Young-Hee Ryu1, Seung-Ki Min This email address is being protected from spambots. You need JavaScript enabled to view it.1, Alma Hodzic2 

1 Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
2 National Center for Atmospheric Research (NCAR), Boulder, USA

Received: December 8, 2020
Revised: February 15, 2021
Accepted: February 18, 2021

 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.

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Ryu, Y.H., Min, S.K., Hodzic, A. (2021). Recent Decreasing Trends in Surface PM2.5 over East Asia in the Winter-spring Season: Different Responses to Emissions and Meteorology between Upwind and Downwind Regions. Aerosol Air Qual. Res.


  • Recent decreasing PM2.5 and their emission changes need to be well assessed.
  • PM2.5 trends are reasonably captured by WRF-Chem with updated emission estimates.
  • Large and direct responses to reduced emissions are found in upwind source regions.
  • The role of meteorology in PM2.5 variations is larger in downwind regions.
  • More complex variations in secondary aerosols are found in downwind regions.


This study develops and evaluates a WRF-Chem modeling system that utilizes updated anthropogenic emissions for 2013–2018 over East Asia to reflect PM2.5 changes due to recent emission regulations. The WRF-Chem model reasonably reproduces monthly means, daily variations, and vertical profiles in PM2.5 in winter and spring over South Korea and China. Results show that the recent declines in PM2.5 over China are attributed to China’s emission control action effective since 2013. The effects of emission reductions are found to be larger in the severely polluted region (i.e., North China Plain, NCP) than less polluted regions or downwind regions (Yangtze River Delta, YRD, and Seoul Metropolitan Area, SMA). The simulated February-mean PM2.5 is reduced by 39% during 2013–2018 over the NCP and by 17% over the YRD. The SMA shows small changes in PM2.5 in winter but weak decreasing trends in spring. In addition to emissions, meteorology is found to considerably modulate PM2.5. The effects of meteorology on the interannual variations in PM2.5 are larger in the downwind regions (SMA and YRD regions) than in the upwind region (NCP), which can be up to 35% in winter and 45% in spring over the SMA. The corresponding effects over the NCP are 11% in winter and 12% in spring. More complex variations in secondary aerosols that do not always follow the decreasing trends in primary aerosol emissions are found in the downwind regions than in the upwind regions.

Keywords: PM2.5, WRF-Chem, Trends, Emissions

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