Collaborative Research: Topographically Bound Balanced Motions

本项目研究沿着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，以及沿着智利和秘鲁海岸的低空急流。 该项目的中心假设是，地形低空急流的形成是由于升高的太阳能加热发生沿着地形特征。 更具体地说，将开发一种反演技术，通过反演太阳加热产生的位涡异常来确定地形附近的风场和大气质量场。 该技术是在等熵坐标系中开发的，并考虑了地形和等熵表面的交叉点，这些等熵表面由于太阳能加热而向下朝向地形弯曲。 该方法将用于了解低空急流的特征，包括速度和高度，并为解释复杂的最先进的数值模拟结果提供动力学框架。 该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加热升高的关系，加勒比低层急流和冰盖附近的气流。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大部分水分输送到美国东半部，维持农业。 此外，该项目还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工作者。 最后，将通过软件代码向大气动力学研究人员提供本项目开发的反演方法，以便将其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.