The Microphysical Basis of Fog Optical Characterization.
ARMY ELECTRONICS RESEARCH AND DEVELOPMENT COMMAND WSMR NM ATMOSPHERIC SCIENCES LAB
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The increasing use by the Army of the various types of electro-optical EO devices necessitates a test and evaluation program to determine the performance of these devices under a variety of weather conditions - the foggy condition, in particular. The presence of fogs seriously degrades the effectiveness of visible and infrared sensors, no matter how well-designed and engineered the sensors are. It would be impractical as well as uneconomical to test and evaluate each device individually under different atmospheric conditions. A more logical and direct approach would be to characterize and develop physical and optical models of fogs through extensive microphysical, meteorological, and spectral measurements at selected spectral regions, locations, and at different periods of fog evolution. Thus, microphysical characterization may aptly be said to be the basis of optical characterization under various meteorological foggy conditions. However, microphysical characterization is not without problems of its own. This report presents a brief review of the state of fog microphysics. Careful inspection of fog spectra from numerous journal papers appears to indicate that on the average a large number of fogs and, to some extent, clouds may be adequately represented by six distribution histograms of varying spectral widths.
- Test Facilities, Equipment and Methods