京津冀一次重污染过程的成因和来源

2016年12月16~21日，京津冀地区经历了一次大范围重污染过程.本文基于空气质量监测资料及实况天气图分析了此次极端区域重污染事件的天气成因，并利用嵌套网格空气质量预报模式（NAQPMS）对京津冀主要城市PM_2.5污染来源进行定量解析.结果表明：污染前中期500hPa高空为偏西气流伴空中回暖，后期转槽前偏南气流增温增湿明显；对应地面气压逐渐降低，辐合不断增强；垂直方向上，逆温层不断抬升加厚，中低层暖平流明显，风垂直切变小；大气长时间处于极度静稳状态也是造成此次重污染过程的天气因素.污染期间，京津冀各主要城市PM_2.5污染本地贡献占40%~60%；北京市PM_2.5本地贡献为48%，其中16~17日北京市主要受沿太行山东侧的西南向输送通道（邯郸-邢台-石家庄-保定-北京）影响，其后风速减小，北京本地及周边城市贡献增大.

The causes and sources of a heavy-polluted event in Beijing-Tianjin-Hebei region

From 16 to 21December 2016, the Beijing-Tianjin-Hebei region experienced a large-scale heavy pollution process. By using the pollutant concentration monitoring data, weather charts, the synoptic causes of the heavy air pollution were investigated in the present paper. The sources of PM_2.5 pollution in the main cities of Beijing, Tianjin and Hebei region were also analyzed quantitatively by using the Nested Air Quality Prediction Modeling System (NAQPMS). The results showed that it blew straight west wind in 500hPa accompanied with the warmer air in the early stage. Subsequently, it turned to south airflow ahead of trough accompanied with warm ridge, getting warmer and wetter substantially. Correspondingly, the ground pressure gradually decreased and the convergence increased continuously. In the vertical direction, the inversion layer continued to rise and thicken, the warm advection in the middle and lower layers was obvious, and the vertical shear of the wind was small. In summary, the atmosphere was in a state of extremely static stability, which led to a long and heavy pollution process in North China. During the period of air pollution, the local contribution of PM_2.5 pollution in major cities of Beijing, Tianjin and Hebei region was 40%~60%. The local contribution of PM_2.5 in Beijing was 48%, in which Beijing was mainly affected by the southwest transport channel along the east side of Taihang Mountain from 16 to 17December, then as the result of the decreased wind speed afterwards, local and surrounding cities contributed more.