Study on the thermal environment and its relationship with impervious surface in Beijing city using TM image

Urbanization transforms natural landscape to artificial impervious surface,which alters water and energy exchange between the land surface and the atmosphere and therefore leads to the urban heat island(UHI) effect.UHI is an important impact factor of the regional climate and ecological environment.How to observe and analysis the spatial distribution and impact factors of UHI has become an important issue of urban environmental research.By using a Landsat Thermal Mapper(TM) remote sensing image acquired on July 26,2011,the land surface temperature in Beijing city was retrieved by the generalized single channel method,and the imperious surface cover was calculated by the linear spectral unmixing method and Vegetation-Impervious surface-Soil(VIS) model.Then the surface thermal environment of Beijing city and its relationship with imperious surface were studied.Results indicate that the urban heat island effect in Beijing is obvious and shows a concentrated pattern.The heat island intensity in the southern urban area is stronger than the northern urban area.The spatial distribution of urban thermal environment shows similar pattern with that of impervious surface.Land surface temperature increases with the impervious surface cover and its rate depends on the value of impervious surface cover.When impervious surface cover is below 40%,land surface temperature increases steeply with the imperious surface cover in an exponential manner.When impervious surface cover is above 40%,temperature increases slightly with the imperious surface cover in a linear way.This paper reveals the relationship between the impervious surface and the surface temperature,and suggests that the impervious surface cover can be used as an important indicator of urban heat environment,which provides scientific reference for urban planning and environmental evaluation.