Klaassen, GaryChen, Yongsheng2018-03-012018-03-012017-07-122018-03-01http://hdl.handle.net/10315/34323The first part of this study investigates gravity wave parameterization in the middle atmosphere, focusing on internal waves with a broad spectrum of phase speeds. A column model based on CIRA wind and temperature profiles is employed to assess the characteristics of the Hines Doppler-Spread (1997) and Warner-McIntyre-Scinocca (2001) nonorographic drag parameterizations for internal gravity waves. The Alexander-Dunkerton (1999) variant of Warner-McIntyre-Scinocca scheme is also briefly considered. This study goes into more detail than previous comparisons by performing a spectral analysis of the momentum deposition and drag, and by examining the ability of each scheme to reproduce saturation. Comparisons with pure critical level filtering are also made, and it is found that Hines DSP mainly constitutes an enhancement to critical level absorption, while the Warner-McIntyre-Scinocca scheme produces substantially different wave drag profiles. We find several undesirable characteristics in the drag produced by the Hines scheme. For typical midlatitude profiles, it produces an abrupt onset of large accelerations that are confined to a relatively narrow layer. It is also unable to reproduce wave spectra consistent with observed saturation at high vertical wavenumbers. The second part of this study investigates the generation mechanisms of the gravity waves over Newfoundland and Labrador (NL). We performed a series of simulations for a selection of the strongest peak events using WRF model to further investigate the characteristics and generation mechanisms of gravity wave peak events over NL. We studied three different peak events, 2003, 2008 and 2014. We showed that gravity wave events in the winter hotspot region over NL can have both topographic and jet streak sources. In the cases we examined, one source of waves was the Torngat range on the northern coast of Labrador. However, the other two wave sources were in fact outside the hotspot region, and a combination of advection and propagation caused those packets to enter the hotspot in the middle atmosphere. We have demonstrated that topographic wave packets, which are normally assumed to remain stationary over the source, can in fact be advected far downstream from the source.enAuthor owns copyright, except where explicitly noted. Please contact the author directly with licensing requests.Atmospheric sciencesElectronic Thesis or Dissertation2018-03-01Gravity WavesGravity Wave Drag ParameterizationMomentum DepositionMiddle AtmosphereGravity Wave HotspotsGravity Wave Generation MechanismsNumerical Weather PredictionWeather Research and Forecasting Model