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Das, SK; Chen, JP; Ratnam, MV; Jayaraman, A (2013). Investigation of radiative effects of the optically thick dust layer over the Indian tropical region. ANNALES GEOPHYSICAE, 31(4), 647-663.

Optical and physical properties of aerosols derived from multi-satellite observations (MODIS-Aqua, OMI-Aura, MISR-Terra, CALIOP-CALIPSO) have been used to estimate radiative effects of the dust layer over southern India. The vertical distribution of aerosol radiative forcing and heating rates are calculated with 100 m resolution in the lower atmosphere, using temperature and relative humidity data from balloon-borne radiosonde observations. The present study investigates the optically thick dust layer of optical thickness 0.18 +/- 0.06 at an altitude of 2.5 +/- 0.7 km over Gadanki, transported from the Thar Desert, producing radiative forcing and heating rate of 11.5 +/- 3.3 W m(-2) and 0.6 +/- 0.26 K day(-1), respectively, with a forcing efficiency of 43 W m(-2) and an effective heating rate of 4 K day(-1) per unit dust optical depth. Presence of the dust layer increases radiative forcing by 60% and heating rate by 60 times at that altitude compared to non-dusty cloud-free days. Calculation shows that the radiative effects of the dust layer strongly depend on the boundary layer aerosol type and mass loading. An increase of 25% of heating by the dust layer is found over relatively cleaner regions than urban regions in southern India and further 15% of heating increases over the marine region. Such heating differences in free troposphere may have significant consequences in the atmospheric circulation and hydrological cycle over the tropical Indian region.



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