A new method to diagnose turbulent cascade rates in mesoscale ocean systems and planetary atmospheres

Energy is supplied to Earth at the planetary scale by solar heating. Much of this energy becomes kinetic energy and ultimately arrives at small scales where it is dissipated by molecular processes. Turbulence plays a key role in the Earth system, "cascading" this energy and other properties (e.g., enstrophy) from one scale to another through non-linear advection, facilitating the movement of energy from planetary to dissipative scales. Despite the important role of turbulent cascades in the ocean, cascade rates are notoriously hard to measure due to sparse data and inhomogeneity.

In this presentation we introduce an "advective structure function" method for estimating turbulent cascade rates in large-scale geophysical turbulence. Numerical simulations of idealized large-scale geophysical turbulence show that this new method can estimate cascade rates of energy and enstrophy even when flows are anisotropic and when spatial sampling is unidirectional (e.g., ship-tracks/satellite passes). We will also present a preliminary application of this new method to satellite observations of Jupiter's atmosphere.