[A-AS04] Formation of Air Pollution and Its Interactions with Weather/Climate

[AAS04-10] To what extents do urbanization and air pollution affect fog?To what extents do urbanization and air pollution affect fog?

*Shuqi Yan^1,2,3,4, Bin Zhu^1,2,3,4, Yong Huang^5,6, Jun Zhu⁷, Hanqing Kang^1,2,3,4, Chunsong Lu^1,2,3,4, Tong Zhu⁸ (1.Collaborative Innovation Centre on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing, China, 2.Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science & Technology, Nanjing, China, 3.Key Laboratory of Meteorological Disaster, Ministry of Education (KLME), Nanjing University of Information Science & Technology, Nanjing, China, 4.Special test field of National Integrated meteorological observation, Nanjing University of Information Science & Technology, Nanjing, China, 5.Anhui Meteorology Institute, Key Lab of Atmospheric Science and Remote Sensing Anhui Province, Hefei 230031, China, 6.Shouxian National Climatology Observatory, Shouxian 232200, China, 7.Xiangshan Meteorological Bureau, Xiangshan 315700, China, 8.IMSG at NOAA/NESDIS/STAR, 5830 University Research Ct., College Park, MD 20740, USA)

Keywords:Fog, Urbanization, Aerosol, WRF-Chem

The remarkable development of China has resulted in rapid urbanization (urban heat island and dry island) and severe air pollution (aerosol pollution). Previous studies demonstrate that these two factors have either suppressing or promoting effects on fog, but what are the extents of their individual and combined effects? In this study, a dense radiation fog event in East China in January 2017 was reproduced by the WRF-Chem model, and the individual and combined effects of urbanization and aerosols on fog (indicated by liquid water content (LWC)) are quantitatively revealed. Results show that urbanization inhibits low-level fog, delays its formation and advances its dissipation due to higher temperatures and lower saturations. In contrast, upper-level fog could be enhanced because of the updraft-induced vapour convergence. Aerosols promote fog by increasing LWC, increasing droplet concentration and decreasing droplet effective radius. Further experiments show that the current pollution level in China is still below the critical aerosol concentration that suppresses fog. Urbanization influences fog to a larger extent than do aerosols. When urbanization and aerosol pollution are combined, the much weaker aerosol promoting effect is counteracted by the stronger urbanization suppressing effect on fog. Budget analysis of LWC reveals that urban development (urbanization and aerosols) alters LWC profile and fog structure mainly by modulating condensation/evaporation process. Our results infer that urban fog will be further reduced if urbanization keeps developing and air quality keeps deteriorating in the future.