Diagnostics and energetics of the topographic Rossby waves generated by a typhoon propagating over the ocean with a continental shelf slope
The dynamics of the subinertial response when a typhoon propagates over the ocean with a sloping bottom topography is investigated by carrying out a set of idealized numerical experiments. At least two different topographic Rossby waves (TRWs) are identified at the same along-slope wavenumber and two different subinertial frequencies in the wavenumber–frequency spectra. The diagnostics of vorticity balance demonstrates that the bottom pressure torque plays an important role in both the generation and propagation of TRWs. Two sets of sensitivity experiments show that the spatial structure of the typhoon is a “decisive” parameter in determining the along-slope wavenumber as well as the corresponding frequencies; the along-slope wavenumber of a TRW is first determined as a response to the typhoon-induced perturbation, and the corresponding frequencies are then determined so as to satisfy the theoretical TRW dispersion relationship. The amplitude of TRWs, in contrast, are controlled by both the typhoon radius as well as the typhoon traveling speed. For typhoons with a large radius or slow traveling speed, the resulting TRWs can be comparable to or more energetic than the near-inertial waves. This indicates that the TRWs might play an important role in inducing the near-bottom mixing along the shelf slope by using energy supplied from typhoon winds.
KeywordsTopographic Rossby waves Typhoon radius Typhoon traveling speed Vorticity balance Continental shelf slope Bottom pressure torque
The initial buoyancy field were obtained from the World Ocean Atlas (https://www.nodc.noaa.gov/OC5/woa13/). The model results supporting this paper are publicly available at https://figshare.com/s/6b56e8f8ed33dfea0830. This study was supported by the National Key Research and Development Program of China (Grant No. 2016YFA0601301). L. Zhao thanks the support from the National Natural Science Foundation of China (NSFC, 41876018). H. Wei thanks the support from the National Key Research and Development Program of China (Grant Nos. 2016YFC1401401 and 2017YFC1404403).
- Emanuel KA (2005) Divine wind, the history and science of hurricanes. Oxford University Press, New YorkGoogle Scholar
- Gill AE (1982) Atmosphere-ocean dynamics. Academic, New YorkGoogle Scholar
- Miller AJ, Lermusiaux PFJ, Poulain PM (1996) A topographic Rossby-mode resonance over the Iceland-Faeroe Ridge. J Phys Oceanogr 26:2735–2747. https://doi.org/10.1175/1520-0485(1996)026,2735:ATMROT.2.0.CO;2 CrossRefGoogle Scholar
- Thompson RORY, Luyten JR (1976) Evidence for bottom trapped topographic Rossby waves from single moorings. Deep-Sea Res 23:629–635Google Scholar