Intraseasonal variation of the northeast Asian anomalous anticyclone and its impacts on air 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 in the North China Plain (NCP) on the interannual timescale. However, there is considerable intraseasonal variability in the NAAA in early winter (November to January), and the corresponding mechanism of its impacts on air pollution in the NCP is not well understood. Here, we find that the intraseasonal NAAA usually establishes quickly on day −3 with a life span of eight days, 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 under this background, the probability of regional air pollution for at least three days in the NCP is as high as 69 % (80 % at least two days) in NDJ period 2000−2021. In particular, air quality in the NCP tends to deteriorate on day 2 prior to the peak day of the NAAA and reaches a peak on day −1 with a life cycle of four days. In the course of air pollution, a shallower atmospheric boundary layer and stronger surface southerly wind anomaly associated with the NAAA in the NCP appear 1 day earlier than poor air quality, which provides dynamic and thermal conditions for the accumulation of pollutants and finally occurrence of the air 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 buildup of the NAAA. The present results quantify the impact of the NAAA on air pollution in the NCP on the intraseasonal timescale.

Key Role of Arctic Sea‐Ice in Subseasonal Reversal of Early and Late Winter PM2.5 Concentration Anomalies Over the North China Plain

“…In addition, a shallower boundary layer height due to the anomalous temperature inversion in ND supports the accumulation of pollutants (Figure 3b). These conditions are related to the anticyclonic anomaly over Northeast Asia as a part of zonal wave train shown in Figure 2a (An, Chen, Fu, et al., 2022; An, Chen, Hu, et al., 2022), and together result in a higher PM 2.5 concentration anomaly over the NCP in early winter (Figures 1a and 1c). For example, such anticyclonic anomaly not only increases atmospheric stability through anomalous descent (Figure 3b), but also increases temperature and humidity by weakening the East Asian winter monsoon and transporting the anomalous warm and moist air flows (Figures 2a, 3a, and 3d).…”

“…Daily PM 2.5 concentration data in China was from Tacking Air Pollution (Geng, Xiao, et al., 2021), which has a horizontal resolution of 10 km since March 2000. This PM 2.5 data set was widely used to study air pollution in China (e.g., An, Chen, Hu, et al., 2022; Yin, Duan, et al., 2022).…”

Recent progress in understanding the interaction between ENSO and the East Asian winter monsoon: A review

“…El Niño is usually accompanied by a weakening of the EAWM, which advects warm and moist air to East Asia such as southern China, Japan, and Korea; reversed conditions are observed in the La Niña winters, but with smaller amplitudes (e.g., Kug et al, 2012;Son et al, 2014;Ma et al, 2018a). Air pollution over northern China tends to get worse (lighter) during the El Niño (La Niña) winters due to the weakening (strengthening) of EAWM (An et al, 2022a;An et al, 2022b;Zhao et al, 2022).…”