Wave Activity Budget and the Variabilities of the Extratropical Climate

高空天气图通常显示与构成中纬度地区日常天气的地面锋、气旋和反气旋密切相关的大尺度波型。这些波的运动，以及与之相关的地表天气模式，在很大程度上是由它们传播的平均西风急流驱动的。平均急流反过来又受到波浪行为的强烈影响，因此波浪-平均流相互作用的主题对于理解和预测中纬度天气是必不可少的。经典的波-平均流相互作用理论提供了强有力的见解，但它是基于线性波动动力学的，因此只在形式上对小振幅或无穷小的波有效。考虑到现实世界大气的波动性，这是一个实质性的限制，PI已经投入了相当大的努力来发展一个更普遍的理论，该理论适用于有限振幅的波（见AGS-1151790和AGS-0750916）。目前的工作将这一理论应用于大气动力学的几个主题，包括在南半球风暴路径的涡流动能中发现的20-30天振荡（见AGS-1343080）。初步研究表明，这种振荡符合波作用守恒关系，其周期性与波引起的极向表面热通量有关。另一个主题是大气阻塞事件的动力学，并且开发了一个局部版本的波平均流框架来解决这个问题。其他主题包括边界层阻尼和凝聚加热在波-平均流相互作用中的作用。这项工作是结合对气象资料（来自再分析产品）的分析，以及利用共同体大气模式（共同体地球系统模式的大气成分模式）的各种配置进行模拟。这项工作在科学和社会意义上都具有更广泛的影响，因为PI开发的概念框架可以被研究人员用于研究与气候变率和变化有关的各种现象。在进一步的下游，该框架所提供的更好的理解有助于月度到季节性时间尺度的天气预报，并有助于更好地理解用于决策支持的未来气候预测的结果。除了研究本身的好处之外，该项目还通过一个由大约30名研究生和早期职业科学家参加的大气动力学暑期学校来支持教育。暑期学校包括讲座、示范和实践活动。此外，该项目还支持一名研究生和一名博士后，从而培养该研究领域的下一代劳动力。

Upper-level weather charts typically show large-scale wave patterns which are closely associated with the surface fronts, cyclones, and anticyclones that make up daily weather in the middle latitudes. The movements of these waves, and the surface weather patterns connected to them, is driven in large measure by the mean westerly jet streams along which they propagate. The mean jet streams are in turn strongly affected by the behavior of the waves, thus the topic of wave-mean flow interaction is essential for understanding and predicting midlatitude weather. Classical wave-mean flow interaction theory offers powerful insights, but it is based on linear wave dynamics and thus is only formally valid for small amplitude, or infinitesimal, waves. This is a substantial limitation given the waviness of the real-world atmosphere, and the PI has devoted considerable effort to the development of a more general theory which holds for waves of finite amplitude (see AGS-1151790 and AGS-0750916). The present work applies this theory to several topics in atmospheric dynamics, including the 20-30 day oscillation found in the eddy kinetic energy of the Southern Hemisphere storm track (see AGS-1343080). Preliminary work suggests that the oscillation satisfy a wave action conservation relationship and the periodicity is related to wave-induced poleward surface heat flux. Another topic is the dynamics of atmospheric blocking episodes, and a localized version of the wave-mean flow framework is developed to address this problem. Other topics include the roles of boundary layer damping and condensational heating in wave-mean flow interaction. The work is conducted through a combination of analysis of meteorological data (from reanalysis products) and simulations with various configurations of the Community Atmosphere Model (the atmospheric component model of the Community Earth System Model).The work has broader impacts in both a scientific and societal sense, as the conceptual framework developed by the PI can be used by researchers to study a variety of phenomena related to climate variability and change. Further downstream the improved understanding provided by the framework can benefit weather prediction on monthly to seasonal timescales and contribute to better understanding of the results of future climate projections used for decision support. Beyond the benefits of the research itself, the project supports education through a summer school on atmospheric dynamics attended by about 30 graduate students and early career scientists. The summer school includes a combination of lectures, demonstrations, and hands-on activities. In addition, the project supports a graduate student and a postdoc, thereby training the next -generation workforce in this research area.