VARIABILITY OF EXTREME PRECIPITATION EVENTS IN SOUTHEAST BRAZIL AND RELATIONSHIPS WITH TROPICAL INTRASEASONAL VARIATIONS

The South Atlantic Convergence Zone (SACZ) is the dominant summertime cloudiness feature of subtropical South America and the western South Atlantic Ocean. It is readily seen in climatologies of outgoing longwave radiation (OLR) and precipitation. Anomalous precipitation in the region of southeast South America that is influenced by the SACZ, particularly excess amounts for short periods of time (< 1 week), can result in agricultural ruin and the displacement of many people. Studies of atmospheric teleconnections suggest that variations of tropical convection in the western Pacific Ocean can influence the region through Rossby wave dispersion. Furthermore, spectral analysis of OLR along the SACZ reveals intraseasonal variability associated with the Madden-Julian Oscillation (30-60 days) as well as additional intraseasonal variance (27, 16, 10 and 8 days). The work presented here is an attempt to quantify relationships between the Madden-Julian oscillation and precipitation variability on times scales of less than a week.