Dynamical Downscaling of Climate Anomalies in Tropical South America

.Tropical South America is characterized by steep topography, complex landuse patterns and significant rainfall gradients which are poorly represented in global atmospheric general circulation models (AGCMs). A regional climate model (RegCM) is employed to study the response of regional circulations, moisture transport, and precipitation to improved resolution. Seasonal integrations of the RegCM driven by NCEP reanalyses using a domain encompassing tropical South America will be presented for January-April of 1983 and 1988. The simulations are compared against the driving reanalyses and rainfall observations for the two anomalous years. Regional circulation differences are examined between the two seasons with emphsis on the structure and role of the low level jet east of the Andes in transporting moisture from the Amazon. The potential added value of this downscaling method will be discussed