Microphysical and Radiative Effects of Ice Clouds on Tropical Equilibrium States: A Two-Dimensional Cloud-Resolving Modeling Study

Abstract

The microphysical and radiative effects of ice clouds on tropical equilibrium states are investigated based on three two-dimensional cloud-resolving simulations imposed by zero vertical velocity and time-invariant zonal wind and sea surface temperature. An experiment without ice microphysics (ice microphysical and radiative effects; C00), another experiment without ice radiative effects (CI0), and the control experiment (CIR) are carried out. The model with cyclic lateral boundaries is integrated for 40 days to reach equilibrium states in all experiments. CI0 produces a colder and drier equilibrium state than CIR and C00 do through generating a larger IR cooling, a larger vapor condensation rate, and consuming a larger amount of water vapor. A larger surface rain rate occurs in CI0 than in CIR and C00. The ice radiative effects on thermodynamic equilibrium states are stronger than the ice microphysical effects so that the exclusion of ice microphysics yields a colder and drier equilibrium state in C00 than in CIR. The ice radiative effects and the ice microphysical effects on surface rainfall processes are largely offset, which leads to similar zonal-mean surface rain rates in C00 and CIR.