基于地表通量特征的城市不透水表面定量热红外遥感反演

城市不透水地表格局通过改变城市下垫面结构,引起地表反照率、比辐射率、地表粗糙度的变化,从而对地表辐射和能量平衡产生直接影响。不透水地表能增强地表显热通量,导致地表波文比升高,因此地表波文比的空间差异可推算城市人工不透水表面的分布。本研究选择北京市为实验区,应用Landsat TM卫星热红外遥感数据,采用PCACA模型及理论定位算法,对城市地表波文比进行反演,进而计算遥感地表波文比空间分布数据与城市不透水表面比例数据之间的相关关系,构建回归方程,实现北京市城区与近郊区人工不透水表面百分比分布的定量估算,最后以高分辨率遥感数据获取的城市人工不透水表面比例数据进行结果验证。结果表明,采用PCACA模型定量反演城市地表波文比数据,利用地表波文比数据与不透水表面比例数据之间的相关关系可实现城市人工不透水表面百分比数据的定量估算;波文比值不仅可在遥感像元水平定性判定不透水像元,还可对混合像元中的不透水比例进行较高精度的定量反演,其相关系数R²值为0.731。此方法有效地揭示了城市不透水下垫面对地表热通量影响的机制以及空间定量关系。

The Surface Flux Characteristics Based Quantitative Thermal Infrared Remote Sensing Inversion of Urban Impervious Surfaces

Urban impervious surface pattern causes changes of surface albedo, emissivity and surface roughness by changing the structure of urban surface, and thereforeinfluences the balance of surface radiation and energy directly. Impervious surfaces will increase the surface sensible heat flux, resulting in a rise of surface Bowen ratio,which provides a physical basis forpredicting the distribution of urban artificial impervious surfaces through spatial differences of Bowen ratio. In this study, we selected Beijing as the experimental areaand appliedthe PCACA model and theoretical positioning algorithm to calculate the Bowen ratio of urban surfaces with Landsat TM satellite thermal infrared remote sensing data. Furthermore, based on the correlation between the spatial distribution of surface Bowen ratio and the proportion of urban impervious surfaces, a regression equation was built to estimatethe percentage of Beijing urban artificial impervious surfaces distribution. The result was tested and verifiedwith the artificial impervious surface ratio of the city extracted from high-resolution remote sensing data. The result shows that in the method which inverts urban surface Bowen ratio data using the PCACA model, and then estimates the ratio of urban artificial impervious surface percentage distribution based on the correlation between the surface Bowen ratio data and the proportion data of urban impervious surfaces, Bowen ratio can be used not only to qualitatively determine if a remote sensing pixel is the impermeable at a pixel level, but also to calculate with high accuracy the proportion of the impermeable part of a mixed pixel, and the correlation coefficient R2value between the estimated impervious surface ratio based on Bowen ratio and the real proportion was 0.731.This method reveals the mechanism of the impact of the urban impervious land surfaceson heat flux and their spatial quantitative relationship.