Analysis Of Deep Moist Convection Development In High And Low Aerosol Concentration Environments

CANCELADA, MAITE; SALIO, PAOLA; NESBITT, STEPHEN W.

San Pablo

Workshop; Sao Paulo School of Advanced Science on Atmospheric Aerosols; 2019

Instituto de Fisica de la Universidad de San Pablo

Southeastern South America (SESA) has been recognized as one of the regions with most intense convection in the world, capable of producing severe weather such as hail, intense precipitations, wind gust, lightning activity, and even tornadoes. Besides, during the dry season (August to November), strong biomass burning activity is observed in central Amazon associated principally with deforestation for agricultural purposes. The evidence of an increase in aerosol loading in SESA during biomass burning season, together with favorable conditions for deep moist convection development, motivate the study of a possible convective invigoration effect that could impact on the intensity of the storms that initiate in this region.In this work, deep moist convection events were selected from Radar precipitation features (RPFs) database derived from Tropical Rainfall Measuring Mission (TRMM) and their initiation location was determined with a threshold adaptive area-overlapping tracking technique with infrared data. Source regions for environment air previous to convective initiation were defined with backward trajectories calculated with the lagrangian dispersion model FLEXPART and overlapped with AOD fields from reanalysis MERRA-2 to obtain "polluted" and "non-polluted" samples. A higher maximum height of 40 dBz reflectivity was found for "polluted" cases suggesting an invigoration effect of the aerosols, however, an analysis of the dynamic and thermodynamic characteristics of the environment showed that aerosol presence in the region implies a strong low level jet development creating favorable conditions for extreme convection. Therefore, this must be taken into account before establishing relationships between aerosols presence and convection intensity.