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A Modeling Investigation Of Sea Breeze Rainfall

Shirley V. Almazan
1992

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.

Influence Of Environmental Conditions On Tropical Waves

Bernardo M. Soriano, Jr.
1992

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).

Rainfall Probability Forecasting At Selected Airport Stations In The Philippines

Esperanza O. Cayanan, Lourdes V. Tibig, Carina G. Lao
1992

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.

Fabrication And Development Of Meteorological Balloons

Teodora B. Domingo
1992

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.