Collaborative Research: Topographically Bound Balanced Motions

该项目研究沿山脉斜坡和其他地形特征发现的持续性低层大气流动的基本动力学。重要的例子包括大平原低空急流，安第斯山脉东侧的南美低空急流，以及智利和秘鲁海岸发现的低空急流。该项目的中心假设是，地形低空急流是由于沿地形特征发生的太阳加热升高而形成的。更具体地说，将开发一种反演技术，通过对太阳加热产生的潜在涡度异常的反演来确定地形附近的风场和大气质量场。这项技术是在等熵坐标下发展起来的，并考虑了地形和等熵表面的相交，由于太阳加热，地形和等熵表面向下弯曲。该方法将用于了解低空急流的特征，包括速度和高度，并提供一个动力学框架来解释复杂的最先进的数值模拟结果。这项分析将应用于一些低层地形急流，以及其他问题，包括亚洲季风的爆发及其与青藏高原升温、加勒比低空急流和冰盖附近气流的关系。由于低层急流对区域气候的重要性，这项工作具有社会意义。例如，大平原低空急流负责向支持农业的美国东部输送很大一部分水汽。此外，该项目将支持和培训两名研究生，从而培养这一研究领域未来的科学队伍。最后，本项目开发的反演方法将通过软件代码提供给大气动力学的研究人员，以便它们可以应用于广泛的科学问题。

This project examines the fundamental dynamics of persistent low-level atmospheric flows which are found along the slopes of mountain ranges and other topographic features. Important examples include the Great Plains low-level jet, the South American low-level jet on the east side of the Andes, and the low-level jet found along the coast of Chile and Peru. The central hypothesis of the project is that topographic low-level jets form due to the elevated solar heating that occurs along the topographic features. More specifically, an inversion technique will be developed to determine the wind and atmospheric mass fields in the vicinity of topography through inversion of the potential vorticity anomalies generated by solar heating. The technique is developed in isentropic coordinates and accounts for the intersection of the topography and the isentropic surfaces, which bend downward toward the topography due to solar heating. The method will be used to understand features of the low-level jets including speed and elevation, and to provide a dynamical framework for interpreting the results of complex state-of-the-art numerical simulations. The analysis will be applied to a number of low-level topographic jets, and to other problems including the onset of the Asian monsoon and its relationship to elevated heating on the Tibetan plateau, the Caribbean low-level jet, and flows near ice sheets.The 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. In addition, the project will support and train two graduate students, thereby developing the future scientific workforce in this research area. Finally, the inversion 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.