Key Role of Arctic Sea-Ice in Subseasonal Reversal of Early and Late Winter PM_2.5 Concentration Anomalies Over the North China Plain

The PM2.5 (fine particulate matter with diameter <= 2.5 mu m) concentration anomalies over the North China Plain (NCP) in early and late winter sometimes show a subseasonal reversal, which brings a great challenge for precise control of air pollution, and mechanisms are not well understood. This paper reveals the key role of the Barents Sea sea-ice in this reversal. In early winter, a negative Scandinavian-like pattern causes an anticyclonic anomaly over Northeast Asia and thus leads to the positive PM2.5 concentration anomaly over the NCP. In addition, anomalous warm advection associated with the positive North Atlantic Oscillation-like pattern accelerates winter sea-ice loss in the Barents Sea, especially in late winter, which increases the surface turbulent heating flux. These heating causes a negative Polar/Eurasian-like pattern that induces a cyclonic anomaly over Northeast Asia and eventually leads to a negative PM2.5 concentration anomaly over the NCP in late winter. Vice versa.