The Geographical Processes Associated with drought

Drought is the denouement of a prolonged period of high pressure systems over the land surface which lack moist air.

When temperatures in the Pacific Ocean augment an average of 0.5 Degrees Celsius, and is suspended for less than 5 months, it is classified to be an El Niño. El Niño's warm ocean currents can raise the surface pressure over Australia inaugurating drought where ever it goes. The Southern Oscillation is the atmospheric component of El Niño. It is a major air pressure shift between the Asian and east Pacific regions and is measured in SOI (Southern Oscillation Index). Meticulously, when the pressure measured at Darwin is compared with that measured at Tahiti, the difference between the two can be used to initiate an "index" number. When there is a positive number, we have a La-Niña (or ocean cooling), but when the number is negative we have an El-Niño (or ocean warming).

Some have put the accountability of Australia's increasing drought period on the phenomenon of global warming. Global Warming is the increment in average temperatures of the earths near-surface air and oceans. Global warming can deminish the possibility of rainfall and the rising temperatures amplify evaporation resulting in decreasing water levels in dams, rivers and reservoirs. With the limited avaliablity of water drought will ensue.

The Indian Ocean Dipole (IOD) is another oceanographic phenominon which manipulates the climate of Australia. The IOD has three phases - positve, neutral and negitive. In the positive phase, greater than average sea-surface tempreatures along with greater rainfall, is present in the western Indian Ocean region. Also the waters of the eastern Indian Ocean are cooled. All this results in drought in Australia as it is contiguous to the Indian Ocean. The Opposite happens in the negitive phase of the IOD, with the Indian Ocean experiencing warmer sea-surface tempreatures with greater rainfall and Australia subjected to cooler drier conditions.

In 2009, a study by Ummenhofer et al. at the University of New South Wales authenticated that every major South Australian Drought in 1889 has coincided with a positive/neutral IOD oscillation. The IOD positive phase influences drought by weakening winds which transport moisture across south Australia which, in turn decreases the average rainfall in that area, inducing drought.