北京城区热岛环流对山地-平原风的调节作用

Modulation of Urban Heat Island Circulation on Mountain-Plain Wind in the Beijing Area

利用2002年北京市自动气象站网的逐时资料,采用统计方法对北京城市水平风场的散度、"城市热岛"强度和风向频率的日变化特征进行了分析,并总结归纳出在弱天气系统形势下(地面风速<3级)北京地区风场的基本形态。结果表明:1)北京"城市热岛"环流是存在的,但只是对区域性的山地-平原风起调节作用。2)在作用相当的因素(如山地-平原风、热岛强度和大气稳定度)控制下,夏季的"城市热岛"环流造成城区风场的辐合特征。3)其他季节的"城市热岛"环流,主要由山地-平原风控制,即刮山地风时,北京城郊的风场表现为向城区的辐合;刮平原风时,北京城区风场表现为辐散特征。

By statistically analyzing hour-to-hour data of Urban Automatic Weather Station Network recorded in Beijing City during 2002, diurnal characteristics of urban heat island intensity, wind convergence/divergence, and wind direction frequency are presented, and then wind field patterns are induced under weak weather conditions in the Beijing area. The analysis demonstrates that urban heat island circulation （UHIC） possibly exists under weak weather conditions, but it only modulates the regional mountain-plain wind system. In summer and under the control of factors such as mountain-plain wind, urban heat island and atmospheric stability, which are almost equal in action, UHIC results in convergence of wind field in urban area in other seasons, UHIC mainly is controlled by mountain-plain wind, namely, when mountain wind blows, wind convergences from suburban to urban center when plain wind blows, wind divergences from urban center to suburban.