Atmospheric Boundary Layer Studies

大气边界层（ABL）通常是湍流的，典型深度约为1公里，是我们大多数人生活，工作和娱乐的地方。我的研究小组过去曾研究过许多与ABL流相关的问题，包括使用模型和实地研究的复杂地形（例如丘陵和粗糙度变化）上的流。尽管许多研究小组对大气边界层的研究有很长的记录，但在我们对一些重要的实际问题（如雾和地表条件）的理解和预测方面仍有重大改进的机会。 未来5年的一个目标是研究边界层内的雾，并仔细探索雾发展和消散的条件。这些涉及到热量、水（蒸汽和水滴）、辐射（长波和短波）和云物理过程的湍流传输。 另一个重要的应用ABL研究领域是冬季道路条件的研究。除了湍流传输，加上表面和次表面的条件，这些可以在很大程度上取决于太阳和长波辐射通量，强烈影响的存在下，低层次的云。例如，与改进的ABL模型相结合，可以扩展加拿大环境部17年前开发的广泛使用的METRo预测模型。 我们的主要方法将继续是湍流边界层模拟。有两种基于计算机的方法，大涡模拟（LES）和求解雷诺平均Navier-Stokes方程（RANS）与某种形式的湍流封闭。我的研究小组过去在不同的项目中使用过这两种方法。我们将在这里集中在RANS建模，但也有LES具有优势的情况下，例如，调查雾“斑块”，和车辆尾流的情况。 我还计划探索RANS模型中的详细闭包问题。一般而言，RANS模型将湍流动能（TKE）作为变量之一，并将“主长度尺度”l或TKE耗散率作为另一变量。这些在大多数情况下似乎是令人满意的，并且在某种程度上依赖于这样的概念，即能量在大尺度下被投入湍流谱，然后通过谱“级联”被耗散并在非常小的尺度（<1 mm）下转化为热量。在某些情况下，例如风力涡轮机尾流或车辆后面的尾流，存在中间尺度（叶片或车辆宽度）的TKE的附加输入。我们将研究如何有效地表示这个过程。 主要的研究目标将是扩大ABL研究的范围，我的团队有一个专业知识，并包括辐射效应。其中包括对道路和航空安全有重大影响的应用，如雾。我们将有兴趣通过行业或政府合作开发这些潜力，但依赖于NSERC发现补助金支持基础研究，以启动和支持更多的应用研究。

The, usually turbulent, atmospheric boundary layer (ABL) with a typical depth of about 1 km, is where most of us live, work and play. My research group have worked on many issues related to ABL flows in the past, including the flow over complex terrain (hills and roughness changes for example) using both models and field studies. Despite a long record of ABL studies by many research groups there are still opportunities for significant improvements in our understanding and forecasting of some important practical issues, such as fog and land surface conditions. One objective over the next 5 years will be to study fog within the boundary layer and to carefully explore the conditions under which it can develop and later dissipate. These involve a mix of turbulent transfer of heat, water (vapor and droplets), radiation (long and short wave) and cloud physics processes. Another important applied ABL research area is a study of winter road conditions. In addition to turbulent transfers, plus surface and sub-surface conditions these can depend to a considerable extent on solar and long wave radiation fluxes, strongly influenced by the presence of low level cloud. Coupling with an improved ABL model would, for example, allow an extension of the very widely used METRo forecast model, developed 17 years ago at Environment Canada. Our main approach will continue to be turbulent boundary-layer modeling. There are two computer-based approaches, Large Eddy Simulation (LES) and solving the Reynolds Averaged Navier-Stokes (RANS) equations with some form of turbulence closure. My research group has used both in the past for different projects. We will focus here on RANS modeling, but there are situations where LES has advantages, for example to investigate fog "patchiness", and vehicle wake situations. I also plan to explore a detailed closure issue in RANS models. In general RANS models will include turbulence kinetic energy (TKE) as one of the variables and either a "master length scale", l, or a TKE dissipation rate, , as another. These appear satisfactory in most cases and rely to some extent on the concept that energy is put into the turbulence spectrum at large scales and then "cascades" through the spectrum to be dissipated and converted to heat at very small scales (< 1mm). In some cases such as wind turbine wakes, or wakes behind vehicles, there is an additional input of TKE at an intermediate scale (blade or vehicle width). We will investigate ways to effectively represent this process. The main research goal will be to expand the range of ABL studies that my group have an expertise in and to include radiative effects. These include applications, such as fog, with significant impacts on road and air safety. We will be interested in exploiting these potentials through industry or government collaboration but rely on NSERC Discovery grant support for the fundamental research needed to initiate and support the more applied studies.