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.
