Abstract：In the visible and near IR，absorption is negligible so that the atmospheric extinction can be derived by atmospheric scattering which is mainly contributed by fog droplet, rain droplet, another types of droplet and small articles.The forward-scattering visibility meter (FVM) works by illuminating with near IR light a small sample volume of about 100 mL of air and measuring the intensity scattered in the angular range of 30° to 36° degrees.The scattered intensity is proportional to the extinction coefficient regardless of the article size distribution and after wavelength calibration.The ratio of scattered signal to extinction coefficient of fog and haze can be achieved by comparative test of FVM outputs and manual observations.Nevertheless, as a result of the application of the measurement during rain with the ratio of fog and haze, an unacceptable error is raised.To obtain an accuracy extinction measurement during rain, an appropriated ratio of scattered signal to extinction coefficient of rain would be found.The calculation for different size distributions of fog and rain with Mie theory has been made in this paper.And a comparison of extinction measurements made with two FVMs and manual observations during fog and rain has been made.The result shows that during rain the FVM extinction coefficient is from 20% to 60% greater than that of manual observations.This result can be used to define correction factors so that the FVM using forward-scattering near IR spectroscopy not only can be used to estimate extinction during fog and haze as well as during rain.
王缅,刘文清,陆亦怀,赵雪松,宋炳超,张玉钧,王亚萍,连翠华,陈军,程寅,刘建国,魏庆农. 基于前向近红外散射光谱测量雾和雨天大气消光的应用研究[J]. 光谱学与光谱分析, 2008, 28(08): 1776-1780.
WANG Mian,LIU Wen-qing,LU Yi-huai,ZHAO Xue-song,SONG Bing-chao,ZHANG Yu-jun,WANG Ya-ping,LIAN Cui-hua,CHEN Jun,CHENG Yin,LIU Jian-guo,WEI Qing-nong. Study on the Measurement of the Atmospheric Extinction of Fog and Rain by Forward-Scattering Near Infrared Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2008, 28(08): 1776-1780.
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