Date of Award
Doctor of Philosophy (PhD)
Sharon L. Vadas
As a key link connecting different atmosphere layers, gravity waves are the leading uncertainty and one of the most puzzling elements in modern general circulation and chemical climate models. In this dissertation, we aim to establish a vertical picture of gravity waves at McMurdo, Antarctica from near the surface to the thermosphere and to improve the understandings of gravity wave coupling via investigating wave characteristics, propagation, dissipation, and generation.
Utilizing lidar observations along with theory and model simulations, we investigate the causality of gravity wave events among different altitude regions. The sources of the stratospheric gravity waves are traced to the orographic gravity waves in the troposphere, along with possible in-situ wave sources in the stratosphere. The sources of the Mesosphere and Lower Thermosphere persistent gravity waves are traced back to the secondary gravity wave generation in the upper stratosphere and lower mesosphere. The origins of the ~1.5 hr fast gravity waves in the Thermosphere-Ionosphere Fe/Fe+ (TIFe) layer are linked to both secondary gravity wave generation and possible sources in the troposphere. This vertical picture reflects the sophisticated wave coupling in Antarctica.
Along the research, we characterized the seasonal variations of gravity wave parameters such as vertical wavelengths, ground-relative periods, vertical phase speeds, and potential energy densities. A spectral proportion method was developed to accurately estimate wave energy from observations.
Overall, a complex gravity wave vertical picture from the lower to the upper atmosphere was established. This picture incorporates different gravity wave mechanisms over different altitudes and seasons. Not only can it provide physical bases for gravity wave parameterization in atmospheric models, but also can it provide a representative reference to the gravity wave research across the globe. This research paves its own way to human’s ultimate understandings of atmospheric dynamics in terms of gravity wave coupling.
Zhao, Jian, "Lidar Exploration of a Vertical Picture of Gravity Waves in Antarctica from Near the Surface to the Thermosphere" (2018). Aerospace Engineering Sciences Graduate Theses & Dissertations. 237.