1. Climate of Australia Ian Rutherfurd

2. World rainfall

3. Global Position Topography

4. This lecture … 1.Context of Australia 2.Summary of climate 3.Aridity 4.Present climate pattern 5.ENSO

7. Two climatic zones Tropics = 40% = north of Tropic of Capricorn, a “wet” or summer season and a “dry” or winter season. Temperate = 60% = four distinct (4) seasons = spring, summer, winter and autumn Transition zone

10. General controls on Australian climate: Aridity ( 33% arid, 75% semi-arid 1 million km 2 of sandplain) Global position Flat

11. Northward drift: 50 – 60 m.y.

12. Aridity began 10 - 17 m.y. Growth of west Antarctic Ice sheet Circumpolar current developed (cooler water) Decreased penetration of cool, moist air Desert dunes in place 0.3 m.y. Western palaeochannels dry 0.5m.y. Peak of aridity about 20 - 30,000 BP Origins of aridity

13. Circum-polar current

15. Flat Murray falls 100m from Albury 2200 km from sea Mean height = 300m World average = 700m

16. Consequences of aridity … Landforms Vegetation Animals

17. Palaeo- drainage lines of WA

18. Linear Dunefields

19. Absence of Glaciation! Ice sheets 3 km thick in N.Hemisphere Australia too low < 0.5% glaciated in Pleistocene (much of Tas, but only 50 km 2 mainland)

20. Glaciation

21. Tropical/monsoonal Australia

22. Monsoon Monsoon = a seasonal reversal of wind direction. Dry winter (April – Nov) Wet summer (Oct – March)

27. Cyclones reach the north west in November to April and the north east in January to April

28. Temperate Australia Mediterranean climate Winter = Succession of fronts from SW Summer = dry air from central low pressure system

29. Cold Fronts subtropical high pressure cells passing from west to east. These normally associated with stable conditions, clear skies and low rainfall. Cold fronts between cells

30. Decadal fluctuations = El Nino Droughts in Australia every few decades Australia's most costly natural hazard primarily because it causes lost agricultural production The 1994/95 drought = 47% reduction in farm production, a US$2000 million or 0.75% drop in GDP, increased unemployment in sections of rural Australia and a 9% reduction in rural exports

31. El Nino Winter

32. Decadal flow oscillations: Floods droughts and El Nino Southern Oscillation Correlation between floods/droughts and sea-surface temperatures in the Eastern Pacific (eg. Peru) Warm current Eastern Pacific = Floods in Peru = drought in Australia + failure of monsoon

34. Floods droughts and El Nino Southern Oscillation This month SOI = 7.7

36. Global Position Topography Arid Position + Flat Tropical/monsoonal Temperate