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Climate change has great significance in Asia in general, and India in particular; and atmospheric aerosols have a decisive role in this. The climate forcing potential of aerosols is closely linked to their optical, microphysical and chemical properties. Systematic efforts to characterize these properties over the Indian region started about 5 decades ago, and evolved over the years through concerted efforts in the form of long-term scientific programmes as well as concerted fields experiments. All these have resulted in this activity becoming one of the most vibrant fields of climate research in India and have brought several important issues in the national and international foci. The field experiment, RAWEX--GVAX (Regional Aerosol Warming Experiment--Ganges Valley Aerosol Experiment), conducted during 2011-12 jointly by the US Department of Energy, Indian Space Research Organization and Department of Science and Technology, has emerged as a direct outcome of the above efforts. This overview provides a comprehensive account of the development of aerosol--climate research in India and south Asia, and the accomplishment and newer issues that warranted the above field campaign. Details of RAWEX--GVAX, the major outcomes and the subsequent and more recent efforts are presented, followed by the way forward in this field for the next several years to come. [ABSTRACT FROM AUTHOR]

Extensive measurements of columnar aerosol optical depth (AOD), composite (MT) and black carbon aerosol 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 latitudinal 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 corresponding 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. [ABSTRACT FROM AUTHOR]