Remote Sensing Image-based Analysis of the Relationship between Urban Heat Island and Vegetation Fraction

As the relationship between land surface temperature (LST) and Normalized Difference Vegetation Index (NDVI) can not be able to effectively apply after NDVI reached saturation[1]. In this study, the vegetation fraction, which derived from Dimidiate Pixel Model, as the indicator of vegetation abundance has been introduced to analyze remote sensing of the change of urban heat islands (UHIs). Landsat TM and ETM+ images of Wuhan from 1988 to 2002 were selected to retrieve the brightness temperatures and vegetation fraction. Results show that, from 1988 to 2002, the intensity of UHI was increased and the average vegetation fraction of the whole region was decreased. The urban ratio index (URI) of the study area was increased from 0.153 to 0.170 and the average vegetation fraction decreased from 58.41% to 50.45%. Our analysis showed that the UHI effect has become more prominent in areas of rapid changes as its vegetation fraction decreasing in the past decade. The brightness temperature had strong correlation with vegetation fraction,and the coefficient of determination value (R^2) was 0.867, 0.843, 0.841, 0.843 of 1988, 1991, 1996 and 2002.