Joint Occurrence of Heavy PM2.5 Pollution Episodes and Persistent Foggy Days in Central East China

Frontiers in Environmental Science

Yuanjian Yang³  Dong Liu⁴  Caixia Yu⁵ 

[1] Anhui Province Key Laboratory of Atmospheric Sciences and Satellite Remote Sensing, Anhui Institute of Meteorological Sciences, Hefei, China;Key Laboratory of Atmospheric Optics, Anhui Institute of Optics and Fine Mechanics Chinese Academy of Sciences, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China;School of Remote Sensing and Geomatics Engineering, Nanjing University of Information Science and Technology, Nanjing, China;Science Island Branch, Graduate School of USTC, Hefei, China;Shouxian National Climate Observatory, Typical Farmland Eco-Meteorology Field Scientific Test Base of China Meteorological Administration in Huaihe River Basin, Shouxian, China;

关键词: PM2.5 pollution episodes;    fog process;    wet deposition;    subsidence motions;    rebound;   

DOI  :  10.3389/fenvs.2021.821648

来源: DOAJ

【 摘 要 】

Although many severe pollution events in Central and East China have been analyzed in recent years, the heavy PM2.5 pollution episode happened on persistent foggy days from January 13 to 18, 2018 was unique, characterized by explosive increase and sharp decrease in PM2.5 (particles with kinetic equivalent diameter less than or equal to 2.5 microns) concentration. Based on hourly data of ground level meteorological parameters, PM2.5 data and CALIPSO-based (the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) aerosol data, combined with ECMWF (European Centre for Medium-Range Weather Forecasts) reanalysis data and radiosonde temperature profile, a comprehensive analysis was conducted to reveal the meteorological reasons for the evolution of the episode at horizontal and vertical scales. The PM2.5 concentration experienced four stages: a slow-increase phase, rapid-increase phase, rapid-decrease phase, and rebound phase. Results show that because Central and East China (CEC) were located at the back of a high-pressure system, humid southerly winds and near surface inversion (NSI) were responsible for the slow accumulation of pollutants. The rapid-increase phase was attributed to pollution transport at both ground level and in the lower troposphere because of weak cold air invasion. The significant subsidence at 500 hPa and 700 hPa intensified the NSI and led to dense fog. In that case, corresponding to the supersaturated atmosphere, the particles entered the fog droplets and were scavenged partly by deposition at night and were resuspended on the next day when the atmosphere was unsaturated. Our findings provide convincing evidence that surface PM2.5 rapid-decrease phase and the rebound phase were closely associated with dense fog process.

【 授权许可】

Unknown