Numerical study on development of a multi-layer urban canopy model
Numerical study on development of a multi-layer urban canopy model
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多层城市冠层模型开发的数值研究
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发表时间：
2009
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通讯作者：
Jiang Wei
中科院分区：
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作者：
Jiang Wei
基于三维建筑几何假设，建立了一个多层城市冠层模型，用于研究大气运动与城市发展的关系。该模型由一组带阻力的动态方程组成，主要参数为：建筑物宽度、建筑物间距和垂直楼层密度分布，即高于某一水平的建筑物数目与所考虑的城市地区所有建筑物的比率分布。此外，还引入了一个树冠内的辐射过程，该模型的几何形状假定为在水平方向上均匀排列的无限大的规则排列的建筑物。每个模型由六个面(屋顶、地板和四面垂直墙)组成。建筑物的阻力和辐射过程，包括辐射遮挡和俘获效应，都取决于地面密度在垂直方向的分布。对冠层模型进行离线验证表明，模拟结果与风洞试验数据和子域观测数据吻合得很好。作为一种新的城市地面方案，冠层模型与南京大学区域边界层模式(NJU-RBLM)进行了耦合。并于2004年8月4日在北京市进行了模拟试验。模拟结果与一个密集业务观测网的观测结果进行了对比。对比结果表明，耦合方案(MUCM方案)正确地再现了气温(与观测值相差1-2K)和风速(与观测值相差约1m/S)，并且优于土壤植被改良方案(平板方案)，特别是对于夜间温度的模拟。此外，对于模拟夜间温度，耦合方案(MUCM方案)比土壤植被改良方案(SLARE方案)更好将地面温度模拟结果与陆地卫星观测结果进行对比，结果表明，新的城市地面处理方案显著改善了城市下垫面的模拟性能，更合理地考虑了三维建筑物结构中的辐射过程。
Based on the assumption of 3-dimension building geometry,a multiplayer urban canopy model were developed to research the relationship between atmospheric movement and the urban developing.The canopy model,which consists of a set of dynamic e-quations with a drag force,and there are three major parameters:building width,distance between buildings,and vertical floor density distribution,which is the distribution of a ratio of the number of the buildings that are taller than some level to all the buildings in the urban area under consideration.In addition,an irradiative process in the canopy is introduced,in which the model geometry is assumed to be an infinitely extended regular array of uniform buildings in the horizontal,each of which is composed of six faces(roof, floor,and four vertical walls).Both of the drag force of the buildings and the irradiative process,including the radiation shadowing and trapping effect,depend on the floor density distribution in the vertical.The off-line validation of the canopy model shows that the simulation is agreed with wind tunnel test data and the observation data in sub-domain very well.As a new urban land-surface scheme,the canopy model was then coupled with Regional Boundary Layer Model of Nanjing University(NJU-RBLM),and on-line cases were performed for 4 August 2004 in Beijing city.The simulation result compared with observations from a dense operational observational network.The comparison result shows that the coupled scheme(MUCM case) correctly reproduces the temperature (within 1 - 2 K difference from the observations) and wind speed(about 1 m/s difference from the observations),and is better than the soil vegetation modified scheme(SLAB case),especially for temperature simulation in night time.Besides,the comparison of ground surface temperature between simulated and observed results by Landsat satellite shows that the new urban land-surface process scheme improved the simulation performance at urban underplaying remarkably for taking care of the more reasonable radiation process in three-dimension buildings structure.