How Extreme South West Rainfall Has Changed

1
How Extreme South West Rainfall Has Changed

• It is likely that climate change will be felt
  most through changes in extreme events.

2
Trends in Rainfall Events
Perth Airport June and July -
3
Summer 1-Day Maxima
4
Winter 1-Day Maxima
5
Climate Change

• A drying trend is indicated for SWWA
• Rising temperatures imply increased
  moisture-carrying capacity
• Most models simulate an increase in extreme daily
  rainfall as a global trend
• Can occur even given a drying trend
• Not evident in Winter rainfall for SWWA at this
  time

6
Linkages Implications

• Links have been found with changes in atmospheric
  circulation
• Likely to be natural variability enhanced
  greenhouse effect
• Antecedent wetness is generally lower since the
  rainfall decrease
• Negative impact on flood magnitudes of all
  frequencies
• We can say little as yet about very rare events

7
The Future

• Models simulate a drying trend in SWWA
• Globally, extreme events can be expected to
  become more frequent
• Projections for regions such as SWWA are not yet
  clear
• Integrating hydrologic and climate models is
  vital
• Long term data sets are crucial

8
Summary

• Winter changes are very subtle
• Increase in summer events
• Natural variability enhanced greenhouse effect
• Spatial patterns and atmospheric drivers being
  studied
• Very little can be said about rare events
• Few data
• Limits of modelling capability