computations of convergence impracticable. Therefore, the wind discontinuities which emerged from the analyses were really the assymptote of confluence in the streamlines in the lower 2000 to 4500 feet of the atmopshere, so that it was not practicable to take into account any slope in the surface of separation between two airstreams in the present study. Since the analyses show that the wind discontinuity can undergo considerable displacement in one day and because near the coast its position may also be affected by the difference between land and sea temperatures, analyses of the wind field have been made twice daily, at 0000 GMT and 1200 GMT, respectively.
For the determination of the rainfall patterns, rainfall observations are available at 46 synoptic stations in the Philippines, representing an average spacing of approximately 70 miles between stations. It was realized that, with an observing network over land, the diurnal temperature variation might have an influence on rainfall, and therefore separate precipitation charts for the periods 1800-0600 GMT and 0600-1800 GMT (each of which includes a time of wind observations) have been analyzed so that any diurnal effect would be discernible and, if appreciable, could be investigated. The analyses have been extended over the surrounding seas with the aid of cloud pictures from weather satellites.
The period examined in this study is June to October, 1964-1967, and the major wind discontinuity is discernible over the Philippines on 473 of the 12-hourly wind charts drawn during this period.
It was found that, in the majority of cases, rainfall was greater at one or both sides of the wind discontinuity than at the discontinuity itself. Since the most likely explanation of this is that the surface of wind-discontinuity possesses slope, a new investigation requiring special observations over a long period has been proposed. Another proposal for further investigation has been made in relation to the diurnal variation of rainfall.
Justo B. Valbuena
Before the application of regression analysis, the conditions of its applicability such as the conditions of normality and constancy of variance of the rainfall data were verified. The results of statistical tests to verify the above stated conditions were fairly conclusive. The relationship between mean rainfall and each of the three predictors were studied through the measure of correlation. The values of the correlation coefficients r are suggestive of the fact that there exist a fair degree of association between rainfall and each of the factors altitude, latitude and longitude.
Catalino P. Alcances, Jr.
At the fifth session of the WMO, Commission of Aeronautical Meteorology, it was recommended that further information on the characteristics of clouds associated with aircraft icing be obtained from other parts of the world, especially the tropics. It is because of this recommendation that the author attempted to present the fundamental facts about aircraft icing. Although the author would like very much to help compile needed data on this subject, he can not do otherwise since research facilities here are very nil if not totally out of reach of our present monetary means. However, this paper was prepared so that in the future when we have adequate means to conduct our own researches for the safe operation of aircraft, particularly on the subject of aircraft icing, it may serve as a reference for the topics badly needing further study. The preparation of this paper has been made possible by the result of extensive ice-prevention and meteorological researches conducted by the NASA (previously known as the NACA), the U.S. Weather Bureau, some airline companies of the United States and various individuals interested in solving the problem of icing, whose tireless effort make possible the safety of aircraft operations around the world.