Precipitation Efficiency and its Role in Cloud-Radiative Feedbacks to Climate Variability

Precipitation efficiency (PE) is a useful concept for estimating precipitation under a given environmental condition. PE is used in various situations in meteorology such as to evaluate severe precipitation associated with a single storm event, as a parameter of cumulus convective parameterization, and to separate clouds and precipitation in climate projection studies. PE has been defined in several ways. In this review, we first introduce definitions of PE from microscopic and macroscopic perspectives, and provide estimates of PE based on observational and modeling approaches. Then, we review PE in shallow and organized deep convective systems that provide either a conceptual framework or physical constraints on representations of convection in models. Specifically, we focus on the roles of PE in cloud-radiative feedbacks to climate variability. Finally, we argue the usefulness of PE for investigating cloud and precipitation changes in climate projection studies.