12 October 1988 High Altitude Cirrus Effects On Spectral Measurements
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Abstract
The Kuiper Infrared Technology Experiment (KITE) program has operated over the last two years (1985-1987). Characteristics of atmospheric background radiance levels related to seasonal, diurnal, geographic and altitude effects are currently being studied because these effects are of interest to programs where the atmospheric background limits sensor performance. Correlating data from the KITE program with archived spectral data and model code predictions has established a number of important facts. First, the 11 pm window in the infrared appears to be "filled-in", i.e., the predicted troughs are not seen. This contributes to the second point: the background radiance levels predicted by the LOWTRAN model code in a window band centered at 11.2 pm appear to be too low by a factor of 2-3 or more. The high backgrounds observed are for the quiescent atmosphere in the south Pacific (Marshall Islands); clouds are highly variable and very difficult to predict due to convective processes (the intertropical convergence zone (ITCZ) borders the area). There appears to be little diurnal variability in the 11 pm window band in the tropics; however, seasonal effects are plausible, i.e., variation of the ambient atmospheric background radiance levels in response to the seasonal temperature dependence. Moreover, there appears to be a seasonally dependent linear relation between the 7.2- and 11.2- μm data. Persistence of "holes" in high altitude .thin cirrus cloud layers is a feature of primary concern in the area of forecasting. These optically thin cirrus clouds, sometimes called "cirrus evadus", may be the prime contributor to elevated background radiance levels by providing a means for thermal scattering of energy radiated by the Earth. They are often detected by means of a ground-based lidar; however, prediction capabilities do not exist at present. A full-scale climatology study to determine the growth of cloud formations and to establish a statistical database is recommended.
© (1988) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Eric O Schmidt, "High Altitude Cirrus Effects On Spectral Measurements", Proc. SPIE 0924, Recent Advances in Sensors, Radiometry, and Data Processing for Remote Sensing, (12 October 1988); doi: 10.1117/12.945696; https://doi.org/10.1117/12.945696
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