Impacts of land use /cover change on spatial variation of land surface temperature in Urumqi, China

摘要

Land use/cover change (LUCC) has significant impacts on regional environment. Land surface temperature (LST) is an important indicator for assessment of regional environment especially in big cities where urban heat island is very obvious. In this study, remote sensing and geographic information systems (GIS) were used to detect LUCC for assessment of its impacts on spatial variation of LST in Urumqi, a big city in northwestern China. Two Landsat TM/ETM+ images respectively in 1987 and 2002 were examined for LUCC detection. LST and NDVI were computed from the images for different land use/cover types. Impacts of LUCC on regional environment can be assessment through LST difference during the period. Our results showed that land use/cover changes were very obvious in Urumqi between 1987 and 2002 due to rapid expansion of the city. Urban/built-up land increased by almost twice in the period, while the barren land, the forestland and water area declined. The increase of urban/built-up land was mainly from the barren land. Spatial distribution of LST in the city has been highly altered as a result of urban expansion. The urban/built-up area had LST increase by 4.48% during the period. The LST difference between built-up land and other land use/cover types also significantly increased between 1978 and 2002, with high LST increase area corresponding to the urban expansion regions. Moreover, changes of vegetation also had shaped many impacts on spatial variation of LST in the city. We found that NDVI has a negative correlation with LST among the land use/cover types. This probably is due to the ecological function of vegetation in cooling down the surface from high evapotranspiration. The study demonstrated that combination of remote sensing and GIS provided an efficient way to examine LUCC for assessment of its impacts on regional environment in big cities.