Modeling Dynamics and Impacts of a new class of Kelvin-Helmholtz Instabilities that Drive Enhanced Turbulence and Mixing in the MLT

用于天气和气候预测的最先进的大气环流模式(GCM)将中层大气中的湍流混合量低估了高达2倍，结果是错误地描述了二氧化碳和其他主要大气成分的输送和全球分布。GCMS将混合归因于一个单一的动力来源，该来源忽略了新发现的、被认为在中层大气及更远的地方普遍存在的、甚至可能无处不在的小范围湍流过程。该项目将通过观测指导的高分辨率模拟研究，确定这些独特的“管和结”(T&amp；K)不稳定动力学及其对混合的影响。先进的湍流和化学分析能力将被用于解决不同范围的大气研究社区的科学目标。由此产生的T&P；K驱动的动量输送和沉积的知识将有助于GCM中改进的混合参数的发展，并产生更高精度的天气和气候预报，以满足关键的社会需求。它还将支持科罗拉多大学博尔德大学的一名研究生和犹他州立大学的一名本科生的教育，同时促进向周围社区中未被充分代表的大学预科学生推广气候科学教育的外联活动。该项目将通过高分辨率建模识别和量化开尔文亥姆霍兹不稳定(KHI)T&amp；K动力学和混合在MLT中的影响，利用内部模型CGCAM和SAM的独特能力来表征扩展到湍流尺度的不稳定动力学，并在具有现实环境的深层区域混合。这些结果将通过解决GCM低估涡旋扩散系数Kzz的问题来改进天气和气候模式中的混合参数化方案。这项研究的目标是识别和量化大尺度(平均和潮汐)和GW环境，并说明它们的空间尺度和强度；通过高分辨率模拟来量化KHI T和K动力学的多样性，以及它们对能量耗散、混合和对MLT中的影响的影响；以及使用我们的KHI T&K模拟来评估它们相对于GW破坏预期的能量耗散率、混合和隐含的Kzz的增强。针对这些研究目标的分析和建模方法将使用KHI T&amp；K观测，由USU高级中间层温度映射器(AMTM)OH气辉成像和GATS Saamer雷达以及激光雷达对智利火地岛和阿拉斯加Poker Flat的风、温度和钠密度进行剖析，以指导典型的模拟环境(例如，GW和潮汐切变、多尺度叠加)。受这些观测结果的影响，将进行广泛的KHI T&A；K模拟，以捕捉不同环境条件下响应的多样性，并评估KHI T&A；K混合，从而能够定义决定具有代表性的剪切层尺度以及Richardson数和Reynolds数的KHI Kzz的参数。这项研究将直接导致更好地了解MLT中未解决的混合动力学以及它们如何影响组成粒子和能量传输到更高层次的大气。该奖项反映了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。

State-of-the-art general circulation models (GCMs) used for weather and climate prediction underestimate the amount of turbulent mixing in the middle atmosphere by up to a factor of 2, and as a result, mischaracterize the transport and global distributions of CO2 and other primary atmospheric constituents. GCMs attribute mixing to a single dynamical source that neglects newly discovered, small-scale turbulent processes thought to be widespread, and perhaps even ubiquitous, in the middle atmosphere and beyond. This project will identify these unique “tube and knot” (T&K) instability dynamics and their implications for mixing through observationally guided, high-resolution modeling studies. Sophisticated turbulence and chemical analysis capabilities will be employed to address scientific goals among a diverse range of atmospheric research communities. The resulting knowledge of T&K-driven momentum transport and deposition will aid the development of improved mixing parameterizations in GCMs and yield higher accuracy weather and climate forecasting to address a critical societal need. It will also support the education of a University of Colorado Boulder graduate student and a Utah State University undergraduate student while facilitating outreach events that promote climate science education to under-represented pre-college students in the surrounding communities.This project will identify and quantify Kelvin Helmholtz instability (KHI) T&K dynamics and implications for mixing in the MLT via high-resolution modeling, utilizing the unique capabilities of in-house models CGCAM and SAM to characterize instability dynamics extending to turbulence scales and mixing in deep domains with realistic environments. The results will improve mixing parameterization schemes in weather and climate models by addressing GCM underestimation of the eddy diffusion coefficient Kzz. The goals of this research are to identify and quantify the large-scale (mean and tidal) and GW environments that enable KHI T&K dynamics, and account for their spatial scales and intensities; to quantify the diversity of KHI T&K dynamics, and their implications for energy dissipation, mixing, and influences in the MLT via high-resolution modeling; and to employ our KHI T&K modeling to assess their enhancements of energy dissipation rates, mixing, and implied Kzz relative to those expected for GW breaking. The analysis and modeling approach addressing these research goals will employ KHI T&K observations by USU Advanced Mesospheric Temperature Mapper (AMTM) OH airglow imaging and GATS SAAMER radar and lidar profiling of winds, temperatures, and Na densities in Tierra del Fuego, Chile, and Poker Flat, Alaska, to guide representative modeling environments (e.g., GW and tidal shears, multi-scale superpositions). Informed by these observations, a wide range of KHI T&K simulations will be performed to capture the diversity of responses for varying environmental conditions and evaluate KHI T&K mixing, enabling definition of the parameters dictating a KHI Kzz for representative shear layer scales and Richardson and Reynolds numbers. This research will directly result in a better understanding of unresolved mixing dynamics in the MLT and how they impact constituent particles and energy transport to higher levels of the atmosphere.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.