Intraseasonal Variability over South America from 20th- and 21st-Century Simulations

CAROLINA S. VERA; PAULA L. M. GONZÁLEZ; ANDREA CARRIL

La Plata, Provincia de Buenos Aires

Jornada; Final CLARIS Meeting; 2007

CLARIS - A Europe-South America Network for Climate Change Assessment and Impact Studies

South America is a dipolar pattern known as the South American Seesaw (SASS). Enhanced precipitation over the subtropics is associated with southward intensification in the South American Low Level Jet (SALLJ) and increased moisture flux from the Amazon region, while in the opposite phase of the SASS an enhancement in the South American Convergence Zone (SACZ) is accompanied by a weakening of the SALLJ and decreased rainfall in the subtropical plains. The dipolar pattern exhibits variability associated with the Madden-Julian Oscillation (MJO) with periods of 30-60 days, and also on timescales around 22-28 days, implying that an interaction among different intraseasonal fluctuations might be controlling its activity. Different works have shown that intraseasonal variability in the circulation over South America is related to the influence of Rossby wave patterns.The main objective of this work was to assess the ability of 20th-century simulations of the WCRP/CMIP3 models to reproduce the main features of the observed intraseasonal variability over South America. Additionally, the intraseasonal variability depicted by the 21st-century simulations of the WCRP/CMIP3 models was explored.