Stratified Turbulence in the Atmosphere

大气中的层状湍流

• 批准号: RGPIN-2015-05008
• 负责人: Waite, Michael
• 金额: $ 2.99万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=634123
• 关键词: Stratified; Turbulence; Atmosphere

The turbulent fluid dynamics of the atmosphere span an amazing range of length scales, from weather systems of thousands of kilometres across, down to hurricanes, thunderstorms, and small eddies. The mesoscale is an intermediate range of length scales from hundreds of kilometres to kilometres, which plays an important role in the dynamics of the atmosphere. Density stratification — the layering of heavier air under lighter air — has a profound effect on  mesoscale dynamics, in addition to several other phenomena, including the Earth's rotation, clouds, and surface forcing. The mesoscale acts as a turbulent cascade, transferring energy from large scales, where it is injected by solar heating, down to smaller and smaller scales, where it is eventually dissipated by the viscosity of air. However, the details of this cascade are still not fully understood. In addition, the small-scale end of this cascade, where mesoscale turbulence breaks down into smaller-scale turbulence at sub-kilometre scales, is often not well represented in atmospheric models. The work proposed here will use carefully designed experiments with a variety of numerical models of the atmosphere to answer important open questions about the mesoscale cascade. The role of gravity waves, which has been debated for several years, will be addressed with improved diagnostics for identifying waves in model output. The nature of the breakdown of mesoscale turbulence at small scales will be investigated with large, high-resolution simulations. In addition, methods for better representing the effects of small-scale turbulence, which are not always explicitly captured by atmospheric models, will be developed. The outcomes of this research program will assist modellers in assessing their simulations, comparing models, and more accurately representing unresolved turbulence, in addition to advancing our fundamental understanding of the atmosphere.

大气的湍流流体动力学跨越了惊人的长度尺度范围，从数千公里的天气系统，到飓风、雷暴和小涡流，中尺度是从数百公里到公里的中间尺度范围，除了其他几个因素之外，密度分层（较重的空气在较轻的空气下分层）在大气动力学中起着重要作用。包括地球自转、云层和表面强迫在内的中尺度充当湍流级联，将能量从大尺度（通过太阳加热注入）转移到越来越小的尺度（最终被粘度消散）。然而，该级联的细节仍未完全了解。此外，该级联的小尺度末端，中尺度湍流分解为更小尺度。亚公里尺度的湍流通常无法在大气模型中得到很好的体现，这里提出的工作将使用精心设计的各种大气数值模型的实验来回答有关中尺度级联重力波的作用的重要开放性问题。这个已经争论了好几年的问题将通过改进模型输出中的波识别来解决。此外，还将通过大型高分辨率模拟来研究小尺度下中尺度湍流分解的性质。为了更好地表示大气模型并不总是明确捕获的小规模湍流的影响，该研究计划的结果将帮助建模者评估他们的模拟，比较模型，并更准确地表示未解决的湍流。除了增进我们对大气的基本了解之外。