Trends and projections of storm formation in coupled climate models

Changes in the characteristics of southern hemisphere storms, in all seasons, during the second half of the twentieth century, were related to changes in the annual cycle of Southern Hemisphere baroclinic instability. In particular, significant negative trends in baroclinic instability were found in a mid-latitude zonal band in all months; a similar band of significant positive trends occurs further poleward. Corresponding to this decrease\ increase in baroclinic instability there was a decrease\increase in storm formation at these latitudes, and in some cases a preference for storm formation further poleward than normal. These changes in the weather systems are consistent with the observed negative trends in southern Australian rainfall. Future projections of trends in baroclinicity, under the RCP8.5 scenario, show a similar pattern of negative and positive trends during the second half of the twenty first century. The impact of these trends is continuing decreased and negative trends in southern Australian rainfall. References J. S. Risbey, M. J. Pook, P. C. McIntosh, M. C. Wheeler and H. H. Hendon On the remote drivers of rainfall variability in Australia. Mon. Wea. Rev. 137:3233–3253, 2009. doi:10.1175/2009MWR2861.1 C. S. Frederiksen. , X. Zheng and S. Grainger. Teleconnections and predictive characteristics of Australian seasonal rainfall. Clim. Dyn. 43:1381–1408, 2014. doi:10.1007/s00382-013-1952-0 J. S. Frederiksen and C. S. Frederiksen. Interdecadal changes in southern hemisphere winter storm track modes. Tellus , 59:599–617, 2007. doi:10.1111/j.1600-0870.2007. 00264.x J. S. Frederiksen and C. S. Frederiksen. Twentieth century winter changes in southern hemisphere synoptic weather modes. Adv. Meteorol. 2011:353829, 2011. doi:10.1155/2011/353829 N. A. Phillips. Energy transformations and meridional circulations associated with simple baroclinic waves in a two-level, quasi-geostrophic model. Tellus , 6:273–286, 1954. doi:10.1111/j.2153-3490.1954. tb01123.x D. P. van Vuuren , J. Edmonds, M. Kainuma, K. Riahi, A. Thomson, K. Hibbard, G. C. Hurtt, T. Kram, V. Krey, J.-F. Lamarque, T. Masui, M. Meinshausen, N. Nakicenovic, S. J. Smith and S. K. Rose. The representative concentration pathways: an overview. Clim. Chang. 109:5–31, 2011. doi:10.1007/s10584-011-0148-z K. E. Taylor, R. J Stouffer and G. A. Meehl. An overview of CMIP5 and the experiment design. Bull. Am. Meteorol. Soc. 93:485-498, 2012. doi:10.1175/BAMS-D-11-00094.1 J. S. Frederiksen and C. S. Frederiksen. Role of dynamical modes in changing southern hemisphere climate. ANZIAM J. 52:C56–C72, 2010. http://journal.austms. org.au/ojs/index.php/ANZIAMJ/article/view/3892 E. Kalnay, M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Saha, G. White, J. Woollen, Y. Zhu, A. Leetmaa, R. Reynolds, M. Chelliah, W. Ebisuzaki, W. Higgins, J. Janowiak, K. C. Mo, C. Ropelewski, J. Wang, R. Jenne, and D. Joseph, The NCEP/NCAR 40-Year reanalysis project. Bull Am. Meteorol. Soc. 77:437-471, 1996. 2.0. CO;2">doi:10.1175/1520-0477(1996)077 2.0. CO;2 G. Flato et al. Evaluation of climate models. In: T. F. Stocker et al., editors Climate Change 2013: The Physical Science Basis Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change , Chap. 9, pp. 741–866. Cambridge University Press, Cambridge, UK, 2013 http://www.ipcc. ch/report/ar5/wg1/ C. S. Frederiksen, J. S. Frederiksen, J. M. Sisson and S. L. Osbrough. Changes and Projections in Australian Winter Rainfall and Circulation: Anthropogenic Forcing and Internal Variability. Int. J. Climate Change: Impact. Resp. 2:143–162, 2011. http://ijc.cgpublisher. com/product/pub.185/prod.104 C. S. Frederiksen and S. Grainger. The role of external forcing in prolonged trends in Australian rainfall Clim. Dyn. 45(9):2455–2468, 2015. doi:10.1007/s00382-015-2482-8