The Severe Haze Process in 16-21 December 2016 and Associated Atmospheric Circulation Anomalies

The severe haze occurred over North China and Huanghuai area in 16-21 December 2016 was analyzed and the atmospheric circulation anomalies were diagnosed to reveal one of the important causes. The coverage of this severe haze was 71×10⁴ km², and the duration was six days. The highest measured hourly PM2.5 concentration was above 1100 μg/m³. The East Atlantic/West Russia and West Pacific teleconnections (mid-upper level) and Arctic Oscillation (near surface) were in their positive phases and affected local atmospheric circulations and meteorological conditions, which were favorable for the occurrence of haze. The anti-cyclone over North China and Huanghuai area effectively confined the vertical motion and weakened the surface wind speed. Meanwhile, there existed an obvious weak low pressure system near the surface with warm and humid southerly winds. From the perspective of local meteorological conditions, the weak surface wind and high humidity condition as well as the shallow boundary layer were most important contributors to the occurrence of the severe haze in 16-21 December 2016.