1. Drivers of Climate at Mildura
Dale Grey DPI Cobram Mildura Cropping Agronomist Tuesday, 29th June 2010

3. Annual

4. Annual- 5 year moving average
WWII
Federation
Annual- 5 year moving average

5. Summer
Autumn
Winter
Spring

6. Summer
Autumn demise
Winter
Spring

7. Top of the Goulburn Catchment
Autumn

8. Averaged over the whole year temperature doesn’t actually vary by that much.
Mildura
A 1 degree difference over a year is a massive change.
It could mean the equivalent of 38 extra winter days or 15 extra summer days crammed into the year.

9. Previous droughts have not been as hot.
5 Year moving average of annual rainfall (Mildura)
Previous droughts have not been as hot.
5 Year moving average of annual Max temp anomaly (Mildura)

10. Factors affecting Climate at Mildura
El Niño / La Niña
Indian Ocean Dipole IOD (+/-)
Southern Annular Mode SAM (+/-)
Sub Tropical Ridge STR
Madden Julian Oscillation (phases 1-8)
Pacific Decadal Oscillation (+/-)
North West Cloud Bands
Cut Off Lows

11. Word for the Day
Anomaly- deviation from normal

12. First Some Oceanography 101

13. Argo Robotic Buoy
Satellite
Ships of Opportunity
RAMA

14. 29oC
13oC

15. Young Endeavour, March 2006 “The Rip” taken by M.Pardy

16. El Niño surface temperature anomaly
November 2006
El Niño
Cold off Darwin-Qld
El Niño surface temperature anomaly

17. Classic horseshoe shape of warm water for La Niña
December 31st 2007
La Niña
Warm off Darwin-Qld
Classic horseshoe shape of warm water for La Niña

18. The Walker Circulation A major influence on the Australian climate
El Niño
Cool water north Australia
Warm Pacific Ocean
Weak easterly trade winds
Convection near date line
SOI negative
La Niña
The opposite
Neutral
Sea temperatures are neutral across the pacific
Trade winds extend from East (South Africa) to West (Australia)
Create reasonable rainfall over Eastern Australia, particularly the northern half
El Nino
Warm water in eastern pacific
Cool water around Australia
Reduced trade winds
Reduced rainfall in Australia
La Nina
Cool water in eastern pacific
Warm water around australia
Strong trade winds bring rainclouds to australia
Higher rainfall in Australia
Notice Darwin and Tahiti

19. PNG
Ecuador
Thermocline flat
El Niño
Sub-surface

20. La Niña
Sub-surface
Thermocline sloped

21. World Cloudiness, 2002 El Niño Becomes cloudier at the dateline
cloudy
clear
World Cloudiness, 2002 El Niño
Becomes cloudier at the dateline

22. World Cloudiness. 2007 La Niña Lack of cloud at the date line
cloudy
clear
World Cloudiness La Niña Lack of cloud at the date line

23. Equatorial Wind
El Niño top, trade winds switch to the West
La Niña bottom, winds strengthen to the East

24. Worldwide effects of La Niña and El Niño

25. Indian Ocean Dipole Positive (IOD +ve)

26. Indian Ocean Dipole Negative (IOD -ve)
No IOD- since 1992

27. August 2006
Cool Broome-Brisbane
IOD+

28. September 26th 2007
IOD+
Weak one

29. June 30th 2008
Cool Broome-Brisbane
IOD+

30. September 29th 2008
IOD’s tend to decay from east to west in late September-October

31. El niño
19 years
23 years
La niña
27 years
16 years

32. El niño
17 years
20 years
La niña
24 years
16 years

33. photo taken by a QANTAS navigator above Sydney Oct 2009

34. PNG
Ecuador
We had progress of the cool counter current above the thermocline westwards.
Rapid breakdown from warm to neutral at the surface.
Thermocline now tilting.
Large cold anomalies at depth

35. cloudy
clear
Decreasing cloud around the International Date Line = la Nina
The Coral seas is still less cloudy.
Indonesia has remained cloudy for the last 3 months
Victoria is normal

36. The SOI has ants in its pants
el Niño warning
November fry up
Cyclone Oli
Southern Oscillation Index = SOI = difference in air pressure (Tahiti – Darwin)

37. November 16th 2009
El Niño
In early November the Coral and Arafura sea cooled off as a result of the
plunging SOI in Oct. The long awaited el Niño was finally fully coupled.
This led to the much maligned fry up.

38. December 31st 2009
El Niño
El Niño peaks. At Nino 3 and 3.4 areas of the Pacific were 1.5 and 1.9oC warmer. Much of the ocean to the north was warm.
There was a lack of gradient in the Indian Ocean.

39. June 24th 2010 x x
Currently the Nino 3, 3.4 and 4 areas of the Pacific are -0.35, and -0.02oC warmer, near the -0.8 threshold. The DMI measurement of the IOD is which is neutral.

40. Harvest time, North Dakota Oct 2009

41. Southern Annular Mode, SAM or AAO
The SAM index is calculated by the differences in pressure between 40o and 65o degrees latitude
Southern Annular Mode, SAM or AAO
Measures the strength of polar westerlies in the Southern Ocean.

42. The Southern Annular Mode (AAO) was more negative for the 2009 winter spring year.
Negative SAM
Polar winds weaker
Westerlies closer to Southern Aus
Pushes fronts more northward.
But changes weekly and isn’t the absolute cause of rain in the south

43. SAM has been positive for the last 6 weeks
There is more usefulness in the SAM during winter.
Its more positive Autumn in the last 25 years has been partially blamed for poor Autumns.
+SAM can significant lead to a wetter summer in E Gippsland.
The up and downs over summer in haven’t really affected Victorian rainfall.

44. Most of the upward trend is over Summer and Autumn

45. 10 years
+SAM
13 years
-SAM

46. 10 years
+SAM
13 years
-SAM

47. Sub-tropical ridge
The Sub tropical ridges originate as a result of the Hadley Cells emanating from the
Equator.
One in each hemisphere, dry descending air causing high pressure.
Mediterranean climates and deserts occur in these regions of the world.

48. Sub Tropical Ridge July 2009
Winter pattern, centre of highs over the top of the Bight
Jan 2009
Sub Tropical Ridge
The High pressure belt lying over Australia and at all mid latitudes of the world.
Summer pattern, centre of highs over Melbourne

49. The Sub Tropical Ridge for the month of May was normally positioned and pressure was lower than normal, the ridge down to Tasmania wasn’t helpful

50. For most of the month of June the STR has been in a favourable position but the strength of the high pressures has been greater.

51. Increased high pressure systems in the last 50 years

52. 30 years
27 years
28 years
27 years

53. 30 years
24 years
20 years
24 years

54. A January 2010 day at Metung

55. The latest “Fast Break” analysis for the next three months
Pacific cool (La nina)
Indian slightly warm
Rainfall Average-slightly wetter
Slightly warmer temps

56. The “Fast Break” analysis
for four to six months
Pacific cool (La nina)
Indian slightly warm
Rainfall Slightly wetter
Average- slightly warmer temps

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