Collaborative Research: Toward an Improved Understanding of the Characteristics, Processes, and Impacts of Northerly and Southerly Low-Level Jets in the Central United States

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。低空喷流是对流层下层快速移动的气流。北风（N-LLJs）和南风（S-LLJs）低空急流在美国中部频繁发生，对区域天气和气候、降水和水资源以及风能都有重要影响。低层急流的成因是复杂的，边界层强迫和天气尺度强迫都对急流的发生有贡献。这项研究由密歇根大学迪尔伯恩分校的Claudia Walters博士、密歇根州立大学的Julie Winkler博士和密歇根州立大学的Sharon Zhong博士共同进行，将解决我们对低空喷气机知识的两个重大空白。其中一个目标是更好地了解n - llj的特征、原因和影响，迄今为止，大气科学界对这些问题的关注很少。第一个目标的具体目标是1)表征N-LLJs形成的大尺度天气环境，2)评估N-LLJs的三维结构，3)评估N-LLJs的潜在强迫机制，4)研究N-LLJs对当地/区域天气和气候的影响，5)提高对N-LLJs的气候特征及其年际变化的认识。第二个目标是评估边界层和天气尺度强迫对S-LLJ发生的相对贡献。该目标的具体目标是：1)评估边界层和天气强迫s - llj相对频率的地理变化；2)评估不同类型s - llj对夜间降水的对比影响；3)描述不同s - llj的年际变化。这些目标将通过结合中尺度数值模拟和对地面和高空观测的气候学分析以及区域再分析产品来实现。研究结果将直接有利于短期和季节性的业务天气预报，并为评估受扰动气候下低层喷气机的潜在未来变化提供基线。此外，更好地了解强迫机制可以改进区域和全球气候模式对低空急流的模拟及其验证。此外，研究结果将有助于改善风能评估和水资源管理，这两者都具有广泛的社会影响。除了科学进步之外，这项研究还将为气候数据分析和数值模拟方面的本科生和研究生提供培训，为代表性不足和服务不足的高中生制作教育推广材料，并为业务天气预报社区开发基于网络的低空喷气机推广资源。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Low-level jets are streams of fast-moving air in the lower troposphere. Both northerly (N-LLJs) and southerly (S-LLJs) low-level jets occur frequently in the central United States and have a significant impact on regional weather and climate, precipitation and water resources, and wind energy. The causes of low-level jets are complex, with both boundary-layer and synoptic-scale forcing contributing to jet occurrence. This study being conducted by Dr. Claudia Walters at the University of Michigan-Dearborn, Dr. Julie Winkler at Michigan State University and Dr. Sharon Zhong at Michigan State University will address two substantial gaps in our knowledge of low-level jets. One goal is to better understand the characteristics, causes, and impacts of N-LLJs, which have received little attention to date by the atmospheric science community. The specific objectives of this first goal are to 1) characterize the large-scale synoptic environment in which N-LLJs form, 2) assess the three-dimensional structure of N-LLJs, 3) evaluate the potential forcing mechanisms for N-LLJs, 4) investigate the impacts of N-LLJs on local/regional weather and climate, and 5) improve the understanding of the climatological characteristics of N-LLJs including their interannual variation. The second goal is to evaluate the relative contribution of boundary-layer versus synoptic-scale forcing to S-LLJ occurrence. The specific objectives of this goal are to 1) assess the geographic variations in the relative frequency of boundary-layer versus synoptically-forced S-LLJs, 2) evaluate the contrasting influence of the different types of S-LLJs on nocturnal precipitation, and 3) depict the interannual variability of the different S-LLJs. These objectives will be addressed using a combination of mesoscale numerical modeling and climatological analysis of surface and upper-air observations and regional reanalysis products. The outcomes of the research will directly benefit both short-term and seasonal operational weather forecasting and provide a baseline for evaluating potential future changes of low-level jets in a perturbed climate. In addition, better knowledge of forcing mechanisms can lead to improvements in regional and global climate model simulations of low-level jets and their validation. Furthermore, the results will contribute to improved wind energy assessment and water resources management, both of which have broad societal impacts. In addition to the scientific advancements, this research will also provide training to a diverse pool of undergraduate and graduate students in climate data analysis and numerical modeling, produce educational outreach materials for underrepresented and underserved high school students, and develop a web-based outreach resource on low-level jets for the operational weather forecasting community.