上海地区高温过程中局地气候区尺度城市热岛特征分析

Analyzing the characteristics of the urban heat island on local climate zone scale during a heat wave event in Shanghai

本文以超大城市上海为研究对象,选取2017年7月为夏季代表月,利用自动气象站网观测得到的逐小时气温和风速数据,基于局地气候分区方法分析了上海市各局地气候区(Local Climate Zone,LCZ)在不同天气条件下的气温和城市热岛强度(Urban Heat Island Intensity,UHII)时空特征及其成因。结果表明:由于城市几何形态、建筑材料、表面不透水面占比以及人类活动的不同,上海市夏季典型月各LCZ的气温和UHII表现出明显差异,在高温日,UHII日变化曲线可以分为"W"型、浅"U"型、"V"型、日间型和平稳型这五类。城市建筑形态对城市风、热环境具有较为复杂的影响,UHII与天空可视因子(Sky View Factor,SVF)的相关系数在00时(北京时,下同)为负,而在12、16时为正,这是由于建筑物对城市冠层内的辐射传输的影响和建筑物的热量储存导致的;城乡风速之比与SVF在00、12和16时都为正相关,说明了高大密集的建筑物对风速有衰减作用,同时风速通过影响大气的平流输送进一步影响UHII。

This paper takes the mega-city Shanghai as the research object and selects July 2017 as the representative month of summer.Based on the hourly temperature and wind speed data observed by the network of automatic weather stations,the temporal and spatial characteristics of temperature and Urban Heat Island Intensity(UHII)of each Local Climate Zone(LCZ)in Shanghai under different weather conditions were analyzed by using the local climate zone scheme.Results show that the temperature and UHII of each LCZ in the representative summer month in Shanghai are significantly different due to various urban geometry,building materials,the proportion of impervious surface and human activities.On high temperature days,the diurnal variation curves of UHII can be divided into five types:"W"type,shallow"U"type,"V"type,day type and stable type.The urban architectural form has a complex influence on the urban wind and thermal environment.The correlation coefficient between Sky View Factor(SVF)and UHII is negative at 00∶00 BST and positive at 12∶00 BST and 16∶00 BST,which is due to the influence of buildings on the radiative transfer in the urban canopy and the heat storage of buildings.The ratio of urban and rural wind speed is positively correlated with SVF at 00∶00 BST,12∶00 BST and 16∶00 BST,indicating that tall and dense buildings have attenuation effect on wind speed,and the wind speed further affects the intensity of UHII by affecting the advection transport of the atmosphere.