Mesosphere and Lower Thermosphere Dynamics Studies Employing the Southern Argentina Agile MEteor Radar (SAAMER), Correlative Measurements, and Modeling

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。该奖项支持一系列仪器的继续运行，包括南美洲南端的萨默流星雷达，该雷达被称为Terra del Fuego。该奖项将支持继续研究在中间层和低热层(MLT)中发挥许多作用的大尺度和小尺度动力学。潮汐和行星波(PWS)是较大水平和垂直尺度上的主要变率，因为它们在对流层和平流层的来源没有强烈衰减的情况下大量传播到MLT及以上。这些已经使用MLT雷达、激光雷达和卫星测量进行了多年的研究，它们解释了MLT的主要大尺度变化。小尺度重力波(GW)产生于受对流层天气调制的多种来源，特别是山波(MWs)、对流性GW、惯性GW和次生GW(SGW)，其中来自其他来源的GW获得较大幅度。这些动力学中的大多数都得到了广泛的研究，无论是通过观测还是通过建模，但较小的尺度及其大范围的动力学、相互作用和不稳定性阻碍了对它们的动力学和影响的定量了解。这些大小尺度动力的重要性来自于它们在MLT中的主要影响，并延伸到越来越低和更高的高度。对大小尺度动力学的观测和分析在查明和了解决定大气结构和可变性的各种过程方面发挥着核心作用。在MLT中尤其需要这样的努力，那里的动力学是由能量和动量通量驱动的，这是由于GW从较低海拔的源传播而来，这种传播随对流层天气而变化很大。MLT的响应往往是强非线性的，这是由于GW幅值的大幅增加导致了不稳定、湍流以及平均和大尺度波动的强迫，这些目前还很少被理解。对Aura、MLS和MLT雷达观测的分析将量化关键的PW和潮汐动力学。在TDF和NAVGEM重新分析时对GW响应的观测指导将有助于对MLT中的MW和更一般的GW动力学、不稳定性、强迫和响应进行详细的建模。一所大学。科罗拉多大学(CU)的研究生将接受最先进的GW、KHI以及地球物理湍流建模和超级计算方面的培训。收集、格式化和提供用于NAVGEM数据同化的全球MLT雷达数据也将为雪松社区带来重大好处。主要的大尺度强迫和小尺度强迫和变率是由GWS驱动的，它解释了水平动量驱动MLT动力学的主要垂直通量，其中GW的破裂和耗散导致能量和动量沉积。这导致局地气流加速、混合、对更大尺度动力的反馈，导致GW破裂，并诱导残余环流在较低海拔产生影响。在以前的观测和/或建模研究中，所有这些动力学都得到了不同程度的评估。新的奖项将研究不同的过程，包括：1)GW/潮汐相互作用对较高海拔的潮汐振幅和潮汐相位和GW的影响，2)GW破碎的间歇性、能量和动量沉积和混合的影响，3)GW&A；潮汐切变中大尺度Kelvin-Helmholtz不稳定(KHI)的影响，4)GW“自加速”动力学的来源和效应，对此有重要的模拟和观测支持，但其影响很大程度上是未知的，以及5)在低海拔产生的瞬时PWS对MLT结构和变异性的影响。这些模型的初始条件将由NAVGEM再分析提供，范围扩展到140公里，基于全球MLT雷达风，支持由GATS人员协调的NAVGEM数据同化工作。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This award supports the continued operations of a suite of instruments including the SAAMER meteor radar at the southern tip of South America known as Terra del Fuego. The award will support the continued study of large- and small-scale dynamics that play many roles in the mesosphere and lower thermosphere (MLT). Tides and planetary waves (PWs) account for the major variability on larger horizontal and vertical scales because they propagate largely without strong attenuation from sources in the troposphere and stratosphere into the MLT and above. These have been studied using MLT radar, lidar, and satellite measurements for many years, and they account for the major large-scale variability of the MLT. Smaller-scale gravity waves (GWs) arise from multiple sources modulated by tropospheric weather, especially mountain waves (MWs), convective GWs, inertia-GWs, and secondary GW (SGW) generation where GWs from other sources attain large amplitudes. Most of these dynamics have been studied extensively, both observationally and via modeling, but the smaller scales, and their large range of dynamics, interactions, and instabilities have prevented a quantitative understanding of their dynamics and influences to date. The importance of these large- and small-scale dynamics derives from their major influences in the MLT and extending to lower and higher altitudes. Observations and analyses of large- and small-scale dynamics play central roles in identifying and understanding the diverse processes that determine the structure and variability of the atmosphere. Such efforts are especially needed in the MLT, where the dynamics are driven by energy and momentum fluxes due to GW propagation from sources at lower altitudes that vary strongly with tropospheric weather. MLT responses are often strongly nonlinear due to large GW amplitude increases leading to instabilities, turbulence, and forcing of mean and large-scale wave motions that are poorly understood at present. Analyses of observations by Aura MLS and MLT radars will quantify key PW and tidal dynamics. Observational guidance of GW responses at TdF and NAVGEM re-analyses would aid the detailed modeling addressing MW and more general GW dynamics, instabilities, forcing, and responses in the MLT. A Univ. of Colorado (CU) graduate student would receive training in state-of-the-art GW, KHI, and geophysical turbulence modeling and supercomputing. The collection, formatting, and provision of global MLT radar data for NAVGEM data assimilation would also be a significant benefit for the CEDAR community. The major larger-scale forcing and smaller-scale forcing and variability of the MLT is driven by GWs that account for the major vertical fluxes of horizontal momentum driving MLT dynamics where GW breaking and dissipation cause energy and momentum deposition. These lead to local flow accelerations, mixing, feedbacks on the larger-scale dynamics contributing to GW breaking, and induced residual circulations having impacts at lower altitudes. All these dynamics have been assessed to varying degrees in previous observational and/or modeling studies. The new award would study different processes that include the following: 1)effects of GW/tidal interactions on tidal amplitudes & phases and GWs at higher altitudes, 2) influences of intermittency in GW breaking, energy & momentum deposition, and mixing, 3) influences of large-scale Kelvin-Helmholtz instabilities (KHI) in GW & tidal shears, 4) sources and effects of GW “self-acceleration” dynamics, for which there is significant modeling & observational support, but the implications of which are largely unknown, and 5) influences on MLT structure and variability by transient PWs arising at lower altitudes. Initial conditions for these models would be provided by NAVGEM re-analyses extending to 140 km based on global MLT radar winds supporting the NAVGEM data assimilation efforts coordinated by GATS personnel.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.