Research On Urban Heat Island Effect & Driving Force In Nanjing Based On Landsat Data

The rapid social and economic development has produced a series of problems for the regional ecology,and the urban heat island effect is one of them.Due to man-made fever and changing in the physical and chemical properties of the underlying surface of the city,the urban heat island effect becomes more and more significant.As the capital city of Jiangsu province,Nanjing plays a "leading role" in the economic and technological development of Jiangsu.In recent years,Nanjing has just emerged from the ranking of the top ten stove cities,and the heat island effect has changed dramatically.Therefore,exploring the relationship between the space-time changes of the heat island effect and driving factors,this is of great significance to the future The social and economic development and ecological environment protection of Nanjing and medium-sized and small cities.This article based on GIS and RS theory,selects Nanjing city as the research area,takes Landsat TM/OLI data,Nanjing meteorological data,Nanjing county level vector data and Nanjing statistical yearbook data as the data sources.This article uses atmospheric correction method,tan zhihao single-window algorithm,Based on the image algorithm and universal single channel algorithm to invert surface temperature of Nanjing city in 2017.Based on the inversion results of each algorithm,combined with the theory of earth-air temperature difference and meteorological data of Nanjing city.Finally,this article uses atmospheric correction method to invert surface temperature of Nanjing city.Base on the mean-standard deviation method,Nanjing was divided into five heat island levels to explored space-time of heat island effect and heat island strength changes in Nanjing.Then based on land cover types in Nanjing to explored the relationship between land types and surface temperature.Finally,based on SPSS statistical analysis software,quantitatively analyze the relationship between surface temperature and ecological indexes in Nanjing.The results are as follows:(1)(1)Based on vector data at the county level of Nanjing city heat island effect space changes in 2002-2017:strong heat island area is mainly located in Nanjing city,15 years the expansion trend along the Yangtze river on both sides,Secondary heat island are mainly at the strong heat island area edge,The normal area no obvious change in spatial distribution and the normal area of slightly reduce the trend mainly converted into strong heat island area,green island area and cold island region barely large changes in spatial distribution,But within 15 years,most of the normal areas and the strong heat island area in Liuhe County changed to cold islands.Seasonal distribution characteristics:in spring and winter,the spatial distribution of each grade of heat island is the same,and in summer and autumn,the spatial distribution of each grade of heat island is basically the same.(2)Time-based quantitative analysis of the changes of heat island grades in Nanjing:from 2002 to 2017,the areas of strong heat island area,green island area and cold island area showed an increasing trend,while the areas of secondary heat island and normal area showed a decreasing trend.Seasonal variation of Nanjing heat island effect:cold island area dominated in spring and winter,and normal area dominated in summer and autumn.(3)Change of heat island intensity index(URI):from 2002 to 2017,the time change of spring,summer,autumn and winter all showed a trend of first increase and then decrease,and the intensity of heat island was the same in spring and winter,and the intensity of heat island was the same in summer and autumn.(2)This article uses support vector machine(SVM)model to divide the land use types of Nanjing into bare land,construction land,arable land,forest land and water.Then the classification results overlay on surface temperature raster image to obtain the average temperature of each place from large to small:construction land> bare land> arable land>forest land> water body.(3)Through inversion of vegetation coverage index(FV),soil regulation vegetation index(OSAVI),improved normalized differential water index(MNDWI)and building index(NDBI),the relationship between each index and surface temperature(LST)was obtained:FV,OSAVI,MNDWI and LST were negatively correlated,while NDBI and LST were positively correlated.