An Observational Study On The Rainfall Distribution Structure of TC Jelawat And TC Saomai By Using Satellite Data

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.

The Effect Of El Niño And La Niña On Philippine Rainfall

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.

The Weather Forecasting And Warning Function Of The Philippine Atmospheric, Geophysical And Astronomical Services Administration (PAGASA): An Assessment

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.