Dynamics and Impacts of Mesoscale Gravity Waves

重力波已被证明对天气非常重要。它们可以传递大量的能量和动量，引发和组织对流，并产生大气湍流。观测研究一再证明，在对流层高层急流条纹附近盛行着水平波长为50-500公里的中尺度重力波。然而，这些波的确切产生机制仍不清楚。这项研究的最终目的是了解由对流层高空急流系统和斜压不稳定引发的重力波的动力学和影响。一个具有嵌套能力的高分辨率中尺度模式将首先用来再现斜压波的生命周期，并模拟急流条纹的重力波发射。在这些理想化的模拟中，将详细研究重力波的特征、分布和变化，以及它们与母斜压急流系统的关系。接下来，将通过应用各种平衡/不平衡诊断方法，包括Rossby数、omega方程、非线性平衡和位涡反演，以及通过QG+理论的推广/实施，来研究平衡和不平衡动力学之间在模拟重力波启动过程中的相互作用。QG+是一个系统的渐近框架，从它可以得到Rossby数中的准地转平衡的二阶改正。这项研究的最后阶段将比较理想的斜压波模拟和观测中重力波的特征和动力学，并应用理想研究的结果来理解观测到的重力波的动力学。这项研究的成功完成可能有助于更好地理解和预测局地和区域性天气事件的时间和位置。

Gravity waves have been shown to be very important to weather. They can transfer significant amounts of energy and momentum, initiate and organize convection, and generate atmospheric turbulence. Observational studies have repeatedly demonstrated that mesoscale gravity waves with horizontal wavelength of 50-500-km are prevalent in the vicinity of the upper-tropospheric jet streaks. The exact generation mechanism of these waves, however, remains unknown. The ultimate goal of this research is to understand the dynamics and impacts of the gravity waves initiated by the upper-tropospheric jet-front systems and baroclinic instability. A high-resolution mesoscale model with nesting capability will first be used to reproduce the life cycle of the baroclinic waves and to simulate the gravity wave emission from jet streaks. The characteristics, distribution and variability of the gravity waves and their relationship to the parent baroclinic jet-front system in these idealized simulations will be examined in great details. Next, the interaction between balanced and unbalanced dynamics in the initiation of the simulated gravity waves will be investigated through applications of the various balance/imbalance diagnostics including Rossby number, omega equations, nonlinear balance and potential vorticity inversion and also through an extension/implementation of the QG+ theory. QG+ is a systematic asymptotic framework from which the balanced, next-order corrections of quasi-geostrophy in Rossby number are obtained. The final phase of this research will compare the characteristics and dynamics of the gravity waves in the idealized baroclinic-wave simulations with observations and apply the findings from the idealized study to understand the dynamics of the observed gravity waves.Successful completion of this research may lead to better understanding and prediction of the timing and location of local and regional weather events.