OCEANOGRAPHIC CLIMATE OF HAWAIIAN ISLANDS REGION 



379 



NORTH LATITUDE 



Figure 5. — Meridional profile of the surface temperature 

 in March and September, 10° to 30° N.: panel A, 

 153°-161° W.; panel B, 168°-17f.° W. 



surface temperature decreases in three distinct 

 steps from 80° F. (26.7^ C.) at 10° N. to 67°F. 

 (19.4° C.) at 29° N.: First, between 10° and 16° N. 

 at an average rate of 0.2° F. (0.1° C.) per degree 

 of latitude; then between 16° and 23° N. at 0.5° F. 

 (0.3° C.) per degree of latitude; and, finally, 

 between 23° and 29° N. at 1.5° F. (0.8° C.) per 

 degree of latitude. 



During September, the temperature in the 

 eastern section decreases from 80° F. (26.7° C) 

 at 10° N. to about 77° F. (25° C.) at 29° N. 

 Equivalent temperatures in the western section 

 are 82° F. (27.8° C.) and 78° F. (25.6° C). 

 Thus, there is an average decrease of 0.1° F. 

 (0.06° C.) per degree of latitude in the eastern 

 portion of the survey region and slightly more in 

 the western section. 



Although the changes in slope of the meridional 

 temperature prohh's camiot be explained at this 

 time, they nre believed to be of climatic signif- 

 icance. Tlie temperature dips in September at 

 about 15° N. in the eastern profile and about 

 13° N. in the western profile appro.>dmately 

 correspond with the position of the depth of the 

 mixed layer trough. 



Finally, figures 5A and B siiow tliat tlie annual 

 temperature range between 10° and 15° N. is 

 appro .ximately 2.5° F. (1.4° C.) both in the eastern 

 and western section of the region. This increases 

 to about 10.5° F. (5.8° C.) and 11.5° F. (6.4° C.) 

 at 29° N. in the eastern and western sections, 

 respectively, which is in good agreement with 

 the charts of Schott (1935). 



The mean zonal temperature profiles for 10° to 

 15° N., 15° to 20° N., 20° to 25° N. and 25^ to 

 30° N, for March and September are shown in 

 figure 6. For these months the temperature is 

 approximately 3° F. (1.7° C.) higher in the 

 western than in the eastern part of the region, 

 except during September for the 15° to 20° N. 

 and the 20° to 25° N. profiles, where the increases 

 are 4° F. (2.2° C.) and 5° F. (2.8° C), respectively. 



Figure 6 also shows that the westward increase 

 of temperature is not always gradual as it is 

 between 25° and 30° N. during September, and 

 between 20° and 25° N. during March. Between 

 15° and 20° N. it is stepwise both during March 

 and September. Here, proceeding westward to 

 about 157° W., the temperature decreases slightly 

 and, then, during March, rises rapidly and remains 

 fairly constant west of 160° \V. During Septem- 

 ber, the temperature tends to continue the west- 

 ward increase in a stepwise numner. 



Between 10° and 15° N. the temperature again 

 shows an initial westward decrease and, then, 

 (hu'ing March, an increase west of 160° W. 

 During September, there is an increase west of 

 157° W., followed first by a leveling off and then 

 another westward rise. 



Between 20° and 25° N. the September west- 

 ward temperature rise occurs mostly between 157° 

 and 166° W. Thus, this temperature slope and 

 those found in the eastern portion of tlu- two 

 profiles 10° to 15° N. and 15° to 20° N. nuiy be 

 of climatic significance, possibly delineating 

 boundaries between chmatic regions. 



Finally, figure 7 has been included to show the 

 seasonal temperature variation between 153° 



