Study of Mutual Diffusion Effects in the Upper Atmosphere and Thermospheric Gravity Wave Processes

这项研究是一项为期三年的努力，旨在开发一种独特的二元气体全波模型，该模型将模拟多组分气体，并纳入所有相关的物理过程，如科里奥利力、平均风、热动量的涡流和分子扩散以及反射。这种详细的处理是必要的，因为热层是一种扩散分离的多组分气体，其中单个物种处于静态平衡状态，并根据其单个尺度高度分层。该模型将是对其中一些过程的第一个现实的理论处理，并将应用于各种科学主题，例如热层中声波重力波的耗散以及这种波耗散对平均状态的后续影响。将计算非等温大气中感热、动量和质量的波通量以及波反射，并使用等效重力波方法进行潮汐模拟。在全波模型中，将开发一个辅助模型，用于评估多物种效应。考虑到一个以上物种的存在是必要的，因为物种之间碰撞引起的波耗散是热层的一个重要热源。通过热层传播的重力波使气体脱离静态平衡，导致单个气体以不同的振幅和相位振荡，而相互扩散试图减轻这些差异并恢复扩散平衡。热层中的单个气体可能经历波动，单个气体相对于其他气体所表现出的波的振幅和相位提供了波周期的重要特征，而在大气的这一区域，人们对波周期知之甚少。波效应是组成、波周期和波长、动量和热碰撞耦合、涡流耗散、分子黏性和热传导以及反射的复杂函数。一个同时包含所有这些过程的模式是我们进一步了解重力波在热层中的传播、耗散和波的特征，以及量化与低层大气源相关的热层的波强迫的基本要求。发表的卫星观测将使用详细模型进行分析，以检验模型并推断波周期。该项目的目标是量化高层大气各区域之间的变化和耦合。它还讨论了波性质中的基本扩散过程。这项研究将对高层大气科学领域产生重大影响，因为它对目前未包括在全球大气环流模式中的波浪过程作出了重大贡献。计划向社区提供新模型，以帮助促进发现和理解。一名全日制研究生和一名半全日制本科生将参与研究。

This investigation is a three year effort to develop a unique binary gas full-wave model that will simulate a multi-constituent gas and incorporate all relevant physical processes such as the Coriolis force, mean winds, eddy and molecular diffusion of heat and momentum, and reflection. This detailed treatment is necessary since the thermosphere is a diffusively separated multi-constituent gas in which individual species are in static equilibrium and are stratified according to their individual scale heights. The model will be the first realistic theoretical treatment of some of these processes and will be applied to various science topics such as the dissipation of acoustic gravity waves in the thermosphere and the subsequent effects of this wave dissipation on the mean state. Wave fluxes of sensible heat, momentum, and mass, and wave reflection in a non-isothermal atmosphere will be calculated, and tidal simulations will be produced using the equivalent gravity wave approach. An auxiliary model that sums over two species will be developed and used to assess multi-species effects in the full-wave model. Accounting for the presence of more than one species is necessary since wave dissipation due to collisions between species is an important heat source for the thermosphere. Gravity waves that propagate through the thermosphere drive the gases out of static equilibrium and cause individual gases to oscillate with different amplitudes and phases while mutual diffusion attempts to mitigate these differences and restore diffusive equilibrium. The individual gases in the thermosphere may undergo wave motion and the amplitudes and phases of the waves exhibited by the individual gases relative to each other provide an important signature of wave periods, about which little is known in this region of the atmosphere. Wave effects are a complex function of composition, wave period and wavelength, as well as momentum and thermal collisional coupling, wave dissipation by eddy and molecular viscosity and thermal conduction, and reflection. A model that includes all these processes simultaneously is a fundamental requirement to furthering our understanding of gravity wave propagation, dissipation, and the wave characteristics in the thermosphere and to quantify poorly understood wave forcing of the thermosphere associated with lower atmospheric sources. Published satellite observations will be analyzed using the detailed model to test the model and to infer wave periods. The project addresses the goal of quantifying variations in and coupling between regions of the upper atmosphere. It also addresses fundamental diffusion processes in wave properties. The research will impact the field of upper atmospheric science by contributing substantially to wave processes currently not included in global general circulation models. It is planned to provide the new model to the community to help promote discovery and understanding. A full time graduate student will be involved in the research as well as a half-time undergraduate student.