CoAuthors

Rosemary Morrow (LEGOS, France); Isabelle Pujol (CLS Space Oceanography, France); Gerald Dibarboure (CNES, France); Clement Ubelmann (CLS Space Oceanography, France)

Recent progress in satellite altimetry has greatly improved the observability of mesoscale structures in the ocean. Here we analyze the noise levels and observable spatial scales for the global ocean using the wavenumber spectra of the three-year SARAL/Altika 1Hz and the most recent Sentinel-3A 1Hz Sea Surface Height (SSH) along-track measurements. We observe that noise estimations (for the wavelength range 15-30 km) tend to deviate from a purely white noise spectrum in regions of low eddy energy, and in particular inside the tropical band (15°S-15°N). Noise levels also vary seasonally, with an overall higher noise level during winter months in comparison to summer. The capability for resolving fine spatial scales also varies as a consequence of the noise level seasonality. During winter months, the observable wavelength reduces by about 5 to 20 km with respect to summer season. In general, these variations are less important in western boundary current systems in comparison to less energetic current systems, given the strong signal to noise ratio in western boundary current systems. We will also address an observed shallower spectral slope in certain regions in the 30 to 70 km wavelength band, and the impact of noise and internal wave dynamics here. Potential impacts of these variations for diagnosing processes in the mesoscale to submesoscale wavelength range are also discussed.