New Methods in Storm Track Dynamics Theory

大气动力学中尚未解决的一个重要问题是大气中的喷流是如何从湍流中自发产生的。在这个项目中，法雷尔和他的团队将开发并探索一种新的射流理论，使用一种分析理论，建立在他们之前在随机动力学（随机强迫系统的动力学，如湍流流体流动）方面的工作基础上。在这个理论中，湍流漩涡，也就是我们在天气图上所熟悉的高点和低点，被看作是对纬向平均气流的随机强迫扰动。假设这些涡流是小的扰动，因此它们的方程是线性的，就可以发展出一个关于喷流出现的封闭自洽理论。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测到的非常吻合。在目前的项目中，这项工作将被扩展为：探索射流及其稳定性如何取决于问题的参数：随机强迫的强度和耗散参数的值。将问题推广到包括经向依赖，从而处理涡旋驱动的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喷流，从而处理北半球纬向隔离喷流和风暴路径问题。该项目的更广泛影响在于对气候系统有更深入和更普遍的了解。例如，气候的突变可能与该理论所描述的喷流状态的突变有关。研究生将获得资助。

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.