Spectra of The Stratospheric GWs Induced by A Tropical Cyclone
Abstract
Source spectra of Gravity Waves GWs are prerequisite for gravity-wave-drag parameterization schemes GWD In this presentation an unique spectra of the GWs induced by a tropical cyclone TC will be introduced The spectra was derived from a numerical simulation with a North-Western Pacific typhoon The simulation revealed that pronounced stratospheric GWs with distinct appearance for example spiral wave fronts seen at 20 km altitude were generated during a typhoon passage TC-GWs With conducting spectral analysis with model output spectra of the TC-GWs were found to be also distinctive The salient feature was that predominant GW components exhibited persistent oscillation with time periods around 14-hr In general the shape of momentum flux spectra with respect to horizontal wave-number and frequency was different to those having been already presented in the previous studies where corresponding mechanisms responsible for the respective GW generation have also been proposed such as thermal forcing mechanism mechanical oscillator effect and moving mountain effect The singular momentum flux spectra of the TC-GWs suggests that TC-GWs were triggered by an independent mechanism Extensive investigation on the primary circulation of the TC i e the vorticity in mid-troposphere was conducted with using the empirical orthogonal function EOF method Significant oscillation was seen in the leading EOF vectors representing the evolution of the main body of the cyclone Concurrently the TC related circulation in the mid- to upper troposphere was
- Publication:
-
36th COSPAR Scientific Assembly
- Pub Date:
- 2006
- Bibcode:
- 2006cosp...36.3115C