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Aerosol Indices from SCIAMACHY: More Than a Qualitative Measure for Scattering and Absorbing Aerosols?

Marloes Penning de Vries(1), Tim Deutschmann(2), Michael Grzegorski(2), Ulrich Platt(2) and Thomas Wagner(1)

(1) Max Planck Institute for Chemistry, J.-J.-Becherweg 27, 55128 Mainz, Germany
(2) Institute for Environmental Physics, University of Heidelberg, Heidelberg, Germany

Abstract

The absorbing aerosol index AAI is a well-known indicator for the presence of UV-absorbing aerosols. It is derived from the so-called residue (resλ), which is calculated from the ratio of the measured reflectance at wavelength λ and the reflectance at λ calculated assuming an aerosol-free atmosphere bounded by a Lambertian reflecting surface. The positive part of resλ, AAI, is an indication for UV-absorbing aerosols and is retrieved by different satellite instruments (e.g. TOMS, GOME, SCIAMACHY, OMI). The negative part of resλ, here named scattering aerosol index (SAI), contains effects of scattering aerosols and clouds, and has received much less attention. We have investigated the dependencies and sensitivities of SAI to different aerosol and cloud scenarios in detail. This has convinced us that by coupling cloud information from SCIAMACHY with radiative transfer modeling it will be possible to separate the effects of clouds on the SAI from those of scattering (e.g. sulfate) aerosols. In the future, we intend to include reflectances at other wavelength bands of SCIAMACHY, as well absorption by gases such as O2 and O2-O2 in our aerosol retrieval to obtain accurate information on aerosol optical parameters and vertical profile. In this contribution our AAI and SAI results will be presented, including investigations on cloud effects, along with model studies using the Monte Carlo radiative transfer model McArtim.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry