北京地区局地环流观测分析

摘要

应用2008-2015年逐时自动气象站观测资料,分析了北京地区局地风场的分布特点及季节性变化.结果表明:(1)北京地区局地风场受山谷风和城市热岛环流的共同影响,风速主要沿地形梯度分布.西部、北部高海拔山地风速较大,平原地带风速相对较小.平均而言,东西方向的局地风强度约为0.16 m·s-1,南北方向的局地风强度约为0.07 m·s-1.(2)局地风速在季节分布上以夏季为最大,冬季为最小.其日变化为双峰型结构,于每日09及16时左右达到峰值区.(3)局地风速的u、v分量在正(负)距平的维持时长、日振幅值上存在较明显的差异.低层风场在午后到前半夜以东南风为主,后半夜开始到正午前则以西北风为主.%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.