Indian Ocean Climate Initiative - Western Australia

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Home Research Program Theme 3: Very-high resolution climate change projections for the South west

Theme 3

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Theme 3
Project 3.1
Project 3.2
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Very-high resolution climate change projections for the South west

The points under each project describe the first major deliverables that are currently being addressed and are by no means the full four-year research plan for IOCI Stage 3.

Project 3.1: Statistically Downscaled Climate Change Projections for the South West (Steve Charles)

Planned outcomes:

  • Develop climate change projections of daily rainfall and temperature for multiple south west sites produced for three climate change scenarios (B1, A1B, A2) using statistical downscaling models driven by atmospheric predictors from climate models assessed for their performance over the region.
  • Develop more rigorous and defensible estimates of regional climate change at a spatial scale suitable for use in impacts and vulnerability assessment.

Figure 3.1.1: Time series of anomalies of the JJA extreme rainfall index for SWWA, expressed in %, for 1-day, 1-yr recurrence interval extreme rainfall events

There is an on-going interest in characterizing possible changes in rainfall extreme events, because they not only cause significant damage to agriculture, ecology and infrastructure, but also produce the large portion of streamflow. This figure shows a significant decreasing trend of the winter months (JJA) extreme daily rainfall annual events since the 1970s. This is temporally consistent with the decline of the inflow into the reservoirs of Perth water supply by about 40–65% since the 1970s, for an annual rainfall decrease of only 10–15%.

Project 3.2: Climate Extremes: Potential Forecast Skill and Climate Change Scenarios (Yun Li, Mark Palmer and Eddy Campbell)

Planned outcomes:

  • Develop scenarios for intensity-frequency-duration characteristics of seasonal rainfall under climate change, which can be used for impact and vulnerability assessments.

Figure 3.2.1: Return periods of winter extreme daily rainfall at Manjimup station. Black “o” points represent the empirical return period of winter extreme rainfalls observed in 1930-1965 and red “+” points in 1966-2001. The black and red solid curves represent return period based tail estimates based on fitted generalized Pareto distributions with 95% confidence interval given as black dash lines (1930-1965) and red dot-dashed line (1966-2001). It is evident that the return period of the winter extreme daily rainfall in the post-change period (1966-2001) has greatly increased for the same extreme rainfall levels, which indicates that winter extreme daily rainfall has decreased since 1965.

Figure 3.2.2: Return period of winter extreme rainfall over SWWA between pre-change period 1930-1965 and post-change period 1966-2001 at four stations 9503, 9023, 9591 and 10636. Generally, the return period for winter extreme rainfall of the averaged rainfall series of five stations over SWWA has increased, which implies that extreme rainfall over SWWA has decreased since the change point year 1965.

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