Reduced Sensitivity of Tropical Cyclones to Sea Surface Temperature in a Radiative-Convective Equilibrium Environment

It has been challenging to project the tropical cyclone intensity, structure and destructive potential changes in a warming climate. Here we compare the sensitivities of tropical cyclone intensity, size and destructive potential to sea-surface warming with and without a pre-storm atmospheric adjustment to an idealised state of Radiative-Convective Equilibrium (RCE). Without RCE, we find large responses of tropical cyclone intensity, size and destructive potential to sea surface temperature changes, which is in line with some previous studies. However, in an environment under RCE, the tropical cyclone size is almost insensitive to sea surface temperature changes, and the sensitivity of intensity is also much reduced to 3-4% ^oC^-1. Without the pre-storm RCE adjustment, the mean destructive potential during the mature stage increases by about 25% ^oC^-1. However, in an environment under RCE, the sensitivity of destructive potential to sea-surface warming is only about 3-4% ^oC^-1. Further analyses show that the reduced response of tropical cyclone intensity and size to sea-surface warming under RCE can be explained by the reduced thermodynamic disequilibrium between the air boundary layer and the sea surface due to the RCE adjustment. When conducting large-scale sea-surface warming experiments for tropical cyclone case studies, without any RCE adjustment the tropical cyclone response is likely to be unrealistically exaggerated. The tropical cyclone sensitivity under RCE is very similar to those found in coupled climate model simulations. This suggests global mean intensity projections under climate change can be understood in terms of a thermodynamic response to temperature with only a minor contribution from any changes in large-scale dynamics.