Small-Scale Gravity Waves generated by Hurricanes in the Upper Troposphere - Lower Stratosphere

This thesis presents a detailed study of the small-scale gravity waves in the upper troposphere-lower stratosphere region that are generated by hurricanes. The goal is to understand the spectral properties of the convectively generated gravity waves and their variations with respect to the hurricane intensity, using the high vertical resolution temperature measurements from the GPS-Radio Occultation (RO) and the fine horizontal resolution wind data from the ECMWF reanalysis dataset, with the application of the least squares spectral analysis and wavelet analysis.

Our results show that the pure thermal forcing mechanism generates the primary waves at the surface level in an almost identical way, while the overshooting convection and the background wind filtering seem to weaken as the hurricane intensity drops. The obstacle effect appears to dominate in the lower stratosphere which further contributes to the wave field asymmetry. A two-layer convection model is considered to simulate the hurricane convection that innovatively connects the wave generation and dissipation mechanisms with the ambient background atmosphere.