Abstract:Based on mesoscale numerical simulation data and 15 surface meteorological observation data from 2007 to 2016, characterizing wind speed of local wind field is defined and the climatic characteristics of the diurnal variation of the local circulation in the Beijing Tianjin Hebei Region are analyzed. Also, the influence of air pollution and transportation in this area are analyzed. In addition, the atmospheric heavy pollution process in Beijing Area from 30 December 2016 to 7 January 2017 is studied. The conclusions are as follows. The change of the lower wind field in the Beijing Tianjin Hebei Region is the consequence of the interaction between the atmospheric circulation and the diurnal variation of the local wind fields. The mountain valley breeze causes the prevailing wind in the atmospheric boundary layer along the plains of Taihang Mountain and Yanshan Mountain to blow by north and south. The daily variation of the mountain valley breeze of the Beijing Tianjin Hebei Region has the characteristics of clockwise changes, which means that valley wind turns to mountain wind over night to morning and mountain wind turns to valley wind from afternoon to night. During the turning in the afternoon from valley wind to mountain wind, the “bow” airflow passage from southwest to northeast along east side of the Taihang Mountain and southern side of the Yanshan Mountain is easy to form. This airflow channel is formed at about 21:00 BT January, lasting about 3 h, and in July, it froms at about 18:00 BT lasting about 9 h. During the winter afternoon to the evening, valley wind is very strong, making pollutants accumulate easily in front of mountains by the barrier of the mountain and causing the pollution concentration to increase. The same situation occurs in summer after midnight.