UNCERTAINTY OF MONTHLY RAINFALL ESTIMATES FROM RAIN GAUGES IN THE GLOBAL PRECIPITATION CLIMATOLOGY PROJECT

The Global Precipitation Climatology Project (GPCP), initiated by the World Climate Research Program, has as a main objective the production of monthly global rainfall estimates on a 2.5 degrees x 2.5 degrees l ongitude/latitude grid by combining different sources of information s uch as satellite remote sensing and rain gauges. It:is important to un derstand the accuracy of the rain gauge estimates of mean area rainfal l because these are considered the most reliable estimates for regions with high numbers of gauges. Methods to model the error resulting fro m using rain gauge data to estimate the spatially averaged rainfall ac cumulation have been developed previously. Three of these methods are investigated in this study: an empirical equation derived from rain ga uge data, an analytical equation derived from statistical concepts, an d an empirical equation derived from theory with parameters determined from calibration. Simulations are performed to determine the utility of these three approaches in estimating the error of the rain gauge me an in the context of the GPCP.