How Does Organized Convection Impact Explicitly Resolved Cloud Feedbacks in the Radiative-Convective Equilibrium Model Intercomparison Project?

In simulations of radiative-convective equilibrium (RCE), and with sufficiently large domains, organized convection enhances top of atmosphere outgoing longwave radiation due to the reduced cloud coverage and drying of the mean climate state. As a consequence, estimates of climate sensitivity and cloud feedbacks may be affected. Here, we use a multi-model ensemble configured in RCE to study the dependence of explicitly calculated cloud feedbacks on the existence of organized convection, the degree to which convection within a domain organizes, and the change in organized convection with warming sea surface temperature. We find that, when RCE simulations with organized convection are compared to RCE simulations without organized convection, the propensity for convection to organize in RCE causes cloud feedbacks to have larger magnitudes due to the inclusion of low clouds, accompanied by a much larger inter-model spread. While we find no dependence of the cloud feedback on changes in organization with warming, models that are, on average, more organized have less positive, or even negative, cloud feedbacks. This is primarily due to changes in cloud optical depth in the shortwave, specifically high clouds thickening with warming in strongly organized domains. The shortwave cloud optical depth feedback also plays an important role in causing the tropical anvil cloud area feedback to be positive which is directly opposed to the expected negative or near zero cloud feedback found in prior work. Tropical clouds play an important role in the uncertainty associated with understanding how the Earth's climate responds to an imposed warming. Here, we look at how organized cloud systems associated with the tropics affect the processes that govern the climate response to warming. We find that strongly organized cloud systems reduce how strongly the Earth responds to warming. This is primarily associated with the changes in the optical properties of high clouds. These cloud properties impact the overall understanding of the role tropical clouds play in modulating the Earth's temperature and calls into question prior assumptions of its behavior. Domains with organized convection have cloud feedbacks with the same sign but larger inter-model spread than domains without organization The cloud feedback parameter is less positive, or even negative, for more strongly organized domains In radiative-convective equilibrium, the tropical anvil cloud area feedback is positive due to the shortwave cloud optical depth feedback