16 February 2004 Correction of the ground-based measurements of radiance by the surface contribution for a better estimate of the aerosol radiative forcing
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Abstract
A 'measure’ of the surface effect on downwelling radiance in the solar principal plane (SPP), K, is built by analysing simulations by a radiative transfer code. K describes the solar angle dependence of the radiance measured at a viewing angle θv=40° over radiance measured at θv=70°, both in SPP. The surface effect is described by a surface albedo value, used as an input parameter of the Successive Orders of Scattering code [Deuze et al., 1989]. K is mainly sensitive to the surface albedo but also to the Ångström exponent α and to the real part of the refractive index mR. α is derived from independent measurements of spectral aerosol optical thickness and mR is estimated in a first step of the method from radiance measurements made at θSun=70°. The method is applied on data acquired at the AERONET site of Sede Boker, Israel, in 2000. Results give a high reflective surface with small spectral dependence. An event of increase of vegetation cover (which we suppose is caused by rain falls) is observed as the surface albedo at 675 nm decreases while it remains constant at 870 nm. Aerosol single scattering albedo derived at 675 nm from radiance measurements varies little around 0.90 only if surface albedo change is considered.
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Thierry G. Elias, Thierry G. Elias, Ana Maria Silva, Ana Maria Silva, } "Correction of the ground-based measurements of radiance by the surface contribution for a better estimate of the aerosol radiative forcing", Proc. SPIE 5235, Remote Sensing of Clouds and the Atmosphere VIII, (16 February 2004); doi: 10.1117/12.514226; https://doi.org/10.1117/12.514226
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