ARID PORTIONS OF SOUTH AUSTRALIA. 



45 



per cent of the total for the year. The average rainfall at Copley is 

 about 8.7 inches. At Oodnadatta, where the rainfall is 4.85 inches, the 

 percentage falling in the months mentioned is about the same as at 

 Copley. 



The periodic rainfall in the southern and central portions of South 

 Australia and the more equable distribution in the north are directly 

 related to the seasonal north-south shifting of the climatic complex. 



1903 1905 

 1902 1904 t906 



1903 1905 

 1902 1904 1906 



1901 1903 1905 



1902 1904 1906 



Fio. 11. — Grapha showing the annual (total) and "non-effective" rainfall for 1901-1906 at 

 Oodnadatta (a), Copley (b), and Quorn (c), South Australia, based on recordi 

 supplied by the Adelaide office of the Commonwealth Bureau of Meteorology. 



As Taylor graphically shows (1918: Solar control model), the pre- 

 vailing Une of the center of high pressures in mid-winter coincides 

 nearly with the northern boundary of South Australia, but in midsum- 

 mer it is far south of the state. The prevailing winds in summer, 

 therefore, are from the east, or southeast, and are drying winds. But 

 at this time occasional lows from the northern part of the continent 

 may extend far to the south, reaching the northern part of South 

 Australia, bringing rain. In winter, however, the center of highs, as 

 before remarked, crosses the extreme north of the state, the belt of 

 westerlies touches the extreme south, and a belt of variabes lies be- 

 tween. The dry easterlies are now far to the north, and rain occurs in 



