Further FGGE Forecasts for Amazon Basin Rainfall

Abstract

A series of experiments using real-data general circulation model integrations is performed to study the impact of remote tropical Pacific heating modifications upon the rainfall over the Amazon Basin. In one set of experiments, a heating term is added to the thermodynamic equation in the western tropical Pacific Ocean, and in the second set, the sea surface temperatures are cooled in the eastern Pacific Ocean. The rainfall of northern sections of South America decreases in the first set of experiments and increases in the second set of experiments. Examination of the circulation changes for the second set of experiments suggests that the remote links occur through equatorially trapped flow modifications, perhaps related to the east-west Walker cells, rather than through midlatitude teleconnections via Hadley cells. The time evolution of these patterns suggests them to be clearly relevant for medium range weather prediction in the tropics.