Atmospheric origins of extreme rainfall in the UK

Barnes, Andrew; McCullen, Nick; Kjeldsen, Thomas

Abstract

Drawing causal relationships between physical processes and extreme rainfall is important for understand the extent of the impact these events can have. Current techniques fail to capture the causes of extreme rainfall, relying mostly on correlation techniques.
This study extracts and classifies the storm trajectories of extreme rainfall events accross the UK using a novel trajectory dispersion model (HYSPLIT). These trajectories are then classified using three unsupervised classification techniques which were compared using a known cluster similarity measure, this resulted in the selection and application of the k-means method for identifying six of the key moisture pathways responsible for extreme rainfall. The most frequent pathway originates from the Atlantic and led to 60.58% of the extreme rainfall events, the remainder of the pathways tend to originate from the North Sea. Further to this, we identify the North Sea storms are the more likely to cause above average extreme events especially in Wales. A final comparison is made with the North-Atlantic Oscillation index where this study shows storms originating from the north and western Atlantic are more frequent during a positive NAO phase where as storms originating near the British Isles are more common in a negative phase.

Citation

Barnes, A., McCullen, N., & Kjeldsen, T. (2019). Atmospheric origins of extreme rainfall in the UK

• Conference Name: 4th IMA International Conference on Flood Risk
• Conference Location: Swansea, UK United Kingdom
• Start Date: Sep 12, 2019
• End Date: Sep 13, 2019
• Acceptance Date: Jul 8, 2019
• Online Publication Date: Sep 12, 2019
• Publication Date: Sep 12, 2019
• Deposit Date: Apr 12, 2022
• Public URL: https://uwe-repository.worktribe.com/output/9319925