GACP Projects
Quantifying the Indirect Radiative Forcing of Sulfate Aerosols by a Hybrid Technique
Harshvardhan , Co-PI
Stephen E. Schwartz, Co-PI
Abstract: Proposal is made for a three-year study to elicit the degree to which there is large-scale modification of the radiative properties of low-level marine clouds by the presence of sulfate aerosol. Unlike previous studies, such as with ship tracks, the scope of this study is not local but regional and, in principal, global. The analysis will use AVHRR multi-channel radiances to obtain a quantitative measure of effective cloud drop radius and visible optical depth in areas inside and outside the influence of sulfate aerosols. Fields of contemporaneous column sulfate will be obtained from an observed-meteorology driven global model.
The chief advantage of this study is its potentially global coverage. The output of the sulfate model has been compared with in-situ measurements over land and further comparisons over oceanic areas are under way. The column sulfate fields will act as surrogates for large-scale in-situ observations which are expensive to conduct. An understanding of the conditions under which there is an indirect radiative forcing by sulfate aerosols and an estimate of this effect addresses one of the major objectives of the NRA. In addition, this will be accomplished using a strategy combining satellite data with a global model and will involve investigators with expertise in radiative transfer and tropospheric chemistry.
