1. A new conceptual model for understanding and predicting life-threatening rainfall extremes
- Author
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Paul A. Davies, Hayley J. Fowler, Roberto Villalobos Herrera, Julia Slingo, David L.A. Flack, and Mateusz Taszarek
- Subjects
Extreme rainfall ,Sub-hourly rainfall extremes ,Clausius-clapeyron ,Super-CC scaling ,Conditional instability ,Latent heat ,Meteorology. Climatology ,QC851-999 - Abstract
The motivation of our study is to provide forecasters and users complementary guidance and tools to identify and predict atmospheric conditions that could lead to life-threatening flash floods. Using hourly and sub-hourly rainfall datasets, proximity radiosondes, ERA5 reanalysis of extreme rainfall events in the UK during 2000–2020, and case studies in 2021, we observe a three-layered atmospheric structure, consisting of Moist Absolute Unstable Layers (MAULs) embedded in a conditional unstable layer sandwiched between a stable upper layer and a near-stable low layer. Based on our analysis, we propose a conceptual model to describe the atmospheric properties of a ‘rainfall extreme’ environment, with a particular focus on the thermodynamics associated with sub-hourly rainfall production processes. We then set this model within a wider framework to describe the precursor synoptic and mesoscale environments necessary for sub-hourly rainfall extremes in the mid-latitudes. We show that evolution of the Omega block and Rex Vortex couplet provides the optimal environmental conditions for sub-hourly rainfall extremes. These results provide the potential to develop a ‘4-stage’ warning system to assist in the identification and forecasting of life threatening short-duration extreme rainfall intensities and flash floods.
- Published
- 2024
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