UHF Radar signature of a tsunami approaching coastal area: modelling, experiments and application to tsunami warning

Abstract : Perhaps for the first time, satellite altimeters provided transects of the 12/26/04 tsunami elevation across the Indian Ocean, while the event unfolded. Here we use well-established Ultra High Frequency (UHF) radar technology, to develop a method that could provide warning of an incoming tsunami to coastal populations. When a tsunami reaches the continental shelf, the mostly depth-uniform current it induces greatly increases in speed (maybe up to 10-20 cm/s) and may induce significant Doppler shifts in ocean surface waves, particularly for those of smaller wavelength (high frequency). Given proper processing, such shifts could be identified by shore-based UHF radars as a tsunami signature and trigger a warning. Due to the tsunami slowing down with decreasing water depth, from the shelf break to shore, warning times of 5-15 minutes could be conceivable, depending on the shelf width, which could be sufficient to proceed with vertical evacuation in exposed areas. Here, we use a Higher Order Spectral (HOS) Method to model fully nonlinear sea states caused by wind, down to typical UHF wavelength of order 10 cm, as well as Doppler shifts and wave shoaling/refraction caused by slowly varying depth uniform currents. Such currents can be obtained for selected case studies, e.g., from tsunami propagation modeling, using a standard long wave model. UHF radar backscattering is modeled by a Boundary Element Method, solving Maxwell's equations, developed and validated in earlier work. We present initial results of this modeling study, in terms of spatio-temporal UHF radar signatures and their sentsitivity to governing physical parameters. We also present large-scale laboratory results for radar backscattering spectra measured during wave-current interaction experiments performed in the FIRST basin (La Seyne, France). We intend to apply our detection methodology to Southern Thailand, based on earlier modeling work we performed for the 12/26/04 tsunami propagation.
Type de document :
Communication dans un congrès
American Geoscience Union Fall 2007 Meeting, Dec 2007, San Francisco, United States. American Geoscience Union, 1, pp.1, 2007
Liste complète des métadonnées

https://hal.archives-ouvertes.fr/hal-00193222
Contributeur : Hubert Branger <>
Soumis le : dimanche 2 décembre 2007 - 22:29:08
Dernière modification le : vendredi 15 mars 2019 - 17:02:08

Identifiants

  • HAL Id : hal-00193222, version 1

Citation

Stéphan Grilli, Marc Saillard, Sara Dubosq, Hubert Branger. UHF Radar signature of a tsunami approaching coastal area: modelling, experiments and application to tsunami warning. American Geoscience Union Fall 2007 Meeting, Dec 2007, San Francisco, United States. American Geoscience Union, 1, pp.1, 2007. 〈hal-00193222〉

Partager

Métriques

Consultations de la notice

158