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

首席研究员将对内华达山脉背风处的中尺度气流现象进行研究，包括地形引起的波浪、旋翼和伴随的下坡风暴，以及它们与背风侧山谷中的冷空气池和热强迫流的相互作用。这项研究是地形诱导转子实验（T-REX）的一部分，并建立在先前塞拉转子研究的结果和扩展研究的基础上。大气旋翼是一种强烈的低空水平涡旋，它沿着与山脊峰平行的轴线形成，并在山脊峰的下游形成，最常见的是与振幅较大的山波结合在一起，对航空构成重大危害。尽管旋翼具有重要意义，但由于其空间复杂性和间歇性，关于旋翼尺寸、内部结构、湍流强度和可预测性的知识仍然有限。本研究的主要观测目标是记录大范围环境条件和波/转子强度下山波和转子的全三维结构和时间演变。这项研究将采用实地观测和数值模拟两种方法进行。来自地面和空中、原位和遥感仪器的综合观测T-REX数据集，包括在前体Sierra Rotors研究期间建立的自动地面站中网所获得的测量数据，将在Owens Valley的中心部分内华达山脉南部背风处收集。南内华达山脉是美国境内最高、最陡的准线性地形屏障。中网地面观测资料将在计划于2006年早春进行的为期两个月的T-REX密集观测期之前、期间和之后收集。这项研究的数值模拟工作将包括两个最先进的中尺度数值模型的高分辨率模拟，即耦合海洋-大气模拟预测系统（COAMPS）和天气研究预报（WRF）建模系统。通过高分辨率数值模型模拟和高分辨率观测的综合，将寻求转子和波与冷空气池和热强迫流的演变、结构和相互作用的动力学解释。此外，欧文斯谷中网的长期记录将用于编制内华达山脉风暴的气候学和欧文斯谷热强迫流的模式。智力优势：提高对复杂地形中气流动力学的理解，特别是危险现象，如旋翼，以及其可预测性的限制。了解上游水汽在决定背风面流动响应中的作用，并阐明冷空气池中停滞流动对背风面流动（包括波浪、旋涡和破坏性风暴）的动力学和演变的作用。更广泛的影响：本研究的结果有望改善复杂地形中与旋翼和下坡风暴相关的航空危害的预测。该结果将与区域业务预报机构共享，包括覆盖范围包括内华达山脉背风侧的国家气象局办公室，以及以客座讲座和研讨会的形式更广泛的研究机构。拟议研究的结果也将纳入内华达大学里诺分校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.