SOUTHE fN AUTUMN 

 4 K 



followed by spring and autumn. Winter (Map 6) has the lowest precipita- 

 tion effectiveness, less than one-half of that of summer. This seasonal 

 pattern is quite different from the one shown by the Line Islands, of 

 which Maiden was quoted as an example. It resembles the seasonal 

 pattern of the Gilbert Islands, much farther west. It may be advisable 

 to seek a common factor underlying these similar patterns. 



This factor is provided by the wind pattern (U.S.W.B., 1938). In 

 the southern summer (Map 7a) the outflowing iVsiatic monsoon causes 

 a deflection of the north-east trades, which are greatly strengthened and 

 are able to advance beyond the Equator as far as 175° W. and 15° S. 

 in February. The intertropical front runs farther north than was postu- 

 lated by Bergeron and other authors (Miller, 1946 ; Haurwitz and Austin, 

 1944), approximately along the boundary between Papua and the Terri- 

 tory of New Guinea, south of the Solomons, north of the New Hebrides 

 to a point between the New Hebrides and Fiji, then north' of Fiji 

 to Samoa and Pukapuka. It is important to note that the western 

 anticyclone of the South Pacific is well developed in summer, and its 

 north-westward winds blow steadily as far as Fiji, which is thus 

 kept relatively dry. These winds do not quite cover the New Hebrides, 

 and thus allow the air masses from the Northern Hemisphere to sweep 

 over these islands at times. In other words, the intertropical front is 

 well stabilized north of Fiji, and moves slightly north and south 

 over the New Hebrides, although its average position in February- is 

 just to the north of these islands. 



96 



