Indian Ocean Dipole influence on South American rainfall

Abstract

The rainfall anomalies over South America are found to be influenced by the Indian Ocean Dipole (IOD). Between subtropical La Plata Basin and central Brazil, the IOD excites a dipolar pattern in rainfall anomalies; rainfall is reduced (enhanced) over latter (former) during australspring, when IOD reaches its peak phase. A Rossby wave train extends from the subtropical south Indian Ocean to the subtropical South Atlantic. The associated anomaly in surface circulation suggests an intensification of the South Atlantic High. The anomalous anticyclone in the lower troposphere causes anomalous divergence (convergence) of moisture over central Brazil (subtropical La Plata Basin). These results based on the University of Delaware precipitation analysis and the NCEP-NCAR reanalysis data are corroborated by that of the Scale Interaction Experiment-Frontier version 1 (SINTEX-F1) coupled general circulation model. Copyright 2008 by the American Geophysical Union.