Numerical Simulations of Gravity Wave Instabilities, Wave-Wave and Wave Mean Flow Interactions, Momentum Transport, and Spectral Evolution in the Mesosphere and Lower Thermosphere

该项目将进行全面的建模研究，旨在量化重力波（GW）不稳定动力学和非线性波-波和波-平均流相互作用，这些相互作用驱动中间层和低热层（MLT）GW频谱内的能量和动量沉积以及能量转移。 GW动量输送是中高纬度MLT大尺度环流和热力结构的主要驱动力，在赤道纬度似乎起着重要作用。 观测和建模还表明，GW动量通量强烈调制潮汐和行星波（PW）和变量GW动量通量可以反过来调制这些大规模的运动和映射的GW过滤到更高的高度的影响。尽管这些过程的至关重要性，GW的不稳定性和相互作用的动态控制这些大规模的反应已被量化，只有在非常理想的环境中。 在各种大尺度大气环流模式、气候和数值天气预报模式中，通过GW参数化描述这些动力学被广泛认为是这些动力学在许多应用中的差近似，尽管它们对整个大气的大尺度动力学有重要影响。 该项目的目标是充分定义大域和宽GW谱的各种不稳定动力学，以提供对最重要组件的关键理解和指导，这些GW影响的参数化设计具有价值，这将大大提高依赖于它们的各种天气和气候模型的性能。 为了尽可能全面地量化最重要的GW不稳定性和相互作用动力学及其平均和变量响应，将进行非常高分辨率的直接数值模拟（DNS）和大涡模拟（LES），以评估不同不稳定性类别之间的竞争（包括波与波的相互作用），以及其中一个或另一个明显主导各种全球Ws尺度，频率，和振幅在各种环境中; GW耗散，振幅（和动量通量）的限制，和频谱演变的GW不稳定事件的本地化的重要性; GW（和平均剪切）叠加不稳定的发生和类型和湍流混合和运输的后果。 该项目的目的是提供一个更定量的表征GW动量沉积，光谱演变，平均和大尺度强迫的MLT这些动态。

This project will perform comprehensive modeling studies intended to quantify gravity wave (GW) instability dynamics and nonlinear wave-wave and wave-mean flow interactions that drive energy and momentum deposition and energy transfers within the GW spectrum in the mesosphere and lower thermosphere (MLT). GW momentum transport is the major driver of the large-scale circulation and thermal structure of the MLT at middle and high latitudes and appears to play an important role at equatorial latitudes. Observations and modeling also suggest that GW momentum fluxes are strongly modulated by tides and planetary waves (PWs) and that variable GW momentum fluxes can in turn modulate these larger-scale motions and map the effects of their GW filtering to much higher altitudes. Despite the critical importance of these processes, the GW instability and interaction dynamics controlling these large-scale responses have been quantified only in very idealized environments to date. The descriptions of these dynamics via GW parameterizations in various large-scale general circulation model, climate, and numerical weather prediction models are widely recognized to be poor approximations of these dynamics in many applications, despite their important influences on larger-scale dynamics throughout the atmosphere. The goal of the project is to define the various instability dynamics for large domains and broad GW spectra sufficiently well to provide a critical understanding of the most important components and guidance that is of value in the design of parameterizations of these GW influences that would substantially improve the performance of the various weather and climate models that depend on them. To quantify the most important GW instability and interaction dynamics and their mean and variable responses as fully as possible, very high resolution direct numerical simulations (DNS) and large-eddy simulations (LES) will be done in order to assess the competition between different instability classes (including wave-wave interactions) and the circumstances where one or the other is clearly dominant for various GWs scales, frequencies, and amplitudes in various environments; the importance of localization of GW instability events in GW dissipation, amplitude (and momentum flux) constraints, and spectral evolution; the consequences of GW (and mean shear) superposition for instability occurrence and type and turbulent mixing and transport. The project aims to provide a more quantitative characterization of these dynamics on GW momentum deposition, spectral evolution, and mean and large-scale forcing of the MLT.