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| Titel |
Improved cloud mask algorithm for FY-3A/VIRR data over the northwest region of China |
| VerfasserIn |
X. Wang, W. Li, Y. Zhu, B. Zhao |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 3 ; Nr. 6, no. 3 (2013-03-01), S.549-563 |
| Datensatznummer |
250017831
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| Publikation (Nr.) |
 copernicus.org/amt-6-549-2013.pdf |
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| Zusammenfassung |
| The existence of various land surfaces always leads to more difficulties in
cloud detection based on satellite observations, especially over bright
surfaces such as snow and deserts. To improve the cloud mask result over
complex terrain, an unbiased, daytime cloud detection algorithm for the
Visible and InfRared Radiometer (VIRR) on board the Chinese FengYun-3A
polar-orbiting meteorological satellite is applied over the northwest region
of China. The algorithm refers to the concept of the clear confidence level
from Moderate Resolution Imaging Spectroradiometer (MODIS) and the unbiased
structure of the CLoud and Aerosol Unbiased Decision Intellectual Algorithm
(CLAUDIA). Six main channels of VIRR centered at the wavelengths of 0.455,
0.63, 0.865, 1.595, 1.36, and 10.8 μm are designed to estimate the
degree of a pixel's cloud contamination judged by the clear confidence
level. Based on the statistical data set during four months (January, April,
July, and October) in 2010, seasonal thresholds are applied to improve the
accuracy of the cloud detection results. Flags depicting snow and
water are also generated by the specific threshold tests for special
surfaces. As shown in image inspections, the cloud detection results over
snow and deserts, adopting the proposed scheme, exhibit better correlations
with true-color images than the VIRR official cloud mask results do. The
performance of the proposed algorithm has been evaluated in detail for four
seasons in 2011, using cloud mask products from MODIS and the ground-based
observations. The evaluation is based on, overall, 47 scenes collocated with
MODIS and 96 individual matchups between VIRR and the ground-based
observations from two weather stations located in the research region. The
quantitative validations suggest that the estimations of clear-sky regions
have been greatly improved by the proposed algorithm, while a poor
identification of the cirrus clouds occurs over deserts. |
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