Revisiting Rainfall Extremes with Ensembles of Convective Objects aNd their Continuum of Interactions with the Large-scale Environment

As climate changes, weather becomes more severe.

This has been of long-standing concern, and difficulties arise in connecting the two different ranges of scales involved.

Hail, rainshowers and strong winds result from the local dynamics of cloud updrafts, while the general circulation determines the relative occurrence of convective regimes to maintain energy balance.

Historically, limitations in computing power mostly led to separate analyses of cloud dynamics and the large-scale circulation.

The mesoscales, in-between, host a rich ecosystem of weather features, organized in a diversity of shapes and morphologies but overly simplified in traditional climate models.This scale separation leads to large uncertainties in the projection of future extremes: the dynamic adjustment of weather systems to the large-scale flow is unconstrained, and small-scale perturbations may feed back onto the global climate state.RECONCILE revisits how the multi-scale character of extreme precipitation emerges from the interaction between storms and the large-scale circulation.

It introduces a novel approach by focusing on the dynamics of storm populations rather than individual storm objects. This paradigm of populations is borrowed from ecology and scarcely used in climate physics.

It allows to overcome strong biases present in operational climate models, by allowing for a diversity in the represented cloud structures and an explicit two-way interaction across the continuum of scales.The current emergence of global storm-resolving models is an unprecendented opportunity to investigate this dynamic coherence across multiple scales of motion.

RECONCILE proposes a way forward, at the intersection of two WCRP's grand challenges: Weather and Climate Extremes, and Clouds, Circulation and Climate Sensitivity, with strong implications for climate model evaluation.