[Impact of Mountain-Valley Wind Circulation on Typical Cases of Air Pollution in Beijing].

The impact of mountain-valley wind circulation on the typical examples of pollution was analyzed through the selected pollution process, combining with the hourly PM concentrations and meteorological data in Haidian, Shangdianzi and Lishuiqiao in Autumn and Winter from 2013 to 2015, and also the data of Tower of atmospheric, wind profile of Haidian and automatic meteorological stations in the same period. The analysis showed that the average wind speed of valley wind was greater than that of the mountain wind, and they both would be "broken" during the conversion time in the mountain-valley wind days. In contrast with the mountain wind, the average duration of valley wind in autumn was longer than that in winter, and the start time of valley wind in autumn was earlier than the same wind in winter; influenced by the topography of Beijing area, the direction boundary of the transformation between mountain-valley wind was northeast-southwest.