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Abstract A global climate model is run in radiative‐convective equilibrium including a slab ocean with a specified ocean heat transport analogous to what is seen in the tropical Pacific. The insolation is varied to create a range of global mean equilibrium temperatures. These results are compared with experiments that do not include a specified ocean heat transport. The ocean heat transport cools the coldest Sea Surface Temperatures (SSTs) and increases the SST contrast. The warmest SSTs change much less with the addition of ocean heat transport because increased atmospheric transport moves energy away from the warm region. The ocean heat transport also increases the efficiency of cooling by outgoing longwave radiation in the subsiding region, allowing for a cooler global mean SST. At colder global mean temperatures ocean heat transport creates a high‐contrast state in which abundant low clouds play a strong role in maintaining the SST contrast. This high‐contrast state abruptly transitions to a warmer, low‐SST‐contrast state as the climate is warmed by increasing insolation. At warmer temperatures comparable to the current tropics, the low cloud response is less important than longwave emission in maintaining the SST contrast. Although ocean heat transport cools the climate, it does not much affect the sensitivity of the model climate to increasing insolation. Comparison of the model results to ERA5 reanalysis data shows that mechanisms responsible for the SST distribution and energy budget changes in this idealized model are analogous to variability that occurs over the tropical Pacific Ocean. 

Abstract We describe internal, low‐frequency variability in a 21‐year simulation with a cloud‐resolving model. The model domain is the length of the equatorial Pacific and includes a slab ocean, which permits coherent cycles of sea surface temperature (SST), atmospheric convection, and the convectively coupled circulation. The warming phase of the cycle is associated with near‐uniform SST, less organized convection, and sparse low cloud cover, while the cooling phase exhibits strong SST gradients, highly organized convection, and enhanced low cloudiness. Both phases are quasi‐stable but, on long timescales, are ultimately susceptible to instabilities resulting in rapid phase transitions. The internal cycle is leveraged to understand the factors controlling the strength and structure of the tropical overturning circulation and the stratification of the tropical troposphere. The overturning circulation is strongly modulated by convective organization, with SST playing a lesser role. When convection is highly organized, the circulation is weaker and more bottom‐heavy. Alternatively, tropospheric stratification depends on both convective organization and SST, depending on the vertical level. SST‐driven variability dominates aloft while organization‐driven variability dominates at lower levels. A similar pattern is found in ERA5 reanalysis of the equatorial Pacific. The relationship between convective organization and stratification is explicated using a simple entraining plume model. The results highlight the importance of convective organization for tropical variability and lay a foundation for future work using coupled, idealized models that explicitly resolve convection.