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Modelling the Seasonal SST Cycle of the Eastern Equatorial Pacific

Paper Reviewed
Song, Z.Y., Liu, H.L., Wang, C.Z., Zhang, L.P. and Qiao, F.L. 2014. Evaluation of the eastern equatorial Pacific SST seasonal cycle. Ocean Science 10: 837-843.

Acknowledging that the coupled general circulations models (CGCMs) of the Coupled Model Intercomparison Project Phase 3 (CMIP3) were pretty much failures in their ability to accurately model the seasonal sea surface temperature (SST) cycle of the eastern equatorial Pacific (EEP), Song et al. (2014) set out to see how well the new-and-improved CMIP5 models perform in this regard. And what did they learn by so doing?

The five researchers report that although the newer models can do certain things better than the CMIP3 models, they still fall short of adequately portraying reality when it comes to reproducing the in-phase SST relationship between EEP region 1 (EP1) and EEP region 2 (EP2) in August and September of each year. In terms of amplitude simulations, for example, they note that "the model SST in EP1 shows weaker seasonal variation than the observations due to the large warm SST biases from the southeastern tropical Pacific in the boreal autumn." And in the case of EP2 they say there is "a quasi-constant cold bias associated with poor cold tongue simulations in the CGCMs."

As a result of these findings, Song et al. write, in the concluding sentence of their paper, that "to improve the capability of the CGCMs in simulating a realistic SST seasonal cycle in the EEP, both the local and remote climatological SST biases (Wang et al., 2014) that exist in both CMIP3 and CMIP5 CGCMs, such as the climatological simulation of the cold tongue region and the southeastern tropical Pacific, must be resolved," which is something that obviously has yet to be accomplished.

Wang, C., Zhang, L., Lee, S.-K., Wu, L. and Mechoso, C.R. 2014. A global perspective on CMIP5 climate model biases. Nature Climate Change 4: 201-205.

Posted 24 February 2015