The two-way feedback mechanism between unfavorable meteorological conditions and cumulative aerosol pollution in various haze regions of China

Abstract

Abstract. Accompanied by unfavorable meteorological conditions with stable stratification in various haze regions of China, persistent heavy aerosol pollution episodes (HPEs) lasting more than 3 consecutive days frequently occur, particularly in winter. In the North China Plain (NCP), explosive growth of fine particulate matter smaller than 2.5 µm in diameter (PM2.5), which occurs during some HPES, is dominated by a two-way feedback mechanism between more unfavorable meteorological conditions and cumulative aerosol pollution. However, the existence of a two-way feedback mechanism such as this in other key haze regions in China is uncertain; these regions include the Guanzhong Plain (GZP), the Yangtze River Delta (YRD) region, the Two Lakes Basin (TLB; a large outflow basin connected to Hubei Province and Hunan Province), the Pearl River Delta (PRD) region, the Sichuan Basin (SB), and the Northeast China Plain (NeCP). In this study, using surface PM2.5 and radiation observations, radiosonde observations, and reanalysis data, we observed the existence of a two-way feedback mechanism in the six abovementioned regions. In the SB, this two-way feedback mechanism is weak due to the suppression of cloudy mid-upper layers. In the more polluted NCP, the GZP, and the NeCP, the feedback is more striking than that in the YRD, the TLB, and the PRD. In these regions, the feedback of worsened meteorological conditions on PM2.5 explains 60 %–70 % of the increase in PM2.5 during the cumulative stages (CSs). For each region, the low-level cooling bias becomes increasingly substantial with increasing aerosol pollution and a closer distance to the ground surface. With PM2.5 mass concentrations greater than 400 µg m−3, the near-ground bias exceeded −4 ∘C in Beijing and reached up to approximately −4 ∘C in Xi'an; this result was caused by accumulated aerosol mass to some extent. In addition to the increase in PM2.5 caused by the two-way feedback, these regions also suffer from the regional transport of pollutants, including inter-regional transport in the GZP, trans-regional transport from the NCP to the YRD and the TLB, and southwesterly transport in the NeCP.

Exploring wintertime regional haze in Northeast China: role of coal and biomass burning

“…(Haze-I) and 1% (Haze-II) reported in this study (Figure 4), suggesting that the contribution of industrial emissions to regional haze in Northeast China is much smaller than that in the NCP. Many studies have summarized formation mechanisms of general regional haze in North China: regional transport of air pollutants (Zheng et al, 2015b), massive formation of secondary aerosols (Shao et al, 2019), and two-way feedback between adverse meteorological conditions and pollutant accumulation (Zhong et al, 2019). We found that the Haze-I formation in this study can be attributed to these three formation mechanisms (Figure 8).…”

“…In China, regional heavy hazes frequently occur in the North China Plain (NCP) (Zhao et al, 2013) and Northeast China (Ma et al, 2018) during winter. In the past decades, the regional haze formation mechanisms in the NCP have been intensely investigated (Chen et al, 2017b;Cheng et al, 2016;Li et al, 2015;Liu et al, 2017c;Tao et al, 2014;Tian et al, 2015;Wang et al, 2016;Wang et al, 2019;Wang et al, 2014;Xing et al, 2019;Zheng et al, 2015b;Zhong et al, 2019). Adverse meteorological conditions (e.g., low wind speeds and stable atmospheric boundary layer ) can induce preliminary formation of hazes during winter (Zheng et al, 2015b;Zhong et al, 2019).…”

“…In the past decades, the regional haze formation mechanisms in the NCP have been intensely investigated (Chen et al, 2017b;Cheng et al, 2016;Li et al, 2015;Liu et al, 2017c;Tao et al, 2014;Tian et al, 2015;Wang et al, 2016;Wang et al, 2019;Wang et al, 2014;Xing et al, 2019;Zheng et al, 2015b;Zhong et al, 2019). Adverse meteorological conditions (e.g., low wind speeds and stable atmospheric boundary layer ) can induce preliminary formation of hazes during winter (Zheng et al, 2015b;Zhong et al, 2019). Massive numbers of primary particles from industries, households, and vehicular exhaust emissions (e.g., fly ash, metal, primary organic matter, and soot particles) are the major aerosols in winter hazes (Chen et al, 2017b;Tian et al, 2015;Wang et al, 2019).…”

“…Rapid production of secondary aerosols (e.g., sulfates, nitrates, and secondary organics) via heterogeneous reactions under high RH mainly elevates haze levels and causes regional hazes (Liu et al, 2017c;Wang et al, 2016;Xing et al, 2019). The two-way feedback between accumulation of air pollutants and depression of the atmospheric boundary layer also aggravate haze pollution (Wang et al, 2014;Zhong et al, 2019). Moreover, regional transport of air pollutants is one of the important factors for the long duration of regional haze (Li et al, 2015;Tao et al, 2014;Zheng et al, 2015b).…”

Multi-scale processes in severe haze events in China and their interactions with aerosols: Mechanisms and progresses

“…研究 还显示, 该反馈机制与气溶胶浓度密切相关, 当气溶胶 浓度较低时反馈效应不明显, 而当气溶胶浓度较高时 反馈效应显著增加 [65] . Zhong等人 [125] 味 着 液 相 非 均 相 反 应 在 气 -粒 过 程 中 发 挥 主 导 作 用 [13,70] . Liu等人 [70] 的研究显示, 边界层高度的下降在 [126] ; 二是气溶胶粒 子作为云凝结核改变云的物理和微物理特征, 改变云 的辐射特征和降水过程, 影响太阳能在地气系统中的 分配(间接效应) [127~130] .…”