| In recent years,with global warming accelerating and urban thermal environment deteriorating,the heat island effect has become increasingly significant,which has brought a lot of influences on people's production,life and environment.Therefore,the study of urban heat island effect,dynamic changes and green space cold island effect is helpful to better understand the urban heat island effect,and targeted to alleviate the urban heat island effect.Based on the theories of landscape ecology and landscape architecture,this paper adopted Arc GIS,ENVI,SPSS and other softwares to explore the spatiotemporal succession characteristics of summer heat island effect and the influencing factors of green space cold island effect in the main urban area of Harbin city,and utilized the rules of green space temperature decreasing effect to plan a green space system with good temperature decreasing effect by taking Qunli New District of Harbin city as a practical case.The main conclusions were as follows:(1)From 2001 to 2017,strong heat island area(135.28-257.35km~2),heat island area(157.76-435.73km~2)and sub heat island area(600.61-836.10km~2)in the main urban area of Harbin city continued to expand,while moderate temperature area(1893.80-1439.23km~2)and sub cool island area(1567.99-1302.96km~2)decreased correspondingly.Before 2008,the change of heat island area was not obvious,while it increased obviously after 2008.The spatial distribution of heat island expanded from the Second Ring Road to the Fourth Ring Road,and also from the southern side of Songhua River to the northern side.(2)From 2001 to 2017,the area of construction land(5.06%)and green land(7.22%)in the main urban area of Harbin increased significantly.Agricultural and forestry land(-9.95%)and bare land(-5.11%)decreased significantly.In terms of spatial distribution,the construction land expanded outwards from the Second Ring Road,the bare land in the Third Ring Road and the agricultural and forestry land outside the built area continuously decreased.The green space coverage area gradually expanded to the northern side of Songhua River,while the green space area within the southern side significantly reduced.The average land surface temperatures of green space,water body,agricultural and forestry land were lower than those in the study area,while the average surface temperatures of construction land and bare land were higher.In the main urban area of Harbin city,the construction land made the largest contribution to the heat island.The"cold spots"on the apparent region of the heat island were mostly urban green space.(3)Based on the analysis of 72 green space samples in Harbin city,it was found that the temperature decreasing effect of green space has rised with the increase of green space area and circumference.When the green space area was 0.7-5hm~2or the circumference was 0.35-1.5km,the temperature decreasing effect was the most significant.When the green space area was 5-30hm~2or the circumference was 1.5-3km,the temperature decreasing effect came the second.In the same area,the more complex was the shape of green space(i.e.the higher green patches shape index),the better took the temperature decreasing effect.(4)Green space system planning of Qunli New District in Harbin city was made based on the temperature decreasing effect regularity of different influencing factors of green space.In the west of Qunli New District,a large area of park green space was planned to form"cold surfaces",while in the east,the planned area with high quality temperature decreasing effect was 0-5hm~2to form"cold spots",and the strip park served as a"cold line"to connect"cold surfaces"and"cold spots".It is estimated that by 2035,the green space rate of the planned area will reach to 29.79%,the green space area per capita to 26m~2,the park green space area per capita to 11m~2,and the urban and rural green space rate to 41.61%.After planning,the cooling coverage rate of park green space,protective green space and square land will increase from 21%to 35%,2.2%to 5.0%,and 5.0%to6.4%respectively.This research has certain scientific significance.The results can provide theoretical basis and data support for for the future development and construction of Harbin City,and also provide reference for other cities to alleviate the urban heat island effect of green space system planning. |
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