Surface aerosol radiative forcing derived from collocated ground-based radiometric observations during PRIDE, SAFARI, and ACE-Asia

An approach is presented to estimate the surface aerosol radiative forcing by use of collocated cloud-screened narrowband spectral and thermal-offset-corrected radiometric observations during the Puerto Rico Dust Experiment 2000, South African Fire Atmosphere Research Initiative (SAFARI) 2000, and Aerosol Characterization ExperimentAsia 2001. We show that aerosol optical depths from the Multiple-Filter Rotating Shadowband Radiometer data match closely with those from the Cimel sunphotometer data for two SAFARI-2000 dates. The observed aerosol radiative forcings were interpreted on the basis of results from the Fu-Liou radiative transfer model, and, in some cases, cross checked with satellite-derived forcing parameters. Values of the aerosol radiative forcing and forcing efficiency, which quantifies the sensitivity of the surface fluxes to the aerosol optical depth, were generated on the basis of a differential technique for all three campaigns, and their scientific significance is discussed.