The Relationship between Incident and Double-Way Transmittances: An Application for the Estimate of Surface Albedo from Satellites over the African Sahel

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  • a L.A.M.P./O.P.G.C., Université de Clermont II, LA/CNRS n° 267, 63170 Aubière, France
  • | b L.O.A., Université des Sciences et Techniques de Lille, 59655 Villeneuve d'Ascq Cedex France
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Abstract

The inference of surface reflectance from satellite observations requires the knowledge of the double-way transmittance through the atmosphere. Since the existing pyranometer networks routinely provide measurements of the incident transmittance over sensitive climatic regions, it would be useful for subsequent applications to relate this ground-based measurement to the corresponding double-way transmittance. A variety of satellite radiance simulations corresponding to clear sky conditions has been made in order to derive a suitable parameterized expression between the two quantities. The accuracy of this expression when making use of additional meteorological observations is shown and discussed. Finally, the derived expression is used to improve a method recently proposed by Pinty et al. for retrieving surface albedo over the African Sahel from METEOSAT radiances.

Abstract

The inference of surface reflectance from satellite observations requires the knowledge of the double-way transmittance through the atmosphere. Since the existing pyranometer networks routinely provide measurements of the incident transmittance over sensitive climatic regions, it would be useful for subsequent applications to relate this ground-based measurement to the corresponding double-way transmittance. A variety of satellite radiance simulations corresponding to clear sky conditions has been made in order to derive a suitable parameterized expression between the two quantities. The accuracy of this expression when making use of additional meteorological observations is shown and discussed. Finally, the derived expression is used to improve a method recently proposed by Pinty et al. for retrieving surface albedo over the African Sahel from METEOSAT radiances.

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