Two-way coupled long-wave isentropic ocean-atmosphere dynamics

The events following the 15 January 2022 explosions of the Hunga Tonga-Hunga Ha'apai volcano highlighted the need for a better understanding of ocean-atmosphere interactions when large amounts of energy are locally injected into one (or both). Starting from the compressible Euler equations, a t...

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Bibliographic Details
Published in:Journal of fluid mechanics 2023-03, Vol.959, p.22-53, Article A22
Main Authors: Winn, S.D., Sarmiento, A.F., Alferez, N., Touber, E.
Format: Article
Language:English
Subjects:
Acoustic waves
Atmosphere
Atmospheric models
Atmospheric pressure
Bathymetry
Compressibility
Deep water
Deformation
Energy transfer
Engineering Sciences
Euler-Lagrange equation
Explosions
Far fields
Fluid mechanics
Ground stations
JFM Papers
Linear analysis
Mechanics
Mountains
Ocean-atmosphere interaction
Ocean-atmosphere system
Oceans
Physics
Pressure distribution
Satellites
Sound waves
Spherical shells
Stratification
Topography
Tsunamis
Volcanoes
Warning systems
Water depth
Wave generation
Wave propagation
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Summary:The events following the 15 January 2022 explosions of the Hunga Tonga-Hunga Ha'apai volcano highlighted the need for a better understanding of ocean-atmosphere interactions when large amounts of energy are locally injected into one (or both). Starting from the compressible Euler equations, a two-way coupled (TWC) system is derived governing the long-wave behaviour of the ocean and atmosphere under isentropic constraint. Bathymetry and topography are accounted for along with three-dimensional atmospheric non-uniformities through their depth average over a spherical shell. A linear analysis, yielding two pairs of gravito-acoustic waves, offers explanations for phenomena observed during the Tonga event. A continuous transcritical regime (in terms of water depth) is identified as the source of large wave generation in deep water bodies, removing the singularity-driven Proudman-type resonance observed in one-way coupled models. The refractive properties, governing the interaction of the atmospheric wave with step changes in water depth, are derived to comment on mode-to-mode energy transfer. Two-dimensional global simulations modelling the propagation of the atmospheric wave (under realistic conditions on the day) and its worldwide effect on oceans are presented. Local maxima of water-height disturbance in the farfield from the volcano, linked to the atmospheric wave deformation (in agreement with observations), are identified, emphasising the importance of the TWC model for any daylong predictions. The proposed framework can be extended to include additional layers and physics, e.g. ocean and atmosphere stratification. With the aim of contributing to warning system improvement, the code necessary to simulate the event with the proposed model is made available.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2023.131