P1.27
Does a climate model reproduce consistent ENSO precipitation signals in southern South America?
Alice M. Grimm, Federal University of Parana, Curitiba, Brazil and International Research Institute for Climate Prediction, Palisades, NY; and C. F. Ropelewski and S. Mason
Southern South America experiences consistent and strong precipitation anomalies associated with the various stages of El Nino and La Nina events. The timing of the anomalies varies throughout SSA due to different processes leading to precipitation anomalies. The purpose of this paper is to examine whether a climate model currently used for seasonal forecast purposes is able to reproduce these consistent anomalies when forced by observed SST anomalies. The outputs of the ECHAM3 model runs, with T42 resolution and forced with observed SST, are used is this analysis for the period 1956-1992. Precipitation data given by the ensemble mean of 8 model runs are submitted to the same analysis as observed data from a set of 134 stations in Southern South America. Composites of precipitation percentiles for every month within the El Nino/La Nina cycle are generated, along with the assessment of the consistency of the anomalies, given by a test based on the hypergeometric distribution. This analysis shows that the main features of the observed precipitation anomalies during the ENSO cycle seem to be best reproduced by the model during La Nina events. The composites of circulation anomalies from the model outputs and NCEP/NCAR reanalysis data are compared for November of El Nino years to diagnose the differences between the modeled and observed rainfall anomalies.
Poster Session 1, Data, Modeling and Analysis in Hydrometeorology
Tuesday, 11 January 2000, 6:00 PM-7:30 PM
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