The urban heat island intensity in Hefei city

The urban heat island is a phenomenon that the atmosphere temperature of the sky of the city near the ground is higher than the one outside the city, and it has business with the land use. Based on the Mono-window algorithm, the urban surface temperature of two imagines is retrieved by using of the Landsat TM data. The urban temperature is divided into five classes according to the mean-standard deviation, in which the first two classes are considered as the urban heat island. The geostatistics is used to analyze the change tend of the urban heat island and its centre of gravity. Then the images are extracted through a multi-step hierarchical classification method. Based on ArcGIS, the relationship of the land use and the surface temperature is analyzed. And the results show that the area of urban heat island increases and the trend of island expansion changes. The temperatures of different types land use are different and change as time goes by.