Reconciling Compensating Errors Between Precipitation Constraints and the Energy Budget in a Climate Model

Abstract

Precipitation microphysics and the effective radiative forcing due to aerosol-cloud interactions (ERFaci) contribute to some of the largest uncertainties in general circulation models (GCMs) and are closely interrelated. This study shows that a sophisticated, two-moment prognostic precipitation scheme can simultaneously represent both warm rain characteristics consistent with satellite observations and a realistic ERFaci magnitude, thus reconciling compensating errors between precipitation microphysics and ERFaci that are common to many GCMs. The enhancement of accretion from prognostic precipitation and accretion-driven buffering mechanisms in scavenging processes are found to be responsible for mitigating the compensating errors. However, single-moment prognostic precipitation without the explicit prediction of raindrop size cannot capture observed warm rain characteristics. Results underscore the importance of using a two-moment representation of both clouds and precipitation to realistically simulate precipitation-driven buffering of the cloud response to aerosol perturbations.