Aerosols over Delhi during pre-monsoon months: Characteristics and effects on surface radiation forcing

The surface fluxes in the wavelength range 280 - 2800 nm were measured during the pre-monsoon period, April June 2003 along with the spectral distribution of aerosol optical depth (AOD) in the visible and near infrared wavelengths. The Angstrom exponent alpha retrieved from the data showed abundance of desert aerosols over Delhi during this period. The aerosol composition constructed using the OPAC model indicated a typical mixture of two aerosol types: urban and desert. Due to this the aerosol mixture had a very low value of single scattering albedo similar to 0.67. The average total radiative forcing efficiency observed at the surface in the broad wavelength band ( 280 - 2800 nm) was estimated and compared with the SBDART model calculated values.