Because Australia is a land of meteorological and climatic extremes – of “droughts
and flooding rains” (State of the Environment Advisory Council, 1996) – it has a
large year-to-year variability. Seasonally, its northern part is subject to monsoonal
rainfall, and its southern coasts come under the influence of mid-latitude weather
systems. Yet its centre, under the climatological influence of the sub-tropical highpressure
belt, is arid and dry. During periods when the atmospheric circulation over
the whole of the Pacific Ocean undergoes an El Niño Southern Oscillation event
(an ENSO), the dryness can extend over considerable parts of the country, which
are then prone to wild fires. Conversely, in anti-ENSO years, when mid-latitude
systems are enhanced and monsoonal influences prevail, then substantial flooding
may result.