| In recent years,the area available for urban land-use decreases with the rapid development of urbanization,leading to the urban development under higher and denser modes.It changes the urban spatial pattern and surface property to a certain degree,which affects the urban thermal environment and thereby causes a series of thermal environmental problems such as urban heat island.Thermal environment is closely related to urban planning.Urban planning can control surface structure of urban landscapes.Therefore,effective urban planning policies and designs can change the regional thermal environment and improve human settlements.How to minimize the negative impact of thermal environmental problems through rational urban planning is one of the key issues to be solved.Thus,study of the influence of urban planning on thermal environment has important social demands and scientific significance.Taking Jiangbei New Area in Nanjing city of Jiangsu Province as study area,our study firstly designed three comparative experiments according to the land use status and urban planning scheme with WRF(Weather Research and Forecasting Model,WRF)model,which were used to verify whether the input of the real land use data and the addition of urban canopy mode could improve the simulation accuracy and thereby analyzed the response of thermal environment to the type of land use in urban planning.Secondly,the ENVI-met model was used to simulate the current situation of region nearby Dingshan street with great change after urban planning.Then the measured data from Dingshan meteorological station were used to verify the simulated accuracy of air temperature using WRF model and ENVI-met model respectively.Further,the second type of residential land in the Dingshan street was selected to be used in different schemes of residential area planning,which were designed to discuss the influence of H/W(ratio of the building height to width)and building layout change on urban thermal environment.Our study can provide theoretical basis for urban planning.The main conclusions of this work were as follows:(1)The use of land-use data with high spatiotemporal resolution coupled by urban canopy model could significantly improve the accuracy of near-surface air temperature simulated by WRF model and this simulated data could accurately reflect the change of temperature inside the city.Thermal environment was significantly affected by the land-use change in urban planning.The daily average temperature in the expanded area of urban land-use increased by 0.9?.Compared with natural surface,the urban land was characterized by rapid-warming and slow-cooling.The area and intensity of urban heat island increased in the year 2030 compared with 2013.Therefore,in addition to effectively controlling the increase in urban land-use,it is necessary to consider the decentralized layout of urban land-use in urban planning.According to the status of urban land-use,it is more beneficial to minimize its impact on thermal environment,which is more conductive to the ecological planning and construction of Jiangbei New area.(2)Using the measured data from Dingshan meteorological station to verify the accuracy of ENVI-met model and WRF model,it was found that the correlation coefficient between the measured and derived air temperature simulated from different models were both 0.96,with the higher accuracy for ENVI-met model.The RMSE value was 0.33?,which was lower than that of WRF model.(3)Based on different H/W and pattern of buildings,this work conducted the sensitivity experiments to investigate the impact of the change of building planning elements on urban thermal environment.The obtaining results found that the simulated temperature in our study area was the highest when H/W=0.7 and the lowest when H/W=2.8.The simulated wind speed reached the maximum when H/W=1.4.Their results suggested that controlling the H/W value could affect the thermal environment to a certain extent.Changes of the building layout also had impact on thermal environment.Each group of the block layout was independent,and the thermal environment was related to the layout of each group.The enclosed layout had low air temperature during the daytime and its layout form had strong hindrance to wind speed.For the axial layout,air temperature was generally high at night and the heat island effect was remarkable.Using the simulation experiment and analysis,their results showed that it was very important to implement reasonable planning of residential area according to local conditions.In order to enhance the ventilation effect,the road could be inclined at a certain angle to the dominant wind direction and low-rise buildings could be set in the vicinity.Under the premise of meeting the requirements of building spacing specifications,it could reasonably increase the height of the building.Additionally,we can also develop the greening construction,vigorously advocate multi-dimensional greening and improve the vegetation index and green space rate index of residential areas.These above-mentioned approaches can achieve the purpose of air temperature-reducing. |
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