Wave Activity Budget and the Variabilities of the Extratropical Climate

高层天气图通常显示大尺度的波型，这些波型与构成中纬度地区日常天气的表面锋、气旋和反气旋密切相关。 这些波的运动以及与它们相关的地面天气模式在很大程度上是由它们沿着传播的平均西风急流驱动的。 平均急流反过来又强烈地受到波的行为的影响，因此波-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。 经典的波浪-平均流相互作用理论提供了强有力的见解，但它是基于线性波浪动力学，因此只对小振幅或无穷小的波浪有效。 考虑到现实世界大气的波度，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适用于有限振幅波的更一般的理论（参见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，包括在南半球风暴轴的涡动动能中发现的20-30天振荡（见AGS-1343080）。初步研究表明，振荡满足波动作用守恒关系，周期性与波浪引起的向极表面热通量有关。 另一个主题是大气阻塞事件的动力学，和波平均流框架的本地化版本的开发来解决这个问题。 其他的题目包括边界层阻尼和凝结加热在波-平均流相互作用中的作用。 这项工作是通过分析气象资料相结合（来自再分析产品）和用群落大气模式的各种配置进行的模拟（社区地球系统模型的大气部分模型）。这项工作在科学和社会意义上都有更广泛的影响，由于PI开发的概念框架可被研究人员用于研究与气候变率和变化有关的各种现象。 在下游，框架提供的更好的理解可以有利于每月到季节时间尺度的天气预测，并有助于更好地理解用于决策支持的未来气候预测结果。 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关于大气动力学的暑期学校来支持教育。 暑期学校包括讲座，演示和动手活动的组合。 此外，该项目还支持一名研究生和一名博士后，从而培养这一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.