Study On Urban Heat Island Effect Of Hohhot Based On Remote Sensing Data

With the rapid development of urbanization,the types of land cover have changed,and the amount of artificial heat source has increased,which makes the city produce heat island effect.The heat island effect has a very serious impact on the life of urban residents.The study of the evolution of urban heat island and its influencing factors has certain reference significance for urban planning and ecological city construction.Based on Landsat-5 TM?Landsat-8 OLI/TIRS and MODIS remote sensing data in 1994,1997,2009,2016 and 2019,this paper uses atmospheric correction method and split window algorithm to retrieve the surface temperature of the central urban area of Hohhot,and uses urban-rural gradient analysis,profile analysis and center of gravity migration analysis methods to explore the distribution characteristics of surface temperature,urban heat island evolution law and urban heat island weight from the inter annual,seasonal and daily time scales The migration path of the heart.At the same time,through remote sensing data,statistical yearbook data,meteorological data and DEM elevation data,the influence of land cover type,human factors,meteorological factors and terrain factors on urban heat island effect is studied.The conclusion is as follows:(1)In terms of temporal and spatial analysis of the surface temperature,it is found that the urban temperature of Hohhot is higher than that of the suburb in summer,and lower than that of the suburb in spring,late autumn and early winter.In the summer of 2016,from the initial ring with a radius of 2km to the ninth ring with a distance of 6km from the city center,the surface temperature difference was relatively large,with a difference of 2.38?;in the spring,late autumn and early winter of 2016,the temperature difference between the ninth ring and the initial ring was0.61?,-0.66?and-0.26?,respectively,with a relatively small surface temperature difference.(2)In terms of time and space analysis of urban heat island,it is found that from 1994 to 2019,the heat island area is expanding,and the newly added heat island area is mainly distributed in Ruyi Industrial Park,Baita Airport Logistics Park,Jinqiao Technology Development Zone and Jinchuan Industrial Park South Zone,which is related to the urban construction and development policy of"Control the north,optimize the East,expand to the South and connect the West"implemented by Hohhot municipal government.The phenomenon of heat island appears in the urban area of Hohhot in summer,and cold island appears in spring,late autumn and early winter.In the interannual analysis of urban heat island,from 1994 to 2019,the area of heat island was the smallest,95.85km~2;in2016,the area of heat island was the largest,227.06km~2.In the seasonal analysis of urban heat island,the area of cold island in spring,late autumn and early winter in 2016 is 66.08km~2,73.42km~2 and 113.85km~2respectively,and the area of cold island in early winter is the largest.In the daily variation analysis of urban heat island,the area of heat island in daytime and night is 155.03km~2 and 264.92km~2 respectively,109.89km~2more than that in daytime.(3)From 1994 to 2019,the urban center of gravity of Hohhot mainly moved to the southeast.From 1994 to 2009,the center of gravity of the city shifted 40.81°to the east by south,with an offset distance of 397.4m;from 2009 to 2019,the center of gravity of the city shifted 14.86°to the east by south,with an offset distance of 1148.34m.On the whole,the law of the transfer of the center of gravity in the heat island area(high temperature area)is basically the same as that in the city,and the direction of the transfer in the low temperature area is the same as that in the sub low temperature area,which is roughly the opposite to that in the high temperature area.(4)According to the type of surface coverage,the average surface temperature of construction land is the highest,followed by bare land,semi bare land and vegetation,and the average surface temperature of water body is the lowest.The results show that there is a positive correlation between construction land and surface temperature,while there is a negative correlation between vegetation and surface temperature.It shows that the type of urban surface coverage has a great impact on the surface temperature.The urban construction land is dense and the greening degree is low,so there will be serious heat island phenomenon.In terms of human factors,the increase of total carbon emissions and population in urban areas shows that the increasing of human heat sources aggravates the urban heat island effect in Hohhot.Therefore,the total carbon emissions and population in urban areas have a greater impact on the urban heat island effect.In terms of terrain factors,it is found that the lower the average altitude is,the higher the average surface temperature is,and the lower the average altitude is in Huhhot city than in the suburbs.Therefore,topography has an impact on the temperature difference between urban and suburban areas,and it is also the main factor affecting the urban heat island effect of Hohhot.In terms of meteorological factors,it is found that wind speed and wind direction may affect the spatial distribution pattern of Urban Heat Island(cold island),Higher relative humidity may slow down the urban heat island effect,but wind speed,wind direction and relative humidity have less impact on urban heat island.