Preprints
https://doi.org/10.5194/acp-2022-48
https://doi.org/10.5194/acp-2022-48
 
16 Feb 2022
16 Feb 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Regional PM2.5 pollution confined by atmospheric internal boundaries in the North China Plain: 2. boundary layer structures and numerical simulation

Xipeng Jin1, Xuhui Cai1, Mingyuan Yu2, Yu Song1, Xuesong Wang1, Hongsheng Zhang3, and Tong Zhu1 Xipeng Jin et al.
  • 1College of Environmental Sciences and Engineering, State Key Lab of Environmental Simulation and Pollution Control, Peking University, Beijing 100871, China
  • 2School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 3Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China

Abstract. This study reveals and summarizes mesoscale planetary boundary layer (PBL) structures for various pollution patterns in the North China Plain. Three pollution categories have been classified, in terms of the influence of the atmospheric internal boundary (AIB) that significantly determines the distribution and concentration of PM2.5. The Weather Research and Forecast model is used to simulate the PBL structure in this region, and its performance is firstly evaluated using surface observations and intensive soundings data. Observed AIBs and PBL evolution are reasonably reproduced. Simulation results for three pollution categories illustrate respective PBL structures, as well the relationship with the mesoscale AIBs. The first category corresponds to the severest pollution and occurs most frequently (~41 %). The PBL structure is laterally confined by a warm front as a sharp AIB and vertically suppressed by a dome-like elevated temperature inversion, which constitutes a stable and enclosed circumstance, most favorable to pollution formation. The second category is characterized by wind shear line/zone as AIB, with dynamic convergence in the PBL as the dominant cause for PM2.5 accumulation. Three shear modes consist of this category, two of which are related to pressure troughs with the convergence layer of the order of the PBL depth. Another shear mode presents a much thicker convergence layer with a depth of about 3000 m, under the saddle-shaped pressure field. This category corresponds to lighter air pollution, with a frequency of 29 %. The PBL of the third category is laterally delineated by a cold-air damming AIB at the foot of the mountains on the windward side. It manifests as a low-temperature and weak-wind air mass accompanied by an elevated inversion and a convergent flow with a thickness as high as mountains. This PBL structure maintains through day and night within the AIB confined zone, while the ordinary diurnal variation of the PBL occurs outside this zone. 14 % of pollution episodes belong to this category. There remain about 16 % pollution episodes undefined by the AIB influence. They may need to be analyzed separately in the future.

Xipeng Jin et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-48', Anonymous Referee #1, 21 Mar 2022
    • AC1: 'Reply on RC1', Xipeng Jin, 13 May 2022
  • RC2: 'Comment on acp-2022-48', Anonymous Referee #2, 19 Apr 2022
    • AC2: 'Reply on RC2', Xipeng Jin, 13 May 2022

Xipeng Jin et al.

Xipeng Jin et al.

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Short summary
Meteorological discontinuities in the vertical direction define the lowest atmosphere as the boundary layer, while in the horizontal direction identify the contrast zone as the internal boundary. Both of them determine the polluted air mass dimension over the North China Plain. This study reveals the boundary layer structures under three categories of internal boundaries, which are modified by thermal, dynamical, and blending effects. It provides a new insight to understand regional pollution.
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