Intraseasonal variation of the northeast Asian anomalous anticyclone and its impacts on PM<sub>2.5</sub> pollution in the North China Plain in early winter

Abstract

Abstract. The canonical view of the northeast Asian anomalous anticyclone (NAAA) is a crucial factor for determining poor air quality (i.e., higher particulate matter, PM2.5 concentrations) in the North China Plain (NCP) on the interannual timescale. However, there is considerable intraseasonal variability in the NAAA in early winter (November–January), and the corresponding mechanism of its impacts on PM2.5 pollution in the NCP is not well understood. Here, we find that the intraseasonal NAAA usually establishes quickly on day 3 prior to its peak day with a duration of 8 d, and its evolution is closely tied to the Rossby wave from upstream (i.e., the North Atlantic). Moreover, we find that the NAAA with a westward tilt might be mainly related to the wavenumbers 3–4. Further results reveal that against this background, the probability of regional PM2.5 pollution for at least 3 d in the NCP is as high as 69 % (80 % at least 2 d) in the Nov–Jan (NDJ) period 2000–2021. In particular, air quality in the NCP tends to deteriorate on day 2 prior to the peak day and reaches a peak on the next day with a life cycle of 4 d. In the course of PM2.5 pollution, a shallower atmospheric boundary layer and stronger surface southerly wind anomaly associated with the NAAA in the NCP appear 1 d earlier than poor air quality, which provides dynamic and thermal conditions for the accumulation of pollutants and finally occurrence of the PM2.5 pollution on the following day. Furthermore, we show that the stagnant air leading to poor air quality is determined by the special structure of temperature in the vertical direction of the NAAA, while weak ventilation conditions might be related to a rapid build-up of the NAAA. The present results quantify the impact of the NAAA on PM2.5 pollution in the NCP on the intraseasonal timescale.

Synergistic Effect of El Niño and Arctic Sea‐Ice Increment on Wintertime Northeast Asian Anomalous Anticyclone and Its Corresponding PM2.5 Pollution

“…(1982). The EOF1 represents changes in intensity of the NAAA (An, Chen, Hu, et al., 2022), with the corresponding principal component time series indicating a remarkable interannual variation (Figure 1d). The second EOF mode (EOF2), which accounts for 25.4% of the total variance, exhibits a north‐south seesaw pattern in the target with one center around 30°N, 140°E, and the other around 55°N, 140°E.…”

“…To investigate the spatial and temporal features of the interannual time‐scale NAAA in the early winter, the EOF analysis is used to obtain main modes of NDJ‐mean geopotential height anomaly at 500 hPa over the domain 25°–55°N, 100°–160°E during 1979–2019 (Figure 1). According to previous research, this domain can capture features of the NAAA to the most extent (e.g., An et al., 2020; An, Chen, Hu, et al., 2022; Song et al., 2016; L. Wang et al., 2009; W. Zhong et al., 2019).…”

“…The NAAA, which refers to an out‐of‐phase of the cyclonic anomaly here leading to a deeper East Asian trough, is characterized by the strongest positive deviation from the zonal mean over Northeast Asia (An, Chen, Hu, et al., 2022; Song et al., 2016; L. Wang et al., 2009). The NAAA has a quasi‐barotropic structure, and this structure is more evident in the mid‐to‐lower troposphere (An, Chen, Hu, et al., 2022; J. Wang et al., 2020; Yin, Li, & Wang, 2019; Yin, Wang, & Ma, 2019). The NAAA is usually accompanied by southerly wind anomaly and a lower atmospheric boundary layer height in North China, which is responsible for heavy haze here (e.g., An et al., 2020; An, Chen, Hu, et al., 2022; Chang et al., 2016; J. Wang et al., 2019; Yin et al., 2017).…”

“…The NAAA has a quasi‐barotropic structure, and this structure is more evident in the mid‐to‐lower troposphere (An, Chen, Hu, et al., 2022; J. Wang et al., 2020; Yin, Li, & Wang, 2019; Yin, Wang, & Ma, 2019). The NAAA is usually accompanied by southerly wind anomaly and a lower atmospheric boundary layer height in North China, which is responsible for heavy haze here (e.g., An et al., 2020; An, Chen, Hu, et al., 2022; Chang et al., 2016; J. Wang et al., 2019; Yin et al., 2017). The NAAA is linked to teleconnection in the form of the Rossby wave train, which can be induced by external forcing factors like sea surface temperature or sea ice.…”

“…It is well known that the major circulation related to the autumn and winter haze in North China is northeast Asian anomalous anticyclone (NAAA) (e.g., An et al., 2020; An, Chen, Hu, et al., 2022; An, Sheng, et al., 2022; J. Wang et al., 2020; Yin et al., 2017). The NAAA, which refers to an out‐of‐phase of the cyclonic anomaly here leading to a deeper East Asian trough, is characterized by the strongest positive deviation from the zonal mean over Northeast Asia (An, Chen, Hu, et al., 2022; Song et al., 2016; L. Wang et al., 2009). The NAAA has a quasi‐barotropic structure, and this structure is more evident in the mid‐to‐lower troposphere (An, Chen, Hu, et al., 2022; J. Wang et al., 2020; Yin, Li, & Wang, 2019; Yin, Wang, & Ma, 2019).…”