CEDAR Postdoc: Analysis and Modeling of Breaking Short Period Gravity Waves and Their Effects on the Dynamic Mesosphere and Lower Thermosphere

该项目将进行一项建模和观测研究，以调查短周期重力波的破碎以及在中层和低热层区域的实际风和热条件下由此产生的能量和动量沉积。 短周期（5-30分钟）、小尺度（10-100公里）重力波在整个中高层大气中提供了很大一部分波能。 这些包括水平和垂直传播的波，以及在较短周期内，由大规模热或风结构引导以水平传播的波。 这种波是由广泛的过程产生的，包括对流层强迫通常与对流天气系统和雷暴有关，以及主要由于局部对流和切变不稳定性或非线性共振相互作用而产生的原位强迫。 通过对重力波对中层顶气辉调制的广泛地面观测，结合数值和理论模拟研究，近几十年来对小尺度重力波的产生、传播和方向性/季节性的理解有了显着提高。 然而，目前很少有人知道的能量和动量的最终沉积通过打破短周期重力波包，特别是那些强烈控制的背景大气结构。 该项目将侧重于两个具体问题，以解决这一认识上的差距：（1）中纬度中间层/低热层的大尺度动态结构如何决定短周期重力波的稳定性和破碎？(2)如何打破或消散短周期重力波修改当地中层/低热层结构通过动量和能量沉积？ 为了回答这些问题，将进行一项结合数值和观察的研究。 利用最近的，二维，完全非线性模型的重力波传播和气辉调制，大气不稳定性和波破碎的作用和影响将探讨短周期重力波在准现实条件下。 这将由气辉图像数据集与可用的雷达和激光雷达风数据一起补充，以确定背景动力学对短周期波浪破碎和整体大气动力学稳定性的作用。开发了要使用的模型之一的收件人。 通过该项目产生的短周期重力波对能量和动量沉积进行量化，将有益于中间层/低热层科学。

This project will conduct a modeling and observational study to investigate the breaking of short-period gravity waves and the resulting energy and momentum deposition under realistic wind and thermal conditions in the mesosphere and lower thermosphere region. Short-period ( 5-30 min), small-scale ( 10-100 km) gravity waves provide a significant fraction of wave energy throughout the middle and upper atmosphere. These include waves which propagate horizontally and vertically and, at shorter periods, those which are ducted by large-scale thermal or wind structure to propagate horizontally. Such waves are generated by a broad range of processes, including tropospheric forcing often associated with convective weather systems and thunderstorms, and in situ forcing due primarily to localize convective and shear instabilities, or to nonlinear resonant interactions. Through extensive ground-based observations of mesopause airglow modulation by gravity waves, in conjunction with numerical and theoretical modeling studies, understanding of small-scale gravity wave generation, propagation, and directionality/seasonality has improved significantly over recent decades. However, very little is currently known about the final deposition of energy and momentum via breaking of short-period gravity wave packets, particularly those which are strongly controlled by background atmospheric structure. The project will focus on two particular questions to address this gap in understanding: (1) How does the large-scale dynamic structure of the mid-latitude mesosphere/lower thermosphere dictate the stability and breaking of short-period gravity waves? (2) How does breaking or dissipating short-period gravity waves modify the local mesosphere/lower thermosphere structure through momentum and energy deposition? To answer these questions, a combined numerical and observational study will be carried out. Utilizing recent, two-dimensional, fully-nonlinear models of gravity wave propagation and airglow modulation, the role and effects of atmospheric instability and wave breaking will be explored for short-period gravity waves under quasi-realistic conditions. This will be complemented by airglow image data-sets together with available radar and lidar wind data to determine the role of background dynamics on short-period wave breaking, and overall atmospheric dynamic stability.The broader impact of the project is that it supports the efforts of a new Ph.D. recipient who has developed one of the models to be used. The quantification of energy and momentum deposition by short period gravity waves resulting from this project will benefit mesosphere/lower thermosphere science.