Breakdown of Balance and the Generation of Inertia-Gravity Waves in Upper-Tropospheric Jets and Fronts

平衡流动及其分解对地球物理流体动力学和天气预报具有重要意义，但与之相关的动力学在很大程度上仍不为人所知。该项目的目的是调查对流层上层急流和锋面的平衡性质，它破裂的条件和惯性重力波的产生，以及造成这种平衡的物理机制。方法是从一个简单的两层原始方程开始，用于检查基本动力学，然后扩展到越来越复杂的框架，例如包括平流层。使用这些模型的数值模拟将考察斜压波的生命周期，在此过程中锋面系统发展并产生惯性重力波。根据数值研究的结果，将发展一个理想化的解析模式来描述惯性重力波产生的基本动力学行为。这项计划将加深对天气预报中重要的惯性重力波的理解。这项工作的重要性不仅限于教学应用，还包括对航空和天气预报的潜在好处。如果能够建立一种分析方法来预报由某种气流不平衡产生的显著重力波活动，那么它将直接应用于与高空急流相关的晴空湍流的预报，以及重力波强迫引起的恶劣天气的产生。该项目的结果可以证明来自锋面系统的破碎波可能在大气环流中发挥的作用。

The topic of balanced flow and its breakdown is of fundamental importance to geophysical fluid dynamics and weather prediction, yet the dynamics associated with it remain largely unknown. The objective of this project is to investigate the nature of balance in upper-tropospheric jets and fronts, the conditions for it to breakdown and the generation of inertia-gravity waves, and the physical mechanisms responsible for it. The approach is to start with a simple two-layer primitive equation for the examination of the fundamental dynamics and then extended to frameworks with increasing complexity, such as including the stratosphere. Numerical simulations using these models will examine the life cycles of baroclinic waves in which frontal systems develop and inertia-gravity waves are generated. Based on the results from the numerical studies, an idealized analytic model will be developed to describe the essential dynamic behavior of the generation of inertia-gravity waves.This project will enhance the understanding of the inertia-gravity waves that are important to weather forecasting. The importance of this work extends beyond the pedagogical applications to include potential benefits to aviation and weather forecasting. If an analytical approach for forecasting significant gravity wave activity generated by some kind of flow imbalance can be formulated, then it will have direct applications to forecasts of clear-air turbulence associated with upper-level jet streams, and to the generation of severe weather resulting from gravity wave forcing. Results from the project can demonstrate the roles that breaking waves from frontal systems may play in the atmospheric general circulation.