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Collaborative Research: New Pathways to Enhanced Turbulence and Mixing via Kelvin-Helmholtz Instability Tube and Knot Dynamics

合作研究：通过开尔文-亥姆霍兹不稳定管和结动力学增强湍流和混合的新途径

基本信息

批准号：
2128443
负责人：
David Fritts
金额：
$ 74.86万
依托单位：
GLOBAL ATMOSPHERIC TECHNOLOGIES AND SCIENCES, INC.
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-11-01 至 2024-10-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2128443&HistoricalAwards=false
关键词：
Collaborative Research New Pathways Enhanced

项目摘要

The project seeks funding to investigate atmospheric turbulence generation. Shear layers in the atmosphere, where a layer slides over another, can result in instabilities that are commonly seen in thin cloud layers and resemble a series of ocean waves breaking on a beach. These instabilities, called Kelvin-Helmholtz instabilities, cause turbulence and mixing throughout the atmosphere and the oceans where shears are strong. Spacing between these “billows” can vary in the atmosphere from a few meters near the ground to 10 km or larger at altitudes as high as 100 km. Those seen in clouds usually have spacings (or wavelengths) from a few hundred meters to a km or so. The turbulence and mixing when these billows “break” influence the atmospheric structure and weather, especially near the ground, but their effects are not described well in weather prediction models. This research will explore a new type of instability causing breaking and turbulence that was recently discovered in thin clouds at very high altitudes that the research team expects to occur at all altitudes, and to significantly increase the turbulence and mixing due to these processes. If shown to occur for a wider range of conditions, this would significantly influence our ability to model the atmosphere near the ground and improve weather prediction that impacts all of us. The same instabilities occur in the oceans and are expected to also improve prediction of ocean circulations and structure when these processes are more fully understood. The project will involve a graduate student and a postdoctoral researcher experience in state-of-the-art modeling and super-computing. New observations of thin Polar Mesospheric Clouds and airglow layers at high altitudes (~80-90 km) have revealed the occurrence of a new type of instability leading to turbulence arising from mis-aligned Kelvin-Helmholtz (KH) billows accompanying variable geophysical forcing. These instabilities arise due to interactions among adjacent KH billow cores, rather than within single billows, and initial modeling of these dynamics have shown them to be much stronger, and to lead to much more intense turbulence, than occur in their absence. These dynamics arise from interactions between KH billow cores and large-scale vortex tubes that are excited where KH billows are mis-aligned or discontinuous due to initial conditions. Initial modeling employing direct numerical simulations that enable quantitative assessments of these dynamics, their stronger instabilities, and their more intense turbulence suggest that they may also cause enhanced turbulence and mixing in regions, and for conditions, in which turbulence was not previously expected. The research team believes that these enhanced KH billow dynamics are likely to be widespread and that they will allow us to update how these dynamics are modeled, enabling improved weather prediction, and of similar responses in the oceans. Because KH instabilities also play significant roles of other fields of physics, specifically magnetospheric physics and astrophysics, the benefits of this research may prove to be very broad.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目寻求资金以研究大气湍流的产生。大气中的剪切层，一层在另一层上滑动，会导致不稳定，这在薄云层中很常见，就像一系列海浪在海滩上破碎。这些不稳定性称为开尔文-亥姆霍兹不稳定性，在大气和海洋中引起湍流和混合，在那里剪切力很强。这些“巨浪”之间的间距在大气层中可以从近地面的几米到10公里或更大，高度高达100公里。在云层中看到的那些通常具有从几百米到一公里左右的间距（或波长）。这些巨浪“破裂”时的湍流和混合会影响大气结构和天气，尤其是近地面的天气，但天气预测模型中并没有很好地描述它们的影响。这项研究将探索一种新的不稳定性，这种不稳定性会导致最近在非常高的高度薄云中发现的破裂和湍流，研究小组预计这种不稳定性会在所有高度发生，并显着增加这些过程引起的湍流和混合。如果在更广泛的条件下发生，这将显著影响我们模拟地面附近大气的能力，并改善影响我们所有人的天气预测。同样的不稳定性也发生在海洋中，当这些过程得到更充分的理解时，预计也会改善对海洋环流和结构的预测。该项目将涉及一名研究生和一名博士后研究员在最先进的建模和超级计算方面的经验。对高海拔（~80-90 km）极区中间层薄云和气辉层的新观测揭示了一种新型不稳定性的发生，这种不稳定性导致了伴随着可变地球物理作用力的非对齐开尔文-亥姆霍兹（KH）巨浪引起的湍流。这些不稳定性的出现是由于相邻的KH巨浪核心之间的相互作用，而不是在单一的巨浪，这些动态的初始建模表明，他们要强大得多，并导致更强烈的湍流，比发生在他们的缺席。这些动态产生的KH波涛核心和大规模的涡流管，激发KH波涛是不对齐或不连续的初始条件下，由于之间的相互作用。初始建模采用直接数值模拟，使定量评估这些动态，其更强的不稳定性，其更强烈的湍流表明，它们也可能导致增强的湍流和混合的区域，并为条件，在湍流是以前没有预料到的。研究小组认为，这些增强的KH巨浪动力学很可能是广泛的，它们将使我们能够更新这些动力学的建模方式，从而改善天气预测以及海洋中的类似反应。由于KH不稳定性在其他物理学领域，特别是磁层物理学和天体物理学中也发挥着重要作用，因此这项研究的好处可能会被证明是非常广泛的。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。