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CMIP5 Assessments of Indian Ocean Basin-Wide and Dipole Modes

Paper Reviewed
Chu, J.-E., Ha, K.-J., Lee, J.-Y., Wang, B., Kim, B.-H. and Chung, C.E. 2014. Future change of the Indian Ocean basin-wide and dipole modes in the CMIP5. Climate Dynamics 43: 535-551.

According to Chu et al. (2014), the Indian Ocean sea surface temperature (SST) variability has been represented at different times by two dominant variability modes: the Indian Ocean basin-wide (IOBW) and dipole (IOD) modes. In investigating potential changes in the two modes and the relationship between their mean states and the El Niño and Southern Oscillation (ENSO) phenomenon, Chu et al. employed 20 coupled models that participated in phase five of the Coupled Model Intercomparison Project (CMIP5) to assess their ability to simulate the climatology and variability of the Indian Ocean SST during the historical period of 1950-2005.

In so doing the six scientists say they identified "considerable biases" in the models' simulations over the Indian Ocean. One notable bias was that "more than half of the CMIP5 coupled models have difficulty in capturing the spatial distribution of the IOD mode, particularly over the equatorial Indian Ocean." Another bias was that some models tend to have negative anomalies that extend far west along the equator in the positive phase of the IOD, while yet another anomaly was that a few of the models had north-south dipoles rather than east-west ones.

In light of their several findings, Chu et al. conclude their paper by noting that an understanding of the models' deficiencies - three of which they identified - is of importance for more reliable estimations of future changes in Indian Ocean variability.

Posted 27 October 2014