Anthropogenic sulphate aerosol from India: estimates of burden and direct radiative forcing

A one-box chemical-meteorological model had been formulated to make prelimi nary estimates of sulphate aerosol formation and direct radiative forcing o ver India. Anthropogenic SO2 emissions from India, from industrial fuel use and biomass burning, were estimated at 2.0 Tg S yr(-1) for 1990 in the ran ge of previous estimates of 1.54 and 2.55 Tg S yr(-1) for 1987. Meteorologi cal parameters for 1990 from 18 Indian Meteorological Department stations w ere used to estimate spatial average sulphate burdens through formation fro m SO2 reactions in gas and aqueous phase and removal by dry and wet deposit ion. The hydrogen peroxide reaction was found dominating for undepleted oxi dant-rich conditions. Monthly mean sulphate burdens ranged from 2-10 mg m(- 2) with a seasonal variation of winter-spring highs and summer lows in agre ement with previous GCM studies. The sulphate burdens are dominated by sulp hate removal rates by wet deposition, which are high in the monsoon period from June-November. Monthly mean direct radiative forcing from sulphate aer osols is high (-3.5 and -2.3 W m(-2)) in December and January, is moderate (-1.3 to -1.5 W m(-2)) during February to April and November and low ( -0.4 to -0.6 W m(-2)) during May to October also in general agreement with prev ious GCM estimates. This model, in reasonable agreement with detailed GCM r esults, gives us a simple tool to make preliminary estimates of sulphate bu rdens and direct radiative forcing. (C) 1999 Elsevier Science Ltd. All righ ts reserved.