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Climate of Australia

Climate of Australia. Ian Rutherfurd. World rainfall. Global Position Topography. This lecture …. Context of Australia Summary of climate Aridity Present climate pattern ENSO. Two climatic zones.

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Climate of Australia

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  1. Climate of Australia Ian Rutherfurd

  2. World rainfall

  3. Global Position • Topography

  4. This lecture … • Context of Australia • Summary of climate • Aridity • Present climate pattern • ENSO

  5. 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

  6. General controls on Australian climate: Aridity(33% arid, 75% semi-arid1 million km2 of sandplain) • Global position • Flat

  7. Northward drift: 50 – 60 m.y.

  8. 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

  9. Circum-polar current

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

  11. Consequences of aridity … • Landforms • Vegetation • Animals

  12. Palaeo-drainage lines of WA

  13. Linear Dunefields

  14. 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 km2 mainland)

  15. Glaciation

  16. Tropical/monsoonal Australia

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

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

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

  20. 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

  21. 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

  22. El NinoWinter

  23. 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

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

  25. Arid • Position + Flat • Tropical/monsoonal • Temperate • Global Position • Topography

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