Regulation of Synoptic Circulation in Regional PM_2.5 Transport for Heavy Air Pollution: Study of 5‐year Observation Over Central China

Abstract

Regional transport of air pollutants is modulated by large‐scale synoptic circulation, which has been poorly understood for heavy air pollution in the downstream receptor region. In the present study of 5‐year (2015–2019) observation, we targeted the Twain‐Hu Basin (THB), a region of heavy PM2.5 pollution over central China, to investigate the regulation of synoptic circulation governing regional PM2.5 transport for heavy air pollution. It was found that regional transport of PM2.5 predominated 65.2% of the heavy pollution events (HPEs) over the THB based on the statistics of observational environment and meteorology. By employing the FLEXPART‐WRF model, the regional transport of PM2.5 from upwind areas in central and eastern China (CEC) to receptor region in the THB was identified with three prominent pathways in the northerly, northeasterly, and easterly directions respectively. We then used T‐mode principal component analysis in conjunction with the K‐means cluster method to categorize synoptic circulations, and it was recognized that three regional PM2.5 transport pathways for the HPEs over central China were governed respectively by three patterns of synoptic circulation over CEC with (a) weak high air pressure to the north (13.3%), (b) strong high air pressure to the northeast (46.7%), and (c) weak high air pressure to the east (40.0%). This study reveals a significant modulation of large‐scale synoptic circulation for regional transport of air pollutants in environmental change.

Improving Below‐Cloud Scavenging Coefficients of Sulfate, Nitrate, and Ammonium in PM2.5 and Implications for Numerical Simulation and Air Pollution Control

“…The significance of washout on cleaning PM 2.5 compounds were quantified by the improved Λ schemes in a typical precipitation event following a haze (PM 2.5 > 75 μg m −3 ) over CC. Before the rainfall event, a strong transport process was first identified by specific atmospheric circulations (Hu et al., 2022) (Figure S21 in Supporting Information ) and non‐stagnant meteorological conditions (C. Yu et al., 2020) (Figure S22 in Supporting Information ), which rapidly increased PM 2.5 and its composition concentrations and promoted haze formation (Figure S23 in Supporting Information ). To clarify the effects of transport on PM 2.5 compounds, the SNA concentrations were scaled by CO to exclude impacts of meteorology (Bertschi, 2005; Ge et al., 2018; T. Wang, 2004).…”

“…Central China (CC) is impacted by air pollutants from its upwind source regions due to the unique basin terrain (X. Sun et al., 2022; C. Yu et al., 2020) and specialized atmospheric circulation (Hu et al., 2022). It often suffers severe PM 2.5 pollution in winter (Yan et al., 2021).…”

“…Sun et al, 2022;C. Yu et al, 2020) and specialized atmospheric circulation (Hu et al, 2022). It often suffers severe PM 2.5 pollution in winter (Yan et al, 2021).…”

Application of stable index and transport index for regional air pollution over Twain-Hu Basin

“…To sum up, the STI cannot fully reflect the variation characteristics of PM 2.5 concentration in the THB. The THB is significantly affected by transmission pollution (Bai et al, 2022;Hu et al, 2022), so the construction of the TRI is also significant. The combination of STI and TRI can better interpret the regional air pollution process in the THB.…”

“…The transit of cold front drives pollutants from the upper wind to the lower reaches, leading to regional polluted weather, which is also an essential meteorological reason for heavily polluted weather (Kang et al, 2019;Hu et al, 2022). Simulation results show that PM2.5 in central and eastern China contributes 60.3% to particulate matter pollution in the THB (Shen et al, 2022).…”