Aerosol black carbon over Arabian sea during intermonsoon and summer monsoon seasons

Abstract

Extensive, collocated measurements of the mass concentrations of composite and black carbon (BC) aerosols were made over coastal Arabian Sea, adjoining Indian Peninsula, for the first time during the inter-monsoon and summer monsoon periods, of 2003, as part of Arabian Sea Monsoon Experiment (ARMEX). Results showed that the diurnal variations are weak in March, and vanish completely by May/June, associated with the change in the synoptic circulations. The concentration of BC (and its share to total aerosol mass) decreases continuously, from ~700 ng m^-3 (2.5%) in March to ~104 ng m^-3 (0.5%) by June. Consequently, the net atmospheric forcing (heating) efficiency decreases from ~70 W m^-2 (for reported winter conditions) to ~30 W m^-2 for inter-monsoon and to ~15 W m^-2 for summer monsoon seasons. These will have implications on regional climate forcing.