Wei-Kuo Soong1, Chung-Hsuang Hung This email address is being protected from spambots. You need JavaScript enabled to view it.2 

1 Department of Military Meteorology, Air Force Institute of Technology, Kaohsiung 820, Taiwan
2 Department of Safety Health and Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 824, Taiwan

Received: January 15, 2024
Revised: June 26, 2024
Accepted: June 28, 2024

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.240015  

  • Download: PDF

Cite this article:

Soong, W.K., Hung, C.H. (2024). Rapid Built-up of PM10 in the Ambient Air of the Leeward Side Resulting from Strong Pressure Gradient Force Associated with Density Current. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.240015


  • Strong winds induced by significant pressure gradient force blow up river dust.
  • A large horizontal pressure gradient stimulates a density current in Taiwan.
  • PM10 is transported efficiently into Kaohsiung by the density current.


Meteorological factors can result in air pollution. Some studies have indicated that the leeward side effect’s weak flow and subsidence play major roles in inducing high PM10 (particulate matter with a diameter of ≤10 µm) in southern Taiwan during winter due to topographic blocking. However, the results of this research showed that the rapid build-up of high PM10 in Kaohsiung city (KHC) during evenings is not completely explained by weak flow and subsidence. In northern Taiwan, topographic blocking on northwesterly enhances a significant pressure gradient force (PGF) induced strong winds. According to the Froude number (above 0.5), the flow in northern Taiwan can pass the terrain, producing subsidence warming in central Taiwan, which is located at the leeward side of the northeastern Central Mountain Range (CMR). In addition, strong winds blowed river dust in the middle of Taiwan under a stable atmosphere and stimulated density current, transporting PM10 to southern Taiwan. A large horizontal pressure gradient was still formed in central western Taiwan between the cold flow originating from northern Taiwan and the warm flow by subsidence warming. The strong PGF and the interaction between the flow and the terrain in northern Taiwan should favor the density current. After PM10 was transported into KHC efficiently in a short time by the density current, the local effect of weak rear flow and subsidence in KHC enhanced and maintained PM even more than it did in central Taiwan.

Keywords: PM10, Density current, Inversion, Pressure gradient force

Share this article with your colleagues 


Subscribe to our Newsletter 

Aerosol and Air Quality Research has published over 2,000 peer-reviewed articles. Enter your email address to receive latest updates and research articles to your inbox every second week.

Aerosol and Air Quality Research (AAQR) is an independently-run non-profit journal that promotes submissions of high-quality research and strives to be one of the leading aerosol and air quality open-access journals in the world. We use cookies on this website to personalize content to improve your user experience and analyze our traffic. By using this site you agree to its use of cookies.