SOUTHERN WINTER 



The winter distribution of pressure systems over the southern Pacific 

 has already been mentioned above. The eastern anticyclone sends strong 

 winds which give rise to a shearing front between 135° and 145° W. 

 when they meet the winds from the western anticyclone (Map 7b). The 

 result is the relatively high precipitation effectiveness of the Marquesas 

 in winter, much higher than that of the islands farther north or south 

 (Map 6). Between 14:5° and 155° W. the winds from both anticyclones 

 proceed in a parallel direction (•U.S.W:B., 1938), and the precipitation 

 effectiveness falls. Between 155° W., 12° S., and 150° E., 5° S. a much 

 more effective shearing front develops between the westward flow from the 

 eastern anticyclone, the west-north-westward flow from the westward 

 one, and the strong north-westward flow from the Australian v/inter 

 anticyclone under monsoonal influence (Map 7b) . It is especially over the 

 Santa Cruz and north of the Solomons that the shearing angle grows to 

 nearly 45 degrees, thus giving rise to a much more effective front than was 

 the case farther east. 



The trades which arise from the western anticyclone continue to 

 reduce the precipitation effectiveness of Fiji throughout the year. 



The eastern shearing front which affects the Marquesas in winter 

 disappears in the course of spring (Map 5) because the western anti- 

 cyclone is greatly weakened (U.S.W.B., 1938). A new feature develops 

 at this time farther south, between the Societ}^ Island and the Tubuai 

 or Austral Islands, a small anticyclone centred at about 140° W. 35° S. 



98 



