A modeling study of the regional haze over Hebei and surrounding areas
河北及周边地区霾污染特征的模拟研究

MM5-Models-3/CMAQ air quality modeling system was applied to simulate the regional air pollution over Hebei and surrounding areas. Six cities, including Shijiazhuang, Xingtai, Beijing, Tianjin, Taiyuan and Zhengzhou, were chosen to analyze the characteristics of the regional haze in this area. First, the hazy days were identified for the ten years from 2001 to 2010. It was found that the haze occurrence showed clear seasonal variations. The haze pollution was the most serious in wintertime, followed by summer and autumn. The lowest frequencies appeared in May, then April and June. During the modeling period (Dec. 2007), the average PM2.5 concentrations in hazy days were 1.6~3.1 times of those in non-hazy days, and the occurrence of the hazy days in the six cities showed very clear regionally synchronous characteristics. The compositions of PM2.5 in hazy days showed obvious differences as well. The concentrations of secondary particles such as sulfate and nitrate had a distinct increase in haze days, indicating that the secondary particles might be an important reason for the formation of the regional haze over Hebei and surrounding areas.