Generation of unbalanced motion at horizontal boundaries in the atmosphere and the oceans

在大气和海洋的水平边界处产生不平衡运动

• 批准号: NE/F002807/1
• 负责人: Jacques Vanneste
• 金额: $ 23.54万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF002807%2F1
• 关键词: Generation; unbalanced; motion; horizontal; boundaries

The dynamics of the atmosphere and oceans at mid-latitudes is well described by focusing on the slow, large-scale motion, in nearly hydrostatic and geostrophic balance. However, fast small-scale motion in the form of gravity waves and associated instabilities plays a crucial role in a number of processes (such as momentum transport, turbulence, vertical mixing, and dissipation), which impact on large-scale circulations, middle-atmospheric circulation and ocean thermohaline circulation in particular. The mechanisms of generation of the fast, unbalanced motion have therefore received a great deal of attention in recent years. However, the so-called spontaneous-generation mechanisms, whereby the evolving hydrostatically and geostrophically balanced motion directly excites unbalanced motion, remain poorly understood, in spite of their importance. One difficutly is that these mechanisms are only efficient when the balanced motion evolves sufficiently rapidly, and that such a rapid evolution is rather atypical in the bulk of the atmosphere and oceans. Near horizontal boundaries, however, a rapid evolution is typical. By horizontal boundaries, we refer not only to the ocean surface and solid earth, but also to the tropopause, which plays a similar role. Not coincidentally, these are precisely the regions where strong unbalanced activity is observed. These also are regions where unbalanced motion has crucial consequences, the effect of turbulence on airplanes being the most obvious, if not the most important. The proposed research will examine how the generation of unbalanced motion at horizontal boundaries takes place. This will be done by analysing simple models which isolate the key feature of the boundary dynamics that is reponsible for unbalanced-motion generation, namely the formation of very active structures in the surface temperature, with both small spatial scales and short temporal scales. This feature has been well demonstrated in the context of the (balanced) surface quasi-geostrophic model, but its impact on unbalanced motion remains to be described. The proposed research will carry out this task for the first time. It will consider not only situations of frontal collapse but also the more complex cascade of small-scale instabilities which characterise surface evolution and leads to a form of turbulence. The aim is to relate the characteristics of the unbalanced motion to those of the surface fields with, as ultimate goal, the parameterisation of its impact on mixing and dissipation.

通过关注接近静水和地转平衡的缓慢、大规模运动，可以很好地描述中纬度地区大气和海洋的动态。然而，以重力波形式出现的快速小尺度运动和相关的不稳定性在许多过程（例如动量传输、湍流、垂直混合和耗散）中发挥着至关重要的作用，这些过程对大尺度环流、中流层和中流层产生影响。特别是大气环流和海洋温盐环流。因此，近年来，快速、不平衡运动的产生机制受到了广泛的关注。然而，尽管所谓的自发发生机制很重要，但人们对这种机制仍然知之甚少，即不断发展的静水和地转平衡运动直接激发不平衡运动。一个困难是，这些机制只有在平衡运动演化得足够快时才有效，而如此快速的演化在大部分大气和海洋中是相当不典型的。然而，在水平边界附近，典型的是快速演变。水平边界不仅指海洋表面和固体地球，还指对流层顶，它起着类似的作用。并非巧合的是，这些正是观察到强烈不平衡活动的区域。这些区域也是不平衡运动产生重大后果的区域，湍流对飞机的影响即使不是最重要，也是最明显的。拟议的研究将研究水平边界不平衡运动是如何发生的。这将通过分析简单的模型来完成，这些模型隔离了负责不平衡运动生成的边界动力学的关键特征，即在表面温度中形成非常活跃的结构，具有小空间尺度和短时间尺度。这一特征已在（平衡）表面准地转模型的背景下得到了很好的证明，但其对不平衡运动的影响仍有待描述。拟议的研究将首次执行这项任务。它不仅会考虑锋面塌陷的情况，还会考虑更复杂的小规模不稳定性的级联，这些不稳定性是表面演化的特征并导致某种形式的湍流。目的是将不平衡运动的特征与表面场的特征联系起来，作为最终目标，参数化其对混合和耗散的影响。

项目成果

Asymptotics of a Slow Manifold

慢流形的渐近

• DOI: 10.1137/070710081
• 发表时间: 2008-10-13
• 期刊: SIAM J. Appl. Dyn. Syst.
• 作者: J. Vanneste

Elliptical instability of a rapidly rotating, strongly stratified fluid

快速旋转、强分层流体的椭圆不稳定性

• DOI: http://dx.10.1063/1.3177354
• 发表时间: 2009
• 期刊: Physics of Fluids
• 影响因子: 4.6
• 作者: Aspden J

Streaming by leaky surface acoustic waves

通过泄漏表面声波进行流传输

• DOI: http://dx.10.1098/rspa.2010.0457
• 发表时间: 2010
• 期刊: Mathematical, Physical and Engineering Sciences
• 作者: Vanneste J

Spontaneous inertia-gravity-wave generation by surface-intensified turbulence

表面强化湍流产生自发惯性重力波

• DOI: 10.1017/jfm.2012.90
• 发表时间: 2012-04-24
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Eric Danioux;J. Vanneste;P. Klein;H. Sasaki
• 通讯作者: H. Sasaki

Gravity Waves Generated by Sheared Potential Vorticity Anomalies

剪切位涡异常产生的重力波

• DOI: 10.1175/2009jas3134.1
• 发表时间: 2024-09-14
• 期刊: Journal of the Atmospheric Sciences
• 影响因子: 3.1
• 作者: F. Lott;R. Plougonven;J. Vanneste
• 通讯作者: J. Vanneste