What influences Australia’s water variability? The unique characteristics of Australia’s rainfall patterns are largely due to the influence of two equally unique climate events — El Niño and La Niña. El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific, known as the El Niño–Southern Oscillation, or ENSO for short. El Niño and La Niña Australian droughts are heavily influenced by what meteorologists call an El Niño event. In a normal year, warm surface water is blown west across the Pacific Ocean towards Australia. This brings heavy rain to northern Australia, Papua New Guinea and Indonesia. On the other side of the Pacific, South America experiences drought. When an El Niño event occurs, these winds and surface ocean currents reverse their direction. The warm, moist air is pushed towards South America, producing rain in South America and drought in Australia.
FIGURE8 Weather events in (a) a typical year and (b) an El Niño year
Warm rising air causes thunderstorms and floods.
(a)
Dry sinking air causes droughts.
Atmosphere
Trade winds blow westwards.
Australia
South America
Strong surface currents
Warm surface water
Upwelling of cold deep water
Ocean
Warm rising air causes thunderstorms and floods.
(b)
Dry sinking air causes droughts.
Atmosphere
Trade winds reverse direction.
Australia
South America
Warm surface currents reverse.
Cold deep water
Ocean
Cold upwelling ceases.
TOPIC9 Water in the world 275
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