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gfdl on-line bibliography > 2007 citations
Indian Ocean variability in the GFDL coupled climate model
| Song, Q., G. A. Vecchi, and A. J. Rosati, 2007: Indian Ocean variability in the GFDL coupled climate model. Journal of Climate, 20(13), 2895-2916. |
| Abstract: The interannual variability of the Indian Ocean, with particular focus on the Indian Ocean dipole/zonal mode (IODZM), is investigated in a 250-yr simulation of the GFDL coupled global general circulation model (CGCM). The CGCM successfully reproduces many fundamental characteristics of the climate system of the Indian Ocean. The character of the IODZM is explored, as are relationships between positive IODZM and El Niņo events, through a composite analysis. The IODZM events in the CGCM grow through feedbacks between heat-content anomalies and SST-related atmospheric anomalies, particularly in the eastern tropical Indian Ocean. The composite IODZM events that co-occur with El Niņo have stronger anomalies and a sharper eastwest SSTA contrast than those that occur without El Niņo. IODZM events, whether or not they occur with El Niņo, are preceded by distinctive Indo-Pacific warm pool anomaly patterns in boreal spring: in the central Indian Ocean easterly surface winds, and in the western equatorial Pacific an eastward shift of deep convection, westerly surface winds, and warm sea surface temperature. However, delayed onsets of the anomaly patterns (e.g., boreal summer) are often not followed by IODZM events. The same anomaly patterns often precede El Niņo, suggesting that the warm pool conditions favorable for both IODZM and El Niņo are similar. Given that IODZM events can occur without El Niņo, it is proposed that the observed IODZMEl Niņo relation arises because the IODZM and El Niņo are both large-scale phenomena in which variations of the Indo-Pacific warm pool deep convection plays a central role. Yet each phenomenon has its own dynamics and life cycle, allowing each to develop without the other. |
| The CGCM integration also shows substantial decadal modulation of the occurrence of IODZM events, which is found to be not in phase with that of El Niņo events. There is a weak, though significant, negative correlation between the two. Moreover, the statistical relationship between the IODZM and El Niņo displays strong decadal variability. |