Study on the Urban Expansion and Urban Heat Island Effects Based on Remote Sensing - a Case Study in Mianyang

Taking Mianyang city as the study area and TM/ETM+ images of 1988, 2000 and 2007 as the data source. At first, image geometric correction must be done, and urban built-up area would be extracted by the methods of NDBI and supervised classification, then the brightness temperature map was generated by the radiometric calibration and retrieving brightness temperature. At last, the author analyzes the tendency of urban expansion and urban heat island effects. The results show that: (1) The urban built-up area of Mianyang city has been expanding rapidly during the past twenty years, which expanded mainly in the northeast from 1988 to 2000, and urban area increased from 18.3 km² to 52.6 km², the increased area is about 34.3 km²; from 2000 to 2007 the outstretched direction is northwest and urban area increased from the 52.6 km² to 88.1 km², the increased area is about 35.5 km², the direction of expansion is limited by the Fujiang river and Anchang river, (2) The city´s expansion resulted in the surface temperature gradually raise, and heat island area also increased from 12.7 km² in 2000 to 26.0 km² in 2007, the increased area of the urban heat island was about 13.3 km² during 7 years, the proportion index of urban heat island increased 5%. And the summer´s heat island intensity was significantly higher than winter, urban expansion and distribution of heat island showed consistency in space.