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The impact of cloud-radiative interactions on the tropical circulation and its response to surface warming are studied in aquaplanet model simulations with prescribed sea-surface temperatures from eight global atmosphere models. Simulations with enabled and disabled cloud-radiative interactions are compared. In a present-day-like climate, the presence of cloud-radiative interactions strengthens the Hadley cell, narrows and strengthens tropical ascent, and widens subtropical descent. These cloud impacts are robust across models and are shown to be related to the energetics and mass constraints of the tropical atmosphere. Cloud-radiative interactions have no robust impact on the circulation response to surface warming but amplify model differences in the response of the ascent and the Hadley cell strength. The lack of robust cloud impacts is consistent with the fact that surface warming-induced changes in atmospheric cloud-radiative effects are small compared to the cloud-radiative effects in the present-day-like climate.

Plain Language Summary The atmospheric circulation is crucial for the global and regional climate and climate change. A main source of uncertainty in climate models is clouds. An important way of how clouds impact the circulation is by absorbing, emitting, and scattering radiation. We study the impact of cloud-radiative interactions on the tropical circulation by considering an ensemble of climate models that simulate a water-covered aquaplanet. In one set of simulations, clouds fully interact with radiation. In another set, clouds are made transparent to radiation, which disables cloud-radiative interactions. We find that cloud-radiative interactions strengthen the tropical Hadley circulation, narrow and strengthen the regions of upward motion, and widen the regions of downward motion. We relate these cloud impacts to basic energetics and mass constraints of the tropical atmosphere. In response to increasing surface temperatures, cloud-radiative interactions have no robust impact on the circulation across the models but amplify model differences. Our results help to better understanding the role of clouds in the climate system and contribute to the World Climate Research Programme's Grand Challenge on Clouds, Circulation, and Climate Sensitivity.