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dc.contributor.authorLi, T.
dc.contributor.authorWang, B.
dc.contributor.authorChang, C.-P.
dc.contributor.authorZhang, Y.
dc.date.accessioned2013-09-25T22:59:57Z
dc.date.available2013-09-25T22:59:57Z
dc.date.issued2003
dc.identifier.citationLi, T. B. Wang, C.-P. Chang, and Y. Zhang, 2003: A Theory for the Indian Ocean Dipole Mode. J. Atmos. Sci., 60, 2119-2135. (Manuscript)
dc.identifier.urihttp://hdl.handle.net/10945/36679
dc.descriptionJ. Atmos. Sci., 60, 2119-2135. (Manuscript)en_US
dc.description.abstractA conceptual coupled atmosphere-ocean model was constructed to understand the origin of the Indian Ocean Dipole Mode (IODM). In the model various positive and negative air-sea feedback processes were involved. Among them were the cloud-radiation- SST feedback, the evaporation-SST-wind feedback, the thermocline-SST feedback, and the monsoon-SST feedback. Numerical results indicate that air-sea interactions in the tropical Indian Ocean support a natural damped mode, which is different from the selfsustained ENSO mode in the tropical Pacific. The difference arises from the distinctive characteristics of the basic state of the coupled system in the tropical Indian and Pacific Oceans. By use of observational analyses and physical reasoning, the authors identified four fundamental differences between air-sea interactions in the two oceans. The first difference is represented by the strong contrast of the cloud-SST phase relationship between the warm pool and cool tongue. The second difference arises from the reversal of the basic-state zonal wind and east-west tilting of the ocean thermocline, which leads to distinctive effects of ocean waves on the SST. The third difference lies in the existence of the Asian monsoon and its negative feedback on the IODM. The fourth difference is that the southeast Indian Ocean is a region where there exists a positive atmosphere-ocean thermodynamic feedback. The phase-locking of the IODM can be, to a large extent, explained by the seasonal dependence of the aforementioned thermodynamic air-sea feedback. In addition, anomalous Indian monsoon also plays a role. Although the El Nino exerts the strongest forcing toward the end of a year, its impact on the anomalous monsoon heating peaks in northern summer. Thus the anomalous monsoon may exert the greatest impact on the IODM toward the end of boreal summer. In the presence of realistic ENSO forcing, the model was capable of simulating most of IODM events during the last 50 years that were associated with ENSO, indicating that ENSO is one of major forcings that trigger the IODM events. The failure of simulation of the IODM events in 1961 and 1994 suggests that other types of climate forcing may also play a role. The authors’ observational analyses revealed that the 1994 event resulted from anomalous heating over Indochina/South China Sea in boreal summer, whereas the 1961 event might be traced back to the preceding winter when there was anomalous heating over the maritime continent.A conceptual coupled atmosphere-ocean model was constructed to understand the origin of the Indian Ocean Dipole Mode (IODM). In the model various positive and negative air-sea feedback processes were involved. Among them were the cloud-radiation- SST feedback, the evaporation-SST-wind feedback, the thermocline-SST feedback, and the monsoon-SST feedback. Numerical results indicate that air-sea interactions in the tropical Indian Ocean support a natural damped mode, which is different from the selfsustained ENSO mode in the tropical Pacific. The difference arises from the distinctive characteristics of the basic state of the coupled system in the tropical Indian and Pacific Oceans. By use of observational analyses and physical reasoning, the authors identified four fundamental differences between air-sea interactions in the two oceans. The first difference is represented by the strong contrast of the cloud-SST phase relationship between the warm pool and cool tongue. The second difference arises from the reversal of the basic-state zonal wind and east-west tilting of the ocean thermocline, which leads to distinctive effects of ocean waves on the SST. The third difference lies in the existence of the Asian monsoon and its negative feedback on the IODM. The fourth difference is that the southeast Indian Ocean is a region where there exists a positive atmosphere-ocean thermodynamic feedback. The phase-locking of the IODM can be, to a large extent, explained by the seasonal dependence of the aforementioned thermodynamic air-sea feedback. In addition, anomalous Indian monsoon also plays a role. Although the El Nino exerts the strongest forcing toward the end of a year, its impact on the anomalous monsoon heating peaks in northern summer. Thus the anomalous monsoon may exert the greatest impact on the IODM toward the end of boreal summer. In the presence of realistic ENSO forcing, the model was capable of simulating most of IODM events during the last 50 years that were associated with ENSO, indicating that ENSO is one of major forcings that trigger the IODM events. The failure of simulation of the IODM events in 1961 and 1994 suggests that other types of climate forcing may also play a role. The authors’ observational analyses revealed that the 1994 event resulted from anomalous heating over Indochina/South China Sea in boreal summer, whereas the 1961 event might be traced back to the preceding winter when there was anomalous heating over the maritime continent.en_US
dc.rightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. As such, it is in the public domain, and under the provisions of Title 17, United States Code, Section 105, may not be copyrighted.en_US
dc.titleA Theory for the Indian Ocean Dipole Modeen_US


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