Precipitation Efficiency Across Different Climates in Radiative-Convective Equilibrium

The precipitation efficiency (PE) of convection is explored in simulations of radiative-convective equilibrium with a cloud-resolving model (the System for Atmospheric Modeling), forced with a wide range of fixed sea-surface-temperatures (SSTs) and using several different microphysics schemes. It is found that PE generally increases with warming at about 1%/K and a framework is developed to diagnose the reasons for this. The re-evaporation of falling precipitation and the detrainment of cloud condensate increase relative to the condensation rate with warming, acting to decrease the PE. This is compensated by the increased rate of conversion of cloud condensate into precipitation relative to the condensation rate, and so the PE increases. In contrast to several recent studies with global climate models, no significant relationship is found between the changes in PE (or, equivalently, the changes in the detrainment efficiency) and the Cess sensitivity of these experiments. These results, which come from small domain simulations, are compared with simulations in a long channel domain with an East-West SST gradient, a set-up which is more relevant for understanding the behavior of Earth’s tropics.