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On the Road to Predicting Changes in the Asian Summer Monsoon

Reference
Zhang, H., Liang, P., Moise, A. and Hanson, L. 2012. Diagnosing potential changes in Asian summer monsoon onset and duration in IPCC AR4 model simulations using moisture and wind indices. Climate Dynamics 39: 2465-2486.
Introducing their work, Zhang et al. (2012) write that "the Asian monsoon is a major component in the global climate system, characterized by remarkable seasonal and inter-annual rainfall variations which have significant social and economic influences on large populations in the region," the complexity of which phenomenon, in their words, "is never overstated." Against this backdrop, using daily precipitable water and 850 hPa monsoon wind data, which in the words of Zhang et al. "represent large-scale moisture and dynamic conditions for monsoon development," the four scientists analyzed "potential changes in Asian monsoon onset, retreat and duration simulated by 13 IPCC AR4 models."

The Chinese-Australian research team reports that there "is no single outstanding model out of the 13 models used in the analysis," noting that "some of the models have shown significant biases in mean onset/retreat dates and some failed to produce the broad features of how [the] monsoon evolves." Over East Asian land, for example, they found that "the models are nearly equally divided about the sign of potential changes of onset/retreat." And sounding rather frustrated, they lament that they "do not know why the models are different in simulating these dominant processes and why in some models the ENSO influence is more significant than others.," adding that "it is unclear what are the key parameterizations leading to the differences in simulating ENSO and its responses to global warming," citing Solomon et al. (2007) and Wang et al. (2009).

The final summing-up sentence of the researchers says it all. "There is a long way ahead before we can make skillful and reliable prediction of monsoon onset, duration, intensity and evolution in [a] warmed climate."

Additional References
Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M. and Miller, H.L. (Eds.) 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom.

Wang, X., Wang, D. and Zhou, W. 2009. Decadal variability of twentieth-century El Niño and La Niña occurrence from observations and IPCC AR4 coupled models. Geophysical Research Letters 36: 10.1029/2009GL037929.

Archived 3 April 2013