1 July 2003 Use of the moving time-window technique to determine surface albedo from TOMS reflectivity data
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Abstract
The seasonal variation of the surface albedo, due to snow or ice, complicates satellite estimation of the high-latitude surface UV irradiance. The TOMS instrument, that measures the backscattered radiances from the Earth's atmosphere and surface, does not distinguish cloud backscattering from surface backscattering. When the TOMS UV algorithm is used, false interpretation of the measured high reflectivity as thick cloudiness leads to substantial underestimation of the surface UV irradiance. While the largest UV irradiance is usually received during the summer, the spring exposure to UV radiation is the main concern in high-latitudes since the sensitivity of some biological organisms to UV radiation is more pronounced at low temperatures, and snowcover enhances the surface UV irradiance. This paper presents a new method for estimation of the surface reflectivity. The method is based on analysis of the TOMS Lambertian equivalent reflectivity data using the moving time-window technique. The new method treats the measured reflectivity data as samples from a distribution whose lower tail corresponds to surface albedo. The basic method assumes that the distribution is homogeneous, i.e. the surface albedo is constant within the window. Adequate statistics is achieved only by using a wide time-window which, unfortunately, leads to underestimation of the surface albedo during spring and autumn transitions. Therefore, the method was developed further to account for transitions. The feasibility of the new method has been studied globally for high-latitude regions, and it is expected to improve springtime UV irradiance estimates of polar regions.
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Aapo Tanskanen, Antti Arola, Jukka Kujanpaa, "Use of the moving time-window technique to determine surface albedo from TOMS reflectivity data", Proc. SPIE 4896, Ultraviolet Ground- and Space-based Measurements, Models, and Effects II, (1 July 2003); doi: 10.1117/12.483407; https://doi.org/10.1117/12.483407
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KEYWORDS
Reflectivity

Ultraviolet radiation

Line edge roughness

Algorithm development

Backscatter

Natural surfaces

Biological research

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