286 



POLAR PROBLEMS 



AUSTRALIAN CLIMATE AND WEATHER 



We may first of all consider the salient features of the Australian 

 climate and weather. Australia is the continent that is marked by 

 the simplest topography of all. It has a very low general elevation 

 and has a very simple coast line, so that it lies like an oval "black- 

 board" ready to assist in the elucidation of climatic problems. The 

 essential features in the climate can be grasped from a consideration 

 of the construction shown in Figure 2. Here the two belts of depres- 

 sions (lows, or rain- 

 storms) are labeled 

 monsoonal (or tropical) 

 and Antarctic rains re- 

 spectively. Between 

 them is the dry region 

 of the anticyclone "cen- 

 ters" (in the south) 

 and the dry region in 

 the belt of trade winds 

 (in the north). Thus 

 the climatic sequence 

 is (i) tropical rains, (2) 

 trade winds arid belt, 

 (3) anticyclone arid 

 belt, and (4) Antarctic 

 rain belt. 



If we now imagine 

 that these climatic 

 belts remain more or 

 less anchored to a sta- 

 tionary sun and imag- 

 ine further that the 

 continent of Australia 

 (beneath the climatic belts) swings north and south in accord with 

 the tilt of the earth's axis, then the actual changes in climate and 

 rainfall are very near to those indicated in our figure. In summer 

 Australia has a position to the north right under the sun. It falls under 

 the influence of the tropical rainstorms in the north, the trade winds 

 in the center, and the dry anticyclone belt in the south. In winter we 

 may picture the tilt of the axis swinging Australia south to the position 

 noted. In winter the trade winds occupy most of the north of 

 Australia, the anticyclones cross the center, and the heavy Antarctic 

 rains affect the south coast. 



Such, then, are the salient climatic controls in Australia. The 

 winds blowing along the northern margins of the anticyclones are 

 easterlies and are in accord with the trade winds. Both are drying 



Fig. 2 — Seasonal changes in Australia. The continent is sup- 

 posed to move from the summer position to the winter position 

 under the atmospheric belts. (After frontispiece in the writer's 

 "Australian Meteorology," Oxford, 1920.) 



