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Record 1 of 3818
Utilizing the MODIS 1.38 micrometer Channel for Cirrus Cloud Optical Thickness Retrievals: Algorithm and Retrieval Uncertainties
External Online Source: doi:10.1029/2010JD014872
Author and Affiliation:
Meyer, Kerry(Oak Ridge Associated Universities, Inc., Oak Ridge, TN, United States)
Platnick, Steven(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Abstract: The cloud products from the Moderate Resolution Imaging Spectroradiometers (MODIS) on Terra and Aqua have been widely used within the atmospheric research community. The retrieval algorithms, however, oftentimes have difficulty detecting and retrieving thin cirrus, due to sensitivities to surface reflectance. Conversely, the 1.38 micron channel, located within a strong water vapor absorption band, is quite useful for detecting thin cirrus clouds since the signal from the surface can be blocked or substantially attenuated by the absorption of atmospheric water vapor below cirrus. This channel, however, suffers from nonnegligible attenuation due to the water vapor located above and within the cloud layer. Here we provide details of a new technique pairing the 1.38 micron and 1.24 micron channels to estimate the above/in-cloud water vapor attenuation and to subsequently retrieve thin cirrus optical thickness (tau) from attenuation-corrected 1.38 p.m reflectance measurements. In selected oceanic cases, this approach is found to increase cirrus retrievals by up to 38% over MOD06. For these cases, baseline 1.38 micron retrieval uncertainties are estimated to be between 15 and 20% for moderately thick cirrus (tau > 1), with the largest error source being the unknown cloud effective particle radius, which is not retrieved with the described technique. Uncertainties increase to around 90% for the thinnest clouds (tau < 0.5) where instrument and surface uncertainties dominate.
Publication Date: Dec 18, 2010
Document ID:
20120002594
(Acquired Feb 27, 2012)
Subject Category: METEOROLOGY AND CLIMATOLOGY
Report/Patent Number: GSFC.JA.5702.2011
Document Type: Journal Article
Publication Information: Journal of Geophysical Research; Volume 115
Publisher Information: American Geophysical Union, Washington, DC, United States
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 13p; In English; Original contains black and white illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: CIRRUS CLOUDS; OPTICAL THICKNESS; SPECTRAL REFLECTANCE; SURFACE PROPERTIES; IMAGING SPECTROMETERS; MODIS (RADIOMETRY); AQUA SPACECRAFT; ABSORPTION SPECTRA; IMAGING TECHNIQUES; SPECTRORADIOMETERS; RADII; ALGORITHMS; DETECTION; ERRORS; ESTIMATING; WATER VAPOR
Availability Source: Other Sources
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