多空间尺度下城市热环境与不透水面聚集密度响应关系

Response relationship between urban thermal environment and impervious surface distribution density at multi-spatial scale:A case study of Beijing

针对以往城市热环境与不透水面聚集密度响应规律研究不足的问题,本文以北京市为例,基于MODIS数据计算城建区与边缘区平均温度差值为热岛强度,结合热岛强度等级特征,选取热岛强度等级期望值较高的6个典型区域(Ⅰ西二旗、西三旗、回龙观,Ⅱ东四、地安门、新街口,Ⅲ丰台区中部,Ⅳ四惠、定福庄、东坝,Ⅴ石景山区,Ⅵ北四环四季青桥附近),研究热岛强度等级与不透水面聚集密度的响应关系;进而利用Landsat数据反演地表温度,研究城建区与精细尺度下地表温度对不透水面聚集密度响应临界点与最优尺度。结果表明:(1)不同热岛强度等级的出现频率、其在白天与夜间的变化程度与不透水面聚集密度有一定相关性,且相近的不透水面聚集密度下所表现出热岛强度的变化特征相似。(2)主要城建区内地表平均温度与不透水面聚集密度的分布特征存在较显著的一致性,随着尺度半径r的增大其响应越明显。且地表温度对不透水面聚集密度的响应存在一个临界点,随着尺度半径r减小,响应临界点逐渐增大:尺度半径r=1000 m时,不透水面聚集密度达到60%后其影响趋于减弱;r=500 m、r=300 m时临界点分别为69%与83%。(3)不同典型区域的最优尺度存在差异,西二旗、西三旗、回龙观最优尺度为150 m,东四、地安门、新街口与四环四季青桥附近为60 m,而季节变化对最优尺度的影响较小。该最优尺度可在一定程度上衡量不同区域不透水面分布的破碎程度及地表类型的单一程度。本研究可为城市规划与管理、城市热岛治理提供参考依据。

In view of the insufficient research on the response law of urban thermal environment and the Impervious Surface Distribution Density(ISDD),this paper selected Beijing as a case study.On the basis of the MODIS data,the average temperature difference between the urban construction and marginal areas was calculated as the UHI intensity(UHII).In combination with the characteristics of the UHII level,six typical regions( Ⅰ Xierqi,Xisanqi,Huilongguan,Ⅱ Dongsi,Xi’anmen,Xinjiekou,Ⅲ the middle of Fengtai District,Ⅳ Sihui,Dingfuzhuang,Dongba,ⅤShijingshan District,Ⅵnear the Sijiqing bridge on the North Fourth Ring Road) with a high expected UHII level were selected to study the response relationship between the UHII level and the ISDD.Finally,Landsat data was used to invert the surface temperature to study the critical point and optimal scale of surface temperature response to the ISDD in urban construction areas and typical regions.Results show that the following.(1) The frequency of occurrence of UHII levels,their variation degree during the day and at night have a certain correlation with the ISDD,and the variation characteristics of the UHII under similar ISDDs are the same.(2) The distribution characteristics of the surface mean temperature in urban construction areas and the ISDD are obviously consistent.As the scale radius r increases,the response is more obvious.Besides,there are critical points for the response of the surface temperature to ISDD.The response of critical points gradually increases with the decrease of scale radius r.When scale radius r=1000 m,the ISDD reaches 60%,and its influence tends to weaken;the critical points of r=500 m and r=300 m are 69% and 83%,respectively.(3) The optimal scales of different typical regions have differences.The optimal scale of Xierqi,Xisanqi,and Huilongguan is 150 m,and that of Dongsi,Di’anmen,Xinjiekou,and Qingqiao near the fourth ring is 60 m.However,seasonal changes have little impact on the optimal scale.The optimal scale can measure the degree of fragmentation of the impervious surface distribution in different regions and the single degree of surface type to some extent.This study can provide a reference for urban planning and UHI governance.