Increasing contribution of the atmospheric vertical motion to precipitation in a warming climate

Abstract

Global warming is already influencing precipitation worldwide, with more intense amounts being recorded in many locations. Although projections of changes in mean precipitation show a tendency for the ‘wet-get-wetter, dry-get-drier’ in many locations, the situations for precipitation extremes and specific regions are more complex, due to changes in dynamic and thermodynamic influences on atmospheric moisture distributions. Here, we build a dynamically interactive model of atmospheric moisture for the present (2006-2025) and the future climate (2081-2100), informed by outputs from coupled ocean-atmosphere general circulation models to investigate the precise processes that influence the daily precipitation around the world. We find that the dynamic process of vertical advection of the atmosphere, augmented by the horizontal convergence of moisture on the previous day, dominates the same-day precipitation, while the smaller impact of the thermodynamic process provides convective available potential energy for several days. As climate warms, we find that (i) the dynamical-induced precipitation more completely exhausts the vertically-integrated moisture in the models, which results in heavier rainfall. This reduces the thermodynamic influence and horizontal moisture advection after the precipitation; (ii) the distribution of impacts of the dynamic process on precipitation exhibits a greater spread in the warmer future, leading to more frequent extreme precipitation. The findings imply that the contribution of the atmospheric vertical motion in heavy rainfall increases as climate warms. Our results demonstrate that identifying the precise role and interactions among dynamic and thermodynamic processes is crucial for resolving the differentiated future precipitation responses to global warming.