Simulations of Radiative-Convective-Dynamical Equilibrium

Small-domain cloud-resolving model and single-column model simulations have historically applied one of three representations of large-scale vertical motion, w(LS). In simulations of radiative-convective equilibrium, w(LS) = 0, and a balance develops between convective heating and radiative cooling. Under the weak-temperature gradient approximation and related approaches, w(LS) is diagnosed based on the model's thermodynamic profile. Finally, for real-case simulations, w(LS) may be prescribed as a time-varying field derived from observations. Here, we propose one additional setup, namely, a prescribed but time-invariant vertical motion. In this case, the atmosphere evolves toward an equilibrium state characterized by a three-way balance between radiative and adiabatic cooling and convective heating, with the relative contribution of radiation decreasing with increasing w(LS). We refer to this state as radiative-convective-dynamical equilibrium (RCDE). In this preliminary study we highlight the characteristics of the RCDE state through a suite of simulations performed with a single cloud-resolving model and single-column model. An appealing aspect of these simulations is the wide variety of equilibrium states achieved, ranging from dry and strongly unstable for small w(LS) to approximately moist neutral for large w(LS). This makes RCDE a propitious framework for future model intercomparisons.