The role of the southern annular mode in dynamical global coupled model

Abstract

The interannual and decadal variability of the Southern Annual Mode (SAM) was examined in the ECHAM 4.5-MOM3-SA ocean-atmosphere coupled general circulation model (OAGCM). The analysis placed emphasis on the behavior of the SAM when its variability and impact becomes noticeable in the extra-tropical subcontinent. Further, the coupling interaction of the SAM with vertically intergraded moisture flux, rainfall and sea surface temperature (SST) was also investigated and compared with observations. The result revealed that the model was successful in capturing observed features of the oscillation. Nevertheless, the model SAM was found to exert more influence on the underlying atmosphere. The analysis unfolded that the low-frequency signal (11years cycle) was more likely explained by natural variability. Further, the model has shown potential in predicting the austral winter slowly evolving climate signal when the temporal vacillation of the SAM is adjusted.