Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 4 2009 10.5194/hess-13-467-2009 http://www.hydrol-earth-syst-sci.net/13/467/2009/ http://www.hydrol-earth-syst-sci.net/13/467/2009/hess-13-467-2009.html http://www.hydrol-earth-syst-sci.net/13/467/2009/hess-13-467-2009.pdf 467 479 2009-04-07 On the relationship between large-scale climate modes and regional synoptic patterns that drive Victorian rainfall D. C. Verdon-Kidd A. S. Kiem Sinclair Knight Merz, Newcastle, New South Wales, Australia Environmental and Climate Change Research Group, School of Environmental and Life Sciences, University of Newcastle, New South Wales, Australia In this paper regional (synoptic) and large-scale climate drivers of rainfall are investigated for Victoria, Australia. A non-linear classification methodology known as self-organizing maps (SOM) is used to identify 20 key regional synoptic patterns, which are shown to capture a range of significant synoptic features known to influence the climate of the region. Rainfall distributions are assigned to each of the 20 patterns for nine rainfall stations located across Victoria, resulting in a clear distinction between wet and dry synoptic types at each station. The influence of large-scale climate modes on the frequency and timing of the regional synoptic patterns is also investigated. This analysis revealed that phase changes in the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and/or the Southern Annular Mode (SAM) are associated with a shift in the relative frequency of wet and dry synoptic types on an annual to inter-annual timescale. In addition, the relative frequency of synoptic types is shown to vary on a multi-decadal timescale, associated with changes in the Inter-decadal Pacific Oscillation (IPO). Importantly, these results highlight the potential to utilise the link between the regional synoptic patterns derived in this study and large-scale climate modes to improve rainfall forecasting for Victoria, both in the short- (i.e. seasonal) and long-term (i.e. decadal/multi-decadal scale). In addition, the regional and large-scale climate drivers identified in this study provide a benchmark by which the performance of Global Climate Models (GCMs) may be assessed. Ashok, K., Guan, Z., and Yamagata, T.: Influence of the Indian Ocean Dipole on the Australian winter rainfall, Geophys. Res. Lett., 30, doi:10.1029/2003GL017926, 2003. Cavazos, T.: Using self-organizing maps to investigate extreme climate events: An application to wintertime precipitation in the Balkans, J. Clim., 13, 1718–1732, 2000. Cavazos, T., Comrie, A. C., and Liverman, D. M.: Intraseasonal variability associated with wet monsoons in southeast Arizona, J. Clim., 15, 2477–2490, 2002. Chiew, F. H. S., Piechota, T. C., Dracup, J. A., and McMahon, T. A.: El Nino Southern Oscillation and Australian rainfall, streamflow and drought - links and potential for forecasting, J. Hydrol., 204, 138–149, 1998. Drosdowsky, W.: The latitude of the subtropical ridge over Eastern Australia: The L index revisited, Int. J. Climatol., 25, 1291–1299, 2005. Erskine, W. D. and Warner, R. F.: Geomorphic effects of alternating flood and drought dominated regimes on a coastal NSW river, in: Fluvial Geomorphology of Australia, Academic Press, Sydney, Australia, 223–244, 1988. Folland, C. K., Parker, D. E., Colman, A. W., and Washington, R.: Large scale modes of ocean surface temperature since the late nineteenth century, in: Beyond El Nino: Decadal and Interdecadal Climate Variability, Springer, Berlin, Germany, 73–102, 1999. Franks, S. W. and Kuczera, G.: Flood frequency analysis: Evidence and implications of secular climate variability, New South Wales, Water Resour. Res., 38(5), doi:10.1029/2001WR000232, 2002. Hewitson, B. C. and Crane, R. G.: Self-organizing maps: application to synoptic climatology, Clim. Res., 22, 13–26, 2002. Hope, P. K., Drosdowsky, W., and Nicholls, N.: Shifts in the synoptic systems influencing southwest Western Australia, Clim. Dynam., 26, 751–764, 2006. Kiem, A. S. and Verdon-Kidd, D. C.: Climatic