长春市城市扩张及其微气候响应

Evolution of Urban Expansion and Its Microclimate in Changchun

针对目前城市化和热岛效应研究多为单一定性评价和半定量化研究,缺乏耦合分析的问题,提出了一种可行的定量耦合分析方法。分析了长春市建设用地扩张和热岛效应的时空演变特征及其关系。首先收集遥感数据,采用归一化差分复合指数阈值分类法提取建设用地,之后采用辐射传输法反演地表温度,以此为基础计算扩张强度、热岛强度等指数,进而将城市扩张与微气候变化进行相关性分析。结果表明,长春市建设用地1990—2016年间增加了608.85 km^2,2000年后陡增,扩张模式由面状扩张变为沿道路辐射状扩张、飞地式扩张。城市扩张初期,相对热岛效应显著,随着建设用地的扩大,热岛面积增大,但是强度下降。相关性分析表明,单位格网内城市用地所占面积高于40%时地表温度上升明显。

In view of the problem that the current studies on urbanization and heat island effect are mostly single qualitative evaluation and semi-quantitative research and are lack of coupling analysis,a feasible quantitative coupling analysis method was proposed.This study analyzed the spatial and temporal evolution characteristics of construction land expansion and heat island effect in Changchun and their relationship.Firstly,collect remote sensing data,and use the threshold classification method of normalized difference composite index to extract construction land.Secondly,use radiation transfer method to retrieve surface temperature,and to further calculate the index of expansion intensity and heat island intensity.And then,analyze the correlation between urban expansion and microclimate change.The results show that the construction land in Changchun increased by 608.85 km^2 from 1990 to 2016,and increased sharply after 2000.The expansion mode changed from planar expansion to radial expansion along the road and enclave expansion.In the initial stage of urban expansion,the relative heat island effect is significant.With the expansion of construction land,the area of heat island increases,but the intensity decreases.The correlation analysis shows that the surface temperature increases obviously when the area of urban land in the unit grid is more than 40%.