Collaborative Research: Modeling of Secondary and Tertiary Gravity Waves from Orographic Gravity Wave Forcing and Comparison with Satellite Observations

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This collaborative project involving both NWRA and Hampton University supports a study of atmospheric dynamics within the region of the Earth's atmosphere that is not accessible by low Earth orbiting satellites or by balloons. Air that is associated with the wind flow over mountainous terrain is disturbed by a class of 'primary' atmospheric gravity waves (GWs) that is called 'mountains waves' (MWs). These waves break or reach critical levels in the lower or middle atmosphere at altitudes below 70 km. This process not only creates small-scale secondary GWs with horizontal wavelengths considerably less than that of the MWs, but also creates horizontal 'body forces' (i.e., horizontal accelerations localized in space and time). These in turn are thought to excite a broad spectrum of secondary GWs with horizontal wavelengths larger than that of the MWs. The main objective of the research is to quantify to the extent possible the effect that secondary and tertiary GWs from MW attenuation has on the thermosphere (the neutral atmosphere above 200 km) via this multi-step coupling process. The research includes a unique combination of detailed, targeted modeling combined with data analyses studies. A graduate student associated with Hampton University would participate in the research work described.Several different simulations would be used in sequence to simulate the entire process. Data from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite would be analyzed to extract GWs parameters observed for specific regions on Earth, and the simulations will be compared to these satellite observations. The project will involve applying these results to the study of MWs to investigate the extent to which secondary and tertiary waves that affect the thermosphere are produced. The research if successful should significantly advance the research community's understanding of the process of momentum transfer from orographic forcing to the thermosphere via GWs in this multi-step coupling process. This research is expected to lead to a much better appreciation of the variability and structure of the thermosphere from these processes (i.e., space weather from below) thus helping to achieve a significant broader impact because a predictive capability might possibly be developed for such thermospheric wave structures were this momentum transfer process be understood much more completely as a result of research work represented by this award.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.