Characterization of aerosols over oceanic regions around India during pre-monsoon 2006

Ship cruise observations of aerosol optical properties have been carried out over oceanic areas around India during pre-monsoon season of 2006. The results reveal rather significant day-to-day variability in aerosol optical thickness (AOT). Aerosol loading is found to be relatively high over the Bay of Bengal (BoB) i.e., AOT at 500 nm is 0.36 ± 0.12 which is higher than those over Arabian Sea (AS) i.e., 0.23 ± 0.09 and North Indian Ocean (NIO) i.e., 0.26 ± 0.10. Dominance of fine-mode (α = 1.21 ± 0.11) and coarse-mode (α = 0.86 ± 0.20) aerosol particles has been observed, respectively, over the BoB and AS regions. Second order Angstrom exponent shows predominant positive and negative curvatures over BoB and AS, respectively. High fine-mode aerosol loading over BoB is found to be associated with air masses originating from northeastern Indo-Gangetic plains and southeastern Myanmar. The observed short wave solar flux decrease due to aerosol extinction is found to be 24, 19 and 21 W m−2 for the BoB, AS and NIO, respectively.