Dust events in Kanpur, northern India: Chemical evidence for source and implications to radiative forcing

Dust samples were collected and analyzed during May 2004 in Kanpur (in Ganga basin), Northern India for the first time. Chemical evidence along with the air mass trajectories suggests three major sources of the mineral dusts transported to the Ganga basin. High concentration of Pb and Cd indicates possible mixing with the anthropogenic pollution. The composite aerosol model reveals low single scattering albedo (similar to 0.74) due to the presence of black carbon. During the dust storms, shortwave (SW) clear-sky diurnally averaged top of the atmosphere (TOA) and surface forcing come out to be +11 +/- 0.7 and -2 +/- 63 W m(-2), respectively. Corresponding forcings in the longwave (LW) region are +1.9 +/- 0.6 and +1.6 +/- 0.4 W m(-2). Net atmospheric forcing (i.e., SW+LW, 36 W m(-2)) corresponds to heating rate of similar to 1.02 degrees K/day in the lower atmosphere. Dust alone has resulted in the net TOA and surface forcings of +7 and -12 W m(-2).