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�ꡡ�ܡ�Arctic and Antarctic Oscillations in a 20-member ensemble simulation

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Arctic and Antarctic Oscillations in a 20-member ensemble simulation (��¼ ����) ȯɽ�׻� :

  
  A 20-member simulation has been conducted with the CCSR/NIES  
 atmospheric GCM(AGCM) to investigate the time-space characteristics  
 of the Arctic and Antarctic Oscillations(AO and AAO, respectively).  
 Each of the 20 AGCM integrations is forced by the identical global SST  
 and sea ice history observed for 1959-1998, and differs only in the  
 initial conditions. Our analysis focuses on the boreal winter season.  
  
  AO and AAO appear as the first EOF modes of the ensemble-mean variability  
 and resemble very much their observed counterparts.  
 In the Northern Hemisphere, the ensemble mean reproduces reasonably well the  
 quasi-decadal oscillation that was particularly pronounced in the AO time series  
 for the recent three decades. In the Southern Hemisphere, the ensemble-mean  
 AAO time series is correlated with the equatorial Pacific ENSO.  
  
  Recent empirical studies raise a question of whether the AO is a true mode  
 of climate variability or an artifact of EOF analysis. At issue is the  
 correlation among AO's three centers of action. Our analysis shows that   
 variability in these three centers of action is highly correlated with  
 in the ensemble mean, indicating that the AO is indeed a SST-forced response.  
 The correlation for the ensemble mean is particularly larger than it in all but  
 one ensemble members in Pacific, suggesting that the formation of   
 the spatial pattern of the AO is strengthed to give SST-forcing  
 which is influenced significantly in Pacific. 
  

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