Extensive measurements of columnar aerosol optical depth (AOD), composite (MT) and black carbon aero-
sol mass (MB) concentrations were made over the tropical Indian and Southern Oceans as a part of the
Pilot Expedition to the Southern Ocean during the boreal winter. The AOD, MT and MB show large lati-
tudinal gradient towards south up to ITCZ. Beyond ITCZ, up to 56°S, AOD and MB show very low and        
steady values. However MT shows large variations in the Southern Ocean due to the enhanced production
of sea salt aerosols associated with high sea surface winds. The short wave aerosol radiative forcing at the
surface over north of equator is in the range – 10 to – 23 W m–2, whereas that over the Southern Ocean
was in the range – 4 to – 5 W m–2. The correspondin g atmospheric forcing was in the range of 6–13 W m–2 and 0.8–1.4 W m–2. This large north–south change in the aerosol radiative forcing has important implications
to the meridional circulation and hence to climate.