Xiujuan Zhao This email address is being protected from spambots. You need JavaScript enabled to view it.1, Zhaobin Sun1, Yele Sun2, Ting Yang2, Dan Chen1, Ziming Li3, Yajun Xiong3, Guiqian Tang2 

1 Institute of Urban Meteorology, Chinese Meteorological Administration, Beijing 100089, China
2 State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
3 Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, Beijing 100089, China


Received: October 13, 2020
Revised: March 20, 2021
Accepted: April 25, 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.


Download Citation: ||https://doi.org/10.4209/aaqr.200593  

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Cite this article:

Zhao, X., Sun, Z., Sun, Y., Yang, T., Chen, D., Li, Z., Xiong, Y., Tang G. (2021). Three-dimensional Thermal and Dynamic Structure in Synoptic and Local Scale and its Influence on Haze Formation during Autumn in Beijing. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.200593


HIGHLIGHTS

  • Indicators of vertical meteorological conditions on haze formation were studied quantitatively
  • The debatable question on regional transport under surface stagnant condition was explained.
  • Effects of interaction between topography and meteorology on haze evolution were investigated.
 

ABSTRACT


The vertical thermal and dynamic structures in synoptic and local scale that contribute to the haze formation are investigated in three-dimensional view. In synoptic scale, heavy haze corresponds to significant horizontal transport by southerly winds or strong vertical stability with descending motion in the layer below ~1500–3000 m. Average meteorological elements below ~1500 m are better indicators of pollutant transport and dispersion than on-surface measurements. The dynamic changes are characterized by ascending motion accompanied by enhanced southerly winds from the surface to above ~1500 m, can transport pollutants from surrounding areas to Beijing, resulting in a rapid increase of PM2.5 within a few or several hours, even when the surface wind remains weak. This explained the debatable question on regional transport under surface stagnant condition and partially approved the important role of regional transport in haze formation. In addition, local mountain–plain breeze circulation is prominent during stable stage of haze episodes. The plain wind in daytime pushes the pollutants to areas along the mountains and then to Beijing, resulting in a day-by-day increase of pollutants. This is different from observation in winter haze events that local pollution accumulation is the main cause for haze worsening in stable meteorological conditions. The coupling effect of easterly winds and local topography can cause special dissipation and formation processes of haze. The orographic effect can uplift haze to higher layers, where PM2.5 is transported to the southeast. Then the polluted plume aloft is carried back to Beijing along the mountain front with southerly winds, merges with surface pollutants by vertical mixing, and finally enhances the next haze episode.


Keywords: Haze formation, Vertical thermal and dynamic structure, Mountain-plain breeze circulation, Topographic effect




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