| 英文摘要: | 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. |