Convective Self-Aggregation and Climate Sensitivity in a Multi-Model Ensemble of Radiative-Convective Equilibrium Simulations
Abstract:
The Radiative-Convective Equilibrium Model Intercomparison Project (RCEMIP) is an intercomparison of multiple types of numerical models, including atmospheric general circulation models (GCMs), cloud-resolving models (CRMs), global cloud-resolving models (GCRMs), large eddy simulation models (LES), and single column models (SCMs), configured in radiative-convective equilibrium (RCE). RCE is an idealization of the tropical atmosphere that has long been used to study basic questions in climate science, and is employed here to investigated the response of clouds and convective activity to warming, cloud feedbacks and climate sensitivity, and the aggregation of convection and its role in climate.
Results are presented from the RCEMIP ensemble of more than 30 different models. The robustness of the RCE state across the RCEMIP ensemble is assessed and the occurrence of self-aggregation is identified. While there are large differences across the RCEMIP ensemble in the representation of mean profiles of temperature, humidity, and cloudiness, in a majority of models anvil clouds rise, warm, and decrease in area coverage in response to an increase in sea surface temperature (SST). Nearly all models exhibit selfâaggregation in large domains and agree that selfâaggregation acts to dry and warm the troposphere, reduce high cloudiness, and increase cooling to space. There is no clear tendency for either an increase or decrease in self-aggregation with warming, but changes in self-aggregation with warming partially explain the extreme spread in simulated climate sensitivities across the RCEMIP ensemble.
