The velocity distribution of barotropic turbulence

We study the statistical properties of the velocity and velocity gradient d istributions in barotropic turbulence. At large enough Reynolds number, the velocity distribution becomes non-Gaussian outside the vortex cores, and i ts characteristics are completely determined by the properties of the far f ield induced by the coherent vortices. The velocity gradients are always no n-Gaussian inside coherent vortices, due to the spatial velocity correlatio ns associated with the ordered flow in the vortex cores, and become non-Gau ssian also in the background turbulence at large enough Reynolds number. (C ) 2000 American Institute of Physics. [S1070-6631(00)51110-6].