90 



FREQUENCY OF WAVE CONDITIONS 



especially if a sea of any considerable size is running upon it, as so 

 commonly happens. 



No reports of swell were received for the Sea of Okhotsk for Jan- 

 nary or February. In the Japan Sea, a high swell is more common 

 in winter (0 to 10 percent) than at the end of the summer (0 percent). 

 Little change take place, however, in this respect, from summer to 

 winter at the mouth of the Yellow Sea, while the most noticeable alter- 

 ation, in the swell pattern of the South China Sea, from the one sea- 

 son to the other, is that the belt where a high swell is the most com- 

 mon (upwards of 10 percent) withdraws northward, away from the 

 coasts of Borneo and of Palawan. And the frequency with which 

 the surface has been reported as wholly free from swell, alters but 

 little from summer to winter in any partially enclosed seas of eastern 

 Asia (table 23). 



Table 23. — Percentage frequency with which unit areas of the Japan and South 

 China Seas have been reported wholly free from swell in summer and winter 



SOUTH PACIFIC 



The reports from the South Pacific were so few in number that it 

 is doubtful whether such month-to-month differences as they indicate 

 are of much significance, while large areas are necessarily left blank 

 on the charts (pis. IX to XVI) . Combination, however, of the reports 

 for July with those for August, yields a pattern consistent enough to 

 be accepted as representative of the late summer state. 



Features of the July- August charts (pis. IX and X) of special 

 interest are: (a) the demonstration that the west equatorial smooth 

 belt (contour for 60 percent "low" seas) is confined even more closely 

 to the vicinity of the equator in the Southern Hemisphere than in the 

 Northern; (b) the delineation of the approximate boundaries of the 

 midequatorial '"pool" where high seas are reported during more than 10 

 percent of the time at that season of the year, with waves even as large 

 as 20 feet occasionally (p. 88) ; and (c) the illustration of the pre- 

 vailing roughness, in general, of the southern half of the South Pacific 

 during the months in question, when winds averaging up to 16 to 18 

 miles per hour in velocity, northward as far as about latitude 30° S., 

 generate high waves more than one-fifth of the time, equatorward past 



