Periodic extreme rainfall in a warmer climate due to stronger convectively coupled waves.

Abstract

Tropical regions may experience periodic extreme precipitation and suffer from associated periodic deluges in a warmer climate. Recent studies conducted small-domain (around 100 kilometers by 100 kilometers) atmospheric model simulations and found that precipitation transitions from a steady state to a periodic oscillation state in a hothouse climate when the sea surface temperature reaches 320 to 325 kelvin. Here, we conduct global-scale atmospheric model simulations with varying complexity. We find that tropical precipitation in convective regions already transitions to a [Formula: see text](10-day) periodic oscillation state with a [Formula: see text] amplitude at 305 to 310 kelvin, about 15 kelvin lower than previously reported and within reach in a century under a high-carbon emission scenario. Using a low-order analytical model, we attribute the onset of the periodic extreme precipitation to the intensification of convectively coupled waves that were not considered in the previous small-domain simulations. Our mechanism highlights the importance of the interaction between convection and atmospheric wave dynamics for climate change.