Study On Urban Heat Island In The Central City Of Chengdu Based On Landsat 8

In 2014, China’s total GDP exceeded ten trillion US dollars mark, <2012 Chinese New Urbanization Report> pointed out that China’s urbanization rate has exceeded 50%. Each year, more than 12 million people will become urban residents, it is estimated that China’s urbanization rate will reach 55% by 2020. Since China’s reform and opening up, the growth of economy, industrialization and urbanization in China made a stunning impression all around the world.At the same time, as the rapid advance of urbanization developing at a world wonder scale and speed, the severe environmental degradation problems it brought become more obvious. With the urban development, the structure and type of city’s underlying surface has been undergone tremendous changed. The original forest vegetation, farmland, water and other natural landscape is replaced by impervious surfaces, such as low reflectivity and highly endothermic buildings or roads. Urban area is still keeping expand outward. Since the intensity of urban construction is much higher than the suburbs, compared with suburban soil, vegetation, asphalt and concrete pavement heat faster, amount of heat has been stored in the daytime and turned those heat into the atmosphere in the evening, plus calorie from artificial heat, greenhouse gases and air pollution, and many other causes gathered in the city space range, culminating the urban heat island effect which is urban atmosphere and land surface temperature significantly higher than the outskirts.In recent decades, global urbanization continues to accelerate; behind the prosperity of the city is increasing issues of air pollution and frequent extreme weather caused by the ongoing natural environment damage. In 1833, while Howard was first time researching London’s urban climate characterized, he discovered the urban heat island effect, after then, the urban heat island as a relatively poor product recessive urbanization attracted people’s attention. Urban heat island itself does not direct a result of any major weather disasters like typhoons, rainstorms and other strong weather. But it often effects ongoing and indirect harm to human’s life by altering the balance of power in some areas, the water cycle, structure, propagation and diffusion of pollutants rule of the atmospheric boundary layer. The requirements of the urban environment has been highly increased by human’s need, making the urban heat island has become an urgent issue, caused widespread concern in the world of scholars. Due to the problems that led to urban heat island are complex, the factor that affecting heat island intensity are varied, and the heat island not only changes over time, but also with spatial variation, variation patterns variety. Researching on Urban Heat Island Effect, either deepens the role of human activity in the rational study of natural ecosystems machine, and it also can be applied to the development of urban heat island mitigation strategies. According to the research status, the urban heat island has become an interdisciplinary cross-cutting issue.As the earliest development city of the southwest region in China, at the same time as political, economic and cultural center of the southwest, in the continuous advance of western development, Chengdu has the most particularly rapid developed over the past decade. The outside of city limits keep expanding and the heat island effects changing significantly are both the reason why we choose Chengdu to take the advantage of the most significance and research value of the heat island effect in relative researching area. In research methods, we combine technical expertise OF Acquisition Urban Heat Island region using remote sensing inversion method, using statistical methods to further analyze the relevant contact surface parameters and land surface temperatures. We also consider Landsat Landsat spectral characteristics have a strong, high-resolution, data-rich, and easy to obtain advantage Landsat 8 selected image as the primary data source while selecting the image data. Reference Landsat TM / ETM’s land surface temperature inversion method respectively the use of RTE, SC, IB, MW and SPW algorithm implemented in five land surface temperature inversion image of Landsat 8, and comparative analysis of the inversion results.In this paper, the remote sensing image of Landsat 8 in the April 20, 2013 as the main data source, mainly made the following findings and understanding:1) To use four single-band algorithms(RTE algorithm, IB algorithm, SC algorithm and MW algorithm) and the Split Window Algorithm(SWA algorithm) for the study area retrieving land surface temperature, the results of land surface temperature get from the five algorithm were analyzed and accuracy verification. The results show that the single-band algorithm of land surface temperature inversion which is suitable for Landsat TM / ETM is also equally suitable for Landsat8. In the five algorithms of this experiment, the result of land surface temperature inversion get from Split Window Algorithm is closer to the real situation more than other algorithms and reflects the characteristic because of Landsat8 has two Thermal infrared band and it can be calculated the land surface temperature more accurately.2) With Ring Road of Chengdu(first ring road, second ring road, third ring road, beltway) and administrative boundaries as the division unit. To gather the land surface temperature statistics with the central city of Chengdu and analyze the pattern of space distribution of Urban Heat Island of study area:the more closer to the city center, the ratio of heat island area is bigger and more distant from the city center, the more widely distributed low temperature zone and sub-medium temperature zone; large study area of UHI distributed centralized in second ring road to beltway, this is shows the urban development is extending to the periphery large-scale, we need a reasonable plan in the urban construction of future to reduce the urban heat island effect.3) Numerous studies show that the change of land using / cover or the change of urban surface materials is an important factor in urban heat island effect, in order to verifying there’s a particular correlation between the land surface temperature and land surface. Three kind of normalized difference index include NDVI,MNDWI and NDISI in the study areas were calculated, they represented the distribution of vegetation, water, impervious surface. Building regression equation of the surface parameters and land surface temperature by spatial sampling, the study shows that: the impervious face has a positive correlation effect on urban heat island effect, while the water and vegetation has a negative effect, especially the vegetation has a significant effect to cool off the city.