The Contribution of Mesoscale Convective Complexes to Rainfall across Subtropical South America

Abstract

This study uses a database consisting of 330 austral warm-season (October?May) mesoscale convective complexes (MCCs) during 1998?2007 to determine the contribution of MCCs to rainfall across subtropical South America (SSA). A unique precipitation analysis is conducted using Tropical Rainfall Measuring Mission (TRMM) 3B42 version 6 data. The average MCC produces 15.7 mm of rainfall across 381 000 km2, with a volume of 7.0 km3. MCCs in SSA have the largest precipitation areas compared to North American and African systems. MCCs accounted for 15%?21% of the total rainfall across portions of northern Argentina and Paraguay during 1998?2007. However, MCCs account for larger fractions of the total precipitation when analyzed on monthly and warm-season time scales. Widespread MCC rainfall contributions of 11%?20% were observed in all months. MCCs accounted for 20%?30% of the total rainfall between November and February, and 30%?50% in December, primarily across northern Argentina and Paraguay. MCCs also produced 25%?66% of the total rainfall across portions of west-central Argentina. Similar MCC rainfall contributions were observed during warm seasons. An MCC impact factor (MIF) was developed to determine the overall impact of MCC rainfall on warm-season precipitation anomalies. Results show that the greatest impacts on precipitation anomalies from MCC rainfall were located near the center of the La Plata basin. This study demonstrates that MCCs in SSA produce widespread precipitation that contributes substantially to the total rainfall across the region.