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

知识价值：引力波在大气中无处不在，在各种大气过程中起着重要作用，这些过程对对流层天气、平流层动力学、臭氧化学和大气环流具有重要影响。它们可以传递大量的能量和动量，发起和组织对流，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的影响。要更好地了解这些过程，就需要完全了解重力波产生的机制，以及它们的特征、分布和变化。虽然过去的观测研究反复表明，许多水平波长为50-500 km的中尺度重力波与中纬度斜压射流锋系统密切相关，但这些波的确切产生机制仍不确定。在干动力学研究的基础上，本研究的最终目标是了解对流层斜压射流锋系统产生的中尺度重力波的动力学和影响及其与湿对流的相互作用。本研究将通过斜压波的高分辨率干湿理想模拟、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：1)在理想的干动力学模拟中扩展重力波的研究，通过使用射线追踪技术进一步跟踪波源起源和时空变化，并通过直接计算波的强迫和响应进一步区分平衡与不平衡在波产生中的作用；Ii)对理想湿斜压波进行高分辨率模拟，研究模拟重力波的特征和动力学，探索重力波与对流的相互作用；iii)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度斜压急流锋系统相关的重力波，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，改进对流触发和调节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以为中尺度资料同化和中尺度预报提供指导。对重力波过程的更好理解也有助于更好地参数化非地形和非对流中尺度重力波在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.