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Aerosol Direct Radiative Effect from OMI Concept and First Results

Aerosol Direct Radiative Effect from OMI Concept and First Results. B. Veihelmann, P. Wang, J.P. Veefkind, P.F. Levelt Royal Netherlands Meteorological Institute. Overview. Aerosol Direct Radiative Effect (DRE) at the top of the atmosphere from OMI Concept Comparison with reference data

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Aerosol Direct Radiative Effect from OMI Concept and First Results

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  1. Aerosol Direct Radiative Effect from OMIConcept and First Results B. Veihelmann, P. Wang, J.P. Veefkind, P.F. Levelt Royal Netherlands Meteorological Institute

  2. Overview • Aerosol Direct Radiative Effect (DRE) at the top of the atmosphere from OMI • Concept • Comparison with reference data • 2 nice images • Conclusions

  3. Concept • multi-wavelength algorithm (OMAERO product) • radiance in 14 wavelength bands, 340-500 nm • Aerosol Optical Thickness (AOT) best fitting aerosol model (out of 50 models) refractive index, size distribution, height • model atmosphere of best fitting aerosol model • upwelling flux at TOA • Direct Radiative Effect DRE = flux(0) – flux(tfit)

  4. Concept • fluxes at TOA parameterized • precalculations with Doubling Adding Code KNMI (DAK) • spherical albedo S • transmission term T • flux at top of the atmosphere for black surface Fpath • efficient flux calculations for any given • Lambertian surface albedo a • sun-satellite geometry • elevation

  5. Comparison with reference data • EUCAARI intensive observation phase • cloud - aerosol measurement campaign • May 2008 at Cabauw, the Netherlands • radiative transfer simulations • AOT & SSA from ground-based sun-photometer • profiles from radiosondes • excellent agreement with ground-based measurements of broad-band flux • => reference for DRE from OMI • l-range 362-452 nm • at top of atmosphere

  6. Comparison with reference data

  7. March 2006 aerosol transport event sun-glint 0 2 4 6 8 AOT -40 -30 -20 -10 0 DRE (W/m2)

  8. Conclusion • DRE at TOA from OMI? • first test indicates that numbers are meaningful • relevance of DRE in UV-VIS? • 340-500 nm ~15% of irradiant solar energy • percentage of DRE larger: • aerosol scattering & absorption ~ l-a • Rayleigh scattering enhances absorption by aerosols • sensitivity to surface albedo • ocean BRDF implementation envisaged • land BRDF? • cloud screening using independent information • MODIS cloud mask?

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