Future shifts in synoptic systems and total rainfall over southwest Western Australia from a range of GCMs under a range of forcing

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Future shifts in synoptic systems and total
rainfall over southwest Western Australia from
a range of GCMs under a range of forcing

• Pandora Hope
• Bureau of Meteorology Research Centre
• Indian Ocean Climate Initiative

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Motivation

• Rainfall decline in southwest is a big concern
• Will it continue?
• How have the rain-bearing storms changed?

Hope 2006 Projected future changes in synoptic
systems influencing southwest Western Australia
Climate Dynamics Background Hope et al. 2006
Shifts in the synoptic systems influencing
southwest Western Australia Climate Dynamics
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Acknowledgements

• IOCI
• Wasyl Drosdowsky
• Aurel Moise
• PCMDI WGCM, CMIP
• Julie Arblaster
• Bertrand Timbal
• Zhihong Li
• Scott Power
• Debbie Hudson
• Neville Nicholls

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Outline

• Background
• Synoptic types Self-Organising Map
• Models and Forcing
• Direct model output Rainfall Decline in
  1970s and future changes
• Projected future shifts in synoptic systems
• Conclusions and further work

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Perth South West Western Australia Rainfall
Decline in mid 1970s
Monthly rainfall in south west
May-July Rainfall Change since 1976
June and July rainfall for southwest Perth
Airport
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Self Organising Map NCEP/NCAR 1948-2003 June
July 0 12Z MSLP
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Rainfall anomaly Reddrier Bluewetter
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Models, Resolution, 20C3M forcing
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Scenarios SRES A2 and B1
2100
2000
Prentice et al. 2001 in IPCC TAR WG1
MRI JMA (ISAM model)
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Rainfall NCC data Direct Model Output
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Rainfall change from 1901-2000
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Difference 2046-2065 cf 1961-2000
MRI-CGCM2.3.2
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SRES B1 2081-2100 Difference
CSIRO-Mk3
GFDL-CM2.0
GISS-ER
MIROC3.2(med)
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SRES A2 2081-2100 Difference
CSIRO-Mk3
GFDL-CM2.0
GISS-ER
MIROC3.2(med)
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Conclusions

• Increasing levels of greenhouse gases lead to a
  growing reduction in the occurrence of deep
  troughs in the SWWA region in most GCMs.
• All GCMs examined here show a decline in direct
  model output rainfall with increasing greenhouse
  gas concentrations.
• These results suggest that, as greenhouse gas
  concentrations rise in the future, it is likely
  that rainfall in SWWA will continue to be low.
  However, decadal variability must also be
  considered.