Abstract/Summary

Air pollution is a major issue in China and one of the largest threats to public health. We investigated future changes in atmospheric circulation patterns associated with haze events in the Beijing region, and the severity of haze events during these circulation conditions, from 2016 to 2049 under two different aerosol scenarios: a maximum technically feasible aerosol reduction (MTFR) and a current legislation aerosol scenario (CLE). In both cases greenhouse gas emissions follow the Representative Concentration Pathway (RCP) 4.5. Under RCP4.5 with CLE aerosol the frequency of circulation patterns associated with haze events increases due to a weakening of the East Asian winter monsoon via increased sea level pressure over the North Pacific. The rapid reduction in anthropogenic aerosol and precursor emissions in MTFR further increases the frequency of circulation patterns associated with haze events, due to further increases of the sea level pressure over the North Pacific and a reduction in the intensity of the Siberian high. Even with the aggressive aerosol reductions in MTFR periods of poor visibility, represented by above normal aerosol optical depth (AOD), still occur in conjunction with atmospheric circulation patterns currently associated with haze in the current climate. However, the intensity of poor visibility decreases in MTFR, so that haze events are less dangerous in this scenario by 2050 compared to CLE, and relative to the current baseline. This study reveals the competing effects of aerosol emission reductions on future haze events through their direct contribution to haze and their influence on the atmospheric circulation patterns. A compound consideration of these two impacts should be taken in future policy making.