AN EVALUATION OF THE SPATIAL AND INTERANNUAL VARIABILITY TROPICAL PRECIPITATION AS SIMULATED BY GCMS

Precipitation is one of the most difficult variables to simulate in a General Circulation Model and arguably one of the most important. The Atmospheric Model Intercomparison Project (AMIP) provides an opportuni ty to examine the simulation of precipitation in a wide array of model s. Monthly precipitation fields produced by a subset of 19 currently a vailable AMIP model experiments are evaluated for the tropical region using a land-only observed dataset for the period 1980-1988. The model s show large variations in their ability to reproduce observed tropica l precipitation, although spatial correlations indicate that some of t he models simulate the pattern of observed precipitation fields fairly well. The correlations are strongest during boreal winter (DJF) and w eakest during the boreal summer (JJA). Comparison between model and ob served precipitation time series for two Central Pacific locations sho w that most models are unable to reliably reproduce interannual precip itation variability in this region.