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Proceedings Paper

Assessing cloud spatial and vertical distribution with cloud infrared radiometer CIR-7
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Paper Abstract

Recently developed, the Cloud Infrared Radiometer CIR-7, operates 7 infrared sensors, each with a 6-degree field of view, and spectral range 8-14 μm. The sensors are mounted on a semi-circular band at angles 0, 12, 24, 36, 48, 60 and 72°. A "hemispherical" mosaic of 181 brightness temperature measurements centered on the zenith is obtained by the rotation of the band around the vertical axis, performing 30 scans, every 12° from 0° (North) to 348 °. We present an algorithm that utilizes the brightness temperatures from the CIR-7 given the precipitable water vapor amounts and vertical profiles of the thermodynamic state of the atmosphere from independent measurements. It estimates the total cloud amount, the amount of low, middle and high clouds, maps out the spatial distribution of the cloud field and determines the vertical distribution of the clouds by computing cloud base heights. The algorithm is validated through comparisons with well studied ground-based and satellite retrieval techniques. Initial analyses show good cloud amount assessment and spatial mapping abilities. The estimated mean absolute cloud amount difference for day time is 12.3% when compared to the amount of opaque clouds derived with a total sky imager (TSI). For night time, this difference is 19.4% comparing to the effective cloud fraction derived with an atmospheric emitted radiance interferometer (AERI). The vertical distribution understanding is currently limited; however, the amounts of low, middle and high clouds could be determined and studied further.

Paper Details

Date Published: 30 November 2004
PDF: 10 pages
Proc. SPIE 5571, Remote Sensing of Clouds and the Atmosphere IX, (30 November 2004); doi: 10.1117/12.564234
Show Author Affiliations
Iliana Genkova, Pacific Northwest National Lab. (United States)
Chuck Long, Pacific Northwest National Lab. (United States)
Thierry Besnard, ATMOS SARL (France)
Didier Gillotay, Belgian Institute for Space Aeronomy (Belgium)

Published in SPIE Proceedings Vol. 5571:
Remote Sensing of Clouds and the Atmosphere IX
Adolfo Comeron; Michel R. Carleer; Richard H. Picard; Nicolaos I. Sifakis, Editor(s)

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