Research On The Relationship Between Urban Green Space And Thermal Environment Within Beijing Sixth Ring Road

This study based on GIS and RS technology,using Landsat data to carry out the inversion of surface temperature and the extraction of underlying surface monitoring types in the fourth period from 1999 to2017.And then analyzed the spatial and temporal variation characteristics of the two.The normalized vegetation index(NDVI)of the four stages was calculated,and the correlation between NDVI and surface temperature was analyzed.The normalized surface temperature data of urban green space are collected,and the surface temperature characteristics of different types of urban green space are analyzed from the vertical and horizontal aspects.The effective cooling distance of urban green space is calculated and counted.Finally,based on the perspective of urban thermal environment,the paper puts forward some Suggestions on the optimal layout of urban green space.This study mainly has the following conclusions:(1)From 1999 to 2017,the spatial distribution of surface temperature has changed to a certain extent,which is closely related to the change of the underlying surface cover type.Among them,the heat island phenomenon in 1999 was basically distributed in the region within the fifth ring,and the heat island in the region between the fifth ring and the sixth ring also had a certain proportion.For the areas within the fifth ring road,the proportion of urban green space increased gradually from 2005 to 2017,which eased the heat island effect within the fifth ring road.From 2011 to 2017,the heat island effect in the region between the fifth ring road and the sixth ring road has been further intensified due to the increase of impermeable surface and the decrease of vegetation in the process of urban construction.Urban heat island also gradually from the original mainly in the fifth ring inside the state of aggregation to the fifth ring outside the regional expansion.(2)There was a negative correlation between the normalized vegetation index and the surface temperature from 1999 to 2017.For every 0.1 increase in the normalized vegetation index,the surface temperature could be reduced by about 0.90℃-2.06℃.(3)In the urban green space,the normalized surface temperature in the shallow mountain area is the lowest,followed by the suburban cultivated land,country parks,urban park green space,small patches of attached green space,etc.For the park green space in the central urban area,the surface temperature of the green space with single vegetation layer is significantly higher than that of the green space with abundant vegetation layer at the similar urban geographical location.Among all vegetation patches,the normalized surface temperature of the small patch is the highest,and the temperature of the attached green space in the road and traffic facilities decreases with the increase of its width.The surface temperature of the green space patch with high green coverage rate,low building density and continuous green space is obviously higher than that of the green space with low green coverage rate and fragmented green space patch.(4)For the landscape index of 30 sampled green Spaces in this study,the area of urban green space patches showed a significant correlation with the surface temperature at the level of 0.05.The larger the patch,the colder the surface temperature.(5)For the 15 sample green Spaces,the effective cooling range ranges from 150 m to 400 m,and most of them are between 200 m and 300 m.The degree of cooling varies from distance to distance.Based on the above conclusions,the following Suggestions are put forward to solve the problem of urban thermal environment.Reasonable control of the construction of urban gray space,and pay attention to the construction of ventilation corridor,reasonable planning of urban green space structure,construction of continuous green space patch,improve the rate of urban green.The green space with low ecological benefit should be reduced as far as possible,and the vegetation structure inside the green space should be rationally planned to form a multi-level and high-density urban green space with arbor,shrub and grass.