Universality of k(-1) noise, the enstrophy cascade, and the large-scale atmospheric spectrum.

Direct numerical simulations of two-dimensional (2D) incompressible Navier-Stokes turbulence can model large-scale atmospheric dynamics when driving and dissipation cover wide ranges of length scales. Natural assumptions for the 2D energy balance lead to the robust k(-1) vorticity spectrum (k=2pi, length scale) observed in the atmosphere. Scaling in k space is related to hyperbolicity of large-scale 2D flow in physical space. The mechanism of this scaling has similarities with a recent model of dissipative self-organized criticality.