Analysis of the relationship between urban heat island and vegetation cover through Landsat ETM+:A case study of Shenyang

Urban heat island is a phenomenon that the temperature of urban area is higher than surrounding rural area or suburban area, which is considered as one of major problems in the 21^st century posed to human beings. With the extension of urban area, the phenomenon shows an increasing trend. So we must find the critical factor and analyze the relationship between them in order to resolve the problem of urban heat island. In this paper the heat island in Shenyang and the relation between urban heat island and vegetation were analyzed based on Landsat ETM+ data. After correcting the data using the 6s radiative transfer code and atmospheric correction tool developed by Barsi et al., the land surface temperature was derived from thermal infrared data according to Planck function and vegetation index (NDVI) was derived according to the ratio visible band and near infrared band. The results show that the temperature difference is large so that the urban heat island effect is obvious in Shenyang city and there is a strong linearly negative correlation between land surface temperature and NDVI. This is probably due to the ecological function of vegetation in cooling down the surface from high evapotranspiration. Though the urban heat island is complex and the vegetation is only an influential factor, the result of this study can be useful for policy-makers, planners, and the general public to understand urban heat island and realize what kinds of urban heat land mitigation strategies are available.