Representation of a 1961-90 Climatological Rainfall Baseline

Major advances have been made on the study of climate change. For this reason, a higher resolution of climate baseline is required. It is important that the climate baseline be an accurate representation of the mean state over time and space.

Our goal is to establish such a climate baseline; a climatology that is better than other terrestrial climatologies, despite the limited number of spatial data available. Several interpolation
techniques are studied and compared in order to find out which one is best suited for the Philippines. The effect of topography was also considered, as studies have shown that topography does have a significant effect on climate. Among the interpolation methods
studied are: Simple Inverse Distance, Weighted Inverse Distance with varying weights on topography, and Cressman Objective Analysis.

Results indicate that the best interpolation method to use is Weighted Inverse Distance with the effect of topography magnified 50 times. Sensitivity test shows that this kind of interpolation technique provides the least error.

[Presented at the Samahang Pisika ng Pilipinas (SPP) Congress, 2001.]