Open-path, closed-path, and reconstructed aerosol extinction at a rural site

Abstract

Although light extinction, which is directly related to visibility, is not directly measured in U.S. National Parks, existing IMPROVE protocols can be used to accurately infer visibility for average humidity conditions, but during the large fraction of the year when humidity is above or below average, accuracy is reduced substantially. Furthermore, nephelometers, which are used to assess the accuracy of IMPROVE visibility estimates, may themselves be biased low when humidity is very high. Despite reductions in organic and sulfate particles since the 1990s, hygroscopicity, particles' affinity for water, appears unchanged, although this conclusion is weakened by the previously mentioned nephelometer limitations.

Development of a three-dimensional variational assimilation system for lidar profile data based on a size-resolved aerosol model in WRF-Chem model v3.9.1 and its application in PM<sub>2.5</sub> forecasts across China

“…and fss(RH) reflect the effects of hygroscopicity of fine, coarse, and sea-salt aerosols in various relative humidity (HR) conditions on extinction efficiency, respectively. The values of parameters given by Gordon et al (2018) are used in this study. The variables (in the square brackets) at each grid cell are obtained by combining the 16 control variables using the following method:…”