A Study On The Change Characteristics Of The Urban Heat Island And Its Relation With Land Use

Accelerate as the process of global change,.the speed that climate and land use/ cover change is added ceaselessly fast according to natural and human factors. The relevant researches become more and more. As one phenomenon of it, the urban heat island has caused wide public concern. It is a result of comprehensive effect of climatic conditions, anthropogenic heat and so on. And it has close relation among the urban surface. As Chinese urbanization process is accelerating, many natural surfaces are continuously substituted by urban artificial surface, and the effect of urban heat island has become more evident. It makes that the studies on the urban heat island added. Recently, as technology evolves, the development of spatial information gathering methods and analyzing technology, especially the development of sensor technology and thermal infrared remote sensing theory, it comes true that we can study urban heat island continuous and dynamic in large scale. The domestic and foreign scholars have done substantial researches on the distribution characteristics, structural form, change features, driving mechanism, impact factors and so on, based on the relevant theories and the data of various sensors.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 four, five and six classes according to the equal interval and mean-standard deviation, in which the first two or three classes are considered as the urban heat island, and the best result is used to the research. The statistical analysis is used to analyze the change tend of the urban heat island and its centre of gravity. Additionally, the the urban surface temperature image in 2007 minus the image in 1995, the figure shows the areas where the temperature changes. Then the images are extracted through a multi-step hierarchical classification method. Based on ArcGIS and natural, social and economic materials, the relationships of the land use and the surface temperature is analyzed. Then some solutions are raised. The results show that:Firstly, the phenomenon of urban heat island in the two years is obvious. The temperature in the centre of the city is higher than the surrounding area.Secondly, the centers of gravity and the trend ellipses are shown in the image based on the statistical analysis of GIS. The urban heat island moves to southwest.Thirdly, the land use images are obtained step by step. The building areas expand towards southwest. The direction is in line with the expanding direction of urban heat island. And the distribution is the same.Fourthly, the surface temperature images are clipped by the different land use types. The result indicates that the temperature of building area is higher than other types. The temperature of vegetation and water is comparatively low. The temperature in 2007 is higher than in 1995. The mean temperature of building area is higher than other types, but the mean temperature of building area in 2007 is lower than in 1995. It may be the result of errors or the vegetation increase.Fifthly, the distribution of temperature in a city is not the conception of heat island that the temperature in the city is higher than that outside the city, but the comprehensive result that the reaction for the radiation of the different kinds of land. So the effect on life that the urban heat island exerts can be reduced, if the ecological infrastructure, such as the greenbelts and central town park, are built scientifically and rationally.