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World-wide urbanization has significantly modified the landscape, which has important climatic implicationsacross all scales due to the simultaneous removal of natural land cover and introduction of urban materials. Thisresulted in a phenomenon known as an urban heat island(UHI). A study on the UHI in Xiamen of China was carriedout using remote sensing technology. Satellite thermal infrared images were used to determine surface radianttemperatures. Thermal remote sensing data were obtained from band 6 of two Landsat TM/ETM+ images of 1989and 2000 to observe the UHI changes over 1 1-year period. The thermal infrared bands were processed throughseveral image enhancement technologies. This generated two 3-dimension-perspective images of Xiamen's urbanheat island in 1989 and 2000, respectively, and revealed heat characteristics and spatial distribution features of theUHI. To find out the change of the UHI between 1989 and 2000, the two thermal images were first normalized andscaled to seven grades to reduce seasonal difference and then overlaid to produce a difference image by subtractingcorresponding pixels. The difference image showed an evident development of the urban heat island in the 11 years.This change was due largely to the urban expansion with a consequent alteration in the ratio of sensible heat flux tolatent heat flux. To quantitatively compare UHI, an index called Urban-Heat-Island Ratio Index(URI) was created.It can reveal the intensity of the UHI within the urban area. The calculation of the index was based on the ratio ofUHI area to urban area. The greater the index, the more intense the UHI was. The calculation of the index for theXiamen City indicated that the ratio of UHI area to urban area in 2000 was less than that in 1989. High temperaturesin several areas in 1989 were reduced or just disappeared, such as those in old downtown area and GulangyuIsland. For the potential mitigation of the UHI in Xiamen, a long-term heat island reduction strategy of planting shadetrees and using light-colored, highly reflective roof and paving materials should be included in the plans of the cityplaners, environmental managers and other decision-makers to improve the overall urban environment in the future.
