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Contribution of large-scale midlatitude disturbances to hourly precipitation extremes in the United States

Lookup NU author(s): Dr Renaud Barbero, 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

© 2018 The Author(s) Midlatitude synoptic weather regimes account for a substantial portion of annual precipitation accumulation as well as multi-day precipitation extremes across parts of the United States (US). However, little attention has been devoted to understanding how synoptic-scale patterns contribute to hourly precipitation extremes. A majority of 1-h annual maximum precipitation (AMP) across the western US were found to be linked to two coherent midlatitude synoptic patterns: disturbances propagating along the jet stream, and cutoff upper-level lows. The influence of these two patterns on 1-h AMP varies geographically. Over 95% of 1-h AMP along the western coastal US were coincident with progressive midlatitude waves embedded within the jet stream, while over 30% of 1-h AMP across the interior western US were coincident with cutoff lows. Between 30–60% of 1-h AMP were coincident with the jet stream across the Ohio River Valley and southeastern US, whereas a a majority of 1-h AMP over the rest of central and eastern US were not found to be associated with either midlatitude synoptic features. Composite analyses for 1-h AMP days coincident to cutoff lows and jet stream show that an anomalous moisture flux and upper-level dynamics are responsible for initiating instability and setting up an environment conducive to 1-h AMP events. While hourly precipitation extremes are generally thought to be purely convective in nature, this study shows that large-scale dynamics and baroclinic disturbances may also contribute to precipitation extremes on sub-daily timescales.

Publication metadata

Author(s): Barbero R, Abatzoglou JT, Fowler HJ

Publication type: Article

Publication status: Published

Journal: Climate Dynamics

Year: 2019

Volume: 52

Issue: 1-2

Pages: 197-208

Print publication date: 01/01/2019

Online publication date: 27/02/2018

Acceptance date: 02/02/2018

Date deposited: 12/03/2018

ISSN (print): 0930-7575

ISSN (electronic): 1432-0894

Publisher: Springer Verlag

URL: https://doi.org/10.1007/s00382-018-4123-5

DOI: 10.1007/s00382-018-4123-5

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