9408941 Hobbs With this award, Dr. Hobbs will attempt to quantify the effects of aerosols on climate through their effects on clouds through a series of airborne observations. Measurements will be obtained of key parameters for a variety of aerosols, for various cloud types, and in several climatological regimes. The measurements include cloud condensation nucleus (CCN) efficiencies (i.e., the number of CCN produced by unit mass of a chemical species) of various types of atmospheric aerosols, the effects of these aerosols on cloud droplet concentrations and size distributions and the radiative properties of clouds (particularly near cloud tops). The measurements will be made in strongly polluted air in the northeastern United States, in the smoke produced by biomass burning in the Amazon Basin, and in moderately polluted as well as quite clear air in the Pacific Northwest and Alaska. This project will contribute to a better understanding of climate processes and the potential for global climate change. It is being funded under the Role of Clouds, Energy, and Water in Global Climate Change Research Opportunity. ***
