GPCP and the Global Characteristics of Precipitation

Abstract

Global precipitation means and variations over the last 40 years are described using information from the Global Precipitation Climatology Project (GPCP). The GPCP international program is outlined along with the satellite and conventional data and techniques used. Global climatological values and patterns are examined and are shown to compare generally well to recent measurements from new satellite missions and with results from water balance studies. Global precipitation totals are tied to ENSO events, with small global increases during El Ninos, and noticeable global decreases associated with major volcanic eruptions. A very slight significant trend is noted in the global precipitation mean value during this period of planetary warming, with a rate of ~1%/K. However, there is a pattern of larger positive and negative trends across the planet with increases over tropical oceans and decreases over some middle latitude regions. Significant trends in intensity at the monthly time scale are noted with the GPCP analyses, with larger rainfall magnitudes increasing, moderate rainfall values decreasing and dry areas expanding. These results indicate the value of the GPCP data set, but also call for continuing revision and improvement as the record lengthens, and as new, more sophisticated observations are integrated into this type of analysis system.