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Assessing OMI UVB Data Quality with Ground-based Measurements

Explore the quality of OMI UVB data through comparison with ground measurements, examining biases like cloud interference and latitude effects. Our study uses an advanced model to estimate UVB and identify potential attributions for biases in the OMI UVB product. Key findings suggest overestimations in Europe and reveal latitude-dependent bias in OMI UVB estimates. We propose improvements by incorporating site-specific aerosol and albedo information. Collaboration with various European sites has enriched our analysis.

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Assessing OMI UVB Data Quality with Ground-based Measurements

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  1. Arjan van Dijk, Peter den Outer and Harry Slaper One year of OMI, FMI, Helsinki, Finland, June 24-27, 2008 European ground-based UV-measurements used for assessment of OMUVB data quality

  2. Our plan: • Compare the OMUVB product from overpass data with UVB ground measurements • Check for forms of bias (clouds, latitude, etc…) • Use our own AMOUR-model to estimate UVB from OMI ozone and OMI reflectivity • Use these AMOUR UVB estimates to assess possible attributions for the bias in the OMUVB product

  3. Ground measurements:

  4. Ratio OMUVB / ground measurement (1/2)

  5. Ratio OMUVB / ground measurement (2/2)

  6. The effect of clouds:Ratio(OMUVB/Measured) vs CMF (1/2)

  7. The effect of clouds:Ratio(OMUVB/Measured) vs CMF (2/2)

  8. Attempts to assess cloud correction Site: Bilthoven Other satellite, our algorithm: “the good old times” OMUVB product Our algorithm on OMI ozone and NEW OMI cloud radiative fraction (overpass) Our algorithm on OMI ozone and OLD OMI reflectivity (gridded)

  9. Cloud Modification Factor: UVB vs pyranometer EPTOMS OMI

  10. Radiative Cloud Fraction: grid vs overpass

  11. Latitude dependence of ratio OMUVB/Measured “AMOUR_Local” uses: our algorithm + OMI ozone + new cloud product as if it were CMF from pyranometer + site-info for aerosols and albedo!

  12. Latitude dependence of ratio OMUVB/Measured “AMOUR_Local” shows the potential of OMI products!

  13. Conclusions • For Europe, OMUVB gives overestimates • Overestimation is strongest in very clouded situations • The new “cloud reflection factor” behaves as a pyranometer CMF • OMUVB has a latitude-dependent bias • With site-info for aerosols and albedo, we have shown major improvement of (the bias in) OMI-UVB estimates • Please, resurrect the old-style reflectivity product! • Overpass data (ozone and reflection) and gridded data seem not in agreement

  14. Thank you very much for your kind permission to use the following ground measurements (collected for SCOUT-O3): Finland:Jussi Kaurola, Anders Lindfors (Jokioinen, Sodankyla) Greece: Alkis Bais, Andreas Kazantzidis (Thessaloniki) Czech Republic: Michael Janouch (Hradec Kralove) Germany: Uwe Feister (Lindenberg, Potsdam) Sweden: Weine Josefsson (Norrkoping) Belgium: Didier Gillotay, Hugo de Backer (Ukkel)

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