caa a22 4500 605473668 CHVBK 20210128100344.0 cr unu---uuuuu 210128e20150401xx s 000 0 eng 10.1007/s00382-014-2299-x doi (NATIONALLICENCE)springer-10.1007/s00382-014-2299-x Tropical impact on the interannual variability and long-term trend of the Southern Annular Mode during austral summer from 1960/1961 to 2001/2002 [Elektronische Daten] [Hui Ding, Richard Greatbatch, Gereon Gollan] 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. Springer-Verlag Berlin Heidelberg, 2014 SAM nationallicence ENSO nationallicence Tropical forcing nationallicence Partially coupled model nationallicence Relaxation technique nationallicence Ding Hui GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany aut Greatbatch Richard GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany aut Gollan Gereon GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany aut Climate Dynamics Springer Berlin Heidelberg 44/7-8(2015-04-01), 2215-2228 0930-7575 44:7-8<2215 2015 44 382 https://doi.org/10.1007/s00382-014-2299-x text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00382-014-2299-x text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ding Hui GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany aut NATIONALLICENCE 700 1- Greatbatch Richard GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany aut NATIONALLICENCE 700 1- Gollan Gereon GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany aut NATIONALLICENCE 773 0- Climate Dynamics Springer Berlin Heidelberg 44/7-8(2015-04-01), 2215-2228 0930-7575 44:7-8<2215 2015 44 382