Many previous studies have focused on the impacts of urbanization on regional mean temperatures. Relatively few have analyzed changes in extreme temperatures. Here, we examine the impact of urbanization on extreme war...Many previous studies have focused on the impacts of urbanization on regional mean temperatures. Relatively few have analyzed changes in extreme temperatures. Here, we examine the impact of urbanization on extreme warmest night temperatures from 33 stations in the Bohai area between 1958 and 2009. We compute the Generalized Extreme Value（GEV） distribution of extreme warmest night temperatures and analyze long-term variations in its characteristic parameters. A new classification method based on the factor analysis of changes in extreme night temperatures is developed to detect the efects of urbanization in diferent cities. Of the three parameters that characterize the GEV distribution, the position parameter is the most representative of long-term changes in extreme warmest night temperatures. During the period of rapid urbanization（i.e., after 1978）, all three parameters of the GEV distribution are larger for the urban station group than for the reference station group, so are the magnitudes of their variations, and the urban areas have been experiencing higher extreme warmest night temperatures with larger variability. Diferent types of cities in the Bohai area have all experienced an urban heat island efect, with an average urbanization efect of approximately 0.3 per decade.展开更多
Background:Increasing urbanization as well as global warming requires an investigation of the infuence of diferent construction methods and ground surfaces on the urban heat island efect(UHI efect).The extent of the i...Background:Increasing urbanization as well as global warming requires an investigation of the infuence of diferent construction methods and ground surfaces on the urban heat island efect(UHI efect).The extent of the infuence of the urban structure,the building materials used and their surfaces on the UHI efect can be signifcantly reduced already in the planning phase using a designated OpenFOAM-based solver“uhiSolver”.Results:In the frst part of this research work,it is shown that inner building details and components can be neglected while still obtaining sufciently accurate results.For this purpose,the building model was divided into two layers:a surface layer without mass,where the interaction with radiation takes place,and a component layer,which contains all relevant components and cavities of the building represented with mass-averaged material properties.It has become apparent that the three parameters—albedo,heat capacity and thermal resistance—which have a decisive infuence on the interaction,have diferent efects on the component temperatures and the surface temperatures.In the second part of this research work,dynamic 3D computational fuid dynamics(CFD)simulations are performed with uhiSolver for a residential block in Vienna.Comparing the simulation results with measurement data collected on site,it is shown that the simplifed assumption of homogeneous material data for building bodies provides very good results for the validation case investigated.However,the infuence of the greening measures in the courtyard of the residential block on the air temperature is found to be negligible.Furthermore,it was observed that due to locally higher radiation density,lower air velocities and higher air humidity,the apparent temperature in the courtyard is sometimes perceived to be higher than in the adjacent streets,despite the lower air temperature.Conclusions:Simplifying the modeling process of the uhiSolver software by reducing the model complexity helps to reduce manual work for setting up appropriate boundary conditions of buildings.Compared to market competitors,good results are obtained for the validation case Kandlgasse presented in this research work,despite the simplifcations proposed.Thus,uhiSolver can be used as a robust analytical tool for urban planning.展开更多
基金Supported by the National Basic Research and Development (973) Program of China (2010CB951600)National Science and Technology Support Program of China (2012BAC22B05)+1 种基金National Natural Science Foundation of China (40605021)China Meteorological Administration Special Fund for Climate Change (CCSF201224)
文摘Many previous studies have focused on the impacts of urbanization on regional mean temperatures. Relatively few have analyzed changes in extreme temperatures. Here, we examine the impact of urbanization on extreme warmest night temperatures from 33 stations in the Bohai area between 1958 and 2009. We compute the Generalized Extreme Value（GEV） distribution of extreme warmest night temperatures and analyze long-term variations in its characteristic parameters. A new classification method based on the factor analysis of changes in extreme night temperatures is developed to detect the efects of urbanization in diferent cities. Of the three parameters that characterize the GEV distribution, the position parameter is the most representative of long-term changes in extreme warmest night temperatures. During the period of rapid urbanization（i.e., after 1978）, all three parameters of the GEV distribution are larger for the urban station group than for the reference station group, so are the magnitudes of their variations, and the urban areas have been experiencing higher extreme warmest night temperatures with larger variability. Diferent types of cities in the Bohai area have all experienced an urban heat island efect, with an average urbanization efect of approximately 0.3 per decade.
基金funded byÖsterreichische Forschungsförderungsgesellschaft FFG—feasibility study,Grant number 873045.
文摘Background:Increasing urbanization as well as global warming requires an investigation of the infuence of diferent construction methods and ground surfaces on the urban heat island efect(UHI efect).The extent of the infuence of the urban structure,the building materials used and their surfaces on the UHI efect can be signifcantly reduced already in the planning phase using a designated OpenFOAM-based solver“uhiSolver”.Results:In the frst part of this research work,it is shown that inner building details and components can be neglected while still obtaining sufciently accurate results.For this purpose,the building model was divided into two layers:a surface layer without mass,where the interaction with radiation takes place,and a component layer,which contains all relevant components and cavities of the building represented with mass-averaged material properties.It has become apparent that the three parameters—albedo,heat capacity and thermal resistance—which have a decisive infuence on the interaction,have diferent efects on the component temperatures and the surface temperatures.In the second part of this research work,dynamic 3D computational fuid dynamics(CFD)simulations are performed with uhiSolver for a residential block in Vienna.Comparing the simulation results with measurement data collected on site,it is shown that the simplifed assumption of homogeneous material data for building bodies provides very good results for the validation case investigated.However,the infuence of the greening measures in the courtyard of the residential block on the air temperature is found to be negligible.Furthermore,it was observed that due to locally higher radiation density,lower air velocities and higher air humidity,the apparent temperature in the courtyard is sometimes perceived to be higher than in the adjacent streets,despite the lower air temperature.Conclusions:Simplifying the modeling process of the uhiSolver software by reducing the model complexity helps to reduce manual work for setting up appropriate boundary conditions of buildings.Compared to market competitors,good results are obtained for the validation case Kandlgasse presented in this research work,despite the simplifcations proposed.Thus,uhiSolver can be used as a robust analytical tool for urban planning.
