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CR prepress abstract   -  DOI:

Atmospheric characteristics favorable to the development of Mesoscale Convective Complexes in southern Brazil

Flávia D. S. Moraes*, Francisco E. Aquino, Thomas L. Mote, Joshua D. Durkee, Kyle S. Mattingly

*Corresponding author:

ABSTRACT: Mesoscale Convective Complexes (MCCs) are meteorological events that are difficult to forecast and result in severe storms, hail, flood, and tornadoes. In South America (SA), MCCs are usually larger and last longer than in the United States. Southern Brazil (SB) is one of their preferred regions of occurrence. This study’s objective is to contribute to the identification of the main physical characteristics and atmospheric environment that favors the occurrence of MCCs in SB and how these events are unique relative to other subtropical SA (OSSA). The results indicate that SB MCCs last longer than OSSA MCCs (+ 3h) and are at least 50,000 km2 larger on average of the maximum extent. The atmospheric environment of SB MCCs meets the criteria already indicated in previous studies, with northerly low-level jet (LLJ) bringing humidity from the Amazon Basin to SB MCCs genesis area and coupling with the upper-level jet (ULJ). Moreover, the SB MCCs have the South Atlantic as their second source of moisture, which is advected by an anticyclonic circulation located in southwestern South Atlantic. This indicates that SB MCCs have unique characteristics when compared to OSSA MCCs, including two main atmospheric circulation systems responsible for moisture advection to the SB genesis region. For comparison, OSSA MCCs are more dependent on the South Atlantic Convergence Zone (SACZ) and the advection of moisture by the LLJ from the Amazon Basin to north-central Argentina and to west-central and southeast Brazil.