Atmospheric circulation anomalies related to the winter PM2.5 mass concentration rapid decline cases in Beijing, China,Atmospheric Research

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Atmospheric circulation anomalies related to the winter PM2.5 mass concentration rapid decline cases in Beijing, China
Atmospheric Research ( IF 4.5 ) Pub Date : 2024-09-03 , DOI: 10.1016/j.atmosres.2024.107665
Yuanliurui Ren , Wei Chen , Bo Pang , Riyu Lu

In this study, we investigate the atmospheric circulation anomalies related to the PM2.5 mass concentration rapid decline cases in Beijing during winter when the PM2.5 concentration is the highest. From 2014 to 2021, 66 PM2.5 concentration rapid decline days (RDDs) are identified by considering the 90 % thresholds of the difference of PM2.5 mass concentration between two adjacent days. The composite evolution of PM2.5 concentration for the rapid decline cases features a slow increase on the accumulation phase but a rapid decline on RDDs with the average daily PM2.5 concentration decreases by 69.1 %. The composite evolution of atmospheric circulation anomalies in the lower troposphere related to these PM2.5 concentration rapid decline cases exhibits the eastward shift of cyclonic/anticyclonic geopotential height anomalies from the Mongolian Plateau/Northeast Asia to the Japan Sea/western Pacific, coinciding with a southerly-to-northerly reverse of wind anomalies in Beijing. The anomalous northerly on RDDs enhances the wind speed and therefore corresponds to the rapid decline of PM2.5 concentration. Further analysis suggests that the above process is responsible for 72.7 % of RDDs, and other about one-third of RDDs display anomalous southerly in Beijing, which also result in comparable PM2.5 reduction amplitude to that resulted from the northerly RDDs. The rapid decline of PM2.5 concentration for the Southerly RDDs cases is related to the near-surface southeasterly, which extends from 125°E to the west of Beijing, bringing the clean air masses from the Bohai Sea to the Beijing region.

更新日期：2024-09-03

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