A Theoretical Investigation of Cloud/Fog Optical Properties and their Spectral Correlations.
Research and development technical rept.,
ARMY ELECTRONICS RESEARCH AND DEVELOPMENT COMMAND WSMR NM ATMOSPHERIC SCIENCES LAB
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The primary objective of the Electro-Optical Systems Atmospheric Effects Library EO SAEL is to provide the Army with an extensive collection of well-conceived and well-documented atmospheric models which can be used with confidence in predicting atmospheric effects on the performances of a variety of electrooptical weapons and communications systems either in computer simulation or under battlefield conditions. One of the models considered is the well-known relationship between visibility or extinction and the liquid water content of a cloud or fog. However, evidence exists that it varies from one cloud or fog to another with different slopes. This paper reexamines this relationships and its ramifications. In the case of unimodal or quasi-unimodal drop-size spectra, as can be well-represented by the gamma or the lognormal distribution 1 visible extinction appears to correlate well with liquid water content and with infrared extinction, except when the drop-size spectra and relatively narrow 2 the consistency of observed microphysical and spectral measurements may be judged by the degree of agreement with the regression lines of the models 3 by simply increasing or decreasing the liquid water content or alternately, droplet number concentration, a corresponding change in optical property may be effected without regard to spectral shapes and 4 sampling errors would cause a much greater error in the calculation of extinction coefficients when large droplets are missing than when small droplets are.
- Atmospheric Physics