Reponse of precipitation to dynamics in global-storm resolving models

Most climate models show a precipitation increase with warming that is smaller than the increase in moisture, which requires a weakening of the convective mass flux and a slowing of the overturning circulation. In this study we use global-storm resolving models (DYAMOND models) to identify the systematic relationships between the precipitation, the vertical velocity and the overturning circulation in the tropics. The cloud-resolving simulations that are 40-day long in winter allow us to study the dynamical response of precipitation over a wide range of spatial scales. A data reduction and inference method, δ-MAPS, provides an efficient way to reduce the complexity and dimensionality of high-resolution simulations. We use the domains identified in 2d fields of atmosphere mass content of water vapor – interpreted as regions of homogeneous precipitable water – as preferential domains to derive the isentropic distribution of vertical mass transport and the isentropic streamfunction. The isentropic analysis consists in sorting the air parcels in terms of equivalent potential temperature, which offers a simple representation of the convective overturning. A multiscale decomposition allows us to quantify the contribution of the mesoscale circulation in comparison to the large-scale overturning circulation. Finally, the results are compared between the different DYAMOND models to evaluate the intermodel spread. By doing so, we evaluate to what extent the spread in precipitation in model ensemble may arise from the differences in representation of the overturning circulation at different scales.