The Study About Heat Island Effect And Its Mitigation Strategies In Hohhot Urban

With the rapid development of global warming and urbanization,urban heat island effect is more prominent.Urban heat island effect will not only bring a lot of harm to human life,but also increase the possibility of high temperature disaster.At present,the urban heat island effect of Hohhot is increasingly prominent,which has become a major obstacle to the urbanization process and the benign development of urban ecological environment.Therefore,how to mitigate the urban heat island effect is the core problem that must be solved in urban planning and management.Taking Hohhot city as the study area,in 1987,1990,2002,2009,2013 and 2017,6,which based on the data of remote sensing image using single window algorithm surface temperature inversion of Hohhot city,analysis on Hohhot city heat island effect(1987-2017 time and space distribution characteristics of different land use types on the response of the urban heat island effect,explore the relationship between urban heat island effect and the expansion of the construction land;Based on the inversion of surface temperature data in the urban area of Hohhot in 2017,23 park green Spaces in the urban area of Hohhot were selected to analyze the gradient change rule of the cooling effect of park green space with distance,and to study the relationship between the cooling effect distance and cooling amplitude of park green space.Finally,specific measures to alleviate urban heat island effect are proposed.Research shows that:(1)from the perspective of time distribution,from 1987 to 2017,the thermal environment area of Hohhot urban area showed an increasing trend.From the perspective of spatial distribution,the range of urban high temperature grade gradually expands,and the abnormal high temperature area in the urban area is mainly concentrated in the urban center,theindustrial area with large energy consumption,the station and the bare land.The urban heat island effect extends outward from the urban center along transportation routes.(2)the surface temperature of various land use types in Hohhot urban area is significantly different,with the lowest temperature of cultivated land and the highest temperature of construction land and unused land.In terms of the impact of various land use types on the thermal environment,grassland has the smallest contribution to the thermal environment,followed by unused land,water area and woodland,and farmland and urban construction land.Grassland contributes the least to the regional thermal environment,and the regional thermal unit weight index of cultivated land and urban construction land is large.(3)the urban land use and heat island area of Hohhot expand outward around the main urban area,with a consistent spatial distribution.The center of urban land use moved in the same direction as the center of urban heat island from 1987 to 2002.From 2002 to 2009,it moved to the northeast.From 2009 to 2017,they moved up to the southeast.(4)the gradient change types of cooling effect in Hohhot park green space can be divided into parabolic change type,logarithmic change type and even change type,which are related to the layout of surrounding construction land.The cooling effect of urban park green space in Hohhot is mainly distributed between 90 and 210 m.The farther the urban park green space is from the downtown,the greater the cooling distance will be.The quadrantal division of the average cooling range of park green space is: northeast < northwest < southeast < southwest.(5)within a certain range,with the increase of green space area and perimeter,the difference between the cooling range and the maximum temperature shows a gradual upward trend,but gradually flattens out.The more simple and neat the shape of the park green space,the greater the difference between the temperature drop range and the maximum temperature.On the contrary,the more complex the shape of the parkgreen space,the smaller the difference between its cooling range and the maximum temperature.(6)according to the urban land expansion and urban green space layout characteristics of Hohhot,it is concluded that the urban heat island effect can be effectively alleviated by controlling the scale of construction land and urban population,improving the urban greening rate,strengthening the greening construction of the heat island central region and increasing the urban water area,which can provide reference for urban planning and construction.