ANTARCTIC INFLUENCES ON AUSTRALIAN CLIMATE 



287 



HOT MONTHS OCT.-MAR, 



— "Highs 



Antarctic_ 

 -— 22 



COOL MONTHS APR.-SEPT. 

 6 



~ Antarctic 

 41 



Fig. 3 — Percentage in year of lows along the tracks indicated. 

 (N.B. About 30 highs also cross Australia in each six months.) 



winds over all the continent (except the actual east coast). Hence 

 arise the permanently arid center of the continent and the arid 

 northern winter and the arid southern summer. 



The weather of Australia — as opposed to the climate — depends 

 on the passage of the atmospheric eddies of high and low pressure. 

 They occur in three belts as already mentioned. The tropical lows, 

 or depressions, are very much more numerous (25 per cent) in the hot 

 months (see Fig. 3), and more than half of them move to the south- 

 east across West Australia. In the colder months occur about 16 

 per cent of these tropicals, almost wholly down the eastern half of 

 Australia. The Ant- 

 arctic lows are very nu- 

 merous (41 per cent of 

 the whole) in winter 

 and affect the south 

 coast strongly. In the 

 hot months the tracks 

 of the Antarctic storms 

 lie far to the south and 

 can only be approxi- 

 mately indicated in the 

 daily charts. More- 

 over, in summer only 



the northern margins of cyclones to about half the number of ,winter 

 Antarctic lows (i. e. 22 per cent) affect Australia in this season. 



It is in regard to these Antarctic low-pressure eddies that we 

 come closest into touch with conditions in the Antarctic Continent. 

 Before considering other aspects of the Australian climate we may 

 properly discuss the form of these Antarctic lows so far as we know 

 them. The Australasian Antarctic Expedition of 1911-1914 was of 

 particular importance in this connection, because it maintained a 

 meteorological station upon Macquarie Island. This lies about 

 halfway between New Zealand and Antarctica, and the station was 

 in charge of Mr. Ainsworth, an officer of the Commonwealth Weather 

 Bureau. In Figure 4 (taken from Mawson's "The Home of the 

 Blizzard") we see the isobars as plotted from stations in Tasmania 

 (latitude 41°), New Zealand (46°), Macquarie Island (54°), and 

 Adelie Land (Mawson's base at 66° S.). An intense cyclone is centered 

 just to the southwest of Macquarie Island, which registered a reading 

 of 28.34 inches, with strong northeast winds. The Commonwealth 

 meteorologist states that the barometer on the island fell from 29.49 

 at 9 A. M. on April 11 to 27.91 at 6 p. m. on April 12. At Adelie 

 Land the barometer rose from 28.70 to 28.90 as the cyclone passed 

 (eastward) to the north. 



In the course of the years 1912 and 191 3 a number of lows of 



