Long-Term Atmospheric Visibility Trends and Characteristics of 31 Provincial Capital Cities in China during 1957–2016

Abstract

Millions of pulmonary diseases, respiratory diseases, and premature deaths are caused by poor ambient air quality in developing countries, especially in China. A proven indicator of ambient air quality, atmospheric visibility (AV), has displayed continuous decline in China’s urban areas. A better understanding of the characteristics and the factors affecting AV can help the public and policy makers manage their life and work. In this study, long-term AV trends (from 1957–2016, excluding 1965–1972) and spatial characteristics of 31 provincial capital cities (PCCs) of China (excluding Taipei, Hong Kong, and Macau) were investigated. Seasonal and annual mean values of AV, percentage of ‘good’ (≥20 km) and ‘bad’ AV (<10 km), cumulative percentiles and the correlation between AV, socioeconomic factors, air pollutants and meteorological factors were analyzed in this study. Results showed that annual mean AV of the 31 PCCs in China were 14.30 km, with a declining rate of −1.07 km/decade. The AV of the 31 PCCs declined dramatically between 1973–1986, then plateaued between 1987–2006, and rebounded slightly after 2007. Correlation analysis showed that impact factors (e.g., urban size, industrial activities, residents’ activities, urban greening, air quality, and meteorological factors) contributed to the variation of AV. We also reveal that residents’ activities are the primary direct socioeconomic factors on AV. This study hopes to help the public fully understand the characteristics of AV and make recommendations about improving the air environment in China’s urban areas.

Calculation of surface spectral irradiance using the Geant4 Monte Carlo toolkit

“…13) Fig. 2 shows the reference solar spectral irradiance ( − ) ( ) at the top of the atmosphere and the direct normal irradiances received at the ground calculated by Geant4, in the cases of an atmosphere without aerosols and in the presence of aerosols for atmosphere visibilities 23 km, the most common experienced visibility for clear days, and 10 km as an important indicator of haze (Fu et al, 2018).…”

Characteristics of Aerosol during a Severe Haze-Fog Episode in the Yangtze River Delta: Particle Size Distribution, Chemical Composition, and Optical Properties

“…In the boundary layer, aerosol particles can accumulate and cause air pollution in unfavorable dispersion conditions, and then produce adverse effects on human health and atmospheric visibility [6][7][8]. Haze is an atmospheric phenomenon in which the sky clarity is obscured by a large number of fine dry particles, during which the atmospheric visibility and relative humidity (RH) are usually less than 5 km and 80% [9,10]. When more water vapor exists in the air, some dry aerosol particles with strong water absorption will develop and eventually be activated into the CCN [11,12], which produces a larger quantity of fog droplets with a smaller size, which further reduce the visibility.…”

Main Factors Influencing Winter Visibility at the Xinjin Flight College of the Civil Aviation Flight University of China

“…Many studies have been carried out on the trends in visibility and its influencing factors in China, primarily focusing on rapidly developing megacities and polluted areas, such as Beijing, Shanghai, Guangzhou, Southeast China, the Yangtze River Delta, and the Pearl Delta region [17][18][19][20][21][22][23][24][25][26][27]. Visibility in the 31 provincial capital cities in China declined markedly between 1973 and 1986, plateaued between 1987 and 2006, and increased slightly after 2007 [28].…”