| Aerosols influence Earth's heat budget both directly by scattering and absorbing sunlight, and indirectly by acting as nuclei for cloud droplets. To reduce the uncertainties of current estimates of aerosol climate forcing, aerosol optical properties relevant to the computation of direct radiative forcing were measured at a regionally representative site near Mount Mitchell, North Carolina. On the basis of these measurements and model calculations, we have studied (1) the effects of relative humidity on aerosol optical properties and direct aerosol radiative forcing and (2) the influence of long-range transport on black carbon concentrations, its seasonal and weekly patterns, and the effects of black carbon on the regional climate of the southeastern United States. In addition, SAGE II ozone and aerosol measurements and NCEP/NCAR potential vorticity and temperature fields during 1985–1999 have been analyzed to study the spatial and temporal distributions of aerosol and ozone associated with the Antarctic polar vortex processes and to investigate the impact of polar stratospheric clouds on aerosol distribution and ozone depletion. Using the measurements during the volcanically unperturbed years, we have derived empirical relationships between ozone, temperature, and potential vorticity in the Antarctic stratosphere. |
