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Optical Engineering

Accurate method for prediction of atmospheric transmission according to weather
Author(s): Itai Dror; S. Atar; Shlomit Grossman; Norman S. Kopeika
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Paper Abstract

Path-integrated atmospheric transmittance for visible wavelengths over a 5.5-km horizontal path is measured using black target contrast ratio. Measurements of on-line particulate distributions by particulate measuring system instrumentation (PMS) and of meteorological parameters are also performed. The extinction coefficients, primarily scattering, of aerosols are calculated using the PMS data, and those arising from molecular absorption are calculated by MODTRAN. Both extinction coefficients—the directly measured path-integrated ones and those calculated from particulate distribution and meteorological parameters near the receiver—are compared. Good agreement exists, especially when relative humidity is low, despite the fact that the second method involves aerosol size distribution by data collected from only a single point along the atmospheric path. Disagreement between both methods under high values of relative humidity can be explained by classification errors of the PMS instrumentation because of changes in the index of refraction of particles in a humid environment. Statistical regression analysis is made relating the measured transmittance values to online meteorological data. A simple and accurate model is obtained to predict dependence of the extinction coefficient on weather. The regression coefficients model shows that other meteorological parameters in addition to relative humidity are responsible for the changes in the atmospheric scattering coefficients. This contradicts the MODTRAN and Kasten-Hanel models for a continental atmosphere, which are based upon specific types of aerosols rather than a mixture of them.

Paper Details

Date Published: 1 September 1996
PDF: 8 pages
Opt. Eng. 35(9) doi: 10.1117/1.600863
Published in: Optical Engineering Volume 35, Issue 9
Show Author Affiliations
Itai Dror, Ben-Gurion Univ. of the Negev (Israel)
S. Atar, Ben-Gurion Univ. of the Negev (Israel)
Shlomit Grossman, TAAS/Hancal (Israel)
Norman S. Kopeika, Ben-Gurion Univ. of the Negev (Israel)

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