An objective technique for Arctic cloud analysis using multispectral AVHRR satellite imagery

• Main Author: Barron, John P.
• Other Authors: Durkee, Philip A., Wash, Carlyle H.
• Format: Thesis
• Language: English
• Published: Monterey, California. Naval Postgraduate School 1988
• Subjects: arctic cloud analysis; AVHRR channel 3; snow/cloud discrimination; Meteorology; Arctic; Sea ice
• Online Access: https://hdl.handle.net/10945/23335

An established cloud analysis routine has been modified for use in the Arctic. The separation of clouds from the snow and sea ice backgrounds is accomplished through a multispectral technique which utilizes VHRR channel 2 (visible), channel 3 (near infrared) and channel 4 (infrared) data. The primary means of cloud identification is based on a derived channel 3 reflectance image. At this wavelength, a significant contrast exists between liquid clouds and the arctic backgrounds, unlike in the standard visible and infrared images. The channel 3 reflectance is obtained by first using the channel 4 emission temperature to estimate the thermal emission component of the total channel 3 radiance. This thermal emission component is subsequently removed from the total radiance, leaving only the solar reflectance component available for analysis. Since many ice clouds do not exhibit a substantially greater reflectance is channel 3, the routine exploits differences in transmissive characteristics between channels 3 and 4 for identification. The routine was applied to six case studies which had been analyzed by three independent experts to establish 'ground truth'. Verification of the cloud analysis results, through a comparison to the subjective analyses, yielded impressive statistics. A success rate of 77.9% was obtained with an arguably small data base of 131 undisputed scenes Approved for public release; distribution is unlimited. Lieutenant, United States Navy http://archive.org/details/anobjectivetechn1094523335