Atmospheric and oceanic turbulence

大气和海洋湍流

• 批准号: RGPIN-2018-04404
• 负责人: Bartello, Peter
• 金额: $ 3.66万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=712968
• 关键词: Atmospheric; oceanic; turbulence

The requested funds are for the study of atmospheric and oceanic fluid turbulence mainly employing high-resolution numerical simulations, but guided by perturbative analytical techniques, statistical closure theories and dimensional analysis. Turbulence is clearly the most complex outstanding problem in fluid dynamics and understanding it better is absolutely necessary to improve high-resolution environmental and climate models. Of crucial importance to large-scale modellers is how geophysical flows mix the various quantities whose distributions are of such great concern to society. In addition, many fields of study including pollutant dispersion modelling, urban meteorology and wind energy generation, require statistical forecast skill on time scales of hours and length scales of 10's to 100's of kilometers, where my group and I have been exploring the more complicated dynamics that prevail. This application concerns only the fundamental research issues. The applicant also values his longstanding collaborations with the numerical weather prediction community and a new urban meteorology group in Hong Kong, along with their HQP and in-kind funding. Specifically, the influence of rotation and stratification on classical turbulence statistics will be examined. The subject belongs to the family of studies of waves and vortices in some limits and classical theory suggests that large-scale temperature, pressure and wind are balanced in such a way that high-frequency waves have low amplitudes. The last 10 years have seen rapid progress by many groups worldwide in characterising the wave/vortex nature of turbulence at scales smaller than those of the baroclinic eddies in both atmosphere and ocean. This has been in field observations, lab experiments, numerical simulation and theory and the current vigour in the field is explained by the fact that realistic models have now reached resolutions where our lack of dynamical understanding is detrimental to progress. My own group has found that balance dynamics cannot exist in the small-scale regime where rotation is less important. Here, there exists a single turbulent time scale and wave/vortex decompositions break down. At larger scales higher-order balance dynamics give rise to steep wave number to the -3 energy spectra, whereas a breakdown of balance yields a -5/3 spectrum consistent with observations. Spontaneous imbalance occurs primarily in regions of large strain. The next step is to formulate parameterisation schemes that dissipate balanced energy in precisely the right locations at the right time, instead of being based on global averages over long periods. The second novelty is that we now include realistic vertical inhomogeneities, such as the ground, ocean surface, thermocline and tropopause, etc., where it is proposed that we are now ready to include the role of waves in boundary-layer turbulence.

申请的资金用于大气和海洋流体湍流研究，主要采用高分辨率数值模拟，但以微扰分析技术、统计闭合理论和量纲分析为指导。湍流显然是流体动力学中最复杂的突出问题，更好地理解它对于改进高分辨率环境和气候模型是绝对必要的。 对于大规模模型制作者来说，至关重要的是地球物理流如何混合各种数量，这些数量的分布是社会非常关注的。此外，许多研究领域，包括污染物扩散模型，城市气象学和风能发电，需要在小时的时间尺度和10到100公里的长度尺度上的统计预测技能，我和我的团队一直在探索更复杂的动力学。 本申请仅涉及基础研究问题。 申请人还重视他与数值天气预报界和香港一个新的城市气象组织的长期合作，沿着他们的HQP和实物资助。 具体来说，旋转和分层对经典湍流统计的影响将被检查。该主题属于在某些限制下研究波和涡旋的家庭，经典理论表明，大尺度温度，压力和风以高频波具有低振幅的方式平衡。 近10年来，世界范围内的许多研究小组在表征尺度小于大气和海洋中斜压涡旋的湍流的波/涡性质方面取得了迅速进展。这已经在实地观察，实验室实验，数值模拟和理论和目前的活力在该领域的解释是，现实的模型，现在已经达到的决议，我们缺乏动力学的理解是有害的进展。 我自己的团队发现，在旋转不太重要的小尺度区域，平衡动力学不可能存在。在这里，存在一个单一的湍流时间尺度和波/涡分解打破。在更大的尺度上，高阶平衡动力学使-3能谱的波数变陡，而平衡的破坏产生与观测一致的-5/3能谱。自发性失衡主要发生在压力大的地区。 下一步是制定参数化方案，在正确的时间精确地在正确的位置耗散平衡能量，而不是基于长期的全球平均值。第二个新奇是我们现在包括了真实的垂直不均匀性，如地面、海洋表面、温跃层和对流层顶等，其中提出，我们现在准备包括波在边界层湍流中的作用。