8Averaged over the whole year temperature doesn’t actually vary by that much. MilduraA 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.
9Previous 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)
10Factors affecting Climate at Mildura El Niño / La NiñaIndian Ocean Dipole IOD (+/-)Southern Annular Mode SAM (+/-)Sub Tropical Ridge STRMadden Julian Oscillation (phases 1-8)Pacific Decadal Oscillation (+/-)North West Cloud BandsCut Off Lows
15Young Endeavour, March 2006 “The Rip” taken by M.Pardy
16El Niño surface temperature anomaly November 2006El NiñoCold off Darwin-QldEl Niño surface temperature anomaly
17Classic horseshoe shape of warm water for La Niña December 31st 2007La NiñaWarm off Darwin-QldClassic horseshoe shape of warm water for La Niña
18The Walker Circulation A major influence on the Australian climate El NiñoCool water north AustraliaWarm Pacific OceanWeak easterly trade windsConvection near date lineSOI negativeLa NiñaThe oppositeNeutralSea temperatures are neutral across the pacificTrade winds extend from East (South Africa) to West (Australia)Create reasonable rainfall over Eastern Australia, particularly the northern halfEl NinoWarm water in eastern pacificCool water around AustraliaReduced trade windsReduced rainfall in AustraliaLa NinaCool water in eastern pacificWarm water around australiaStrong trade winds bring rainclouds to australiaHigher rainfall in AustraliaNotice Darwin and Tahiti
33photo taken by a QANTAS navigator above Sydney Oct 2009
34PNGEcuadorWe 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
35cloudyclearDecreasing cloud around the International Date Line = la NinaThe Coral seas is still less cloudy.Indonesia has remained cloudy for the last 3 monthsVictoria is normal
36The SOI has ants in its pants el Niño warningNovember fry upCyclone OliSouthern Oscillation Index = SOI = difference in air pressure (Tahiti – Darwin)
37November 16th 2009El NiñoIn early November the Coral and Arafura sea cooled off as a result of theplunging SOI in Oct. The long awaited el Niño was finally fully coupled.This led to the much maligned fry up.
38December 31st 2009El NiñoEl 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.
39June 24th 2010xxCurrently 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.
41Southern Annular Mode, SAM or AAO The SAM index is calculated by the differences in pressure between 40o and 65o degrees latitudeSouthern Annular Mode, SAM or AAOMeasures the strength of polar westerlies in the Southern Ocean.
42The Southern Annular Mode (AAO) was more negative for the 2009 winter spring year. Negative SAMPolar winds weakerWesterlies closer to Southern AusPushes fronts more northward.But changes weekly and isn’t the absolute cause of rain in the south
43SAM 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.
44Most of the upward trend is over Summer and Autumn
47Sub-tropical ridgeThe Sub tropical ridges originate as a result of the Hadley Cells emanating from theEquator.One in each hemisphere, dry descending air causing high pressure.Mediterranean climates and deserts occur in these regions of the world.
48Sub Tropical Ridge July 2009 Winter pattern, centre of highs over the top of the BightJan 2009Sub Tropical RidgeThe High pressure belt lying over Australia and at all mid latitudes of the world.Summer pattern, centre of highs over Melbourne
49The 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
50For most of the month of June the STR has been in a favourable position but the strength of the high pressures has been greater.
51Increased high pressure systems in the last 50 years