Cloud Detection in Nonpolar Regions for CERES Using TRMM VIRS and Terra and Aqua MODIS Data

Objective techniques have been developed to consistently identify cloudy pixels over nonpolar regions in multispectral imager data coincident with measurements taken by the Clouds and Earth's Radiant Energy System (CERES) on the Tropical Rainfall Measuring Mission (TRMM), Terra, and Aqua satell...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2008-11, Vol.46 (11), p.3857-3884
Main Authors: Minnis, P., Trepte, Q.Z., Sun-Mack, S., Yan Chen, Doelling, D.R., Young, D.F., Spangenberg, D.A., Miller, W.F., Wielicki, B.A., Brown, R.R., Gibson, S.C., Geier, E.B.
Format: Article
Language:English
Subjects:
Algorithm design and analysis
Applied geophysics
Calibration
Cloud
cloud detection
cloud mask
Clouds
Clouds and Earth's Radiant Energy System (CERES)
Earth
Earth sciences
Earth, ocean, space
Energy measurement
Exact sciences and technology
Internal geophysics
Moderate Resolution Imaging Spectroradiometer (MODIS)
MODIS
Multispectral imaging
Pixel
Satellites
Testing
Visible and Infrared Scanner (VIRS)
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Summary:Objective techniques have been developed to consistently identify cloudy pixels over nonpolar regions in multispectral imager data coincident with measurements taken by the Clouds and Earth's Radiant Energy System (CERES) on the Tropical Rainfall Measuring Mission (TRMM), Terra, and Aqua satellites. The daytime method uses the 0.65-, 3.8-, 10.8-, and 12.0-mum channels on the TRMM Visible and Infrared Scanner (VIRS) and the Terra and Aqua MODIS. The VIRS and Terra 1.6-mum channel and the Aqua 1.38- and 2.1-mum channels are used secondarily. The primary nighttime radiances are from the 3.8-, 10.8-, and 12.0- mum channels. Significant differences were found between the VIRS and Terra 1.6-mum and the Terra and Aqua 3.8-mum channels' calibrations. Cascading threshold tests provide clear or cloudy classifications that are qualified according to confidence levels or other conditions, such as sunglint, that affect the classification. The initial infrared threshold test classifies ~43% of the pixels as clouds. The next level seeks consistency in three (two) different channels during daytime (nighttime) and accounts for roughly 40% (25%) of the pixels. The third tier uses refined thresholds to classify remaining pixels. For cloudy pixels, ~ 4% yield no retrieval when analyzed with a cloud retrieval algorithm. The techniques were applied to data between 1998 and 2006 to yield average nonpolar cloud amounts of ~ 0.60. Averages among the platforms differ by
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2008.2001351