The Impact of Rotation on Tropical Climate, the Hydrologic Cycle, and Climate Sensitivity

This work explores the impact of rotation on tropical convection and climate. As our starting point, we use the RCEMIP experiments as control simulations and run additional simulations with rotation. Compared to radiative convective equilibrium (RCE) experiments, rotating RCE (RRCE) experiments have a more stable and humid atmosphere with higher precipitation rates. The intensity of the overturning circulation decreases, water vapor is cycled through the troposphere at a slower rate, the subsidence fraction decreases, and the climate sensitivity increases. Several of these changes can be attributed to an increased flux of latent and sensible heat that results from an increase of near-surface wind speed with rotation shortly after model initialization. The increased climate sensitivity results from changes of both the longwave cloud radiative effect and the longwave clear-sky radiative fluxes. This work demonstrates the sensitivity of atmospheric humidity and surface fluxes of moisture and temperature to rotation. Many useful studies of the tropical regions of Earth have neglected to include rotation; however, phenomena such as tropical cyclones and atmospheric waves are fundamentally tied to rotation. This work compares models of the tropics with and without rotation. Compared to experiments without rotation, rotating experiments have a more humid and stable atmosphere. Although water vapor is cycled through the atmosphere at a slower rate, the precipitation rate increases. The climate sensitivity also increases due to changes in both clouds and water vapor. Many of these changes are the result of increased wind speeds. We argue that idealized modeling of Earth's tropical regions should include not just stationary experiments but also experiments that include rotation. Rotation leads to a decreased intensity of the overturning circulation but increased mean precipitation and precipitable water Static stability increases with rotation, net radiative cooling remains approximately constant, resulting in a smaller subsidence velocity Rotating experiments have a larger effective climate sensitivity relative to RCE experiments mostly due to longwave radiative changes