Large‐scale character of an atmosphere in rotating radiative‐convective equilibrium

Abstract

Abstract A rotating radiative‐convective equilibrium on a sphere is reached using a global atmospheric model with prescribed globally uniform sea surface temperature and no insolation. In such an equilibrium state, multiple tropical cyclone‐like vortices coexist in the extratropics, moving slowly poleward and westward. Many vortices have a lifetime longer than 2 months and travel from the tropics to the polar regions. The typical spacing of simulated tropical cyclone‐like vortices is comparable to the deformation radius, while the production of available potential energy is at a scale slightly smaller than those vortices. It is hypothesized that the growth of tropical cyclone‐like vortices is driven by the self‐aggregation of convection, while baroclinic instability destabilizes any vortices that grow significantly larger than the deformation radius. A weak Hadley circulation dominates in the deep tropics, and an eastward propagating wave number 1 Kelvin‐like mode having a period of 30–40 days develops at the equator. The weak Hadley circulation is found to emerge from an initially quiescent atmosphere due to poleward momentum transport by the vortices.