Nonlinear drag, geostrophic turbulence, and heat transport

The possibility of stopping the inverse energy cascade by quadratic drag in forced-dissipative two-dimensional turbulent flow is investigated. Both scaling arguments and numerical experiments support the idea that in a statistically steady state the length scale of energy-containing eddies does not depend on energy input in the system. The only external parameter that defines this scale appears to be the quadratic drag coefficient. A universal form of the spectrum is suggested, and numerical experiments are in good agreement.

Experiments were extended to a two-layer baroclinically unstable flow with nonlinear drag acting on the lowest layer. A new scaling is developed for the heat transport by eddies generated by a supercritical shear and dissipated by such a drag. We explore both theoretically and numerically the limits of strong and weak drag, and discuss the implications for heat transport in the atmosphere.