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A Test of CMIP5 Models to Predict the Past over Southeast Asia

Paper Reviewed
Siew, J.H., Tangang, F.T. and Juneng, L. 2014. Evaluation of CMIP5 coupled atmosphere-ocean general circulation models and projection of the Southeast Asian winter monsoon in the 21st century. International Journal of Climatology 34: 2872-2884.

In a study published in the International Journal of Climatology, Siew et al. (2014) write that "Southeast Asia (SEA) is one of the most populous regions in the world, with more than half a billion human inhabitants," and they say that most of that region's countries are agriculture-based and are areas in which monsoon precipitation is a major water resource for crop and food production," citing Kripalani and Kulkarni (1998) and Preethi et al. (2010). As a result, they further indicate that understanding the future behavior of monsoon precipitation "is crucially important." And thus arises their interest in determining just how well today's state-of-the-art climate models are able to do what they were created to do in this regard, particularly in light of the fact, as they report, that "there has been no previous study to validate CMIP5 models for the SEA region."

Entering this virgin territory, the three Malaysian researchers evaluated the abilities of ten coupled atmosphere-ocean general circulation models (AOGCMs) that participated in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to "predict" the past behavior of the Southeast Asian winter monsoon over the period 1979-2005. And what did they learn?

Siew et al. report two major model accomplishments. However, each of them comes with a "catch." In the first instance, they write that "all the models simulated the broad features of winter monsoon precipitation spatial patterns," but (catch #1) they say that "the spread of the bias magnitudes was very large across the AOCGMs." In the second case, they indicate that "all the models simulated the relationship between the regional rainfall and circulation associated with the El Niño-Southern Oscillation (ENSO)," but (catch #2) they acknowledge that "the strength of the association is relatively weak in the AOGCMs as compared to the observations," which, in turn, "generally results in weaker inter-annual rainfall variation in the simulations."

The take-home message of these findings? Even the best of today's climate models fail to do all that their creators - and we their users - feel we should demand of them.

References
Kripalani, R.H. and Kulkarni, A. 1998. The relationship between some large-scale atmospheric parameters and rainfall over Southeast Asia: a comparison with features over India. Theoretical and Applied Climatology 59: 1-11.

Preethi, B., Kripalani, R.H. and Kumar, K.K. 2010. Indian summer monsoon rainfall variability in global coupled ocean-atmospheric models. Climate Dynamics 35: 1521-1539.

Posted 17 November 2014