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Synoptic Weather Patterns and Associated Air Pollution in Taiwan

Category: Air Pollution Modeling

Volume: 19 | Issue: 5 | Pages: 1139-1151
DOI: 10.4209/aaqr.2018.09.0348
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Chia-Hua Hsu, Fang-Yi Cheng

  • Department of Atmospheric Sciences, National Central University, Taoyuan 32001, Taiwan


  • Apply the cluster analysis to classify the synoptic weather patterns.
  • Study the characteristic of PM2.5, PM10, and O3 in each weather pattern.
  • The weak synoptic weather pattern exhibits the lowest wind speed and highest PM2.5.
  • The worst air pollution problem occurs in the southwestern Taiwan.
  • Due to mountain blocking, the stagnant wind condition forms that traps the air pollutants.


In this study, cluster analysis is applied to the daily averaged wind fields and sea-level pressure observed at surface weather stations in Taiwan from January 2013 to March 2018 to classify the synoptic weather patterns and study the characteristics of corresponding air pollutants, including fine particulate matter (PM2.5), coarse particulate matter (PM10), and ozone (O3). The classification identified six weather types: Clusters 1, 2, and 3 (C1–C3), which are typical winter weather types and associated with high air pollutant concentrations—C3, in particular, influenced by weak synoptic weather, is associated with the lowest wind speeds and the highest PM2.5 and PM10 concentrations and represents the most prevalent weather type that is prone to the occurrence of PM2.5 events; C4, which occurs mostly during seasonal transition months and is associated with the highest O3 concentrations; and C5 and C6, which are summer weather types with low air pollutant concentrations.

Further analysis of the local wind flow using the 0.3° ERA5 reanalysis dataset and surface-observed wind data indicates that in western Taiwan, the land-sea breeze is embedded within the synoptic weather type of C3, which is favorable to air pollutant accumulation. However, when the prevailing northeasterly wind is obstructed by the Central Mountain Range, southwestern Taiwan, being situated on the leeside of the mountains, often exhibits the worst air pollution due to stagnant wind conditions.


Synoptic weather classification Cluster analysis PM2.5 Ozone Stagnant wind

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