The relationship between northern hemisphere winter blocking and tropical modes of variability
The influence of some major tropical modes of variability on northern hemisphere regional blocking frequency variability during boreal winter is investigated and the most important findings will be presented here. Reanalysis data and an experiment with the ECMWF model using relaxation towards the ER...
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ftoceanrep:oai:oceanrep.geomar.de:37906 2023-05-15T17:33:57+02:00 The relationship between northern hemisphere winter blocking and tropical modes of variability Gollan, Gereon Greatbatch, Richard John Jung, Thomas 2017-04-28 text https://oceanrep.geomar.de/id/eprint/37906/ https://oceanrep.geomar.de/id/eprint/37906/3/GGollan_EGU2017_geomar_169_for_pdf.pdf en eng https://oceanrep.geomar.de/id/eprint/37906/3/GGollan_EGU2017_geomar_169_for_pdf.pdf Gollan, G. , Greatbatch, R. J. and Jung, T. (2017) The relationship between northern hemisphere winter blocking and tropical modes of variability. [Talk] In: EGU General Assembly 2017. , 23.-28.04.2017, Vienna, Austria . info:eu-repo/semantics/restrictedAccess Conference or Workshop Item NonPeerReviewed 2017 ftoceanrep 2023-04-07T15:33:12Z The influence of some major tropical modes of variability on northern hemisphere regional blocking frequency variability during boreal winter is investigated and the most important findings will be presented here. Reanalysis data and an experiment with the ECMWF model using relaxation towards the ERA-40 reanalysis data inside the tropics are used. The tropical modes under investigation are El Nino Southern Oscillation (ENSO), the Madden-Julian Oscillation (MJO) and the upper tropospheric equatorial zonal-mean zonal wind (U150). Comparing the impact on blocking frequency of these tropical modes with the impact of two extratropical modes, namely the North Atlantic Oscillation (NAO) and the North Pacific Gyre Oscillation (NPGO), it is found that the tropical influence is of comparable amplitude. Focusing on the Euro-Atlantic sector, it is found that cold ENSO events, late MJO phases, as well as suppressed MJO are all leading to enhanced blocking frequency at lower to middle latitudes (south of 48N) on weekly to monthly timescales. At higher latitudes (north of 48N) over Europe, the blocking anomalies associated with ENSO and the MJO are less clear than at lower latitudes. Instead, at higher latitudes (north of 48N), the westerly (easterly) phase of U150 is associated with reduced (enhanced) blocking frequency. Conference Object North Atlantic North Atlantic oscillation OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Pacific |
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OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
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ftoceanrep |
language |
English |
description |
The influence of some major tropical modes of variability on northern hemisphere regional blocking frequency variability during boreal winter is investigated and the most important findings will be presented here. Reanalysis data and an experiment with the ECMWF model using relaxation towards the ERA-40 reanalysis data inside the tropics are used. The tropical modes under investigation are El Nino Southern Oscillation (ENSO), the Madden-Julian Oscillation (MJO) and the upper tropospheric equatorial zonal-mean zonal wind (U150). Comparing the impact on blocking frequency of these tropical modes with the impact of two extratropical modes, namely the North Atlantic Oscillation (NAO) and the North Pacific Gyre Oscillation (NPGO), it is found that the tropical influence is of comparable amplitude. Focusing on the Euro-Atlantic sector, it is found that cold ENSO events, late MJO phases, as well as suppressed MJO are all leading to enhanced blocking frequency at lower to middle latitudes (south of 48N) on weekly to monthly timescales. At higher latitudes (north of 48N) over Europe, the blocking anomalies associated with ENSO and the MJO are less clear than at lower latitudes. Instead, at higher latitudes (north of 48N), the westerly (easterly) phase of U150 is associated with reduced (enhanced) blocking frequency. |
format |
Conference Object |
author |
Gollan, Gereon Greatbatch, Richard John Jung, Thomas |
spellingShingle |
Gollan, Gereon Greatbatch, Richard John Jung, Thomas The relationship between northern hemisphere winter blocking and tropical modes of variability |
author_facet |
Gollan, Gereon Greatbatch, Richard John Jung, Thomas |
author_sort |
Gollan, Gereon |
title |
The relationship between northern hemisphere winter blocking and tropical modes of variability |
title_short |
The relationship between northern hemisphere winter blocking and tropical modes of variability |
title_full |
The relationship between northern hemisphere winter blocking and tropical modes of variability |
title_fullStr |
The relationship between northern hemisphere winter blocking and tropical modes of variability |
title_full_unstemmed |
The relationship between northern hemisphere winter blocking and tropical modes of variability |
title_sort |
relationship between northern hemisphere winter blocking and tropical modes of variability |
publishDate |
2017 |
url |
https://oceanrep.geomar.de/id/eprint/37906/ https://oceanrep.geomar.de/id/eprint/37906/3/GGollan_EGU2017_geomar_169_for_pdf.pdf |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_relation |
https://oceanrep.geomar.de/id/eprint/37906/3/GGollan_EGU2017_geomar_169_for_pdf.pdf Gollan, G. , Greatbatch, R. J. and Jung, T. (2017) The relationship between northern hemisphere winter blocking and tropical modes of variability. [Talk] In: EGU General Assembly 2017. , 23.-28.04.2017, Vienna, Austria . |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766132616861319168 |