9526402 Hegg Atmospheric aerosol particles are believed to influence the earth's radiation balance either directly by scattering and absorbing incoming solar radiation, or indirectly by altering cloud microphysical properties. This project addresses the effects of heterogeneous sulfate chemistry on cloud droplet number concentrations and size distributions (the aerosol indirect effect). The study uses computer modeling to develop a parameterization of the impact of cloud heterogeneous chemistry on the optical and water active properties of cloud-processed sulfate aerosols. The parameterization utilizes a transfer function to allow estimation of the impact from an array of prognostic variables that are components of standard, bulk-paramerized cloud models. The regional scale modeling approach is a new method for evaluating the influence of cloud heterogeneous chemistry on cloud condensation nuclei (CCN) and optical properties, a refinement not currently possible with existing global climate models (GCMs). The results from the project will provide needed improvements in the current ability of models in generating realistic treatments of cloud/aerosol interactions on a regional scale. This parameterization study will be a key, fundamental step in developing similar parameterizations for GCM's.
