Simulation of Monthly Rainfall Climatology with the MM5 Model

A method for computing climatological rainfall is used to determine the rainfall distribution for Luzon during the month of June. The method consists of simulating the distribution with a fluid dynamical model of the atmosphere and merging the results of the simulation with observed rainfall data from rain gauge stations. The merging is done by using an objective analysis technique called the Cressman correction technique. The output of the technique is a set of rainfall values at a rectangular array of grid points. This set is used to construct a climatological atlas of rainfall. The accuracy of the atlas is evaluated by comparing observed rainfall values at rain gauge stations with corresponding values interpolated from the atlas at the stations. The evaluation indicates that the rainfall distribution, which is produced by the method, is generally accurate in the vicinity of rain gauge stations only. This limitation is due to the fact that the model simulations are not sufficiently realistic. Comparison of the present atlas with a previous atlas based on a different model indicates that the climatological patterns are quite sensitive to the particular model which is used by the method.