Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact

Warm conveyor belts (WCBs) are dynamically important, strongly ascending and mostly stratiform cloud-forming airstreams in extratropical cyclones. Despite the predominantly stratiform character of the WCB's large-scale cloud band, convective clouds can be embedded in it. This embedded convectio...

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Main Authors: Oertel, Annika, Sprenger, Michael, Joos, Hanna, Boettcher, Maxi, Konow, Heike, Hagen, Martin, Wernli, Heini, id_orcid:0 000-0001-9674-4837
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus 2021
Subjects:
Online Access:https://hdl.handle.net/20.500.11850/523869
https://doi.org/10.3929/ethz-b-000523869
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spelling ftethz:oai:www.research-collection.ethz.ch:20.500.11850/523869 2023-08-20T04:08:33+02:00 Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact Oertel, Annika Sprenger, Michael Joos, Hanna Boettcher, Maxi Konow, Heike Hagen, Martin Wernli, Heini id_orcid:0 000-0001-9674-4837 2021 application/application/pdf https://hdl.handle.net/20.500.11850/523869 https://doi.org/10.3929/ethz-b-000523869 en eng Copernicus info:eu-repo/semantics/altIdentifier/doi/10.5194/wcd-2-89-2021 info:eu-repo/grantAgreement/SNF/Projekte MINT/165941 info:eu-repo/grantAgreement/EC/H2020/787652 http://hdl.handle.net/20.500.11850/523869 doi:10.3929/ethz-b-000523869 info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International Weather and Climate Dynamics, 2 (1) info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2021 ftethz https://doi.org/20.500.11850/52386910.3929/ethz-b-00052386910.5194/wcd-2-89-2021 2023-07-30T23:54:29Z Warm conveyor belts (WCBs) are dynamically important, strongly ascending and mostly stratiform cloud-forming airstreams in extratropical cyclones. Despite the predominantly stratiform character of the WCB's large-scale cloud band, convective clouds can be embedded in it. This embedded convection leads to a heterogeneously structured cloud band with locally enhanced hydrometeor content, intense surface precipitation and substantial amounts of graupel in the middle troposphere. Recent studies showed that embedded convection forms dynamically relevant quasi-horizontal potential vorticity (PV) dipoles in the upper troposphere. Thereby one pole can reach strongly negative PV values associated with inertial or symmetric instability near the upper-level PV waveguide, where it can interact with and modify the upper-level jet. This study analyzes the characteristics of embedded convection in the WCB of cyclone Sanchez based on WCB online trajectories from a convection-permitting simulation and airborne radar observations during the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) field campaign (intense observation periods, IOPs, 10 and 11). In the first part, we present the radar reflectivity structure of the WCB and corroborate its heterogeneous cloud structure and the occurrence of embedded convection. Radar observations in three different sub-regions of the WCB cloud band reveal the differing intensity of its embedded convection, which is qualitatively confirmed by the ascent rates of the online WCB trajectories. The detailed ascent behavior of the WCB trajectories reveals that very intense convection with ascent rates of 600 hPa in 30–60 min occurs, in addition to comparatively moderate convection with slower ascent velocities as reported in previous case studies. In the second part of this study, a systematic Lagrangian composite analysis based on online trajectories for two sub-categories of WCB-embedded convection – moderate and intense convection – is performed. Composites of the cloud and ... Article in Journal/Newspaper North Atlantic ETH Zürich Research Collection
institution Open Polar
collection ETH Zürich Research Collection
op_collection_id ftethz
language English
description Warm conveyor belts (WCBs) are dynamically important, strongly ascending and mostly stratiform cloud-forming airstreams in extratropical cyclones. Despite the predominantly stratiform character of the WCB's large-scale cloud band, convective clouds can be embedded in it. This embedded convection leads to a heterogeneously structured cloud band with locally enhanced hydrometeor content, intense surface precipitation and substantial amounts of graupel in the middle troposphere. Recent studies showed that embedded convection forms dynamically relevant quasi-horizontal potential vorticity (PV) dipoles in the upper troposphere. Thereby one pole can reach strongly negative PV values associated with inertial or symmetric instability near the upper-level PV waveguide, where it can interact with and modify the upper-level jet. This study analyzes the characteristics of embedded convection in the WCB of cyclone Sanchez based on WCB online trajectories from a convection-permitting simulation and airborne radar observations during the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) field campaign (intense observation periods, IOPs, 10 and 11). In the first part, we present the radar reflectivity structure of the WCB and corroborate its heterogeneous cloud structure and the occurrence of embedded convection. Radar observations in three different sub-regions of the WCB cloud band reveal the differing intensity of its embedded convection, which is qualitatively confirmed by the ascent rates of the online WCB trajectories. The detailed ascent behavior of the WCB trajectories reveals that very intense convection with ascent rates of 600 hPa in 30–60 min occurs, in addition to comparatively moderate convection with slower ascent velocities as reported in previous case studies. In the second part of this study, a systematic Lagrangian composite analysis based on online trajectories for two sub-categories of WCB-embedded convection – moderate and intense convection – is performed. Composites of the cloud and ...
format Article in Journal/Newspaper
author Oertel, Annika
Sprenger, Michael
Joos, Hanna
Boettcher, Maxi
Konow, Heike
Hagen, Martin
Wernli, Heini
id_orcid:0 000-0001-9674-4837
spellingShingle Oertel, Annika
Sprenger, Michael
Joos, Hanna
Boettcher, Maxi
Konow, Heike
Hagen, Martin
Wernli, Heini
id_orcid:0 000-0001-9674-4837
Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact
author_facet Oertel, Annika
Sprenger, Michael
Joos, Hanna
Boettcher, Maxi
Konow, Heike
Hagen, Martin
Wernli, Heini
id_orcid:0 000-0001-9674-4837
author_sort Oertel, Annika
title Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact
title_short Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact
title_full Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact
title_fullStr Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact
title_full_unstemmed Observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact
title_sort observations and simulation of intense convection embedded in a warm conveyor belt – how ambient vertical wind shear determines the dynamical impact
publisher Copernicus
publishDate 2021
url https://hdl.handle.net/20.500.11850/523869
https://doi.org/10.3929/ethz-b-000523869
genre North Atlantic
genre_facet North Atlantic
op_source Weather and Climate Dynamics, 2 (1)
op_relation info:eu-repo/semantics/altIdentifier/doi/10.5194/wcd-2-89-2021
info:eu-repo/grantAgreement/SNF/Projekte MINT/165941
info:eu-repo/grantAgreement/EC/H2020/787652
http://hdl.handle.net/20.500.11850/523869
doi:10.3929/ethz-b-000523869
op_rights info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by/4.0/
Creative Commons Attribution 4.0 International
op_doi https://doi.org/20.500.11850/52386910.3929/ethz-b-00052386910.5194/wcd-2-89-2021
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