Collaborative Research: A Global View of Topographically Bound Low Level Jets

地形约束的低空急流是低层大气中与山脉和高原等高地特征相关的强烈、持续的风。 例子包括北美洲落基山脉和南美洲安第斯山脉两侧持续的向北和向南气流，以及环绕南极洲的向东气流。该项目的目标是了解这些喷流的原因，并研究它们对气候的影响。 以前的工作开发了一个二维的理论，解释了这样的喷流作为一个平衡的动力学响应的大气层，以响应太阳能加热和红外辐射冷却的高架地形强迫。 使用简化的地形剖面的计算结果表明，在通过安第斯山脉和南极洲的二维横截面中观察到的风的定性协议。 该项目将把理论扩展到三维空间，同时考虑到地球的球形和高架地形的完整形状的影响。 将使用一种新的数值方法计算所得方程的解，该方法在需要的地方细化网格，以最小的计算工作获得精确的解。 解决方案将计算与周围的复杂地形的地球仪，如南极洲，青藏高原，格陵兰岛，落基山脉和安第斯山脉，并通过与观测数据进行比较验证喷流，除了发展我们对大气动力学的基本理解，这项工作具有社会意义，由于低空喷流对区域气候的重要性。例如，大平原低空急流负责将大部分水分输送到美国东半部，维持农业，非洲东海岸的低空急流是印度季风的主要组成部分，极大地影响了印度次大陆生活的许多方面。 该项目还将通过支持和培训两名研究生，并培训一名计算数学和现代科学编程的本科生，为发展未来的科学人才队伍做出贡献。 最后，该项目中开发的方法将通过软件代码提供给大气动力学研究人员，以便它们可以应用于广泛的科学问题。

Topographically bound low-level jets are strong, persistent winds in the lower atmosphere associated with elevated terrain features such as mountain ranges and plateaus. Examples include the persistent northerly and southerly flows on opposite sides of the Rocky Mountains in North America and the Andes Mountains in South America, and the easterly flow that surrounds Antarctica. The goal of this project is to understand what causes these jets and to study their impacts on climate. Previous work developed a two-dimensional theory which explains such jets as a balanced dynamical response of the atmosphere in response to forcing by solar heating and infrared radiative cooling of the elevated terrain. Computed results using simplified terrain profiles showed qualitative agreement with observed winds in two-dimensional cross sections through the Andes and Antarctica. This project will extend the theory to three dimensions, taking into account the effects of the earth's spherical shape and the full shape of the elevated terrain. Solutions of the resulting equations will be computed using a novel numerical method which refines the grid where needed to obtain accurate solutions with minimal computational work. Solutions will be computed for jets associated with several regions of complex terrain around the globe, such as Antarctica, the Tibetan Plateau, Greenland, and the Rockies and Andes, and validated by comparison with observational data.Beyond developing our fundamental understanding of atmospheric dynamics, this work has societal relevance due to the importance of low-level jets for regional climate. For example, the Great Plains low-level jet is responsible for a substantial portion of the moisture transport into the eastern half United States which sustains agriculture, and the low-level jet off the eastern coast of Africa is a major component of the Indian monsoon which greatly affects many aspects of life in the Indian subcontinent. This project will also contribute to developing the future scientific workforce by supporting and training two graduate students in research, and training one undergraduate student in computational mathematics and modern scientific programming. Finally, the methods developed in this project will be made available to researchers in atmospheric dynamics through software codes, so that they can be applied to a wide array of scientific problems.