Sea State Trends and Variability: Consistency Between Models, Altimeters, Buoys, and Seismic Data (1979-2016)
Résumé
Wave hindcasts of long time series (>30 years) have been instrumental in understanding the wave climate. However, it is still difficult to have a consistent reanalysis suitable for study of trends and interannual variability. Here we explore the consistency of a wave hindcast with independent observations from moored buoys, satellite altimeters, and seismic data. We use the Climate Forecast System Reanalysis (CFSR) winds to drive a wave model since extreme events are generally well captured. Unfortunately, the original CFSR winds are not homogeneous in time. We systematically modify this wind field in time and space to produce a wave field that has homogeneous differences against the Globwave/SeaStateCCI altimeter wave height database. These corrections to the winds and resulting waves are validated using independent buoy and microseism data. We particularly use seismic data in the dominant double-frequency band, around 5-s period, that are generated by opposing waves of equal frequencies. The seismic data confirms that our correction of time-varying biases is consistent, even in remote and undersampled region such as the Southern Ocean where the original CFSR biases are strongest. Our analysis is performed on monthly time series, and we expect the monthly statistics to be better suited for climate studies. Remaining issues with time consistency of reanalysis products and associated wave hindcasts are further discussed.
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