Aerosol radiative forcing over a tropical urban site in India

Using collocated measurements of aerosol radiative properties and radiative fluxes, aerosol radiative forcing is estimated at a tropical urban site in India, located between the sub-continent and the Indian Ocean Experiment [INDOEX] sites. Observed sun/sky radiance data are used to derive aerosol spectral optical depth, single scattering albedo [SSA], asymmetry parameter, precipitable water and total column ozone. These serve as inputs to a radiative transfer model, to estimate aerosol forcing at the surface, the top-of-the atmosphere [TOA] and the atmosphere. During the dry season of 2001 and 2002 [November-April], these were found to be -33, 0 and 33 Wm(-2), respectively. Using measured radiative fluxes during different aerosol loading conditions yield a surface forcing of -31 Wm(-2). The surface forcing efficiency as computed from the two independent methods is found to be -88 and -84 Wm(-2), respectively, while mean SSA at 500 nm is found to be 0.81.