Different data (ambient air quality,ground station meteorological observation,L-band radar sounding,wind profile radar sounding,and reanalysis data) and methods (back trajectory analysis,cluster analysis,probability source concentration field (PSCF),and numerical simulation) were used in this study to investigate the effects of meteorological conditions on heavy pollution periods and to reveal the contribution of external pollutants transported by the easterly wind,which creates severe pollution days in Wuhan,China.The results of the study are as follows.1) The easterly wind containing a high concentration of PM_2.5 (tiny particles or droplets in the air that are two and a half microns or less in width)will pass through the southern part of Anhui.The model results show that the easterly and northerly airflows and local circulation play a very important role in forming a repeated pollution zone in Wuhan.Pollution in Wuhan will be aggravated because of the external pollutants transported by easterly small winds.2) The results of the PSCF method show that the main potential pollutant source areas in the autumn-winter season in Wuhan are the Anhui,Jiangsu,Shandong,Henan,Hunan,and Jiangxi provinces,and prefecture-level cities around Wuhan.Therefore,regulating regional transboundary air pollution control (especially in the southern part of Anhui province) in winter is imperative to effectively mitigate urban PM_2.5 loading over Wuhan.The conclusions of this paper will contribute to the forecast and early warning service for pollution incidents in Wuhan,and simultaneously provide a scientific basis for the government to plan and undertake joint pollution prevention and control decisions.