Remote control on NAO predictability via the stratosphere
The phase and the amplitude of the North Atlantic Oscillation (NAO) are influenced by numerous factors, which include Sea Surface Temperature (SST) anomalies in both the Tropics and extratropics and stratospheric extreme events like Stratospheric Sudden Warmings (SSWs). Analyzing seasonal forecast e...
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ftoceanrep:oai:oceanrep.geomar.de:34718 2023-05-15T17:30:08+02:00 Remote control on NAO predictability via the stratosphere Hansen, Felicitas Greatbatch, Richard John Gollan, Gereon Jung, T. Weisheimer, A. 2017-01 text https://oceanrep.geomar.de/id/eprint/34718/ https://oceanrep.geomar.de/id/eprint/34718/1/Hansen_etal_2016_EOR.pdf https://doi.org/10.1002/qj.2958 en eng Royal Meteorological Society https://oceanrep.geomar.de/id/eprint/34718/1/Hansen_etal_2016_EOR.pdf Hansen, F. , Greatbatch, R. J. , Gollan, G. , Jung, T. and Weisheimer, A. (2017) Remote control on NAO predictability via the stratosphere. Open Access Quarterly Journal of the Royal Meteorological Society, 143 (703B). pp. 706-719. DOI 10.1002/qj.2958 <https://doi.org/10.1002/qj.2958>. doi:10.1002/qj.2958 info:eu-repo/semantics/openAccess Article PeerReviewed info:eu-repo/semantics/article 2017 ftoceanrep https://doi.org/10.1002/qj.2958 2023-04-07T15:29:06Z The phase and the amplitude of the North Atlantic Oscillation (NAO) are influenced by numerous factors, which include Sea Surface Temperature (SST) anomalies in both the Tropics and extratropics and stratospheric extreme events like Stratospheric Sudden Warmings (SSWs). Analyzing seasonal forecast experiments, which cover the winters from 1979/80–2013/14, with the European Centre for Medium-Range Weather Forecast model, we investigate how these factors affect NAO variability and predictability. Building on the idea that the tropical influence might happen via the stratosphere, special emphasis is placed on the role of major SSWs. Relaxation experiments are performed, where different regions of the atmosphere are relaxed towards ERA-Interim to obtain perfect forecasts in those regions. By comparing experiments with relaxation in the tropical atmosphere, performed with an atmosphere-only model on the one hand and a coupled atmosphere–ocean model version on the other, the importance of extratropical atmosphere–ocean interaction is addressed. Interannual variability of the NAO is best reproduced when perfect knowledge about the NH stratosphere is available together with perfect knowledge of SSTs and sea ice, in which case 64% of the variance of the winter mean NAO is projected to be accounted for with a forecast ensemble of infinite size. The coupled experiment shows a strong bias in the stratospheric polar night jet (PNJ) which might be associated with a drift in the modelled SSTs resembling the North Atlantic cold bias and an underestimation of blockings in the North Atlantic/Europe sector. Consistent with the stronger PNJ, the lowest frequency of major SSWs is found in this experiment. However, after statistically removing the bias, a perfect forecast of the tropical atmosphere and allowing two-way atmosphere–ocean coupling in the extratropics seem to be key ingredients for successful SSW predictions. In combination with SSW occurrence, a clear shift of the predicted NAO towards lower values occurs. Article in Journal/Newspaper North Atlantic North Atlantic oscillation polar night Sea ice OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Quarterly Journal of the Royal Meteorological Society 143 703 706 719 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
The phase and the amplitude of the North Atlantic Oscillation (NAO) are influenced by numerous factors, which include Sea Surface Temperature (SST) anomalies in both the Tropics and extratropics and stratospheric extreme events like Stratospheric Sudden Warmings (SSWs). Analyzing seasonal forecast experiments, which cover the winters from 1979/80–2013/14, with the European Centre for Medium-Range Weather Forecast model, we investigate how these factors affect NAO variability and predictability. Building on the idea that the tropical influence might happen via the stratosphere, special emphasis is placed on the role of major SSWs. Relaxation experiments are performed, where different regions of the atmosphere are relaxed towards ERA-Interim to obtain perfect forecasts in those regions. By comparing experiments with relaxation in the tropical atmosphere, performed with an atmosphere-only model on the one hand and a coupled atmosphere–ocean model version on the other, the importance of extratropical atmosphere–ocean interaction is addressed. Interannual variability of the NAO is best reproduced when perfect knowledge about the NH stratosphere is available together with perfect knowledge of SSTs and sea ice, in which case 64% of the variance of the winter mean NAO is projected to be accounted for with a forecast ensemble of infinite size. The coupled experiment shows a strong bias in the stratospheric polar night jet (PNJ) which might be associated with a drift in the modelled SSTs resembling the North Atlantic cold bias and an underestimation of blockings in the North Atlantic/Europe sector. Consistent with the stronger PNJ, the lowest frequency of major SSWs is found in this experiment. However, after statistically removing the bias, a perfect forecast of the tropical atmosphere and allowing two-way atmosphere–ocean coupling in the extratropics seem to be key ingredients for successful SSW predictions. In combination with SSW occurrence, a clear shift of the predicted NAO towards lower values occurs. |
format |
Article in Journal/Newspaper |
author |
Hansen, Felicitas Greatbatch, Richard John Gollan, Gereon Jung, T. Weisheimer, A. |
spellingShingle |
Hansen, Felicitas Greatbatch, Richard John Gollan, Gereon Jung, T. Weisheimer, A. Remote control on NAO predictability via the stratosphere |
author_facet |
Hansen, Felicitas Greatbatch, Richard John Gollan, Gereon Jung, T. Weisheimer, A. |
author_sort |
Hansen, Felicitas |
title |
Remote control on NAO predictability via the stratosphere |
title_short |
Remote control on NAO predictability via the stratosphere |
title_full |
Remote control on NAO predictability via the stratosphere |
title_fullStr |
Remote control on NAO predictability via the stratosphere |
title_full_unstemmed |
Remote control on NAO predictability via the stratosphere |
title_sort |
remote control on nao predictability via the stratosphere |
publisher |
Royal Meteorological Society |
publishDate |
2017 |
url |
https://oceanrep.geomar.de/id/eprint/34718/ https://oceanrep.geomar.de/id/eprint/34718/1/Hansen_etal_2016_EOR.pdf https://doi.org/10.1002/qj.2958 |
genre |
North Atlantic North Atlantic oscillation polar night Sea ice |
genre_facet |
North Atlantic North Atlantic oscillation polar night Sea ice |
op_relation |
https://oceanrep.geomar.de/id/eprint/34718/1/Hansen_etal_2016_EOR.pdf Hansen, F. , Greatbatch, R. J. , Gollan, G. , Jung, T. and Weisheimer, A. (2017) Remote control on NAO predictability via the stratosphere. Open Access Quarterly Journal of the Royal Meteorological Society, 143 (703B). pp. 706-719. DOI 10.1002/qj.2958 <https://doi.org/10.1002/qj.2958>. doi:10.1002/qj.2958 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1002/qj.2958 |
container_title |
Quarterly Journal of the Royal Meteorological Society |
container_volume |
143 |
container_issue |
703 |
container_start_page |
706 |
op_container_end_page |
719 |
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1766125937261281280 |