Research On The Climatic Characteristics Of Low-altitude Local Wind Fields In Beijing-Tianjin-Hebei And Its Surrounding Areas

Based on mesoscale numerical simulation data and 15 surface meteorological observations data from 2007 to 2016,the reference wind of local circulation is defined,and the climatic characteristics of the daily variation of the local circulation in the BeijingTianjin-Hebei region are analyzed;at the same time,the WRF numerical simulation model was used to simulate the low air wind field on the plain in Taishan.it also analyzes the influence of air pollution and transportation in this area.In addition,three cases of the atmospheric heavy pollution process in Beijing area inFebruary 2014,December 2015 and December 2016 was studied in this paper.The conclusions are as follows: The change of the lower wind field in the Beijing-Tianjin-Hebei region is the result of the interaction between the atmospheric circulation and the daily variation of the local circulation.In winter,because of the freezing of Bohai and other reasons,the sea and land breeze is weaker.The wind field in Beijing Tianjin Hebei region is mainly controlled by the passing weather system and the valley wind in the local atmospheric circulation;the valley wind circulation has an obvious trend of clockwise change;the mountain wind popular time is 2,the valley wind prevalence was 13 times,mountain and valley wind change time is 11 and 23.In summer,because of the stronger solar radiation,the thermal difference is greater,and the local circulation is dominant in the Beijing Tianjin Hebei region,the sea breeze circulation structure is obvious,land and sea breeze reached prosperity period in 06 and 18,03 and 15 for the change of the breezes of the moment;the mountain valley wind circulation time prevalence was 03,15 times in the valley of the wind,wind and change time were 01 and 13.The mountain valley Breeze leads to the long leading wind direction in the atmospheric boundary layer along the plains of Taihang Mountain and Yanshan,which is north and south;The daily variation of the mountain valley Breeze of the Beijing-Tianjin-Hebei region has the characteristics of clockwise change,mountain wind turn to valley wind in the night to morning,and valley wind turn to mountain wind in the afternoon to night;In the afternoon,during the turn in the valley wind to mountain wind,the "bow" airflow passage along east side of the Taihang Mountain and southern side of the Yanshan and from southwest to northeast is easy to form;The airflow channel was formed at about 21 in January and lasted about 3 hours,it formed at about 18 in July and lasted about 9 hours;During the winter afternoon to the evening,the valley wind is very strong,it makes the pollutants accumulate easily in the front of the mountain by the barrier of the mountain and causing the pollution concentration to increase;the same situation will occur in the summer after midnight.In autumn and winter,the Beijing Tianjin Hebei region in the field were under the control of surface weather system makes the wind field performance of the Beijing Tianjin Hebei region for the southerly wind,is the Beijing Tianjin Hebei region,especially Beijing is an important cause of occurrence of heavy pollution weather process.During the heavy pollution weather process,local atmospheric circulation is dominant,the atmospheric stratification is stable,the local mixing layer height is low,it is easy to cause pollutants to be transported and accumulated locally.