Three forces dry out Australia and leave its middle empty
The continent is the driest place people live, and its rainfall map looks just like its population map.
RealLifeLore · Why 95% of Australia is EmptyLook at a map of rain in Australia and a map of people in Australia, and they are nearly the same map. Most rain falls in a narrow band along the east coast, in the tropical north, around the southwestern corner near Perth, and in Tasmania. Almost everyone lives in those same wet fringes, because three separate forces all work to dry out everything in between.
The first force comes from the west. Cold currents rise from the Southern Ocean near Antarctica and run along Australia's western coast. Cold water does not evaporate easily, so there is too little heat and moisture to build large storm clouds across the western half of the country.
The second force comes from the Pacific side. A long chain of peaks called the Great Dividing Range, Australia's longest chain of mountains, stretches almost the full length of Australia's eastern coastline. Storms moving in from the Pacific hit those mountains and drop their rain on the narrow strip between the peaks and the sea. Behind the mountains, to the west, lies a so-called rain shadow, a vast interior where air arrives after it has already lost most of its moisture.
The third force comes from above. Much of Australia sits in the tropics and subtropics, under a band of high pressure air that circles the globe. High pressure air sinks, and as it sinks it warms and dries, making it harder for clouds to form even when hills push air upward. Australia is also unusually flat and low, so it has few tall peaks that can force air high enough to cool into rain.
Every few years, a climate pattern called El Nino makes it all worse. During El Nino, westerly winds across the southern Pacific weaken, carrying less moisture to eastern and northern Australia, prolonging drought. Many of Australia's worst bushfires have burned during those dry spells.
Together, these forces make Australia the driest inhabited continent on Earth, with deserts or desertlike country covering about 35 percent of its area. The interior is not empty by accident. The air and the oceans leave it with too little water to support cities.
Questions people ask
What exactly is a rain shadow?
A rain shadow is the dry area behind a mountain range. Moist air is forced upward by the peaks, cools, and drops rain on the windward side. By the time the air descends on the far side, it is drier and warmer, so less rain falls there.
Why does cold ocean water mean less rain?
Rain starts with evaporation, and warm water evaporates much faster than cold water. Cold currents off Western Australia keep the overlying air cool and stable, so fewer clouds form. The same effect helps create other coastal deserts, including the Atacama in Chile and the Namib in Africa.
What is El Nino?
El Nino is part of a natural cycle in the tropical Pacific in which sea temperatures and winds shift every few years. During El Nino, trade winds weaken and warm water shifts eastward, changing where storms form. For Australia, it often means less rain, hotter weather, and a higher risk of drought and fire.