The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics
A novel method is introduced to identify and track the life cycle of upper-level troughs and ridges. The aim is to close the existing gap between methods that detect the initiation phase of upper-level Rossby wave development and methods that detect Rossby wave breaking and decaying waves. The prese...
Published in: | Weather and Climate Dynamics |
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Main Authors: | , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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Copernicus Publications
2020
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00053050 2023-05-15T16:30:40+02:00 The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics Schemm, Sebastian Rüdisühli, Stefan Sprenger, Michael 2020-09 electronic https://doi.org/10.5194/wcd-1-459-2020 https://noa.gwlb.de/receive/cop_mods_00053050 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00052703/wcd-1-459-2020.pdf https://wcd.copernicus.org/articles/1/459/2020/wcd-1-459-2020.pdf eng eng Copernicus Publications Weather and Climate Dynamics -- https://www.weather-climate-dynamics.net/ -- 2698-4016 https://doi.org/10.5194/wcd-1-459-2020 https://noa.gwlb.de/receive/cop_mods_00053050 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00052703/wcd-1-459-2020.pdf https://wcd.copernicus.org/articles/1/459/2020/wcd-1-459-2020.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2020 ftnonlinearchiv https://doi.org/10.5194/wcd-1-459-2020 2022-02-08T22:35:40Z A novel method is introduced to identify and track the life cycle of upper-level troughs and ridges. The aim is to close the existing gap between methods that detect the initiation phase of upper-level Rossby wave development and methods that detect Rossby wave breaking and decaying waves. The presented method quantifies the horizontal trough and ridge orientation and identifies the corresponding trough and ridge axes. These allow us to study the dynamics of pre- and post-trough–ridge regions separately. The method is based on the curvature of the geopotential height at a given isobaric surface and is computationally efficient. Spatiotemporal tracking allows us to quantify the maturity of troughs and ridges and could also be used to study the temporal evolution of the trough or ridge orientation. First, the algorithm is introduced in detail, and several illustrative applications – such as a downstream development from the North Atlantic into the Mediterranean – and seasonal climatologies are discussed. For example, the climatological trough and ridge orientations reveal strong zonal and meridional asymmetry: over land, most troughs and ridges are anticyclonically oriented, while they are cyclonically oriented over the main oceanic storm tracks; the cyclonic orientation increases toward the poles, while the anticyclonic orientation increases toward the Equator. Trough detection frequencies are climatologically high downstream of the Rocky Mountains and over East Asia and eastern Europe but are remarkably low downstream of Greenland. Furthermore, the detection frequencies of troughs are high at the end of the North Pacific storm track and at the end of the North Atlantic storm track over the British Isles. During El Niño-affected winters, troughs and ridges exhibit an anomalously strong cyclonic tilt over North America and the North Atlantic, in agreement with previous findings based on traditional variance-based diagnostics such as E vectors. During La Niña, the situation is essentially reversed. The orientation of troughs and ridges also depends on the jet position. For example, during midwinter over the Pacific, when the subtropical jet is strongest and located farthest equatorward, cyclonically oriented troughs and ridges dominate the climatology. Finally, the identified troughs and ridges are used as starting points for 24 h backward parcel trajectories, and a discussion of the distribution of pressure, potential temperature and potential vorticity changes along the trajectories is provided to give insight into the three-dimensional nature of troughs and ridges. Article in Journal/Newspaper Greenland North Atlantic Niedersächsisches Online-Archiv NOA Greenland Pacific Midwinter ENVELOPE(139.931,139.931,-66.690,-66.690) Weather and Climate Dynamics 1 2 459 479 |
institution |
Open Polar |
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Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Schemm, Sebastian Rüdisühli, Stefan Sprenger, Michael The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics |
topic_facet |
article Verlagsveröffentlichung |
description |
A novel method is introduced to identify and track the life cycle of upper-level troughs and ridges. The aim is to close the existing gap between methods that detect the initiation phase of upper-level Rossby wave development and methods that detect Rossby wave breaking and decaying waves. The presented method quantifies the horizontal trough and ridge orientation and identifies the corresponding trough and ridge axes. These allow us to study the dynamics of pre- and post-trough–ridge regions separately. The method is based on the curvature of the geopotential height at a given isobaric surface and is computationally efficient. Spatiotemporal tracking allows us to quantify the maturity of troughs and ridges and could also be used to study the temporal evolution of the trough or ridge orientation. First, the algorithm is introduced in detail, and several illustrative applications – such as a downstream development from the North Atlantic into the Mediterranean – and seasonal climatologies are discussed. For example, the climatological trough and ridge orientations reveal strong zonal and meridional asymmetry: over land, most troughs and ridges are anticyclonically oriented, while they are cyclonically oriented over the main oceanic storm tracks; the cyclonic orientation increases toward the poles, while the anticyclonic orientation increases toward the Equator. Trough detection frequencies are climatologically high downstream of the Rocky Mountains and over East Asia and eastern Europe but are remarkably low downstream of Greenland. Furthermore, the detection frequencies of troughs are high at the end of the North Pacific storm track and at the end of the North Atlantic storm track over the British Isles. During El Niño-affected winters, troughs and ridges exhibit an anomalously strong cyclonic tilt over North America and the North Atlantic, in agreement with previous findings based on traditional variance-based diagnostics such as E vectors. During La Niña, the situation is essentially reversed. The orientation of troughs and ridges also depends on the jet position. For example, during midwinter over the Pacific, when the subtropical jet is strongest and located farthest equatorward, cyclonically oriented troughs and ridges dominate the climatology. Finally, the identified troughs and ridges are used as starting points for 24 h backward parcel trajectories, and a discussion of the distribution of pressure, potential temperature and potential vorticity changes along the trajectories is provided to give insight into the three-dimensional nature of troughs and ridges. |
format |
Article in Journal/Newspaper |
author |
Schemm, Sebastian Rüdisühli, Stefan Sprenger, Michael |
author_facet |
Schemm, Sebastian Rüdisühli, Stefan Sprenger, Michael |
author_sort |
Schemm, Sebastian |
title |
The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics |
title_short |
The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics |
title_full |
The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics |
title_fullStr |
The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics |
title_full_unstemmed |
The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics |
title_sort |
life cycle of upper-level troughs and ridges: a novel detection method, climatologies and lagrangian characteristics |
publisher |
Copernicus Publications |
publishDate |
2020 |
url |
https://doi.org/10.5194/wcd-1-459-2020 https://noa.gwlb.de/receive/cop_mods_00053050 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00052703/wcd-1-459-2020.pdf https://wcd.copernicus.org/articles/1/459/2020/wcd-1-459-2020.pdf |
long_lat |
ENVELOPE(139.931,139.931,-66.690,-66.690) |
geographic |
Greenland Pacific Midwinter |
geographic_facet |
Greenland Pacific Midwinter |
genre |
Greenland North Atlantic |
genre_facet |
Greenland North Atlantic |
op_relation |
Weather and Climate Dynamics -- https://www.weather-climate-dynamics.net/ -- 2698-4016 https://doi.org/10.5194/wcd-1-459-2020 https://noa.gwlb.de/receive/cop_mods_00053050 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00052703/wcd-1-459-2020.pdf https://wcd.copernicus.org/articles/1/459/2020/wcd-1-459-2020.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/wcd-1-459-2020 |
container_title |
Weather and Climate Dynamics |
container_volume |
1 |
container_issue |
2 |
container_start_page |
459 |
op_container_end_page |
479 |
_version_ |
1766020399023259648 |