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Precipitation and Pacific Storm Track Problems in CMIP5 Models

Paper Reviewed
Langenbrunner, B., Neelin, J.D., Lintner, B.R. and Anderson, B.T. 2015. Patterns of precipitation change and climatological uncertainty among CMIP5 models, with a focus on the mid-latitude Pacific storm track. Journal of Climate 28: 7857-7872.

Noting that (1) "projections of modeled precipitation (P) change in global warming scenarios demonstrate marked inter-model disagreement at regional scales," Langenbrunner et al. (2015) employed empirical orthogonal functions (EOFs) and maximum covariance analysis (MCA) to diagnose spatial patterns of disagreement in the simulated climatology and end-of-century P changes in phase 5 of the Coupled Model Intercomparison Project (CMIP5) archive," wherein "the term principal uncertainty pattern (PUP) is used for any robust mode calculated when applying these techniques to a multi-model ensemble."

This work revealed, as the four U.S. researchers report, that (2) "the first storm-track PUP identifies a sensitive region of disagreement in P increases over the eastern midlatitude Pacific where the storm track terminates," due to (3) "uncertainty in an eastward extension of the climatological jet," while (4) "the second PUP portrays uncertainty in a zonally asymmetric meridional shift of storm-track P," related to (5) "uncertainty in the extent of a poleward jet shift in the western Pacific." And, last of all, they add that (6) "both modes appear to arise primarily from inter-model differences in the response to radiative forcing."

Posted 29 January 2016