ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-19009-2009 Aerosol Single Scattering Albedo retrieval in the UV range: an application to OMI satellite validation Ialongo I. 1 Buchard V. 2 Brogniez C. 2 Casale G. R. 1 Siani A. M. 1 Physics Department, University of Rome, Sapienza, Italy Laboratoire d'Optique Atmosphérique (LOA), Université des Sciences et Technologies de Lille, France 14 09 2009 9 5 19009 19033 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/9/19009/2009/acpd-9-19009-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/19009/2009/acpd-9-19009-2009.pdf

The aerosol Single Scattering Albedo (SSA) and Absorbing Aerosol Optical Depth (AAOD) at 320.1 nm are derived at Rome site by the comparison between Brewer and modelled spectra. The UVSPEC radiative transfer model is used to calculate the UV irradiances for different SSA values, taking into account as input data total ozone and Aerosol Optical Depth (AOD) obtained from Brewer spectral measurements. The accuracy in determining SSA depends on the aerosol amount and on Solar Zenith Angle (SZA) value: SSA uncertainty increases when AOD and SZA decrease. The monthly mean values of SSA and AAOD during the period January 2005–June 2008 are analysed, showing a monthly and seasonal variability. It is found that the SSA and AAOD averages are 0.80±0.08 and 0.056±0.028, respectively. AAOD retrievals are also used to quantify the error in the Ozone Monitoring Instrument (OMI) surface UV products due to absorbing aerosols, not included in the current OMI UV algorithm. OMI and Brewer UV irradiances at 324.1 nm and Erythemal Dose Rates (EDRs) under clear sky conditions, are compared as a function of AAOD. Three methods are considered to investigate on the applicability of an absorbing aerosol correction on OMI UV data at Rome site. Depending on the correction methodology, the bias value decreases from 18% to 2% for spectral irradiance at 324.1 nm and from 25% to 8% for EDR.

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