RESULTS FROM THE GPCP ALGORITHM INTERCOMPARISON PROGRAM

Three algorithm intercomparison experiments have recently been conduct ed as part of the Global Precipitation Climatology Project with the go al of (a) assessing the skill of current satellite rainfall algorithms , (b) understanding the differences between them, and (c) moving towar d improved algorithms. The results of these experiments are summarized and intercompared in this paper. It was found that the skill of satel lite rainfall algorithms depends on the regime being analyzed, with al gorithms producing very good results in the tropical western Pacific a nd over Japan and its surrounding waters during summer, but relatively poor rainfall estimates over western Europe during late winter. Month ly rainfall was estimated most accurately by algorithms using geostati onary infrared data, but algorithms using polar data [Advanced Very Hi gh Resolution Radiometer and Special Sensor Microwave/Imager (SSM/I)] were also able to produce good monthly rainfall estimates when data fr om two satellites were available. In most cases, SSM/I algorithms show ed significantly greater skill than IR-based algorithms in estimating instantaneous rain rates.