Research On Shijiazhuang Urban Heat Island Effect Based On Remote Sensing

With the advancement of urbanization,the issue of urban heat island has become increasingly prominent.Urban heat island effect is the result of urban temperature change brought by human production and life in the process of urbanization,and it is a remarkable feature of "urban disease".Urban heat island effect has become one of the core issues explored by scholars today.Shijiazhuang,as a new city,is also the capital city of Hebei Province.In recent years,the urbanization process has been accelerated,and the underlying structure of the city has undergone major changes.In addition,the increase of man-made heat emissions has made the urbanization problem typical,and the urban heat island effect has become increasingly prominent.Therefore,this paper chooses Shijiazhuang as the study area to research the urban heat island effect.In order to explore the time series changes of urban heat island effect,this paper first establishes a comprehensive index model of heat island effect,which eliminates the overall differences of remote sensing temperature retrieval products in different periods,and reflects the internal divergences of thermal environment in the study area,making the data in different years comparable.On this basis,this paper constructs the scale index model of heat island,the spatial distribution model of heat island as well as the thermal environment effect model of landscape pattern,and makes an in-depth analysis on the spatial and temporal distribution characteristics of urban heat island,the development degree of urban heat island,the migration and change of urban heat island,and the relationship between landscape pattern and heat island effect in Shijiazhuang.At last,based on the Landsat 5/Landsat 8 remote sensing images in 2001,2005,2014 and 2020,it analyzes the characteristics of heat island effect in Shijiazhuang by employing the comprehensive index model of heat island effect,the scale index model of heat island,the spatial distribution model of heat island and the thermal environment effect model of landscape pattern constructed in this paper.The results are as follows:(1)Spatial distribution characteristics of heat island in ShijiazhuangIn 2001,the central city was mainly located in the weak heat island area,and the rural residential areas were normal areas.A large number of farmland around the town showed low temperature zone,and the heat island were mainly distributed in spots and blocks.In 2005,compared with 2001,the urban heat island area in the study area expanded to the periphery obviously,and the thermal environment area of each district and county expanded significantly.The remarkable feature in 2014 was that the coverage area of heat island developed rapidly along the traffic lines between urban areas,and high temperature patches were distributed along and near the traffic lines,and the distribution of high-temperature heat island gradually changed from the structure of "point" to the structure of "bead".In 2020,the heat island in the study area gradually developed from the structure of "bead" to the structure of "planar",manifesting a new feature of multi-focus planar distribution.(2)Time distribution characteristics of Shijiazhuang heat islandIn the research area,the most stable change of thermal field intensity is the strong-cold island area,which is mainly distributed in the Huangbizhuang reservoir.From 2001 to 2020,there is no obvious overall change with about 0.3%,while in 2005,the proportion has increased.Relative strong heat island area and weak heat island area reflect an upward trend from 2001 to 2014.With the development of Shijiazhuang and the expansion of cities and counties,the area of heat island and the thermal environment are also correspondingly expanding.The proportion of relative strong heat island and weak heat island respectively increased from 2.83% and 5.03% in 2001 to 4.93% and 22.73% in 2005 to 6.6% and 28.59%in 2014.However,the area of relative strong heat island and weak heat island decreased by0.7% and 0.66% respectively in 2020.Setting the strong heat island,relative strong heat island and weak heat island as heat island area,their proportion are respectively 8.67%,29.32%,35.40% and 34.20%,showing an overall growth trend from 2001 to 2020.(3)Spatial distribution pattern of heat island in ShijiazhuangThe centers of Yuhua District,Qiaoxi District,Xinhua District and Chang 'an District all demonstrated the trend of migration from the downtown to the periphery.The focus of Gaocheng District shifted from east to northeast and then to northwest;The focus of Luquan shifted from north to south,and then to southeast;The focus of Luancheng shifted from southeast to north,and then to northwest,and the focus of Zhengding County shifted from northeast to east,and then to southeast.(4)Thermal environmental effects of landscape patternRelatively strong heat island and strong heat island were mainly located in construction land and unused land,while strong cold island and relatively strong cold island were mainly located in water body.Moreover,relatively strong cold island and weak cold island were mainly distributed in forest land and cultivated land.In terms of the relationship between spatial thermal environment and landscape pattern,the largest patch index,percentage composition of landscape,aggregation index,landscape division index,class area,patch type area of architectural landscape,woodland landscape,water landscape and cultivated land landscape were significantly correlated with surface temperature at the level of landscape types.Therefore,the land cover or use pattern and the composition of landscape structure have significant influence on the surface temperature distribution.Based on this,it is an important way to seek reasonable land use structure,combination mode,scale and spatial distribution so as to effectively change the distribution of thermal environment.