Measuring the Pattern of High Temperature Areas in Urban Greenery of Nanjing City, China

Most studies are concerned with the cooling effect of urban greenery, but some have also revealed that some patches changed from normal temperature areas (NTAs) into high temperature areas (HTAs). Landsat TM images and ArcGIS software are used to analyze the HTA patterns in Nanjing, China. The HTAs' lower limit temperature was defined as the 30.26 degrees C and the percentage of the HTAs in all greenery was 24.87%. The disturbance on the cooling effect existed but not evidently. The average impervious ratio (IR) and surface temperature (ST) of HTAs, respectively, were 3.76 times and higher 2.86 degrees C than those of NTAs. The structure of NTAs' IR levels was extremely uneven but the HTAs' were relatively even. However, the co-coefficient between the IR and ST in the whole greenery was small. Sampling analysis with the same ST and IR revealed that the complex environment in green buffer affected temperature differences; The adjacent HTAs, with its 89.78% in the study area, largely along the green patch, were far more than independent HTAs and presented a ring shape. Thus, the significantly heterogeneous urban environment inevitably resulted in diverse factors forming HTAs.