The Seesaw Pattern of PM<sub>2.5</sub> Interannual Anomalies Between Beijing‐Tianjin‐Hebei and Yangtze River Delta Across Eastern China in Winter
Xiaohui Liu, Bin Zhu, Tong Zhu, Hong Liao
Abstract
Abstract Since 2013, the winter mean fine particulate matter (PM 2.5 ) had been decreased significantly due to stringent emission controls in most of China. Nevertheless, we found a seesaw pattern of PM 2.5 interannual anomalies between Beijing‐Tianjin‐Hebei (BTH) and Yangtze River Delta (YRD). Using the multiple linear regression method, meteorology‐driven PM 2.5 interannual anomalies show that the low (high) PM 2.5 relative difference between BTH and YRD (RD B&Y ) was associated with the strong (weak) East Asian winter monsoon (EAWM). The strong EAWM transported more air pollutants from BTH to YRD. During the COVID‐19 lockdown period, due to the weak EAWM, air pollution still occurred in northern BTH, while the PM 2.5 was relatively low in YRD, causing high RD B&Y values. Our results imply that the activity of EAWM and characteristics of regional transport have obvious interannual variations, which is indispensable in evaluating the achievements of PM 2.5 quality management between up and downstream regions.