GLOBAL PRECIPITATION - A 17-YEAR MONTHLY ANALYSIS BASED ON GAUGE OBSERVATIONS, SATELLITE ESTIMATES, AND NUMERICAL-MODEL OUTPUTS

Gridded fields (analyses) of global monthly precipitation have been co nstructed on a 2.5 degrees latitude-longitude grid for the 17-yr perio d from 1979 to 1995 by merging several kinds of information sources wi th different characteristics, including gauge observations, estimates inferred from a variety of satellite observations, and the NCEP-NCAR r eanalysis. This new dataset, which the authors have named the CPC Merg ed Analysis of Precipitation (CMAP), contains precipitation distributi ons with full global coverage and improved quality compared to the ind ividual data sources. Examinations showed no discontinuity during the 17-yr period, despite the different data sources used for the differen t subperiods. Comparisons of the CMAP with the merged analysis of Huff man et al. revealed remarkable agreements over the global land areas a nd over tropical and subtropical oceanic areas: with differences obser ved over extratropical oceanic areas. The 17-yr CMAP dataset is used t o investigate the annual and interannual variability in large-scale pr ecipitation. The mean distribution and the annual cycle in the 17-yr d ataset exhibit reasonable agreement with existing long-term means exce pt over the eastern tropical Pacific. The interannual variability asso ciated with the El Nino-Southern Oscillation phenomenon resembles that found in previous studies, but with substantial additional details, p articularly over the oceans. With complete global coverage, extended p eriod and improved quality, the 17-yr dataset of the CMAP provides ver y useful information for climate analysis, numerical model validation, hydrological research, and many other applications. Further work is u nder way to improve the quality, extend the temporal coverage, and to refine the resolution of the merged analysis.