Australian deserts - Climatic Change in Deserts - page 424

Figure 22.1. Digital elevation model of Australia. (From Byrne et al., 2008 .)
than 100 mm of rain a year, which is the value that is used to denote the northern
limit of the Sahara. The main factor causing aridity in Australia is its location astride
the Tropic of Capricorn, at the southern end of the Hadley Cell (Diaz and Bradley,
2004 ) in a zone of dry descending air ( Chapter 2 ). Other factors include location in
the rain shadow of the Eastern Highlands ( Figures 22.1 and 22.2 ), distance inland
and the presence of a cold ocean current off the west coast of Australia. Most of
Australia is low and flat, so orographic rainfall is restricted to the Eastern Highlands
and to the Flinders and Mount Lofty ranges in South Australia ( Figure 22.2 ). Aridity
is greatly accentuated inland with increasing distance from sources of moist maritime
air, and rainfall decreases rapidly away from the coastline ( Figure 22.3 ). About 37 per
cent of the land receives less than 250 mm/year, 47 per cent less than 375 mm/year
and 68 per cent less than 500 mm/year (Gentilli, 1977 ). The driest region is around
Lake Eyre ( Figure 22.3 ; Gentilli, 1977 ). In the arid interior, rainfall is erratic and