An Observational Investigation on Gravity Wave Characteristics and Propagation in the Lower Stratosphere and Mesopause

• Main Author: Li, Zhenhua
• Other Authors: Liu, Alan Z., Swenson, Gary R., Rauber, Robert M., Mak, Mankin
• Language: English
• Published: 2011
• Subjects: Gravity Wave; Atmospheric Dynamics; Airglow Imager; South Pole; South pole
• Online Access: http://hdl.handle.net/2142/26160

In this thesis, investigations on gravity waves are conducted in two regions of the middle atmosphere: the lower stratosphere using high-resolution radiosonde at South Pole and the mesopause region using OH airglow imager at Maui, Hawaii and Cerro Pachon, Chile. Wave characteristics at these regions are deduced and the seasonal variation of wave activity, wave sources, and propagation effect are studied. The study of gravity waves in the lower stratosphere at South Pole reveals that sources other than topography are important even for the lower part of middle atmosphere. Horizontal propagation must be included in parameterization schemes to reflect the fact that waves derived from radiosondes have slant propagation paths. They travel long distance horizontally before they reach higher altitudes. Long term gravity wave characteristics over Maui from 2002 to 2007 are deduced from OH airglow imager. Wave parameters from the long term imager observation provide robust statistics of high-frequency gravity wave in the midlatitudes. Poleward wave propagation preference during summer and equatorward wave propagation preference during winter are observed over Maui. They are also opposite to the seasonal mean meridional wind direction which are always pointing toward winter pole. Momentum fluxes deduced from OH imager are also highly anti-correlated with background winds. At least for the part of spectrum observed by airglow imager, gravity waves act as damping mechanism for diurnal tide. Gravity wave occurrence frequency does not follow the variation of local convective sources and convective sources in a large domain when ducted waves are considered. In fact, with a constant wave source and monthly mean background atmospheric condition, the simulated wave transmission resembles the wave occurrence frequency observed by OH airglow imager at Maui. Thus, at Maui the propagation effect dominates the seasonal variation in wave activity. Gravity wave momentum fluxes deduced from airglow imager provide important observation ...