The Study Of Urban Heat Island Effects About Xi’an City Using Landsat Data

Rapid urbanization and industrialization process has a far-reaching influence forurban local climate and ecological environment.With the increase of the surface ofartificial buildings, and the loss of natural landscape, the city’s underlying surfaceproperties changes, which leads to the change between the surface and the atmospherewater thermal cycle, affect the city’s "hot" environment system, then more and morecities appear urban heat island. A series of problems such as energy,which caused byurban heat island has become the bottleneck of urban sustainable development.Xi′an islocated in the middle of the Yellow River, the basin of the GuanZhong Plain. With thedrive of the western development strategy and the construction of internationalmetropolis strategy, Xi′an′s urban scope expands in recent years,whose urban heat islandobvious changes.In this paper,we use Xi′an′s Landsat TM/ETM+/OLI data for September23,2002,July24,2006and September13,2013.With the support of GIS technology and landscapeecology theory, invert the temperature for study area,extract Soil Adjusted VegetationIndex (SAVI), Normal Differential Water Index (NDWI) and Normal DifferentialBuilding Index (NDBI). Comprehensive analysis the changes for urban heat islandintensity for different years and different districts after normalized processing,then dealswith the method of extracting feature profile study the relationship between urban heatisland and vegetation, the relationship between urban heat island and building coverage,the relationship between urban heat island and water.The main conclusions are asfollows:(1)Xi′an city has the phenomenon of urban heat island effect, and it showed a trendof increase. Xi′an′s heat island area presents the characteristics of scattered point tocontiguous then to diffusion transfer. The heat island area scattered point distribute in themain urban area in2002, then group covers the main urban area in2006, finally from the"downtown" diffusion transferred to the "suburb" in2013.(2)In this paper, the districts and counties of the study area presented a trend ofincrease (except the main urban area), of which Gaoling country and Lintong region arethe most increased city. (3)Urban heat island has a negative correlation relationship with water andvegetation, and has a positive correlation relationship with building coverage, therefore,we can appropriate to increase green space, protect the water, control the speed and thescope of urban expansion to alleviate the effect of the urban heat island.