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| Titel |
Comparison of TOMS retrievals and UVMRP measurements of surface spectral UV radiation in the United States |
| VerfasserIn |
M. Xu, X.-Z. Liang, W. Gao, N. Krotkov |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 18 ; Nr. 10, no. 18 (2010-09-16), S.8669-8683 |
| Datensatznummer |
250008775
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| Publikation (Nr.) |
 copernicus.org/acp-10-8669-2010.pdf |
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| Zusammenfassung |
| Surface noontime spectral ultraviolet (UV) irradiances during May-September
of 2000–2004 from the total ozone mapping spectrometer (TOMS) satellite
retrievals are systematically compared with the ground measurements at 27
climatological sites maintained by the USDA UV-B Monitoring and Research
Program. The TOMS retrievals are evaluated by two cloud screening methods
and local air quality conditions to determine their bias dependencies on
spectral bands, cloudiness, aerosol loadings, and air pollution. Under
clear-sky conditions, TOMS retrieval biases vary from −3.4%
(underestimation) to 23.6% (overestimation). Averaged over all sites, the
relative mean biases for 305, 311, 325, and 368 nm are respectively 15.4,
7.9, 7.6, and 7.0% (overestimation). The bias enhancement for 305 nm by
approximately twice that of other bands likely results from absorption by
gaseous pollutants (SO2, O3), and aerosols that are not included
in the TOMS algorithm. For all bands, strong positive correlations of the
TOMS biases are identified with aerosol optical depth, which explains nearly
50% of the variances of TOMS biases. The more restrictive in-situ cloud
screening method reduces the biases by 3.4–3.9% averaged over all sites.
This suggests that the TOMS biases from the in-situ cloud contamination may
account for approximately 25% for 305 nm and 50% for other bands of
the total bias. The correlation coefficients between total-sky and clear-sky
biases across 27 sites are 0.92, 0.89, 0.83, and 0.78 for 305, 311, 325, and
368 nm, respectively. The results show that the spatial characteristics of
the TOMS retrieval biases are systematic, representative of both clear and
total-sky conditions. |
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