Analysis of Mass Extinction Efficiency variation according to relative humidity using lidar and visibility data in Seoul

The mass extinction efficiency(MEE), which indicates the degree of aerosol extinction(scatter and absorption) per unit PM mass concentration, is an important factor in converting optical concentration into mass concentration. Because its value varies depending on the particles' size and composition, which are particles' characteristics. In this study, the extinction coefficients of coarse and fine particles were calculated using the LiDAR data of Seoul observed by NIES(Japan's National Institute of Environmental Studies) and the visibility data of Seoul observed by the Korea Meteorological Administration. In the case of lidar data, two wavelengths (532nm, 1064nm) measured by lidar were used to calculate extinction coefficients, and the wavelength of 532 nm (532P and 532S) were used to classify extinction coefficients into coarse particles(PM10-2.5) and fine particles(PM2.5). In the case of visibility data, the PM10 and PM2.5 extinction coefficients were calculated using the equation of Koschmieder (1924) and Cheng et al. (2017). The PM10, PM10-2.5, and PM2.5 respective MEE were calculated using Seoul data of PM10 and PM2.5 at the same time provided by the Korea Environment Corporation. The relative humidity data provided by the Korea Meteorological Administration were divided into seven sections less than 40%, 40~49%, 50~59%, 60~69%, 70~79%, 80~89%, and 90~100%. According to relative humidity, this study examined the change of the calculated MEE. This study analyzes the effect of relative humidity on the Hygroscopic Growth of PM10, PM10-2.5, and PM2.5.