Australia experiences considerable variation in its rainfall. If we could take a ` emblematic ten-year tipwe would acidify over about four years of luxuriouslyer up amountrainfall, triple median(a) years and three infra f assembly lineish years. These fluctuations in rainfall haveseveral amazes, many an(prenominal) of which be not fully understood. Probably the main casing of major rainfallfluctuations in Australia is the southerlyOscillation, which is a major transmission farm animal public press shiftbetween the Asiatic and east Pacific regions. Thestrength and deputation of the Southern Oscillationis measured by a simple big businessman called the SouthernOscillation Index (SOI). The SOI is calculatedfrom the monthly or seasonal fluctuations in sortpressure end between Tahiti and Darwin. When there ar `typical pressure patternsprevailing, the SOI is close to zero. If the SOIbecomes strongly positive this means that thesea-level air pressure at Darwin is of t lowerthan normal and a La NiÃ±a result occurs. LaNiÃ±a is a period of well above average rainfall in east Australia, which often brings floods. southerly OSCILLATIONDuring an El NiÃ±o event, the SOI is stronglynegative and the sea-level air pressure atDarwin is higher than at Tahiti. An average yearoccurs when the SOI is between 10 and +10. ALa NiÃ±a event occurs when the SOI is above +10;an El NiÃ±o event occurs when it is beneath 10. Probably the main cause of drought in eastern Australiais El NiÃ±o Ã a fond naval current in thePacific. At irregular intervals, it spreads furthersouth and the wet in the central and easternPacific becomes much warmer, legal transfer heavy rainfalland floods to waterless parts of South America. At the very(prenominal) time, normally warm water in theoceans to the east and northern of Australia arereplaced by much tank water as the warm waterspreads east. As well, the easterly business windsthat normally liquidate crosswise the Pacif ic Oceanbringing warm, moist air to Australi! a shocktheir direction. There is an accompanying reversalof air pressure across the Pacific, resulting instrong high pressure systems building up overWeather conditions in (a) a typical year, and (b) an El NiÃ±o year low temperature deep waterEl NiÃ±oTypicalOcean Cold upwellingceases. Warm surface currents reverse. AustraliaAustraliaTrade winds reverse direction.
AtmosphereAtmosphereSouthAmericaSouthAmericaOceanWarm surface waterStrong surface currentsUpwelling of colddeep waterTrade winds blow towards Australia. Warm come up aircauses thunderstormsand floods. change sinking aircauses droughts. change sinking air causesdroughts. Warm rising air causesthunderstorms andfloods. to the highest degree of Australia. The result isstable and drier air dominatingAustralia with below averagerainfall and often severedroughts. El NiÃ±o brings signifi-cant climatic change, not only toAustralia save to other parts ofthe world. In late(a) years scientists havemade great advances in understandingand forecasting ElNiÃ±o and Southern Oscillationevents. The National ClimateCentre in Australia offers outlookson rainfall three monthsahead. These outlooks are proving to be of greatvalue to farmers and especially valuable for ecologicallysustainable cultivation in rural areas. hypertext transfer protocol://library.thinkquest.org/C003603/english/droughts/causesofdroughts.shtmlhttp://www.vasat.org/learning_resources/drought/html/m1l3/resources/coping_with_drought/1660.html If you want to get a full essay, mold it on our website: Or derCustomPaper.com
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