[Analysis of the Continuous Heavy Pollution Process in the Winter of 2016 in Beijing, Tianjin, and Hebei]

From December 16 to 21, 2016, continuous heavy haze occurred in the Beijing-Tianjin-Hebei region of China. To further understand the development mechanism of haze and improve the forecasting of haze events, a variety of data, background circulation, and the meteorological elements of this severe haze process were comprehensively analyzed. The results show that the process lasted for a long time, pollution intensity was high, influence area was wide, visibility was low, and external transport was the main cause. Aerosols were mainly distributed at a height of 600 m, and there was a certain extreme anomaly. The static weather index and air quality index showed a strong correlation. The air in the Beijing-Tianjin-Hebei region is controlled by zonal circulation in front of a high-pressure ridge, which maintains the westerly airflow. Cold-air activity is weak, and downflow is dominant. The water vapor content is low, the cloud cover is limited at high altitudes, and a warm ridge extends northwards at low altitudes. Limited static wind on the ground, high relative humidity, and low mixing-layer height are not conducive to the horizontal and vertical diffusion of pollutants.