CART Raman Lidar Measurements of Atmospheric Aerosol and Water Vapor Profiles for EOS Validation and the DOE ARM Program

Abstract: We propose to use the aerosol extinction and backscattering profiles measured by two separate Raman lidar systems to validate the aerosol climatology models used by two EOS AM sensors, MODIS and MISR. The aerosol retrieval algorithms used by these EOS sensors operate by comparing measured radiances with tabulated radiances which have been computed for specific aerosol models. Since these aerosol models are based almost entirely on surface and/or column averaged measurements and so may not accurately represent the ambient aerosol properties, validation of these aerosol models requires vertical profiles of aerosol optical properties. In addition, vertical profiles of aerosol extinction are required for determination of the effects of aerosols on the clear-sky radiative flux. Since recent studies have demonstrated the inability to compute these profiles from surface aerosol measurements alone, vertical profiles of aerosol optical properties must be acquired to compute aerosol radiative effects throughout the entire atmospheric column. Therefore, to study the effects of aerosols on the clear-sky radiative flux as well as to validate EOS algorithms, we propose to develop, evaluate, and implement algorithms for the Dept. of Energy SGP (Southern Great Plains) CART (Cloud and Radiation Testbed) Raman Lidar to provide profiles of aerosol extinction and backscattering. We propose to use these profiles, along with those measured by the NASA/GSFC Scanning Raman Lidar (SRL), to evaluate the vertical variability of ambient aerosol properties. We shall also use the simultaneous water vapor measurements acquired by both lidar systems to study the effects of water vapor and relative humidity on aerosol extinction and backscattering.

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