The simultaneous near surface measurements of aerosol scattering and absorption coefficients over different environments (Ahmedabad, urban and Gurushikhar, a high altitude remote site) in western India were conducted to estimate SSA and investigate the importance of SSA in aerosol radiative forcing. The surface SSA (0.79, 0.85) is lower than the column SSA (0.92, 0.95) as emission sources for black carbon aerosols (absorbing in nature) are abundant near the surface (Ahmedabad, Gurushikhar). The atmospheric warming over the urban region estimated using column SSA is a factor of 3 lower ( similar to 18 Wm(-2)) than that of the warming ( similar to 52 Wm(-2)) estimated utilising surface SSA. The significant difference in atmospheric warming arises due to the differences in the SSA as aerosol optical depth (a measure of column concentration of aerosols) is the same. Surface and column SSA are comparatively higher over the high altitude remote site as the abundance of absorbing aerosols is less over a non-source region. In addition, the differences between surface and column SSA are less (< 9%) resulting in comparable aerosol radiative forcing estimates. This study highlights the differences that can arise in aerosol radiative effects due to the differences in SSA as a function of altitude (surface vs. column) and environment (urban vs. remote), thereby providing regional bounds on aerosol radiative forcing which can further be used in climate assessment studies.
