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Instantaneous relationships between clouds and large-scale vertical motion are used to study the impact of circulation on the near cancellation of cloud radiative effects that is observed over the tropical west Pacific Ocean. The coverage of deep-convective clouds increases with stronger upward motion, but the proportion of thick, medium, and thin anvil cloud remains nearly constant. Thus, when averaging over scales larger than individual storms, the top-of-atmosphere net radiation is only weakly sensitive to the large-scale flow. The balance in cloud radiative effects is therefore maintained across a wide range of large-scale circulations. The ability of the Community Atmosphere Model Version 5 to reproduce the observed cloud-circulation relationships is investigated. The simulated convective clouds substantially overestimate the proportion of deep and optically thick cloud and underestimate the proportion of anvil cirrus. These results demonstrate that simulating key properties of deep-convective clouds remains challenging for some state-of-the-art climate models.

Plain Language Summary The high-cloud systems that are found over warm tropical oceans typically contain thick, rainy clouds connected to thinner extended ice clouds. The thick clouds have a cooling effect on Earth's climate because of their ability to reflect incoming sunlight back to space, while the thin clouds have a warming effect because of their ability to trap outgoing thermal infrared radiation. These warming and cooling effects cancel one another very closely, but why they do so is unknown. In this study we use satellite data to show that the cancellation is maintained as the large-scale atmospheric circulation varies. We also show that a state-of-the-art climate model does not reproduce this behavior.