Response of Tropical Climate and Extreme Precipitation to Ocean Temperature in Convection-Permitting Aquaplanet Simulations

Tropical climate and weather systems are integral to the global hydrological cycle. Yet, their detected and projected trends are highly uncertain in part due to shortcomings of Earth system models. This study uses novel aquaplanet simulations with different sea-surface temperature and with convection-permitting resolution in the tropics to simulate the response of tropical phenomena to globally uniform warming. The results show a complex response within the tropical circulation. With warming, the tropical troposphere warms and expands vertically alongside a weaker and broader Hadley cell. Simultaneously, the Intertropical Convergence Zone (ITCZ) narrows and strengthens, though its location shows an unclear response to warming. Both dynamic and thermodynamic processes play a role in the ITCZ response, exhibiting patterned changes in vertical velocity and magnitude changes in water vapor. Clouds also show a complex response, particularly with tropical cloud ice showing a non-linear response to tropical warming and likely causing non-linear changes in the radiation budget. At finer scales, tropical precipitation extremes increase non-linearly with warming, exceeding Clausius-Clapeyron scaling at higher percentiles. The prevalence of non-linear responses highlights the necessity of considering multiple scenarios when investigating the response of tropical phenomena to globally uniform warming. This research provides valuable insights into tropical climate sensitivity in a framework that captures multi-scale processes from global to convective scales.