Application of SAR Wave Mode and Wide Swath Mode for Swell Tracking Across Ocean
Husson, Romain1; Collard, Fabrice1; Chapron, Bertrand2; Ardhuin, Fabrice2; Dubus, Laurent3

Swell tracking from ASAR wave mode has been running for 5 years now which provides a global picture of the observed swell systems at global scale and at any time. The swell tracking is based on swell spectra measurements derived from SAR wave mode products and uses linear theory for the propagation of this swell information in deep ocean and without current. An in depth comparison between SAR based swell tracking and in-situ observations by wave-rider buoys and seismometers will be presented to highlight the strength and limitations of this application. In view of recent availability of wave spectra from wide swath mode in north east Atlantic and upcoming Sentinel-1 mission, analysis of SAR acquisitions mode (Wide swath, wave mode with or without leapfrog) and orbits (Envisat vs. Sentinel-1) on swell system sampling will be discussed. Application of swell tracking for the deployment of ''virtual buoys'' at any locations in deep water will be presented. All propagated observations passing in the vicinity of this virtual buoy are merged to provide a time series of all swell systems at this location. A permanent swell monitoring and short term forecasting system, part of the future MCGS activities performed at CLS and extending the pilot service developed for La Reunion island based on this "virtual buoy" concept, will be highlighted. In the future, this service could also be improved by the direct use of wave measurements from future CFOSAT mission. Finally, synthetic swell fields reconstructed from all swell observations originating from the same storm source have been developed to drastically increase the assimilation impact of SAR wave spectral observations in sea state models. They also provide better SAR wave measurement error characterization and new methods for the future calibration/validation activities of Sentinel-1 wave measurements.