Date of Award
Doctor of Philosophy (PhD)
Aerospace Engineering Sciences
Jeffrey M. Forbes
Adrian J. McDonald
The Space-atmosphere interaction region (SAIR) between ~50 and 200 km is one of the key factors enabling our Earth to harbor life. Its fundamental processes are believed to be universal and applicable to the atmospheres of Earth-like planets throughout our galaxy. However, the SAIR remains one of the least observed and understood regions. This thesis aims to advance the observations and characterizations of atmospheric waves that are fundamental to shaping the SAIR, especially exploring the mystery of persistent inertia-gravity waves, discovered by our Fe Boltzmann lidar measurements of temperatures at McMurdo (77.8°S, 166.7°E), Antarctica.
This thesis discovers a new wave phenomenon in the Antarctic middle and upper atmosphere, namely the persistent inertia-gravity waves with periods of 3–10 h. This group of large-amplitude waves dominates the temperature perturbations from the stratosphere to the lower thermosphere (about 30–115 km). They occur so frequently as to appear endless and uninterrupted, impacting the composition, chemistry and thermodynamics of the SAIR. This thesis reports the first simultaneous lidar/radar observations of inertia-gravity waves in Antarctica. Utilizing the lidar data in June from 2011 to 2015, this thesis characterizes the persistent gravity wave properties for the first time. These waves exhibit a uniform dominant vertical wavelength of 20–30 km across periods of 3.5–10 h and vertical phase speeds of 0.8–2 m/s. They possess more than half of the spectral energy for ~93% of the time. An analysis of the 65-h lidar data on 28–30 June 2014 demonstrates multiple wave packets spanning as long as 60 h. Further analysis of May and July data confirms the persistency and dominancy of these waves but reveal a month-to-month variability.
This thesis develops a system of wave analysis methods, including extracting gravity waves from ~30–155 km in the neutral atmosphere for the first time. Our methodologies also include the temporal hodograph methods for simultaneous lidar/radar data; improved 1-D Morlet wavelet transform methods; rigorous pre-whitening and post-coloring spectral analysis techniques; and automated 2-D Morlet wavelet analysis and synthesis methods. Successful application of these methodologies provides new insights into gravity waves, their sources and impacts on the whole atmosphere and space.
Chen, Cao, "Exploration of the Mystery of Polar Wave Dynamics with Lidar/Radar Observations and General Circulation Models & Development of New Wave Analysis Methods" (2016). Aerospace Engineering Sciences Graduate Theses & Dissertations. 146.