New Methods in Storm Track Dynamics Theory

大气动力学中一个尚未解决的重要问题是大气中的急流是如何自发地从湍流中涌现出来的。在这个项目中，Farrell和他的团队将开发并探索一种新的喷流理论的含义，使用一种分析理论，该理论建立在他们之前在随机动力学(随机强迫系统的动力学，如湍流)工作的基础上。在这一理论中，作为天气图上常见的高点和低点的湍流涡旋被视为对纬向平均气流的随机强迫扰动。假设这些涡旋是微小的扰动，使得它们的方程是线性的，就可以建立一个封闭的自洽的喷流产生理论。该理论的初步结果表明，它预测的喷流的规模和结构与在地球大气中观察到的结果很好地一致。在本项目中，这项工作将扩大到：探索喷流及其稳定性如何依赖于问题的参数：随机强迫的强度和耗散参数的值。将问题推广到包括经线相关性，从而处理涡动极地急流与副热带急流共存的问题。将问题推广到非纬向对称急流，以处理北半球纬向孤立急流和风暴路径的问题。该项目的更广泛影响是获得对气候系统的更深入和更一般的了解。例如，气候的突然变化可能与这一理论所描述的喷流制度的突然变化有关。一名研究生将得到资助。

An important unsolved problem in atmospheric dynamics is how the jets in the atmosphere emerge spontaneously from turbulence. In this project, Farrell and his group will develop, and explore the implications of, a new theory of jets, using an analytical theory, that builds on their previous work in stochastic dynamics (the dynamics of randomly forced systems, like turbulent fluid flows). In this theory, the turbulent eddies, which are the familiar highs and lows of weather maps, are treated as randomly forced perturbations to the zonally averaged flow. With the assumption that these eddies are small perturbations, such that their equations are linear, a closed self-consistent theory for the emergence of jets can be developed.Preliminary results from the theory show that it predicts the scales and structures of jets in good agreement with those observed in Earth's atmosphere. In the present project, this work will be extended by:. Exploring how the jets and their stability depend upon the parameters of the problem: the strength of the stochastic forcing and the values of dissipation parameters.. Generalizing the problem to include meridional dependence, so as to treat the problem of an eddy-driven polar jet coexisting with the subtropical jet.. Generalizing the problem to non-zonally symmetric jets, so as to treat the problem of the zonally isolated jets and storm tracks of the Northern Hemisphere.The broader impacts of this project are in obtaining a deeper and more general understanding of the climate system. For example, abrupt changes in climate may be associated with abrupt changes in jet regimes that are described by this theory. A graduate student will be supported.