北京"城市热岛"效应现状及特征

利用2002年北京自动气象站资料,对北京“城市热岛”效应现状进行了分析。为了与20世纪70年代的结果相比较,选择城区代表站为天安门广场站,城郊代表站为朝阳气象站站。与20世纪70年代相比,目前北京的“城市热岛”表现出一些新特点:1)利用城区与城郊日均温差表示的“城市热岛”强度的统计结果表明,现在北京的“城市热岛”效应在夏季最强,秋、冬季次之,春季最弱,2)除夏季“城市热岛”整天存在(午后的平均强度在2℃左右)以外,其他季节的午后,天安门广场地区经常出现“城市冷岛”现象。3)北京“城市热岛”消失的极限风速没有发生系统性变化,当风速>3级时,北京“城市热岛”基本上消失。作者还研究了北京“城市热岛”形成和消失的日变化特征,以及“城市热岛”强度对风速等气象要素变化的响应特征。值得指出的是,对强“城市热岛”的个案分析显示,冬季夜晚“城市热岛”强度经常表现出较大的波动性,与此相伴随,城郊地面风出现风向突变和风速的阵性现象。

The Study of the Urban Heat Island in Beijing City

The urban heat island in Beijing,China,is investigated using near surface temperature and wind data measured at automatic weather stations for 1-year period of 2002.1)Urban heat island(UHI)intensity in Beijing is strongest in summer;moderate in autumn and winter,and weakest in spring,by the measure of mean temperature departure between urban and suburban stations.2)The diurnal change of urban heat island intensity indicates that the installation and disappearance of UHI is very quickly.3)The response of UHI intensity to the change of wind speed is very quickly,and these two factors change with time in inverse phase way.When wind speed is greater than 3 Grade(Beaufort wind scale),UHI disappears.4)In winter evening UHI intensity changes in wave ways by companying with wind direction sharply change and wind gust at suburban surface wind.