Probability density functions of large-scale turbulence in the ocean

Probability density functions (pdfs) of surface velocity and surface velocity gradients in the ocean are calculated using altimetric data from the Topex/Poseidon satellite. These provide information about turbulence in a high-Reynolds-number geophysical flow. :Both velocity pdfs and velocity gradient pdfs calculated over small regions are Gaussian but have more exponential shapes as the size of the region increases. We develop a simple explanation for the non-Gaussianity of velocity pdfs based on the inhomogeneity of eddy kinetic energy in the ocean.