When positive, there is cooler than normal water in the tropical eastern Indian Ocean and warmer than normal water in the tropical western Indian Ocean. The Indian Ocean Dipole (IOD) is a measure of the difference in sea surface temperature in the western and eastern equatorial Indian Ocean. For example, 20, the wettest two year period on record, were dominated by strong La Niña conditions and damaging floods occurred in several areas in Queensland.įor more information, see some of the BoM resources on ENSO: El Niño events generally occur every two to seven years.ĭuring a La Niña, the typical easterly winds across the Pacific are strengthened, bringing above average rainfall to much of Australia, and sometimes flooding. An El Niño generally brings drier conditions and warmer temperatures to much of eastern Australia, and if prolonged, can lead to drought. When this typical pattern is disrupted, and the winds weaken or even reverse, we describe the event as an El Niño. Source: © Commonwealth of Australia 2010, Bureau of Meteorology ( Accessed 16 March 2016.Įl Niño-Southern Oscillation (ENSO): The winds over the Pacific Ocean close to the Equator typically blow from east to west (and their strength is measured by the Southern Oscillation Index, or SOI).
Time zones in australia drivers#
These drivers affect the weather, especially rainfall, in Australia over different regions and seasons.įigure 2: Drivers and influences of Australia’s climate.
the Australian monsoon and the Madden-Julian Oscillation. Drivers of Australia’s climateĪ number of large-scale features in the global climate system affect Australia’s climate (see Figure 2). For many parts of Australia, the frequency and intensity of extreme weather events is an important characteristic of climate for planning and decision-making. More than 80% of the continent has an annual average rainfall of less than 600 mm, although in the Wet Tropics this figure can rise to 1,200 - 8,000 mm.ĭetailed information on Australia’s climate can be found on the Bureau of Meteorology website at (accessed 15 March 2016).Īustralia’s climate can vary greatly from one year to the next, driven by changes in the large-scale atmospheric circulation (see next section), and this in turn can lead to extreme events such as droughts, heatwaves, fires, intense rainfall and floods. In this region, there are four distinct seasons with a more marked temperature contrast between summer and winter.Īs a whole, Australia has a relatively low rainfall. Temperate climates span the coastal hinterland of New South Wales, much of Victoria, Tasmania, the south-eastern corner of South Australia and the south-west of Western Australia. In contrast the dry season between April and October is cooler, with average temperatures a little over 20 oC, and drier. Heavy rainfall in this season often causes flooding. The wet season, which occurs from November to March, is known as the Monsoon season in the Tropics, and is hot (maximum temperatures often above 30 oC, and higher inland) and humid. In these regions there are distinct wet and dry seasons, each lasting about six months. Tropical climates include the equatorial and sub-tropical regions in Figure 1 and are found in the north and north-east of Australia. Source: © Commonwealth of Australia 2014, Bureau of Meteorology ( Accessed 17 March 2016. Figure 1: The major climatic zones of Australia.
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