The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development

This thesis was funded by the Natural Environment Research Council (NERC) and is presented in the alternative format. The thesis comprises two separate journal articles that together form a coherent body of work. In this thesis, the key physical processes responsible for the 23-26 September 2012 UK...

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Main Author: Hardy, Sam
Format: Doctoral or Postdoctoral Thesis
Language:English
Published: 2017
Subjects:
Online Access:https://research.manchester.ac.uk/en/studentTheses/7331bff8-e536-4446-bacf-701aca158c2b
https://pure.manchester.ac.uk/ws/files/60832748/FULL_TEXT.PDF
id ftumanchesterpub:oai:pure.atira.dk:studenttheses/7331bff8-e536-4446-bacf-701aca158c2b
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spelling ftumanchesterpub:oai:pure.atira.dk:studenttheses/7331bff8-e536-4446-bacf-701aca158c2b 2023-11-12T04:19:34+01:00 The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development Hardy, Sam 2017-08-01 application/pdf https://research.manchester.ac.uk/en/studentTheses/7331bff8-e536-4446-bacf-701aca158c2b https://pure.manchester.ac.uk/ws/files/60832748/FULL_TEXT.PDF eng eng Extratropical cyclone Potential vorticity Diabatic heating Ice-phase microphysics Flooding United Kingdom doctoralThesis 2017 ftumanchesterpub 2023-10-30T09:14:54Z This thesis was funded by the Natural Environment Research Council (NERC) and is presented in the alternative format. The thesis comprises two separate journal articles that together form a coherent body of work. In this thesis, the key physical processes responsible for the 23-26 September 2012 UK floods are investigated using a case study approach. The cyclone responsible for the floods developed near the Azores on 20¬-22 September following the interaction between an equatorward-moving potential vorticity (PV) streamer and tropical storm Nadine. Convectively-driven latent heat release associated with the developing cyclone reduced upper-level PV and resulted in the fracture of the PV streamer into a discrete anomaly as the cyclone intensified. In Paper 1, convection-permitting model simulations and diabatic heating rate and PV tendency calculations along trajectories demonstrate that deposition heating strongly reduced upper-level PV in the vicinity of the PV streamer, contributing to its fracture into a discrete anomaly. The cyclone deepened further over the UK on 23-26 September, ahead of a second upper-level PV anomaly. In Paper 2, sensitivity simulations of the storm are presented. PV inversion is used to modify the strength and position of the PV anomaly in the initial conditions and to examine whether the event could have been even more extreme with different upper-level forcing. Results show that quasigeostrophic forcing for ascent ahead of the PV anomaly contributed to the maintenance of the rainfall band over the UK. Counterintuitively however, strengthening the upper-level forcing produced a shallower cyclone with lower rainfall totals. Instead of moving eastward over the UK to interact with the cyclone, the strengthened anomaly rotated cyclonically around a large-scale trough over Iceland, resulting in a fragmented rainfall band. The counterintuitive results suggest that the verifying analysis represents almost the highest-impact scenario possible for this flooding event. Doctoral or Postdoctoral Thesis Iceland The University of Manchester: Research Explorer
institution Open Polar
collection The University of Manchester: Research Explorer
op_collection_id ftumanchesterpub
language English
topic Extratropical cyclone
Potential vorticity
Diabatic heating
Ice-phase microphysics
Flooding
United Kingdom
spellingShingle Extratropical cyclone
Potential vorticity
Diabatic heating
Ice-phase microphysics
Flooding
United Kingdom
Hardy, Sam
The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development
topic_facet Extratropical cyclone
Potential vorticity
Diabatic heating
Ice-phase microphysics
Flooding
United Kingdom
description This thesis was funded by the Natural Environment Research Council (NERC) and is presented in the alternative format. The thesis comprises two separate journal articles that together form a coherent body of work. In this thesis, the key physical processes responsible for the 23-26 September 2012 UK floods are investigated using a case study approach. The cyclone responsible for the floods developed near the Azores on 20¬-22 September following the interaction between an equatorward-moving potential vorticity (PV) streamer and tropical storm Nadine. Convectively-driven latent heat release associated with the developing cyclone reduced upper-level PV and resulted in the fracture of the PV streamer into a discrete anomaly as the cyclone intensified. In Paper 1, convection-permitting model simulations and diabatic heating rate and PV tendency calculations along trajectories demonstrate that deposition heating strongly reduced upper-level PV in the vicinity of the PV streamer, contributing to its fracture into a discrete anomaly. The cyclone deepened further over the UK on 23-26 September, ahead of a second upper-level PV anomaly. In Paper 2, sensitivity simulations of the storm are presented. PV inversion is used to modify the strength and position of the PV anomaly in the initial conditions and to examine whether the event could have been even more extreme with different upper-level forcing. Results show that quasigeostrophic forcing for ascent ahead of the PV anomaly contributed to the maintenance of the rainfall band over the UK. Counterintuitively however, strengthening the upper-level forcing produced a shallower cyclone with lower rainfall totals. Instead of moving eastward over the UK to interact with the cyclone, the strengthened anomaly rotated cyclonically around a large-scale trough over Iceland, resulting in a fragmented rainfall band. The counterintuitive results suggest that the verifying analysis represents almost the highest-impact scenario possible for this flooding event.
format Doctoral or Postdoctoral Thesis
author Hardy, Sam
author_facet Hardy, Sam
author_sort Hardy, Sam
title The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development
title_short The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development
title_full The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development
title_fullStr The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development
title_full_unstemmed The 23-26 September 2012 UK floods: Influence of diabatic processes and upper-level forcing on cyclone development
title_sort 23-26 september 2012 uk floods: influence of diabatic processes and upper-level forcing on cyclone development
publishDate 2017
url https://research.manchester.ac.uk/en/studentTheses/7331bff8-e536-4446-bacf-701aca158c2b
https://pure.manchester.ac.uk/ws/files/60832748/FULL_TEXT.PDF
genre Iceland
genre_facet Iceland
_version_ 1782335962886438912