Research On The Cold Island Effect And Optimization Strategy Of Blue Green Space In The Main Urban Area Of Hangzhou City

With the rapid development of global climate warming and urbanization,urban area continues to expand,leading to a transformation in the nature of urban underlying surfaces.The heat island effect is increasingly strengthening,and the contradiction between urban thermal environment and residents’ lives is becoming increasingly prominent.Research has shown that blue-green spaces in cities can alleviate the heat island effect and lower the temperature of the surrounding environment.Therefore,from the perspective of landscape architecture,it is of great theoretical and practical significance to improve the urban ecological environment and human settlements by optimizing the landscape pattern of blue and green space.Taking the main urban area of Hangzhou as the research object,this paper analyzes the spatial pattern characteristics of summer land surface temperature and landscape pattern index in the main urban area of landscape architecture based on the perspective of landscape architecture,quantificationally analyzes the mechanism of underlying landscape pattern index on land surface temperature,and proposes targeted optimization strategies for the blue green space cold island effect.Research shows:(1)The overall surface temperature in the main urban area of Hangzhou shows a spatial pattern of"high center and low edge",with the strongest heat island intensity in the central urban area.As it moves away from the urban area,the surface temperature gradually decreases,and local areas show a wave like fluctuation.(2)The blue-green space is mainly distributed in extremely low temperature areas,low temperature areas,and sub low temperature areas,while construction land is mainly distributed in secondary high temperature areas,high temperature areas,and extremely high temperature areas.The high temperature is mainly distributed on both banks of Qiantang River,in Shangcheng District,Binjiang District,Xiasha Development Zone of Qiantang District,Science and Technology City and International Airport of Xiaoshan District,and the old city of Linping District;The low temperature is mainly distributed in the West Lake District,Yuhang District,the south of Xiaoshan District,the whole Qiantang River,and the Banshan National Forest Park in Linping District.The proportion of extremely high temperature areas is 1.48%,mainly distributed in small patches in commercial activity areas,such as Hubin,Wulin,Xiasha,the old urban area of Linping,and the south of Yiqiao in Binjiang District.The proportion of extremely low temperature areas is the smallest,only 0.24%,distributed in the Tianzhuling Tangwuling area in the southwest of Yuhang District.(3)The Moran index was used to analyze the spatial correlation of surface temperature.By setting a buffer zone for heterogeneous regions,it was found that the temperature difference in the H-L region is weak and the average temperature is lower than that in the L-H region.The study found that the suppression of the heat island effect by the blue green space cold island effect is much smaller than the contribution of urban construction land to the heat island effect,that is,the blue green space must be greater than or even multiple times the area of construction land in order to effectively alleviate the heat island effect,The integration of blue and green spaces has a significant impact on urban heat island suppression.(4)Construction land(32.38℃)>other types(31.06℃)>grassland(30.58℃)>cultivated land(30.41℃)>forest land(29.53℃)>water body(28.98℃),except for no correlation with other types of land,there is a significant correlation with the other five types.There is a significant positive correlation with construction land,arable land,and grassland,while there is a significant negative correlation with forest land and water bodies.The larger the proportion of forest land and water bodies,the lower the surface temperature,which is inversely proportional;The higher the proportion of construction land,the more significant the surface temperature;Grassland and arable land have little impact on surface temperature.(5)There is a certain correlation between the landscape pattern indices of forest land,water body,grassland,construction land,and cultivated land and surface temperature.At the type level,the more and larger the landscape patches in the blue-green space,the less landscape fragmentation,the more concentrated the distribution,the more complex the landscape morphology,and the lower the average surface temperature.On the contrary,the larger the landscape area of construction land,the less landscape fragmentation,the more concentrated the distribution,the higher the average surface temperature,and the more obvious the urban heat island phenomenon.At the landscape level,there is a significant negative correlation between surface temperature and CONTAG and IJI.The fewer types of small patches in the landscape,the better the connectivity of dominant patches,the more uniform the adj acent distribution,and the lower the surface temperature.(6)By changing the integrated blue-green space and the landscape pattern of construction land,CFD software is used for simulation.The integration degree of green space is 71.61%,the water area increases by 54.80%,and the integration degree of buildings decreases by 52.36%,which can effectively reduce the temperature by 3-5℃.Finally,corresponding green space planning strategies,water body planning strategies,and overall urban blue-green space optimization strategies are proposed based on the characteristics of the main urban area of Hangzhou.