Storm aerosol environments and aerosol sources in Subtropical South America

CANCELADA, MAITE; SALIO, PAOLA; NESBITT, STEPHEN

San Francisco

Congreso; AGU Fall Meeting 2016; 2016

American Geophysical Union

Several studies have shown a strong interaction in the subtropical area of Southeastern South America (SESA) between deep moist convection and the presence of the South American low level jet (SALLJ), which advects humidity and heat from tropical latitudes creating ideal conditions in the environment for convective activity. Moreover, the SALLJ is considered an important mechanism for transport of gases and particulate matter emitted in tropical South America. Biomass burning season associated with deforestation and land clearing for agricultural use is observed in these regions principally from August to October. Past studies have shown, through modeling and in-situ measurements, an increase in optical depth and Angstrom exponent during SALLJ events. Evidence of an increase in aerosol loading during burning biomass season, along with favorable conditions for deep moist convection activity, supports the hypothesis of an indirect effect from aerosols in convective development in SESA. The objective of this work is to characterize aerosol environments in SESA associated with the presence of mesoscale convective system development. High aerosol concentration events during biomass burning season from 2002 to 2015 were detected using corrected aerosol optical depth (CAOD) with 10-km horizontal resolution from Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Products. Environmental variables from NCEP Climate Forecast System Reanalysis (CFSR) were examined to detect SALLJ events and deep moist convection development was observed through infrared channel from GOES.  This combination of aerosol data and SALLJ presence determines a data-set for polluted and non-polluted environments. A remarkable correlation between higher values of CAOD in central Argentina and SALLJ is found.  A case of study with evidence of SALLJ, high CAOD values and strong convection development was examined. A Weather Research and  Forecasting (WRF) simulation has been performed in order to analyze the indirect effect considering aerosol activation in the microphysical parameterization, also trajectories of air parcels were calculated to determine source areas of aerosols interacting with deep moist convection over central Argentina.