Extreme rainfall and temporal loading in Great Britain: Analysis of present and future trends using a convection-permitting climate model

Study Region: Great Britain

Study Focus: While climate change is intensifying rainfall extremes, its effect on temporal loading remains poorly understood. Temporal loading, the distribution of rainfall over storm duration, influences flood risk for storms of a given volume and is critical for urban infrastructure planning. This research presents the first direct investigation of event temporal loading within climate projections, utilising UKCP Local convection-permitting ensemble simulations. At rain gauge locations, we sample the most extreme storm each year at durations from 1.5 to 24 hours and apply two classification metrics to evaluate storm temporal structure.

New Hydrological Insights for the Region: Our analysis confirms that in today’s climate, shorter-duration storms tend to be front-loaded, while longer storms exhibit more centred, symmetrical intensity profiles. Spatial patterns emerge with central and southern England exhibiting a higher proportion of highly asymmetric events. However, no consistent changes in temporal loading are projected under future climates, challenging previous inferences based on temperature–rainfall relationships. These discrepancies may stem from differences in storm-generating mechanisms between Great Britain and tropical regions studied previously. Our findings highlight limitations of current metrics, which inadequately distinguish aspects of storm structure contributing to temporal loading. We recommend developing refined metrics to independently quantify event asymmetry, peak intensity, and timing. Such advancements are crucial for improving design flood modelling alongside future climate scenarios.