| Urban heat island is a local climate phenomenon,which is characterized by higher atmospheric and surface temperatures in urban areas than in the surrounding rural areas.Generally speaking,with the development of urbanization and industrialization,the continuous increase of artificial buildings in cities and the reduction of green land,cultivated land and agricultural land,the nature of the underlying surface of the land and the constant change of the water cycle on the surface of the land,It has seriously affected the local climate and environment of the city,which makes the phenomenon of urban heat island more and more prominent.Nanchang City is located in the north-central part of Jiangxi Province,one of the leading cities in the middle reaches of the Yangtze River.In this paper,the Landsat series images of Nanchang City in 2000,2008,2014 and 2014,which are downloaded from the geospatial data cloud website,are the main data sources,supported by the theory of thermal infrared remote sensing.Based on the radiative transfer equation method,the land surface temperature is inversed and the distribution and variation characteristics of the surface temperature in the study area are obtained.Landscape ecology is introduced into the study of urban heat island effect.The intensity grade of land surface temperature inversion is classified by means of mean-standard deviation method,and the temporal and spatial evolution characteristics of heat island effect in Nanchang city are analyzed.Based on the classification of land use and the inversion of land surface temperature in Nanchang City,this paper analyzes the process of urban construction and development in Nanchang City from 2000 to 2014 by using ENVI remote sensing software platform.Correlation between surface temperature and area change of different land use types.At the same time,the relationship between different remote sensing indices and surface temperature is quantitatively analyzed,and the correlation between NDVI,MNDWI,NDBI and the thermal environment pattern in the study area is expounded.Finally,the influencing factors and mitigation measures for the formation of urban heat island effect in Nanchang City are pointed out.The results of the study are summarized as follows:(1)By analyzing the inter-annual characteristics of the urban heat island effect in Nanchang City,we can find that the heat island effect is increasing year by year.The surface temperature of the city district is obviously higher than that of other counties,and the area of the strong heat island area increases the most,from 6.59% to 17.45%.The urban heat island effect is remarkable.The seasonal characteristic analysis shows that the heat island effect is the most obvious in autumn,and the intensity of heat island in four seasons is as follows: autumn > summer > spring > winter.(2)Through the analysis of the relationship between the area change of different land use types and the surface temperature in Nanchang City in 2000-2014,it can be seen that the land use type determines the nature of the underlying surface of the city and has a significant impact on the surface temperature.The increase of urban construction land and bare land area can promote the urban heat island effect,and the green land and water body can restrain and alleviate the urban heat island effect,which indicates that the urban construction land should be reasonably planned in the process of urban development and construction.At the same time,the area of green space and water area should be increased appropriately.(3)The correlation between surface temperature and remote sensing index is studied.It is shown that NDVI,MNDWI,NDBI is closely related to land surface temperature.NDVI and MNDWI have a negative correlation on surface temperature,while NDBI has a positive correlation on surface temperature. |
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