Abstract's details
Sizing the largest ocean waves using the SWOT mission
Event: 2025 SWOT Science Team Meeting
Session: Oceanography: Wind and Waves
Presentation type: Oral
Winds generate waves over the oceans with a wide range of heights and lengths. The heights and periods of the largest waves are important parameters in the design of marine structures. Extreme waves also play an outsize role in air-sea fluxes and coastal dynamics, and leave imprints on seismic and sediment records. Rare events have
so far escaped measurements, with few wave heights from satellite altimeters exceeding 16 m, and no associated measurement of wave periods. Here we use swells radiated from the largest storms to reveal wave properties in the storms, and their generation mechanism. Long swells are systematically resolved in the Surface Water and Ocean Topography (SWOT) satellite global LR sea level measurements. Patterns of increasing swell wavelength and decreasing swell height away from storms are consistent with a nonlinear transfer of energy from short to long period waves. The spectral shapes commonly used to represent the roll-off of energy towards long periods are not consistent with this inverse energy cascade, overestimating the energy level by a factor 20 at periods 1.2 to 1.4 times the peak period. We propose an updated spectral shape that is consistent with SWOT swell measurements, and we use it to estimate storm wave periods from swell heights. These results holds up to a new record for measured significant wave heights in Storm Eddie (21 december 2024), at 19.7±0.3m, with a corresponding peak period of 20.1±0.5s. These new observations of long period swells should have a wide range of applications from coastal dynamics to seismology. In terms of wave modelling, the SWOT data shows that better parameterizations of wave-wave interactions are needed to correct swell arrival biases.
These large swell events also give rise the large infragravity waves: data in cycle 025 track 580 off the Oregon coast suggest that the SSH at scales under 20 km can be dominated by infragravity waves with a 10 km dominant wavelength and 10 cm height. Fortunately for most SWOT applications this occurence is extremely rare and typical infragravity wave heights are expected to be under 1 cm.
so far escaped measurements, with few wave heights from satellite altimeters exceeding 16 m, and no associated measurement of wave periods. Here we use swells radiated from the largest storms to reveal wave properties in the storms, and their generation mechanism. Long swells are systematically resolved in the Surface Water and Ocean Topography (SWOT) satellite global LR sea level measurements. Patterns of increasing swell wavelength and decreasing swell height away from storms are consistent with a nonlinear transfer of energy from short to long period waves. The spectral shapes commonly used to represent the roll-off of energy towards long periods are not consistent with this inverse energy cascade, overestimating the energy level by a factor 20 at periods 1.2 to 1.4 times the peak period. We propose an updated spectral shape that is consistent with SWOT swell measurements, and we use it to estimate storm wave periods from swell heights. These results holds up to a new record for measured significant wave heights in Storm Eddie (21 december 2024), at 19.7±0.3m, with a corresponding peak period of 20.1±0.5s. These new observations of long period swells should have a wide range of applications from coastal dynamics to seismology. In terms of wave modelling, the SWOT data shows that better parameterizations of wave-wave interactions are needed to correct swell arrival biases.
These large swell events also give rise the large infragravity waves: data in cycle 025 track 580 off the Oregon coast suggest that the SSH at scales under 20 km can be dominated by infragravity waves with a 10 km dominant wavelength and 10 cm height. Fortunately for most SWOT applications this occurence is extremely rare and typical infragravity wave heights are expected to be under 1 cm.
Contribution: ST2025OS4-Sizing_the_largest_ocean_waves_using_the_SWOT_mission.pdf (pdf, 19914 ko)
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