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CMIP5 Projections of Australian Summer Monsoon Onset and Retreat

Paper Reviewed
Zhang, H., Dong, G., Moise, A., Colman, R., Hanson, L. and Ye, H. 2016. Uncertainty in CMIP5 model-projected changes in the onset/retreat of the Australian summer monsoon. Climate Dynamics 46: 2371-2389.

In their most recent climate model study of the yearly onset and retreat of the Australian summer monsoon, Zhang et al. (2016) analyzed daily 850 hPa winds, volumetric precipitable water, and precipitation and temperature data they obtained from 26 CMIP5 models over the courses of two 55-year climate simulations. And what did they thereby learn?

The six scientists discovered that when compared to results of CMIP3 models, (1) "CMIP5 models do not show significant improvement in capturing observed features of the monsoon onset/retreat in the region," that (2) the "wind-rainfall relationship varies with models," that (3) "rainfall-based wet season onsets may not adequately represent the monsoon development," that (4) "ten models simulated delayed onset but it became earlier in another group of 7 models," that (5) "similar model discrepancies are seen in the modelled changes in retreat dates," that (6) "the range of uncertainty in the projected changes is similar in CMIP3 and CMIP5 models," due to (7) "the different influence of a number of drivers in these models" and (8) "the different changes in these drivers themselves in future climate."

Overall, as Zhang et al. thus report, "most of the models showed impacts of ENSO and the Indian Ocean on the Australian summer monsoon onset/retreat," but they also note that (9) "the models differed quite significantly in the magnitude of such impacts." In addition, they write that two other problems are (10,11) "different warming patterns and magnitudes in the tropical Pacific and Indian Oceans."

In closing, the six researchers conclude that (12) "capturing the detailed monsoon activities such as onset/retreat and duration remains as one of the significant challenges for current climate models," citing Kitoh et al. (2013) and Christensen et al. (2013), while another complicating factor is said by them to be the fact that (13) "the linkage between monsoon onset in this region with these drivers can be significantly different, with some models having more ENSO influence than Indian Ocean sea surface temperatures and vice versa."

References
Christensen, J.H., Hewitson, B., Busuioc, A., Chen, X., Gao, I., Held, R., Jones, R.K., Kolli, W.-T., Kwon, R., Laprise, V., Magaña Rueda, L., Mearns, C.G., Menèndez, J., Räisänen, A., Rinke, A., Sarr and P. Whetton, 2007: Regional Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M. and Miller, H.L. (Eds.). Cambridge University Press, Cambridge, United Kingdom and New York, New York, USA.

Kitoh, A., Endo, H., Kumar, K.K., Cavalcanti, I.F.A., Goswami, P. and Zhou, T. 2013. Monsoons in a changing world: a regional perspective in a global context. Journal of Geophysical Research 118: 3053-3065.

Posted 2 August 2015