Synoptic characteristics of heavy air pollution day in winter over Harbin

Based on the data of the daily air quality report from China Ministry of Environmental Protection from 2000 to 2009, the day that air pollution index (API) is more than 200 is selected as the heavy pollution day, and its formation reasons were analyzed in terms of meteorological elements. The results show that the surface wind speed at 20:00 o’clock in the heavy pollution day in Harbin is the first level or calm. There is a temperature inversion phenomenon below 850 hPa for 85% heavy pollution days. The maximum inverse temperature is 0.73 ℃/100 m and occurs between the ground and 925 hPa. There is a descending motion below 850 hPa for 95% heavy pollution days. The primary synoptic situation of heavy pollution days is high pressure edge type, high pressure center type and low pressure edge type. It is not favorable to the horizontal and vertical transport of pollutants for the first two types, while it is favorable to the vertical transport of pollutants for the third type. The classification of synoptic situation could provide references for air pollution forecast.