Kinetic Energy Spectra and Spectral Budget of Radiative-Convective Equilibrium

Abstract

The atmospheric kinetic energy spectrum and energy cascade are investigated in idealised simulations of radiative-convective equilibrium (RCE). WRF is employed to perform cloud-resolving simulation of an idealized radiative-convective equilibrium with and without aggregation with Δx = 4 km. The horizontal kinetic energy (HKE) spectrum for the aggregated simulation in the upper troposphere is steeper than the non-aggregated case and closer to -5/3. The HKE spectra for the non-aggregated simulation in the upper troposphere and the lower stratosphere are much shallower than the -5/3 spectrum. In the upper troposphere, the divergent kinetic energy has a similar magnitude to the rotational kinetic energy in both the non-aggregated simulation and aggregated simulation. Energy is mainly gained from the buoyancy flux and mainly lost from the vertical energy flux for scales larger than 20 km. Downscale energy transfer is found in the upper troposphere. Numerical dissipation is the main source of energy loss at small scales. In the lower stratosphere, the divergent kinetic energy dominates the kinetic energy spectrum in both simulations. Energy is mainly gained from the vertical energy flux and is balanced by the loss from the buoyancy flux term, transfer term and dissipation. An Eliassen-Palm flux analysis suggests that wave-mean-flow interaction may be responsible for the upscale energy transfer found in the lower stratosphere. The magnitudes of our kinetic energy spectra are similar to spectra calculated from aircraft data. Rotation is found to promote aggregation and steepen the energy spectrum.