On the Potentials and Limitations of Attributing a Small‐Scale Climate Event

Abstract

A cloudburst is the result of strong convective mechanisms. Due to its intensity, suddenness and brief duration, it is particularly difficult to adequately drain the resulting surface water, which accordingly may lead to severe flooding and consequently large economic losses. Such flash floods are not uncommon across the world and are devastating when occurring in a densely populated city such as Copenhagen, Denmark-even without additional complicating runoff effects from surrounding more elevated areas (Khajehei et al., 2020;Ricchi et al., 2021). Predicting the precise location, timing and intensity of weakly forced convective events (e.g., initiated by local surface conditions) is notoriously difficult, even for a state-of-the-art, convection permitting Numerical Weather Prediction (NWP) models due to a combination of (a) model resolution not fully resolving either the deep convection mechanism or local interactions related to orography or land/sea contrasts, (b) imprecise depiction of the initial conditions (IC) due to a lack of high-resolution observations (in particular of humidity) and (c) the chaotic behavior and associated sensitivity to IC of the atmosphere in general and convection in particular (Coppola

How to Engage and Adapt to Unprecedented Extremes

“…Initially introduced by Schär et al (1996), this approach investigates how past weather situations might have behaved under future or preindustrial climate conditions, akin to anticipated climate changes (Aalbers et al, 2023;Hawkins et al, 2023). This method has several limitations (inaccuracies in future atmospheric dynamics representations (Rasmussen, 2011;Zhou et al, 2023) and distortions from anomalies in lateral boundary conditions (Matte et al, 2022)) Recent advances have enabled research centers with global models to enhance the study of extreme weather events, including compound events like hot-dry summers (Bevacqua et al, 2023), through large ensembles (Deser et al, 2014), creating diverse climate trajectories by slightly changing initial conditions. Using such ensembles of initialised climate models, it can be assumed that extreme events identified are physically plausibleproviding biases in the model itself are assessed and understood (Thompson et al, 2017;Kelder et al, 2022).…”

Spatial and temporal characteristics of extreme rainfall: Added benefits with sub‐kilometre‐resolution climate model simulations?

“…Convective events can occur as a part of frontal systems or as an effect of solar‐heated air becoming more buoyant than the surroundings. A recent attribution study indicates that the observed warming has already increased the risk of extreme precipitation events in Denmark (Matte et al ., 2022). Climate change will increase the occurrence and size of precipitation events and, as a consequence, further increase the risk of pluvial flooding in northern Europe (IPCC, 2021; Christensen et al ., 2022).…”