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Measuring coastal wave energy from space
Significance Statement
Wave power near the coast can be measured from space using satellite observations. Observing ocean waves with satellite-borne altimeters is nothing new, but applications have generally been over the open ocean. Significant wave height is routinely measured by satellite altimeters and wave period can be estimated from altimeter significant wave height and back-scattering coefficient; the wave power per meter wave crest was consequently derived. The main innovation of the study presented here is that in shallow waters wave period can also be estimated if the water depth is known. A simple algorithm is presented. A key limitation is the low temporal resolution and spatial coverage of the SARAL /AltiKa observations. However, because microsatellites like SARAL are relative small and low-cost there are plans to launch many more. It is therefore likely that global coverage will much improve in the future.
Journal Reference
Geophysical Research Letters, Volume 42, Issue 13, pages 5452–5459, 16 July 2015.
Lonneke Goddijn-Murphy1,*, Belén Martín Míguez2,3, Jason McIlvenny1 , Philippe Gleizon1
[expand title=”Show Affiliations”]- Environmental Research Institute, UHI-NHC, Thurso, UK
- Centro Tecnológico Del Mar, Fundación, Vigo, Spain
- Now at EMODnet Secretariat, InnovOcean, Oostende, Belgium
Abstract
A simple model to estimate wave power at a coastal site from satellite radar altimetry is proposed. We used data from the AltiKa altimeter on board the SARAL satellite because of its superior performance near the coast. The deep water approximation was applied to our 60 m deep site along with a simple empirical model to estimate wave period, T, from altimeter significant wave height, Hs, and backscattering coefficient, σ0. A known relation between zero-crossing period, Tz, and wave energy period, TE, was used in combination with Hs to calculate wave power per meter wave crest (P). The annual and seasonal mean values of P using AltiKa parameters largely agreed with known ranges of P at the site. A comparison with shallower sites and sites closer to the coast revealed that for estimation of Tz from AltiKa the water depth could be taken into account and an empirical relation is given.
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