Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link
Cold spells have severe consequences for society. They require early warnings for elaborate mitigation strategies on sub-seasonal to seasonal time-scales. Intense stratospheric westerlies and a polar vortex breakdown (SSW) may enhance extended-range forecast skill for Eurasian and North American col...
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Stockholms universitet, Meteorologiska institutionen (MISU)
2024
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ftstockholmuniv:oai:DiVA.org:su-224415 2024-02-11T10:02:28+01:00 Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link Finke, Kathrin 2024 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-224415 eng eng Stockholms universitet, Meteorologiska institutionen (MISU) Stockholm : Department of Meteorology, Stockholm University orcid:0000-0002-3636-9622 http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-224415 urn:isbn:978-91-8014-629-6 urn:isbn:978-91-8014-630-2 info:eu-repo/semantics/openAccess Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning Doctoral thesis, comprehensive summary info:eu-repo/semantics/doctoralThesis text 2024 ftstockholmuniv 2024-01-24T23:31:38Z Cold spells have severe consequences for society. They require early warnings for elaborate mitigation strategies on sub-seasonal to seasonal time-scales. Intense stratospheric westerlies and a polar vortex breakdown (SSW) may enhance extended-range forecast skill for Eurasian and North American cold extremes through a dynamic coupling to the troposphere. Understanding the complex interplay remains a challenging task that requires further investigation. Since fine-grained observational stratospheric data is limited to the satellite era, climate model simulations, such as atmosphere-only simulations (AMIP) from the Coupled Model Intercomparison Project Phase 6, can be considered. Application of the common empirical orthogonal function method in Paper II, a tool for multimodel comparison and evaluation, unveiled differences in daily winter 2m temperatures (T2m) across four reanalyses while stratospheric geopotential height varies across AMIP models. Results show a link between a weak polar vortex and cold T2m anomalies over Eurasia in reanalysis data. In addition, quantile regression is a simple but proficient statistical method that neatly enables modeling the response variable’s complete conditional distribution. Thereby, information about extremes, which hide in the distribution’s tails, is extracted. Application to boreal winter ERA5 reanalysis data and teleconnection indices in Paper I reveals significant asymmetries in duration, strength, and direction of the stratosphere-troposphere connection across quantiles. Regionally specific, lagged composite analysis of ERA5 data in Paper III verifies the canonical warm stratosphere - cold Eurasia relation. However, persistent Eurasian cold spells may also coincide with a strong polar vortex. We find stratospheric reflection of upward propagating planetary waves toward the North Atlantic to potentially influence mid-tropospheric circulation anomalies that travel towards Eurasia. By interacting with a quasi-stationary anticyclone over the Barents Sea, which promotes a ... Doctoral or Postdoctoral Thesis Barents Sea North Atlantic Stockholm University: Publications (DiVA) Barents Sea |
institution |
Open Polar |
collection |
Stockholm University: Publications (DiVA) |
op_collection_id |
ftstockholmuniv |
language |
English |
topic |
Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning |
spellingShingle |
Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning Finke, Kathrin Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link |
topic_facet |
Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning |
description |
Cold spells have severe consequences for society. They require early warnings for elaborate mitigation strategies on sub-seasonal to seasonal time-scales. Intense stratospheric westerlies and a polar vortex breakdown (SSW) may enhance extended-range forecast skill for Eurasian and North American cold extremes through a dynamic coupling to the troposphere. Understanding the complex interplay remains a challenging task that requires further investigation. Since fine-grained observational stratospheric data is limited to the satellite era, climate model simulations, such as atmosphere-only simulations (AMIP) from the Coupled Model Intercomparison Project Phase 6, can be considered. Application of the common empirical orthogonal function method in Paper II, a tool for multimodel comparison and evaluation, unveiled differences in daily winter 2m temperatures (T2m) across four reanalyses while stratospheric geopotential height varies across AMIP models. Results show a link between a weak polar vortex and cold T2m anomalies over Eurasia in reanalysis data. In addition, quantile regression is a simple but proficient statistical method that neatly enables modeling the response variable’s complete conditional distribution. Thereby, information about extremes, which hide in the distribution’s tails, is extracted. Application to boreal winter ERA5 reanalysis data and teleconnection indices in Paper I reveals significant asymmetries in duration, strength, and direction of the stratosphere-troposphere connection across quantiles. Regionally specific, lagged composite analysis of ERA5 data in Paper III verifies the canonical warm stratosphere - cold Eurasia relation. However, persistent Eurasian cold spells may also coincide with a strong polar vortex. We find stratospheric reflection of upward propagating planetary waves toward the North Atlantic to potentially influence mid-tropospheric circulation anomalies that travel towards Eurasia. By interacting with a quasi-stationary anticyclone over the Barents Sea, which promotes a ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Finke, Kathrin |
author_facet |
Finke, Kathrin |
author_sort |
Finke, Kathrin |
title |
Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link |
title_short |
Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link |
title_full |
Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link |
title_fullStr |
Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link |
title_full_unstemmed |
Northern Hemispheric Cold Spells and their Tropospheric-Stratospheric Link |
title_sort |
northern hemispheric cold spells and their tropospheric-stratospheric link |
publisher |
Stockholms universitet, Meteorologiska institutionen (MISU) |
publishDate |
2024 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-224415 |
geographic |
Barents Sea |
geographic_facet |
Barents Sea |
genre |
Barents Sea North Atlantic |
genre_facet |
Barents Sea North Atlantic |
op_relation |
orcid:0000-0002-3636-9622 http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-224415 urn:isbn:978-91-8014-629-6 urn:isbn:978-91-8014-630-2 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1790598416677470208 |