drivers of Victorian streamflow – is ENSO the dominant influence?, Austr. J. Water Resour., 13(1), \blackbox\bf page range, 2009. Kohonen, T.: Self-organizing maps, Springer, New York, USA, 501 pp., 1995. Mantua, N. J., Hare, S. R., Zhang, Y., Wallace, J. M., and Francis, R. C.: A Pacific decadal climate oscillation with impacts on salmon production, B. Am. Meteor. Soc., 78, 1069–1079, 1997. McMahon, T. A., Finlayson, B. L., Haines, A. T., and Srikanthan, R.: Runoff variability: a global perspective, in: Influence of Climate Change and Climatic Variability on the Hydrologic Regime and Water Resources, vol. 168. International Association of Hydrological Sciences, Wallingford, England, UK, 3–11, 1987. Meneghini, B., Simmonds, I., and Smith, I. N.: Association between Australian rainfall and the Southern Annular Mode, Int. J. Climatol., 27, 109–121, 2007. Murphy, B. F. and Timbal, B.: A review of recent climate variability and climate change in southeastern Australia, Int. J. Climatol., 28, 859–879, 2007. Nicholls, N.: Sea surface temperatures and Australian winter rainfall, J. Clim., 2, 965–973, 1989. Nicholls, N., Drosdowsky, W., and Lavery, B.: Australian rainfall variability and change, Weather, 52, 66–72, 1997. Pook, M. J., McIntosh, P. C., and Meyers, G. A.: The synoptic decomposition of cool-season rainfall in the southeastern Australian cropping region, J. Appl. Meteor. Clim., 45, 1156–1170, 2006. Power, S., Casey, T., Folland, C., Colman, A., and Mehta, V.: Inter-decadal modulation of the impact of ENSO on Australia, Clim. Dynam., 15, 319–324, 1999. Power, S., Tseitkin, F., Torok, S., Lavery, B., Dahni, R., and McAvaney, B.: Australian temperature, Australian rainfall and the Southern Oscillation, 1910-1992: coherent variability and recent changes, Australian Meteorological Magazine, 47, 85–101, 1998. Reusch, D. B., Alley, R. B., and Hewitson, B. C.: North Atlantic climate variability from a self-organizing map perspective, J.. Geophys. Res., 112, D02104, doi:02110.01029/02006JD007460, 2007. Ropelewski, C. F. and Halpert, M. S.: Global and Regional Scale Precipitation Patterns Associated with the El Niño/Southern Oscillation, Mon. Weather Rev., 115, 1606–1626, 1987. Saji, H. H., Goswami, B. N., Vinayachandran, P. N., and Yamagata, T.: A dipole mode in the tropical Indian Ocean, Nature, 401, 360–363, 1999. Stone, R. and Auliciems, A.: SOI Phase relationships with rainfall in eastern Austalia, Int. J. Climatol., 12, 625–636, 1992. Sturman, A. and Tapper, N.: The Weather and Climate of Australia and New Zealand, Oxford University Press, Melbourne, Victoria, Australia, 2004. Tapper, N. and Hurry, L.: Australia's Weather Patterns – An Introductory Guide, Dellasta Pty Ltd., Mount Waverly, Victoria, 1996. Thompson, D. W. J. and Wallace, J. M.: Annular modes in the extratropical circulation, part I: month-to-month variability, J. Clim., 13, 1000–1016, 2000. Timbal, B. and Jones, D. A.: Future projections of winter rainfall in southeast Australia using a statistical downscaling technique, Clim. Change, 86, 165–187, 2008. Verdon, D. C. and Franks, S. W.: Indian Ocean sea surface temperature variability and winter rainfall: Eastern Australia, Water Res. Res., 41, W09413, doi:09410.01029/02004WR003845, 2005. Verdon, D. C. and Franks, S. W.: Long-term behaviour of ENSO: Interactions with the PDO over the past 400 years inferred from paleoclimate records, Geophys. Res. Lett., 33, L06712, doi:10.1029/2005GL025052, 2006. Verdon, D. C., Wyatt, A. M., Kiem, A. S., and Franks, S. W.: Multi-decadal variability of rainfall and streamflow – Eastern Australia, Water Res. Res., 40, W10201, doi:10210.11029/12004WR003234, 2004. Wright, W. J.: A synoptic climatological classification of winter precipitation in Victoria, Australian Meteorological Magazine, 37, 217–229, 1989. Zanchettin, D., Franks, S. W., Traverso, P., and Tomasino, M.: On ENSO impacts on European wintertime rainfalls and their modulation by the NAO and the Pacific multi-decadal variability described through the PDO index, Int. J. Climatol., 28, 995–1006, 2008.