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Proceedings Paper

Use of the moving time-window technique to determine surface albedo from TOMS reflectivity data
Author(s): Aapo Tanskanen; Antti Arola; Jukka Kujanpaa
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Paper 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.

Paper Details

Date Published: 1 July 2003
PDF: 12 pages
Proc. SPIE 4896, Ultraviolet Ground- and Space-based Measurements, Models, and Effects II, (1 July 2003); doi: 10.1117/12.483407
Show Author Affiliations
Aapo Tanskanen, Finnish Meteorological Institute (United States)
Antti Arola, Finnish Meteorological Institute (United States)
Jukka Kujanpaa, Finnish Meteorological Institute (United States)

Published in SPIE Proceedings Vol. 4896:
Ultraviolet Ground- and Space-based Measurements, Models, and Effects II
Wei Gao; Jay R. Herman; Guangyu Shi; Kazuo Shibasaki; James R. Slusser, Editor(s)

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