T-Rex Observational and Numerical Study of Sierra Nevada Mountain Waves and Rotors

首席调查员将对内华达山脉背风面的中尺度气流现象进行研究，包括地形诱发的波浪、旋风和伴随的下坡风暴，以及它们与背风面深谷中的冷气池和热力强迫流动的相互作用。这项研究是地形诱导旋翼实验(T-REX)的一部分，建立在以前的塞拉旋翼研究成果的基础上，并扩展了之前进行的研究。大气层旋风是沿着平行于山脊和山脊下游的轴线形成的强烈的低层水平涡旋，最常与大幅度的山波结合在一起，对航空构成重大危险。尽管旋翼意义重大，但由于其空间复杂性和间歇性，对旋翼尺寸、内部结构、湍流强度和可预测性的了解仍然有限。这项研究的主要观测目标是记录山波和旋风在各种环境条件和海浪/旋风强度下的完整三维结构和时间演变。这项研究将使用现场观测和数值模拟两种方法进行。将在内华达山脉南部背风处的欧文斯河谷中部收集来自地面和机载、现场和遥感仪器的综合观测T-REX数据集，包括在塞拉利昂前兆转子研究期间建立的自动地面站中间网络获得的测量结果。内华达山脉南部是毗邻的美国最高、最陡、准线性的地形屏障。将在计划于2006年初春进行的为期两个月的密集T-REX观测期之前、期间和之后收集中间网络表面观测数据。这项研究的数值模拟工作将包括用两个最先进的中尺度数值模式--海洋-大气耦合模式预报系统(COAMPS)和天气研究预报系统(WRF)--进行高分辨率模拟。将通过高分辨率最先进的数值模式模拟和高分辨率观测的综合，寻求对转子和波浪与冷气池和热强迫流动的演变、结构和相互作用的动力学解释。此外，来自欧文斯河谷中间网络的较长期记录将被用来汇编内华达山脉风暴的气候学和欧文斯河谷的热强迫气流模式。智力优势：提高对复杂地形中的气流动力学的理解，特别是对转子等危险现象的理解，以及对其可预测性的限制。了解上游水汽在决定背风气流响应中的作用，并阐明冷气池中的停滞气流对背风侧流的动力学和演变的作用，包括海浪、旋风和破坏性风暴。更广泛的影响：这项研究的结果预计将改进与复杂地形中的旋翼和下坡风暴相关的航空危险的预测。结果将以客座讲座和研讨会的形式与区域业务预报社区分享，包括覆盖内华达山脉背风面的国家气象服务办公室，以及更广泛的研究社区。拟议的研究结果还将纳入内华达·雷诺大学和克罗地亚萨格勒布大学的中尺度气象学研究生课程。该项目将涉及至少一名研究生的教育和培训。

The Principal Investigator will conduct a study of mesoscale airflow phenomena in the lee of the Sierra Nevada, including terrain-induced waves, rotors, and attendant downslope windstorms, and their interaction with cold air pools and thermally-forced flows in a deep lee-side mountain valley. This study is part of the Terrain-induced Rotor Experiment (T-REX), and builds on results and extends research conducted under a preceding Sierra Rotors study. Atmospheric rotors, intense low-level horizontal vortices that form along an axis parallel to, and downstream of, a mountain ridge crest, most frequently in conjunction with large-amplitude mountain waves, pose a significant hazard to aviation. Despite the significance of rotors, and because of their spatial complexity and intermittency, knowledge of rotor size, internal structure, turbulence intensity, and predictability is still limited. The main observational objective of this study is to document the full three-dimensional structure and temporal evolution of mountain waves and rotors under a wide range of environmental conditions and wave/rotor strengths. The research will be conducted using both field observations and numerical simulations. Comprehensive observational T-REX data sets from ground-based and airborne, in situ and remotely sensed instruments, including measurements obtained by the mesonetwork of automatic surface stations established during a precursor Sierra Rotors study, will be collected in the central portion of Owens Valley, in the lee of the southern Sierra Nevada. The southern Sierra Nevada is the tallest, steepest, quasi-linear topographic barrier in the contiguous United States. The mesonetwork surface observations will be collected before, during, and after the two-month intensive T-REX observational period, planned for early spring 2006. This study's numerical modeling effort will consist of high-resolution simulations with two state-of-the-art mesoscale numerical models, the Coupled Ocean-Atmosphere Modeling Prediction System (COAMPS) and the Weather Research Forecasting (WRF) modeling system. Dynamical explanations for the evolution, structure and interaction of rotors and waves with cold air pools and thermally forced flows, will be sought through synthesis of high-resolution state-of-the-art numerical model simulations and high-resolution observations. Additionally, longer-term records from the Owens Valley mesonetwork will be used to compile a climatology of the Sierra Nevada windstorms and patterns of thermally forced flow in Owens Valley. Intellectual merit: Improvement in understanding of airflow dynamics in complex terrain, in particular hazardous phenomena such as rotors, and the limits to their predictability. Understanding the role of upstream moisture in determining the flow response in the lee, and elucidating the role of stagnant flow in cold air pools on the dynamics and evolution of the lee side flows, including waves, rotors, and damaging windstorms. Broader impacts: Results of this research are expected to lead to improved prediction of aviation hazards associated with rotors and downslope windstorms in complex terrain. The results will be shared with regional operational forecast community including the National Weather Services offices whose regions of coverage include the lee side of the Sierra Nevada, and wider research community in form of guest lectures and seminars. The findings of the proposed research will also be incorporated into graduate courses in mesoscale meteorology at the University of Nevada Reno and the University of Zagreb, Croatia. The project will involve the education and training of at least one graduate student.