Dynamic change of heat environment in Hefei city based on GIS
More and more environmental problems have appeared with urbanization.Among these problems,urban heat island phenomenon was specially obvious.The paper simulated the ground brightness and the normalized difference vegetation index(NDVI) of Hefei city in the year of 2003 and 2007 based on remote sensing(RS) and geographical information system(GIS) technologies,so as to study the spatial pattern and the regularity of spatial-temporal changes of urban heat field distribution.The result shows as follows:heat-island effects were prominent in the built-up area of Hefei in both of 2003 and 2007.The character of urban thermal distribution in 2003 is similar as that in 2007,but the tendency of heat-island effect was alleviated in 2007.The areas were decreased 1.8 km2 and 52.1 km2 with high temperature and inferior high temperature,while the area with inferior increased 142.61 km2 low temperature.Vegetation coverage was obviously increased in 2007 compared with that in 2003,and the area of high vegetation coverage was increased by 35.56 km2.In 2007,the area which value is under zero of NDVI decreased by 116.57 km2.There is a significant negative correlation between temperature and vegetation level.Urban expansion and industrial district construction were main driving forces of urban heat island effects.Improving afforestation and increase vegetation coverage is a effective measure to alleviate heat-island effect.