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Optical Engineering

Version 2 total ozone mapping spectrometer ultraviolet algorithm: problems and enhancements
Author(s): Nickolay A. Krotkov; Jay R. Herman; Pawan K. Bhartia; Colin J. Seftor; Antti Arola; Jussi Kaurola; S. Kalliskota; Petteri Taalas; Igor V. Geogdzhayev
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Paper Abstract

Satellite instruments provide global maps of surface UV irradiance by combining backscattered radiance measurements with radiative transfer models. The accuracy of the models is limited by uncertainties in input parameters representing the atmosphere and the Earth's surface. To reduce these uncertainties, we have made enhancements to the currently operational TOMS surface UV irradiance algorithm (Version 1) by including the effects of diurnal variations of cloudiness, an improved treatment of snow/ice, and a preliminary aerosol correction. We compare results of the version 1 TOMS UV algorithm and the proposed version. We evaluate different approaches for improved treatment for average cloud attenuation within a satellite pixel, with and without snow/ice on the ground. In addition to treating cloud transmission based only on the measurements at the local time of the TOMS observations, the results from other satellites and weather assimilation models can be used to estimate atmospheric UV irradiance transmission throughout the day. A new method is proposed to obtain a more realistic treatment of the effects from snow-covered terrain. The method is based on an empirical relation between UV reflectivity and measured snow depth. The new method reduces the bias between the TOMS UV estimations and ground-based UV measurements for snow periods. We also briefly discuss the complex problem of estimating surface UV radiation in presence of UV-absorbing aerosols. The improved (Version 2) algorithm can be applied to reprocess the existing TOMS UV irradiance and exposure estimates (since November 1978) and to future satellite sensors (e.g., GOME-2, OMI on EOS/Aura, and Triana/EPIC).

Paper Details

Date Published: 1 December 2002
PDF: 12 pages
Opt. Eng. 41(12) doi: 10.1117/1.1519541
Published in: Optical Engineering Volume 41, Issue 12
Show Author Affiliations
Nickolay A. Krotkov, Univ. of Maryland/Baltimore County and Goddard Earth Sciences and Technology Ctr. (United States)
Jay R. Herman, NASA Goddard Space Flight Ctr. (United States)
Pawan K. Bhartia, NASA Goddard Space Flight Ctr. (United States)
Colin J. Seftor, Raytheon ITSS (United States)
Antti Arola, Finnish Meteorological Institute (Finland)
Jussi Kaurola, Finnish Meteorological Institute (Finland)
S. Kalliskota, Finnish Meteorological Institute (Finland)
Petteri Taalas, Finnish Meteorological Institute (Finland)
Igor V. Geogdzhayev, NASA Goddard Institute for Space Studies and Columbia Univ. (United States)

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