Decadal and interannual variability of the Indian Ocean SST
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The variability of the Indian Ocean on interannual and decadal timescales is investigated in observations, coupled model simulation and model experiment. The Indian Ocean Dipole (IOD) mode was specifically analyzed using a data-adaptive method. This study reveals one decadal mode and two interannual modes in the sea surface temperature (SST) of the IOD. The decadal mode in the IOD is associated with the Pacific Decadal Oscillation (PDO) of the North Pacific SST. The two interannual modes are related to the biennial and canonical components of El Niño-Southern Oscillation (ENSO), consistent with previous studies. This study hypothesizes that the relation between the Indian Ocean and the North Pacific on decadal scale may be through the northerly winds from the western North Pacific. The long simulation of Community Climate System Model version 4 also indicates the presence of IOD modes associated with the decadal PDO and canonical ENSO modes. However, the model fails to simulate the biennial ENSO mode in the Indian Ocean. The relation between the Indian Ocean and North Pacific Ocean is further supported by the regionally de-coupled model experiment.
KeywordsIndian Ocean Pacific Decadal Oscillation Indian Ocean Dipole Singular Spectrum Analysis Community Climate System Model Version
This work was supported by National Science Foundation (Grants ATM-0830062 and ATM-0830068), National Oceanic and Atmospheric Administration (Grant NA09OAR4310058), and National Aeronautics and Space Administration (Grant NNX09AN50G). The authors thank Ben Kirtman for constructive suggestions and NCAR for providing the data of 20C3M simulation, computational time and technical help with model experiments. We also thank two anonymous reviewers for helpful comments which improved the manuscript. This work formed a part of the Ph.D. thesis of Lakshmi Krishnamurthy at George Mason University.
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