ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa


Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2009, Issue 6, Vol. 2, pp. 137-146

An algorithm for retrieving cloud optical parameters from airborne spectral observations of the solar radiance

И.Н. Мельникова 1, С.А. Никитин2, Ш. Гатебе3
1 Научно-исследовательский центр экологической безопасности РАН
2 Балтийский государственный технический университет
3 NASA, Goddard Space Flight Center
Airborne observations of diffuse solar radiance, obtained with the NASAs Cloud Absorption
Radiometer are used for analysis of the transformation of the angular dependence within a cloud layer.
Optical parameters of the clear atmosphere are obtained from measurements above cloud layer. Cloud
optical parameters (the optical thickness, single scattering albedo and phase function asymmetry
parameter) are retrieved from measurements within cloud layer. Earlier there were approaches for
obtaining optical thickness and single scattering albedo from radiative observations. However, in these
approaches the restrictions on optical parameters and certain links between parameters in different
wavelength were a priori accepted. The single scattering albedo was assumed equal to 1 (the
approximation of the conservative atmosphere) in some studies and the semi-infinite optical thickness
was assumed in others. These restrictions on desired parameters do not allow obtaining their true values.
In this paper we use inverse asymptotic formulas to retrieve cloud parameters from observational data.
The procedure is free of a priori restrictions and links put on desired parameters and it is used for every
wavelength independently. The basic demands on observational conditions are large optical thickness
and horizontal extension of cloud layer. The spectral ranges are 0.3-1.0 μm. The full set of necessary
formulas is presented. The area of application and error analysis are considered. The experimental data
and observational conditions are described.
Keywords: solar shortwave radiation, cloud, airborne radiative observation, optical parameters
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