Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002
Tropical influence on the austral summer Southern Annular Mode (SAM) over the ERA-40 period 1960/1961–2001/2002 is investigated using (1) a partially coupled climate model (PCM) driven by observed wind stress and (2) a version of the ECMWF atmospheric model by means of a relaxation technique. We sho...
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ftoceanrep:oai:oceanrep.geomar.de:25682 2023-05-15T18:18:39+02:00 Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 Ding, Hui Greatbatch, Richard John Gollan, Gereon 2015-04-01 text https://oceanrep.geomar.de/id/eprint/25682/ https://oceanrep.geomar.de/id/eprint/25682/1/ding_greatbatch_gollan15.pdf https://doi.org/10.1007/s00382-014-2299-x en eng Springer https://oceanrep.geomar.de/id/eprint/25682/1/ding_greatbatch_gollan15.pdf Ding, H., Greatbatch, R. J. and Gollan, G. (2015) Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002. Climate Dynamics, 44 (7-8). pp. 2215-2228. DOI 10.1007/s00382-014-2299-x <https://doi.org/10.1007/s00382-014-2299-x>. doi:10.1007/s00382-014-2299-x info:eu-repo/semantics/restrictedAccess Article PeerReviewed 2015 ftoceanrep https://doi.org/10.1007/s00382-014-2299-x 2023-04-07T15:14:27Z Tropical influence on the austral summer Southern Annular Mode (SAM) over the ERA-40 period 1960/1961–2001/2002 is investigated using (1) a partially coupled climate model (PCM) driven by observed wind stress and (2) a version of the ECMWF atmospheric model by means of a relaxation technique. We show that the tropical influence in the PCM is dominated by El Niño Southern Oscillation (ENSO) whereas the relaxation experiments suggest an additional influence independent of ENSO. In the observations, we find that the simultaneous influence of ENSO on the summer SAM was much stronger after 1979 than before, with the consequence that the ensemble mean of the PCM captures around 50 % of the interannual variance of the SAM after 1979 and less than 10 % before. Nevertheless, in the ensemble mean of the PCM, the relationship between ENSO and the summer SAM is stable throughout the whole period 1960/1961–2001/2002, and it is the individual ensemble members that exhibit a non-stationary relationship like that found in the observations. It follows that variability not related to the observed wind forcing used to drive the PCM is important for obscuring the ENSO/SAM relationship. The experiments using relaxation show that tropical forcing was important for both the interannual variability and the trend of the summer SAM, even before 1979. Adding the observed extratropical sea surface temperature and sea-ice (SSTSI) to the tropical relaxation runs improves the model performance, indicative of a positive feedback from extratropical SSTSI onto the SAM. Article in Journal/Newspaper Sea ice OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Austral Climate Dynamics 44 7-8 2215 2228 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
Tropical influence on the austral summer Southern Annular Mode (SAM) over the ERA-40 period 1960/1961–2001/2002 is investigated using (1) a partially coupled climate model (PCM) driven by observed wind stress and (2) a version of the ECMWF atmospheric model by means of a relaxation technique. We show that the tropical influence in the PCM is dominated by El Niño Southern Oscillation (ENSO) whereas the relaxation experiments suggest an additional influence independent of ENSO. In the observations, we find that the simultaneous influence of ENSO on the summer SAM was much stronger after 1979 than before, with the consequence that the ensemble mean of the PCM captures around 50 % of the interannual variance of the SAM after 1979 and less than 10 % before. Nevertheless, in the ensemble mean of the PCM, the relationship between ENSO and the summer SAM is stable throughout the whole period 1960/1961–2001/2002, and it is the individual ensemble members that exhibit a non-stationary relationship like that found in the observations. It follows that variability not related to the observed wind forcing used to drive the PCM is important for obscuring the ENSO/SAM relationship. The experiments using relaxation show that tropical forcing was important for both the interannual variability and the trend of the summer SAM, even before 1979. Adding the observed extratropical sea surface temperature and sea-ice (SSTSI) to the tropical relaxation runs improves the model performance, indicative of a positive feedback from extratropical SSTSI onto the SAM. |
format |
Article in Journal/Newspaper |
author |
Ding, Hui Greatbatch, Richard John Gollan, Gereon |
spellingShingle |
Ding, Hui Greatbatch, Richard John Gollan, Gereon Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 |
author_facet |
Ding, Hui Greatbatch, Richard John Gollan, Gereon |
author_sort |
Ding, Hui |
title |
Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 |
title_short |
Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 |
title_full |
Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 |
title_fullStr |
Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 |
title_full_unstemmed |
Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 |
title_sort |
tropical impact on the interannual variability and long-term trend of the southern annular mode during austral summer from 1960/1961 to 2001/2002 |
publisher |
Springer |
publishDate |
2015 |
url |
https://oceanrep.geomar.de/id/eprint/25682/ https://oceanrep.geomar.de/id/eprint/25682/1/ding_greatbatch_gollan15.pdf https://doi.org/10.1007/s00382-014-2299-x |
geographic |
Austral |
geographic_facet |
Austral |
genre |
Sea ice |
genre_facet |
Sea ice |
op_relation |
https://oceanrep.geomar.de/id/eprint/25682/1/ding_greatbatch_gollan15.pdf Ding, H., Greatbatch, R. J. and Gollan, G. (2015) Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002. Climate Dynamics, 44 (7-8). pp. 2215-2228. DOI 10.1007/s00382-014-2299-x <https://doi.org/10.1007/s00382-014-2299-x>. doi:10.1007/s00382-014-2299-x |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1007/s00382-014-2299-x |
container_title |
Climate Dynamics |
container_volume |
44 |
container_issue |
7-8 |
container_start_page |
2215 |
op_container_end_page |
2228 |
_version_ |
1766195298463383552 |