In Earth’s tropics, large-scale circulations are produced by a variety of mechanisms, including mechanisms associated with tropical waves, land-ocean contrasts and sea-surface temperature (SST) gradients. Understanding how tropical circulations may change under future global warming is challenging because of complex interactions between these mechanisms.

In this study, we seek to understand how circulations driven by large-scale SST gradients may change under a future warmer climate. We perform idealized simulations with a cloud-resolving model in which the effect of large-scale circulation on the ascent region is parameterized via the weak-temperature gradient (WTG) approximation. Under this approximation, the free tropospheric temperature profile is constrained to follow that of a reference state, taken here to be the temperature profile under radiative-convective equilibrium (RCE). As the SST is increased from that of the reference state, convection acts to warm the free troposphere. To maintain the free-tropospheric temperature, an implied circulation develops, which causes moisture convergence and hence increased precipitation. Here, we investigate changes in the strength of this implied circulation with respect to changes in relative SST (analogous to changes in large-scale SST gradients) and with respect to changes in the background SST of the RCE reference state (analogous to changes in global-mean SST). We apply an analysis of the moist static energy budget to determine the physical mechanisms that govern the model’s response to both relative and background SST changes. Implications for future changes to large-scale tropical circulations driven by SST gradients are discussed.