Abstract:Based on the hourly observation of automatic weather stations in Beijing area during 2008-2015, the fine spatio temporal distribution characteristics of local circulation are studied. The analysis results are as follows. Firstly, the local wind pattern in Beijing is affected by the combined effect of the mountain valley wind and the urban heat island. Wind speed is basically distributed along the topographic gradient. In the western and northern mountains, the wind speed is greater than that in the plains and urban areas. Local circulation in Beijing area occurs through the whole year, although it varies seasonally. Averagely, the strength of the local wind in east west direction is 0.16 m·s-1 and in south north direction is 0.07 m·s-1. Secondly, local wind speed has seasonal changes. In summer, it is the maximum, followed by winds in spring and autumn, and in winter, it is the minimum. Its diurnal variation shows a bimodal structure, with peak value appearing at about 09:00 BT and 16:00 BT. Finally, there are significant differences with diurnal amplitude and positive or negative duration of anomaly between zonal local circulation component and meridional local circulation component. Analyses of the wind and temperature in Beijing area show that the local circulation presents diurnal variation obviously due to the mountain valley and urban temperature differences.