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Synoptic-Scale Precursors of Extreme U.K. Summer 3-Hourly Rainfall

Lookup NU author(s): Dr Stephen Blenkinsop, Dr Xiaofeng Li, Professor Hayley Fowler

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

©2019. American Geophysical Union. All Rights Reserved. The synoptic-scale meteorological conditions leading up to the 30 most extreme subdaily summer rain events for two regions of the United Kingdom (northwest and southeast) were examined for the period 1979–2013. Using a recently available, quality controlled, national hourly rain gauge data set, we were able to identify extreme 3-hr rainfall accumulations that may be indicative of flash flooding. Composites of the state of the atmosphere leading up to these dates were produced to investigate synoptic-scale processes, thus potentially allowing for them to be identified in coarse resolution reanalyses and in climate models. The results show that the two regions have different dominant synoptic-scale conditions leading to extreme 3-hr rainfall, which is thought to be related to the type of rainfall typically experienced in each region. In particular, positive anomalies in mean sea level pressure and the geopotential height at 200 hPa over the United Kingdom are associated with extreme rainfall in the northwest, where the position of the westerly jet is also important. For the southeast, no clear anomalous synoptic-scale conditions could be identified; however, localized moisture sources and unstable air masses were observed in association with extremes. These results indicate the importance of better understanding of both synoptic-scale and thermodynamic drivers of short-duration extreme rainfall, with potential implications in forecasting and flood warning, as well as for understanding the representation of key processes by regional climate models.


Publication metadata

Author(s): Champion AJ, Blenkinsop S, Li X-F, Fowler HJ

Publication type: Article

Publication status: Published

Journal: Journal of Geophysical Research: Atmospheres

Year: 2019

Volume: 124

Issue: 8

Pages: 4477-4489

Print publication date: 27/04/2019

Online publication date: 13/04/2019

Acceptance date: 30/03/2019

Date deposited: 11/06/2019

ISSN (print): 2169-897X

ISSN (electronic): 2169-8996

Publisher: Blackwell Publishing Ltd

URL: https://doi.org/10.1029/2018JD029664

DOI: 10.1029/2018JD029664


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