Triple cascade and zonal flows in beta-plane turbulence
Seminar Room 1, Newton Institute
At low amplitudes, the beta-plane model has three conservation laws: the energy, the potential enstrophy and the zonostrophy (an additional invariant found by Balk, Nazarenko and Zakharov in 1991). Application of a standard Fjortoft argument to this system leads to a conclusion that these 3 invariants must cascade in an anisotropic fashion, each cascade occupying its own sector in the 2D k-space. It appears that the energy cascade sector corresponds to generation of large-scale zonal flows in the system. I will discuss some recent numerics aimed at checking conservation of zonostrophy and the triple cascade property.