LAUSR

Abstract. The persistent winter haze episodes that occurred in Beijing over the period 1980 to 2016 are examined based on both reanalysis and station data. On both interannual and intra-seasonal timescales, winter haze weather in Beijing is found to be associated with a significant atmospheric teleconnection pattern from the North Atlantic to Eurasia (Beijing). A positive North Atlantic Oscillation (NAO+) phase and a positive East Atlantic/West Russia (EA/WR+) phase can be observed as part of this teleconnection pattern (or an arched wave train). This study focuses mainly on the role of the NAO+ pattern, because the NAO index shows a closer relationship with winter haze frequency, especially after 1999, and the NAO+ pattern leads to the formation of persistent haze events over a longer period of time. Composite analyses show that a robust and consistent daily evolution of the wave train originates from an NAO+ pattern over the North Atlantic 8–10 days prior to the persistent haze events. The wave train continues propagating energy downstream, which leads to the formation and maintenance of a high-pressure center over northeast China, thus creating favorable meteorological conditions for the persistent haze events in Beijing. Thus, the NAO+ pattern is also an essential preceding background for the formation of the wave train, which can be treated as a potential predictor for persistent hazy weather. Corresponding to the NAO+ pattern, a tripolar sea surface temperature mode and intensified zonal wind over the North Atlantic also serve as prior signals for the persistent haze events. In addition, the propagation of the wave train is also associated with preceding significant positive sea ice concentration anomalies in the Barents–Kara Sea. Moreover, comparative analysis demonstrates that NAO+ winters are more advantageous to the formation and maintenance of winter haze weather in Beijing rather than NAO− winters.