Parameterization Errors in Numerical Simulations of Stably-Stratified Atmospheric Boundary Layers Using CASES-99 Observations

了解大气边界层的动态对于更好地了解天气和气候至关重要。 将利用大涡模拟技术和中尺度模式对稳定层结大气边界层的演变进行数值研究。 这项研究将结合联合收割机数值模拟和观测，从最近的外地计划-案例-99。 数值模拟将补充观测，提供关于稳定边界层（SBL）过程的更详细的信息：湍流输送和动量、热量和水分的混合。研究的目标是：1）对典型的、强分层的夜间边界层（NBL）进行长期、高分辨率的模拟; 2）利用广泛的观测数据库验证这些模拟的结果;（3）发展和检验更精确的SBL参数化方案，以适应大尺度模拟的需要。现有的大气湍流和近地面层参数化方案的潜在缺陷导致它们不能准确地反映强稳定层结条件下的全球不稳定性。 假设参数化的失败产生的原因是他们无法解释非线性效应，如破碎的重力波和开尔文-亥姆霍兹巨浪将进行测试。 并行LES和中尺度代码将在大规模并行处理器上使用，以解决从几米（小惯性范围涡流）到几十公里（含能量涡流）的所有动态相关运动尺度。 将特别注意准确地代表重力波和与低空急流和条件下，全球不稳定性发生相关的剪切之间的相互作用。 通过解析大部分湍流涡旋和重力波，将有可能减少中尺度模式中湍流参数化引入的不确定性和偏差。

Understanding the dynamics of the atmospheric boundary layer is crucial to better understanding of both weather and climate. A numerical study of the evolution of a stably stratified atmospheric boundary layer (ABL) will be carried out using a large-eddy simulation (LES) technique and a mesoscale model. This study will combine numerical simulations and observations from a recent field program - CASES-99. Numerical simulations will complement observations in providing more detailed information about stable boundary layer (SBL) processes: turbulence transport and mixing of momentum, heat, and moisture.The goals of the research are: 1) to conduct long-term, high-resolution simulations of canonical, strongly stratified nocturnal boundary layers (NBL); 2) to verify the results of these simulations using an extensive observational data base; and 3) to develop and test more accurate parameterizations of SBLs for large-scale simulations.Underlying deficiencies in current atmospheric turbulence and surface layer parameterizations result in their failure to represent accurately global intermittence under strong stably-stratified conditions. The hypothesis that the failures of parameterization arise from their inability to account for nonlinear effects such as breaking gravity waves and Kelvin-Helmholtz billows will be tested. Parallel LES and mesoscale codes will be used on a massively parallel processor to resolve all the dynamically relevant scales of motion from several meters (small inertial range eddies) to several tens of kilometers (energy containing eddies). Special attention will be given to represent accurately interactions between gravity waves and shear associated with low-level jets and conditions under which global intermittence occurs. By resolving a large fraction of turbulence eddies as well as gravity waves it will be possible to reduce uncertainties and biases introduced by turbulence parameterizations in mesoscale models.