Linkages between the atmospheric transmission originating from the North Atlantic Oscillation and persistent winter haze over Beijing

Abstract

In this study, the persistent winter haze that occurred over Beijing during 1980 to 2016 is examined using reanalysis and station data. On both interannual and daily-to-weekly timescales, the winter haze weather in Beijing is found to be associated with a pronounced atmospheric teleconnection pattern from the North Atlantic to Eurasia (Beijing). A positive western-type North Atlantic Oscillation (WNAO+) phase and a positive East Atlantic/West Russia (EA/WR+) phase are observed as part of this teleconnection pattern (an arched wave train). This study focuses on the role of the WNAO pattern, because the WNAO+ pattern acts as the origin of the atmospheric transmission, 8-10 d before the persistent haze events. Further analyses reveal that the WNAO+ pattern can increase the number of haze days and persistent haze events on interannual and daily-to-weekly timescales. Specifically, strong WNAO+ winters (above the 95th percentile) can increase the number of haze days and persistent haze events by 26.0% and 42.3%, respectively. In addition, a high WNAO index for the 5 d average (above the 95th percentile) predicts a 16.9% increase in the probability of haze days on Day 8 and a higher proportion of persistent haze days compared with an unknown WNAO state. Thus, the WNAO+ pattern is as a necessary prior background condition for the formation of the wave train and is a skillful predictor for persistent hazy weather. Corresponding to the WNAO+ pattern, intensified zonal wind and a north-south sea surface temperature tripolar mode over the North Atlantic also appear before persistent haze events on the daily-to-weekly timescale. On the interannual timescale, winters with a greater number of persistent haze days are also associated with a tripolar sea surface temperature (SST) mode over the North Atlantic that is situated farther northward.