Global wavenumber spectra from SARAL/Altika observations
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Science III: Mesoscale and sub-mesoscale oceanography
Presentation type: Type Poster
The wavenumber spectra of along-track Sea Surface Height from the radar mission SARAL/Altika (1 Hz) are analyzed over the period 2013-2015. Saral is chosen for its low noise levels and improved signal-to-noise. The use of the spectral shape to interpret the surface eddy regime at global scale is revisited. Wavelength range for the spectral slope estimations is determined as a function of local first-baroclinic Rossby radius of deformation (Lr) and the Rhines scale (LR). The wavelength range varies spatially, rather than the fixed wavelength range of previous studies. Results show that spectral slope is generally steeper than k^-3 (where k is the wavenumber) in the extra-tropics (reaching slope values steeper than k^-4 in high energy eddy regions), and flattens towards the equator (values around k^-2). Processing steps of careful editing and corrections, noise removal, and spectral segment lengths can impact on the spectral slope estimates. Results also evidence an important seasonality of the spectral slope values, with an overall flatter spectrum during the winter months in comparison to summer (slope variations are in the order of 0.5 to 1.5 from one season to the other). Analysis of the error levels also exhibit seasonal variations, which suggests a non-negligible contribution of the local sea-state and dynamical regime to the noise levels.