| In recent years, the quick development of the urbanization and the clear trend of global climate warming in the world, a series of deterioration of the urban environment has appears. In the ecological environment study, vegetation cover and urban heat island effect have attracted worldwide attentions. For large and medium-sized cities such as Beijing-Tianjin-Hebei Metropolitan area, with the great expansion of urban scope and urban population, the urban shape, function and other aspects have undergone a strong change, which has brought the large impact on regional ecological environment. So there is the great academic and practical importance to study the temporal and spatial change of regional ecological environment and analyze its evolution rules. The study can also promote the urban planning and construction, recover and protect the regional ecological environment and improve the urban inhabited environment.In this paper, with the help of remote sensing and geographic information system technologies, MODIS satellite remote sensing images of 2001 and 2006 were used to retrieve two parameters vegetation coverage and surface temperature which are closely related to the ecological environmental information. Base on these parameters, the temporal change trend and spatial distribution characters in of Beijing - Tianjin - Hebei Metropolitan area were analyzed. Through comparing and analyzing data from two years, this paper tries to reveal the change and development of the ecological environment in the study area during past six years. The main contents are the following:(1) Study on the temporal and spatial distribution rules of vegetation coverage.On the basis of MODIS vegetation index product in 2001 and 2006, the temporal and spatial distribution rules and advance trend of vegetation coverage were studied. It was found that the vegetation coverage rate between 0.6 and 1.0 was the main kind of vegetation coverage which covers 80% of total study area. The vegetation coverage condition turned for the better. In 2001, the vegetation coverage degree above 0.8 covered about 30% of the total area, while in 2006, it increased to 41%. A serious of vegetation protection measures such as closing forests, construction of protection forests, improving grassland, convert cultivated land into forest and grassland has made prominent effect. At the same time, certain region has a degradation trend of vegetation coverage.(2) Study on the temporal and spatial distribution rules of land surface temperature.Using the MODIS land surface temperature products of 2001 and 2006, by the method of image synthesis, the land surface temperature distribution of spring,summer,autumn and winter in daytime and night were attained. The paper studied the spatial distribution rules of land surface temperature and the seasons change rules of urban heat island in typical cities. In the study region it was found that, the urban heat island and urban cool island coexist in the spring daytime; in summer and autumn, it appeared the urban heat island effect and the intensity in summer was stronger than autumn; in winter, the daytime appeared urban heat island while urban cool island in night.(3) The relationship between urban heat island and land use/coverageIn order to find out the driving factors of urban heat island, the relationships between vegetation index and land use/cover change were studied. It was displayed that there were the clear correlation between the vegetation index and the land surface temperature that the NDVI increases 0.1 every time, the surface temperature will descend 1.48℃. In all kind of land use/cover modes, forest is an effective way to abate the urban heat island.
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