Study of Mesoscale Convective Vortices associated with South Atlantic Convergence

The South Atlantic Convergence Zone (SACZ) is a meteorological phenomenon that plays an important role in the precipitation regime over the region it covers, resulting in high pluviometric indices in South America. This study shows, from the mesoscale analysis prospective that Mesoscale Cyclonic Vortex (MCV) is associated to the SACZ through a feedback process. This study highlights the MCVs associated to the SACZ, identifying the thermodynamic properties of the various stages during its lifetime cycle. This study uses the BRAMS mesoscale model to understand specific MCVs episodes and its relationship with SACZ. Two case studies were conducted over the SACZ, simulated using the BRAMS model, showing the relationship between the MCVs formation and the convective activity near its formation region. In both regions the MCVs present similar characteristics which could be considered as a "signature" for such systems. The case studies also present a lifetime shorter than 24 hours and spatial scale of approximately 200 km2 in addition to intense precipitation, shifting in the flow direction in the lower troposphere, relative vorticity of the same order as the Coriolis parameter (10-4 s-1), warm core above the level of maximum intensity and rapid growth of the cyclonic vorticity center mostly in the lower levels. The vorticity balance and the energy cycle of these systems are then analyzed. The results suggest that the BRAMS model, configured with high spatial and temporal resolutions improves the representation of the MCVs when compared to the NCEP CFSR reanalysis.