NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Cloud properties inferred from 8-12 micron dataA trispectral combination of observations at 8-, 11-, and 12-micron bands is suggested for detecting cloud and cloud properties in the infrared. Atmospheric ice and water vapor absorption peak in opposite halves of the window region so that positive 8-minus-11-micron brightness temperature differences indicate cloud, while near-zero or negative differences indicate clear regions. The absorption coefficient for water increases more between 11 and 12 microns than between 8 and 11 microns, while for ice, the reverse is true. Cloud phases is determined by a scatter diagram of 8-minus-11-micron versus 11-minus-12-micron brightness temperature differences; ice cloud shows a slope greater than 1 and water cloud less than 1. The trispectral brightness temperature method was tested upon high-resolution interferometer data resulting in clear-cloud and cloud-phase delineation. Simulations using differing 8-micron bandwidths revealed no significant degradation of cloud property detection. Thus, the 8-micron bandwidth for future satellites can be selected based on the requirements of other applications, such as surface characterization studies. Application of the technique to current polar-orbiting High-Resolution Infrared Sounder (HIRS)-Advanced Very High Resolution Radiometer (AVHRR) datasets is constrained by the nonuniformity of the cloud scenes sensed within the large HIRS field of view. Analysis of MAS (MODIS Airborne Simulator) high-spatial resolution (500 m) data with all three 8-, 11-, and 12-micron bands revealed sharp delineation of differing cloud and background scenes, from which a simple automated threshold technique was developed. Cloud phase, clear-sky, and qualitative differences in cloud emissivity and cloud height were identified on a case study segment from 24 November 1991, consistent with the scene. More rigorous techniques would allow further cloud parameter clarification. The opportunities for global cloud delineation with the Moderate-Resolution Imaging Spectrometer (MODIS) appear excellent. The spectral selection, the spatial resolution, and the global coverage are all well suited for significant advances.
Document ID
19950031822
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Strabala, Kathleen I.
(Univ. of Wisconsin, Madison, WI United States)
Ackerman, Steven A.
(Univ. of Wisconsin, Madison, WI United States)
Menzel, W. Paul
(NOAA/NESDIS, Madison, WI United States)
Date Acquired
August 16, 2013
Publication Date
February 1, 1994
Publication Information
Publication: Journal of Applied Meteorology
Volume: 33
Issue: 2
ISSN: 0894-8763
Subject Category
Meteorology And Climatology
Accession Number
95A63421
Funding Number(s)
CONTRACT_GRANT: NAS5-31367
CONTRACT_GRANT: NAG1-1177
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available