Surface Boundary Layer Characterization in Urban Areas

首席研究员将利用从世界各地广泛的地理区域和国家收集的城市实地实验的现有数据集。有机会从几个基本的科学角度分析这些综合的城市数据库，以发展普遍的科学关系。这些一般关系将在城市边界层模型层次结构的背景下进行测试，这将提高人们的理解，并允许在未来无法获得如此广泛观测的城市地区建立更准确的模型。在拥有10至100米或更高建筑的城市地区，大部分感兴趣的边界层都在粗糙度元素之下，这就需要发展一般关系，允许在下的冠层边界层与上的冠层之间的过渡。给定城市区域的描述符，如建筑形态，将研究估算地表通量和流场、湍流、稳定性和混合高度的方法。城市边界层的一些特征是由水平不均匀性决定的，这些不均匀性与农村空气流入具有不同表面特征的城市地区有关。由于每个建筑障碍、街区和社区都是独特的，城市边界层永远不会完全处于平衡状态，当空气从一种表面类型传递到另一种表面类型时，需要对新边界层的发展进行近似。例如，在夜间，城市建成区的城市边界层通常是对流的（不稳定的），因为温暖的城市表面加热了流入的较冷的稳定农村空气（即城市热岛效应）。中尺度气象模式需要城市地区更详细的土地利用和边界层参数化。由于全球范围内城市地区不断扩大，城市地区的地表通量、阻力和其他边界层过程对大多数气象现象的影响越来越大。研究成果将包括：1)描述城市边界层平均和湍流结构的一般公式；2)城市和农村流动变量之间的关系；3)描述空气从逆风农村到市中心再返回农村时稳定性变化的关系；4)改进城市效应的参数化。这些产品将有助于完善城市综合基础模式。这项研究将产生广泛的影响，例如与北美、欧洲和亚洲的相关城市研究合作，发展简单但基本的科学关系，并在一些城市地区得到验证，以及加强K-12和本科教育。例如，在基础教材和一般气象学课程中，简化的物理关系将有助于解释城市边界层。

The Principal Investigator will exploit existing data sets from urban field experiments that were collected from a wide array of geographic areas and countries throughout the world. There is an opportunity, to analyze these comprehensive urban data bases from several fundamental scientific perspectives in order to develop universal scientific relations. These general relations will be tested in the context of a hierarchy of urban boundary layer models that should improve understanding and should allow more accurate modeling in the future in urban areas where such extensive observations are not available. In urban areas with buildings 10 to 100 m or more tall, much of the boundary layer of interest is below the roughness elements, which requires development of general relations that allow a transition between the below canopy boundary layer to the above canopy. Given descriptors of urban areas such as building morphology, methods will be studied to estimate the surface fluxes and the flow field, turbulence, stabilities and mixing heights. Several of the features of the urban boundary layer are governed by horizontal inhomogeneities associated with the flow of rural air into the urban area with different surface characteristics. Since each building obstacle and block and neighborhood is unique, the urban boundary layer is never fully in equilibrium, requiring development of approximations for the development of new boundary layers as the air passes from one surface type to another. For example, during the night, the urban boundary layer in the built-up downtown area is often convective (unstable) because the warm urban surface heats the inflowing colder stable rural air (i.e., the urban heat island effect). Mesoscale meteorological models need more detailed land-use and boundary layer parameterizations for urban areas. Since urban areas are growing throughout the globe, the surface fluxes, the drag, and other boundary layer processes in urban areas have increasing influence on most meteorological phenomena. The products of the research will be 1) general formulas that describe the mean and turbulence structure of the urban boundary layer, 2) relationships between urban and rural flow variables, 3) relationships describing the variation of stability as the air passes from upwind rural to downtown and back to rural, and 4) improved parameterizations of urban effects. These products will help to improve comprehensive basic models for urban areas. There will be broad impacts of the research, such as collaborations with related urban studies in North America, Europe, and Asia, development of simple but basic scientific relations that are verified over a number of urban areas, and enhancement of K-12 and undergraduate education. For example the simplified physical relations will be useful for explaining urban boundary layers in basic texts and in general meteorology courses.