Weekly CASPO Seminar: join us on Zoom every Wednesday at 3:30 pm to hear about the latest and greatest in Climate, Atmospheric Sciences, and Physical Oceanography!
We're excited to have our very own Noel Gutierrez-brizuela, Scripps PhD student in physical oceanography, presenting the following talk:
Title: A vorticity-divergence theory of internal wave generation by tropical cyclones: insights from Super Typhoon Mangkhut
Abstract: Mixing, upwelling, and internal wave generation are well-known features of the ocean response to tropical cyclones. For this project, we used data from 6 profiling floats to reconstruct the 3D ocean dynamics beneath Super Typhoon Mangkhut as it swept over the Philippine Sea in September of 2018. Mixing is evidenced in the data by asymmetric cooling of sea surface temperatures (SST) and by observations of unstable stratification that imply turbulent diffusivities as high as κ ~ 10-1 m2 s-1. The generation of a near-inertial internal wave (NIW) is described using observations of isothermal displacement and surface measurements of horizontal divergence (Γ), which indicate upwelling velocities w ~ 8 m h-1. By formulating the linear mixed layer dynamics in terms of its vorticity (ζ), Γ , and thickness (h), we demonstrate that NIW generation arises from the linear coupling of ζ and Γ by the Coriolis force (f). Lastly, we find evidence that narrow streaks of enhanced κ moved away from the storm track in phase with mode-1 internal waves. In summary, our analyses provide a rare observational review of the ocean response to TCs, demonstrate the advantages of ζ and Γ in the representation of internal wave fields, and provide conceptual clarity on the mechanisms that lead to NIW generation behind TCs.
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