Aerosol Absorption, Optical Depth and Vertical Extent Estimates Using UV/blue Satellite Measurements

Cairns, B., and Alexandrov, M.D., Columbia University; Carlson, B.E., and Lacis, A.A., NASA Goddard Institute for Space Studies
Eighth Atmospheric Radiation Measurement (ARM) Science Team Meeting

The radiative balance of the atmosphere and the climatological response of the atmospheric circulation to changes in aerosol loading is principally determined by the vertical extent and single-scatter albedo of the aerosols. Although UV radiance measurements made by the Total Ozone Mapping Experiment Spectrometer (TOMS) instrument have been used to detect UV absorbing aerosols and estimate their properties, the unknown verticalextent of the aerosol affects the sensitivity of the radiances to absorbing aerosols and, therefore, the quantities retrieved. It would therefore be preferable to determine the vertical extent of the aerosol simultaneously with the estimate of aerosol optical depth and single-scatter albedo. The mechanism by which absorbing aerosols are distinguished using UV/blue radiances is that as the vertical extent and absorption of the aerosol layer varies, the amount of Rayleigh scattering above and within the aerosol layer varies. This has a characteristic effect on the spectral reflectance of the atmosphere in the UV, which is used in the TOMS algorithm, and also on the angular distribution and polarization of radiation in the UV/blue. In this poster, we examine to what extent short wavelength multi-angle measurements (MISR) and short wavelength multi-angle polarimetric measurements (POLDER, RSP) can be used to constrain estimates of aerosol single-scatter albedo, vertical extent and optical depth over land surfaces. The use of complementary measurements from the ARM CART site (multi-filter rotating shadowband radiometer [MFRSR], rotating shadowband spectroradiometer [RSS], CIMEL and Raman Lidar) in testing the validity and sensitivity of such retrievals to other factors is also investigated. In particular, the information content of calibration insensitive measures, such as polarization and diffuse to direct ratios, is emphasized.

Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).