Infrared Signatures from Atmospheric Clouds
Scientific rept. no. 3, Mar 1979-May 1980
AERODYNE RESEARCH INC BILLERICA MA
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Clouds are an important source of variations in the IR background radiation was detected by satellite surveillance systems, because clouds absorb and scatter solar radiation and have a blackbody temperature different from that of the earths surface. In the present study, a model which describes the scattering, absorption, and emission of radiation by atmospheric water or ice clouds is synthesized from previous works on the scattering of solar radiation. The cloud model is combined with the LOWTRAN atmospheric transmission model and is used to predict the apparent spectral radiance from scenes containing clouds as detected by a downward-looking observer. The effects of solar scatter, thermal emission, transmitted upwelling radiation, and atmospheric attenuation are included. Calculations using the model have been compared with infrared cloud data from several sources, including radiometer data from the BAMM balloon Altitude Mosaic Measurements Program. These analyses suggest that low altitude cumulus clouds are not an important source of background signal variations in the 2.7-3.1 micrometer region. The BAMM data and model calculations indicate that high altitude cirrus clouds can cause large spatial variations in the background signal in this wavelength region, due to enhanced solar scatter in the wings of the water vapor absorption bands.
- Atmospheric Physics
- Infrared Detection and Detectors
- Radiofrequency Wave Propagation