![]() ![]() The inset in the bottom panel plots the same spectrum on a lin-lin scale and highlights the wide range of wavenumbers around 300 km. The bottom panel highlights the power-law scaling over different k ℓ bands. The top panel highlights the prominent spectral peak due to the ACC, which is more than twice the mesoscale peak. ![]() 2 plot the same spectrum in lin-log and log-log scale, respectively. ![]() 15), which is not possible for EOF analysis, and to disentangle length-scales and time-scales independently and in a self-consistent manner to study interactions between different spatio-temporal scales that link large-scale forcing, the mesoscale eddy field, and the global-scale circulation. Coarse-graining allows us to derive the dynamics governing the evolution of the flow in Fig. 21, 22), which is a statistical approach that requires averaging long time-series. 19, 20) or Empirical Orthogonal Function (EOF) analysis (e.g., refs. Past approaches have used climatological multi-year averaging (e.g., refs. 1 are derived deterministically from a single daily mean of surface geostrophic velocity data without further temporal or statistical averaging. It is worth emphasizing that the flows in Fig. The agreement between AVISO and NEMO is remarkable. North Atlantic currents are also readily observable, including the North Atlantic Current, its northward fork to the Norwegian Atlantic Current, and the southward East Greenland Current. 1, we can see clearly several well-known oceanic gyre structures, including the Beaufort Gyre in the Arctic, the Weddell and the Ross gyres in the Southern Ocean near Antarctica, the subtropical and subpolar gyres in the Atlantic and Pacific basins, and the ACC. The colour intensity illustrates the flow speed and is consistent with expectations that the large-scale flow magnitude is primarily dominated by the western boundary currents, while scales smaller than 10 3 km are dominated by mesoscale fluctuations. The KE (per unit mass, in m 2/s 2) contained in scales larger than ℓ isįigure 1 visualizes the flow from both AVISO satellite data and NEMO reanalysis model data (see “Methods”) from a single daily mean at scales larger than and smaller than 10 3 km, termed “gyre-scale” and “mesoscale”, respectively. 16 used here relies on a generalized convolution operation that respects the underlying spherical topology of the planet, thus preserving the fundamental physical properties of the flow, such as its incompressibility, its geostrophic character, and the vorticity present at various scales. Unlike standard approaches to low-pass filtering geophysical flows, such as by averaging adjacent grid-cells or block-averaging in latitude-longitude, the coarse-graining of ref. Advent of satellite altimetry brought into focus the pervasiveness of mesoscale eddies \(\) that only contains spatial scales larger than ℓ, having had smaller scales removed (see Fig. ![]()
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