Dynamics and Impacts of Mesoscale Gravity Waves in Baroclinic Jet-Front Systems

智力优势：重力波在大气中无处不在，在对对流层天气、平流层动力学、臭氧化学和大气环流具有重要影响的各种大气过程中发挥着基本作用。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。重力波的动量输送和沉积对大气环流有重要影响。要更好地了解这些过程，就需要完全了解产生重力波的机制及其特征、分布和变异性。虽然过去的观测研究一再表明，许多水平波长为50-500公里的中尺度重力波与中纬度斜压急流系统有很强的联系，但这些波的确切产生机制仍不清楚。在利用干动力学取得进展的基础上，本研究的最终目标是了解对流层斜压急流系统产生的中尺度重力波的动力学和影响，以及它们与湿对流的相互作用。这项研究将通过使用斜压波的高分辨率干湿理想化模拟、实际半球模拟和卫星观测逐步解决这一问题。主要目标包括：i)在理想的干动力学模拟中扩大对重力波的研究，通过射线追踪技术进一步追踪波源和时空变化，并通过直接计算波浪强迫和响应来进一步区分平衡和不平衡在波浪产生中的作用；ii)进行理想湿斜压波的高分辨率模拟，研究其中模拟的重力波的特征和动力学，并探索重力波与对流之间的相互作用；将中尺度模式的使用扩展到准半球域，模拟整个冬季与中纬斜压急流系统有关的重力波，将模式结果与卫星观测和理想化模拟进行比较，并定性地评估动量和能量通量及其影响。更广泛的影响：更好地了解中尺度重力波及其与潮湿过程的相互作用可能有助于更好地了解动力学，改进对流触发和调制以及相关恶劣天气的预报。更好地理解气流不平衡和中尺度重力波可能会为中尺度数据同化和中尺度可预报性提供指导。更好地理解重力波过程也可能有助于通过非地形和非对流中尺度重力波更好地参数化对流层和平流层之间的能量和动量输送。

Intellectual Merit: Gravity waves are ubiquitous in the atmosphere and play a fundamental role in a wide variety of atmospheric processes that have important implications to tropospheric weather, stratospheric dynamics, ozone chemistry and general circulation. They can transfer significant amounts of energy and momentum, initiate and organize convection, and produce atmospheric turbulence. The momentum transport and deposition by gravity waves have significant impacts on the general circulation of the atmosphere. A better knowledge of these processes demands a complete understanding of the mechanisms by which the gravity waves are generated, together with their characteristics, distribution and variability. While past observational studies have repeatedly demonstrated that many of the mesoscale gravity waves with horizontal wavelength of 50-500 km are strongly associated with the midlatitude baroclinic jet-front systems, the exact generation mechanisms of these waves remain uncertain. Building on the progress made using dry dynamics, the ultimate goal of this research is to understand the dynamics and impacts of the mesoscale gravity waves generated by the tropospheric baroclinic jet-front systems and their interaction with moist convection. This study will progressively approach the problem by using high-resolution dry and moist idealized simulations of baroclinic waves, real-case hemispheric modeling and satellite observations. Major objectives include: i) expanding the investigation of gravity waves in the idealized simulations of dry dynamics to further track the wave source origins and spatial/temporal variations through the use of the ray tracing technique and to further differentiate the roles of balance vs. imbalance in the wave generation through direct calculations of wave forcing and response; ii) performing high-resolution simulations of idealized moist baroclinic waves, investigating the characteristics and dynamics of the gravity waves simulated therein and exploring the interactions between gravity waves and convection; and iii) extending the use of mesoscale models to a quasi-hemispheric domain to simulate gravity waves associated with midlatitude baroclinic jet-front systems for an entire winter season, comparing the model results with satellite observations and idealized simulations, and qualitatively assessing the momentum and energy fluxes and their impacts. Broader Impacts: Better understanding of mesoscale gravity waves and their interaction with moist processes may lead to better understanding of the dynamics and improved forecasts of convective triggers and modulation as well as the associated severe weather. Better understanding of flow imbalance and mesoscale gravity waves may provide guidance on mesoscale data assimilation and mesoscale predictability. Better understanding of gravity wave processes may also lead to better parameterization of the energy and momentum transport between the troposphere and stratosphere by non-topographic and non-convective mesoscale gravity waves.