The role of boundary layer processes in summer-time Arctic cyclones
Arctic cyclones are the most energetic weather systems in the Arctic, producing strong winds and precipitation that present major weather hazards. In summer, when the sea ice cover is reduced and more mobile, Arctic cyclones can have large impacts on ocean waves and sea ice. While the development of...
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ftcopernicus:oai:publications.copernicus.org:wcd108024 2023-08-15T12:39:35+02:00 The role of boundary layer processes in summer-time Arctic cyclones Croad, Hannah L. Methven, John Harvey, Ben Keeley, Sarah P. E. Volonté, Ambrogio 2023-07-18 application/pdf https://doi.org/10.5194/wcd-4-617-2023 https://wcd.copernicus.org/articles/4/617/2023/ eng eng doi:10.5194/wcd-4-617-2023 https://wcd.copernicus.org/articles/4/617/2023/ eISSN: 2698-4016 Text 2023 ftcopernicus https://doi.org/10.5194/wcd-4-617-2023 2023-07-24T16:24:18Z Arctic cyclones are the most energetic weather systems in the Arctic, producing strong winds and precipitation that present major weather hazards. In summer, when the sea ice cover is reduced and more mobile, Arctic cyclones can have large impacts on ocean waves and sea ice. While the development of mid-latitude cyclones is known to be dependent on boundary layer (BL) turbulent fluxes, the dynamics of summer-time Arctic cyclones and their dependence on surface exchange processes have not been investigated. The purpose of this study is to characterise the BL processes acting in summer-time Arctic cyclones and understand their influence on cyclone evolution. The study focuses on two cyclone case studies, each characterised by a different structure during growth in the Arctic: (A) low-level-dominant vorticity (warm-core) structure and (B) upper-level-dominant vorticity (cold-core) structure, linked with a tropopause polar vortex. A potential vorticity (PV) framework is used to diagnose the BL processes in model runs from the ECMWF Integrated Forecasting System model. Both cyclones are associated with frictional Ekman pumping and downward sensible heat fluxes over sea ice. However, a third process, the frictional baroclinic generation of PV, acts differently in A and B due to differences in their low-level temperature structures. Positive PV is generated in Cyclone A near the bent-back warm front, like in typical mid-latitude cyclones. However, the same process produces negative PV tendencies in B, shown to be a consequence of the vertically aligned axisymmetric cold-core structure. This frictional process also acts to cool the lower troposphere, reducing the warm-core anomaly in A and amplifying the cold-core anomaly in B. Both cyclones attain a vertically aligned cold-core structure that persists for several days after maximum intensity, which is consistent with cooling from frictional Ekman pumping, frictional baroclinic PV generation, and downward sensible heat fluxes. This may help to explain the longevity of ... Text Arctic Sea ice Copernicus Publications: E-Journals Arctic Weather and Climate Dynamics 4 3 617 638 |
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Copernicus Publications: E-Journals |
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English |
description |
Arctic cyclones are the most energetic weather systems in the Arctic, producing strong winds and precipitation that present major weather hazards. In summer, when the sea ice cover is reduced and more mobile, Arctic cyclones can have large impacts on ocean waves and sea ice. While the development of mid-latitude cyclones is known to be dependent on boundary layer (BL) turbulent fluxes, the dynamics of summer-time Arctic cyclones and their dependence on surface exchange processes have not been investigated. The purpose of this study is to characterise the BL processes acting in summer-time Arctic cyclones and understand their influence on cyclone evolution. The study focuses on two cyclone case studies, each characterised by a different structure during growth in the Arctic: (A) low-level-dominant vorticity (warm-core) structure and (B) upper-level-dominant vorticity (cold-core) structure, linked with a tropopause polar vortex. A potential vorticity (PV) framework is used to diagnose the BL processes in model runs from the ECMWF Integrated Forecasting System model. Both cyclones are associated with frictional Ekman pumping and downward sensible heat fluxes over sea ice. However, a third process, the frictional baroclinic generation of PV, acts differently in A and B due to differences in their low-level temperature structures. Positive PV is generated in Cyclone A near the bent-back warm front, like in typical mid-latitude cyclones. However, the same process produces negative PV tendencies in B, shown to be a consequence of the vertically aligned axisymmetric cold-core structure. This frictional process also acts to cool the lower troposphere, reducing the warm-core anomaly in A and amplifying the cold-core anomaly in B. Both cyclones attain a vertically aligned cold-core structure that persists for several days after maximum intensity, which is consistent with cooling from frictional Ekman pumping, frictional baroclinic PV generation, and downward sensible heat fluxes. This may help to explain the longevity of ... |
format |
Text |
author |
Croad, Hannah L. Methven, John Harvey, Ben Keeley, Sarah P. E. Volonté, Ambrogio |
spellingShingle |
Croad, Hannah L. Methven, John Harvey, Ben Keeley, Sarah P. E. Volonté, Ambrogio The role of boundary layer processes in summer-time Arctic cyclones |
author_facet |
Croad, Hannah L. Methven, John Harvey, Ben Keeley, Sarah P. E. Volonté, Ambrogio |
author_sort |
Croad, Hannah L. |
title |
The role of boundary layer processes in summer-time Arctic cyclones |
title_short |
The role of boundary layer processes in summer-time Arctic cyclones |
title_full |
The role of boundary layer processes in summer-time Arctic cyclones |
title_fullStr |
The role of boundary layer processes in summer-time Arctic cyclones |
title_full_unstemmed |
The role of boundary layer processes in summer-time Arctic cyclones |
title_sort |
role of boundary layer processes in summer-time arctic cyclones |
publishDate |
2023 |
url |
https://doi.org/10.5194/wcd-4-617-2023 https://wcd.copernicus.org/articles/4/617/2023/ |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Sea ice |
genre_facet |
Arctic Sea ice |
op_source |
eISSN: 2698-4016 |
op_relation |
doi:10.5194/wcd-4-617-2023 https://wcd.copernicus.org/articles/4/617/2023/ |
op_doi |
https://doi.org/10.5194/wcd-4-617-2023 |
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Weather and Climate Dynamics |
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4 |
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3 |
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617 |
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638 |
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