Radiative Forcing of Carbonaceous Aerosols over Two Urban Environments in Northern India

The radiative forcing of elemental carbon (EC) and organic carbon (OC) has been estimated over two urban environments in Northern India (Jabalpur [JBL] and Udaipur [UDPR]) from November 2011 till November 2012 (till September 2012 over Jabalpur). The elemental carbon concentrations reached 7.36 +/- 1.99 mu g m(-3) over JBL and were as high as 10.78 +/- 4.85 mu g m(-3) over UDPR, whereas the corresponding OC concentrations were much higher in different months (as high as 19.37 +/- 12.6 mu g m(-3) over JBL and 39.71 +/- 13.05 mu g m(-3) over UDPR). The radiative forcing for OC and EC has been estimated using an optical model along with a radiative transfer model. The surface OC radiative forcing was found to range from -2.19 +/- 1.93 W m(-2) to -3.083 +/- 2.29 W m(-2) over JBL and -1.97 +/- 1.37 to -5.89 +/- 2.17 W m(-2) over UDPR, whereas the estimated top of the atmosphere (TOA) forcing ranged from -0.87 +/- 0.49 to -1.87 +/- 0.90 W m(-2) over JBL and from -1.23 +/- 0.31 to -3.44 +/- 1.51 W m(-2) over UDPR. However, the effect of EC forcing (as high as -21.75 W m(-2) at the surface of and +6.3 W m(-2) at TOA over JBL and -38.21 W m(-2) at the surface of and +5.05 W m(-2) at TOA over UDPR) was found to be more than tenfold higher than OC forcing due to its strong atmospheric absorption, in spite of much lower concentrations compared to OC.