What can moist thermodynamics tell us about circulation shifts in response to uniform warming?

Abstract

Aquaplanet simulations exhibit a robust expansion of the Hadley cell and poleward jet shift in response to uniform warming of sea surface temperature. Here moist thermodynamic and dynamic frameworks are combined to make predictions of circulation responses to warming. We show Clausius-Clapeyron (CC) scaling of specific humidity with warming predicts an expansion of the Hadley circulation according to convective quasi-equilibrium dynamics. A poleward jet shift follows from the control-climate relationship between the Hadley cell edge and jet stream position. CC scaling of specific humidity with warming also predicts decreased diffusivity and a poleward shift of the latitude of maximum latent and dry static energy transport according to mixing-length theory. Finally, atmospheric cloud radiative changes shift the latitude of maximum energy transport poleward in most models. Our results show moist thermodynamics can predict meridional shifts of the circulation when combined with dynamical frameworks; however, additional feedbacks are important for the simulated response.