Cooling Effect Of The Emancipation Park And Its Influencing Factors In Wuhan

Construction of urban parks is considered as an effective way to alleviate urban heat island(UHI)effect and improve the urban thermal environment.Clarifying the cooling effect and cooling mechanism of urban parks is of great significance to optimize the spatial structure of parks,improve the urban thermal environment and adapt to climate change by planning and designing.However,previous studies mainly focused on the impact of the internal spatial structure of the park on the cooling effect,but ignored the impact of the surrounding environment of the park,which affected the scientific interpretation of the cooling mechanism of urban parks to a certain extent.This study illustrated the spatial distribution of land surface temperature in and around the Emancipation Park based on the Landsat 8 image.The internal and surrounding spatial structure characteristics of the park were obtained based on Baidu Image Map and River Map,and the types of the surrounding environment of the park were divided.The relationship between each influencing factor and the surface temperature or cooling range was constructed,and then the main influencing factors of the cooling effect of the park and its cooling mechanism were revealed.The main results were as followed:(1)The average surface temperature inside the Emancipation Park was 5.98℃lower than the average surface temperature around the park,which had obvious park cold island effect.However,the cooling effect of the park on different environmental types around it was different.In terms of cooling distance,the cooling distance of the Emancipation Park for three different types was road type(850m)>high-rise building type(380m)>high-density building type(330m).In terms of cooling range,the cooling range of the Emancipation Park for three different types was high-density building type(8.7℃)>road type(8.2℃)>high-rise building type(6.5℃).However,the vegetation type has the same nature as the park,the cooling effect of the park on the vegetation type was affected by the superposition effect.(2)The thermal environment inside the Emancipation Park was mainly influenced by Total Area(TA＿L),Related Circumscribing Circle of hard surface(CIRCLE＿MN＿B)and Largest Patch Index of hard surface(LPI＿B),all of which were indicated to characterize the spatial structure of the landscape.Among them,TA＿L had the highest contribution to the change of thermal environment.There was a negative correlation between TA＿L and the land surface temperature in the park.When the other variables remained unchanged,the land surface temperature was decreased by 0.2℃for each 0.1 hm~2 increase in the TA＿L.The land surface temperature was decreased by 0.8℃for each 10%increase in the CIRCLE＿MN＿B.The land surface temperature was increased by 0.004℃for each 10%increase in the LPI＿B.(3)The cooling effect of the Emancipation Park on the surrounding environment was mainly affected by Normalized Difference Built-up Index(NDBI),Vegetation Area(CA＿V),Disjunct Core Area Density of land(DCAD＿L),Edge Contrast Index of Vegetation(ECON＿MN＿V)and Building Height(BH).The largest contribution to the cooling effect of the park was NDBI.There were positive correlations between the park cooling effect and the indexes of NDBI and ECON＿MN＿V.There were negative correlations between the park cooling effect and the indexes of CA＿V,DCAD＿L and BH.When the other variables remained unchanged,the park cooling range was increased by 1.5℃for each 10%increase in the NDBI.The park cooling range was decreased by 0.5℃for each 0.1 hm~2 increase in the CA＿V.The park cooling range was decreased by 0.07℃for each 10 m increase in the BH.ECON＿MN＿V and DCSAD＿L has little influence on the change of the park cooling range.(4)The main impact factors of Park cooling effect were different in different environmental matrixes,and the contribution of the same index to the cooling effect was also different in different environmental matrixes.The most important factor affecting the cooling effect of the park was Normalized Difference Vegetation Index(NDVI)in the matrix of vegetation.The cooling range of the park was decrease by 1℃for each 10%increase in the NDVI.The cooling effect of the park was mainly affected by the characteristics of hard surface coverage in the matrix of road.The cooling range of the park was increased by 1.8℃for each 10%increase in the NDBI.The cooling effect of the park was mainly affected by DCAD＿L and NDBI in the matrix of high-density buildings.The cooling range was decreased by 0.0016℃for each 10%increase in the DCAD＿L.The cooling range of the park was increased by 1.5℃for each 10%increase in the NDBI.The cooling effect of the park was mainly affected by the change of surface coverage in the matrix of high-rise buildings.The cooling range of the park was increased by 1℃for each 10%increase in the NDVI.The cooling range of the park was increased by 1.6℃for each 10%increase in the NDBI.