Measurements of aerosol optical depths and black carbon over Bay of Bengal during post‐monsoon season

Extensive and collocated measurements of aerosol optical depths (AODs), mass concentration of composite aerosols and aerosol black carbon (BC) were made over the Bay of Bengal(onboard R/V Sagar Kanya during its cruise #197) region during post-Indian summer monsoon period. These data along with MODIS (onboard TERRA satellite) data shows that aerosol visible AODs were in the range of 0.2 to 0.7 (with mean value of 0.43 ± 0.12) and Angstrom wavelength exponent of _0.93 ± 0.21 which in conjunction with a single scattering albedo (w) of _0.94 indicates the presence of weakly absorbing aerosols. The BC mass fraction was _2.9 ± 1.1% during post-monsoon season compared to 5.8 ± 0.6% (with w of _0.88) during premonsoon season. The presence of aerosols over Bay of Bengal during post-monsoon season decreases the short wave radiation reaching the surface by as much as $25 W m^{\mathrm{2}}$ and increases top of the atmosphere reflected radiation by $14 W m^{{2}}$. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 1610 Global Change: Atmosphere(0315, 0325); 1704 History of Geophysics: Atmospheric sciences; 1803 Hydrology: Anthropogenic effects.

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