OCEANOGRAPHIC CLIMATE OF HAWAIIAN ISLANDS REGION 



397 



is absent and that the magnitude ranges from 

 to 0.6° C. mos.-'. 



The short duration and low values of negative 

 advection iiidioate that this is not important when 

 the mean annual advection is considered. Figure 

 23C shows that the latter is positive throughout 

 the region and reveals a distribution similar to 

 that of the distribution of the mean positive 

 advection. Although the trough of low positive 

 advection has other implications, it is sufficient 

 to note at this point that it may indicate a transi- 

 tion zone between two climatic regions, one in the 

 southeast portion and the other in the northwest 

 portion of the Hawaiian region. 



The next step in the analysis involved grouping 

 of the characteristic advection diagrams by sim- 

 ilarity in shape and phase. Upon examination of 

 the 60 diagrams, 2 primary, climatic regions 

 became apparent. One is located in the north- 

 west portion of the Hawaiian region (area A, 

 fig. 24), with dominant positive advection during 

 June and July and a secondary positive advection 

 peak during December and January. The other 

 climatic region is located in the southeast portion 

 of the region (area B, fig. 24), with a dominant 

 advection peak in October and November. The 

 intermediate area is under the influence of both 

 climates. The characteristic advection diagrams 

 were then combined on the basis of climatic 

 similarities and their number thus reduced to the 

 nine presented in appendix B, chart V. 



The diagram characteristic of area A shows a 

 pronounced advection peak of 3.5° C. mos."' in 

 June, which then decreases rapidh^ until the end 



Figure 24. — Climatic areas of the Hawaiian region based 

 on characteristic advection diagrams. 



of November, except foi' a period of little change 

 (hiring October. A secondary advection peak of 

 1.1° C mos.~' occurs during December and 

 January and, finally, advection reaches a minimum 

 of —0.5° C. mos."' during March. 



In area Ai, just south of area A, the June-July 

 advection peak of 2° C. mos."' and the secondary 

 peak of 1.1° C. mos."' in December-January are 

 as pronounced as in area A, and, in addition, there 

 is a secondary peak of 1.2° C. mos."' in October. 

 Area A2, just to the west of the main islands, again 

 exhibits these features: a primary peak of 1.2° C. 

 mos."' in June-July, a peak of 1° C. mos."' in 

 October-November and the third peak of 0.5° C. 

 mos."' in December-January. In area A,, advec- 

 tion reaches a minimum of —0.2° C. mos."' in 

 March and in area A2 —0.3° C. mos."' in March- 

 April. 



In area A3, east of area A, advection peaks of 

 2.1° C. mos."' in June-July, of 1.1° C. mos."' 

 in September-October and of 0.7° C. mos."' in 

 November-December are present. A small advec- 

 tion peak also occurs in Februarv-March, so that 

 this, and the shift in the occurrence of the two 

 secondary peaks, constitutes a departure from the 

 periods of A, A;, and A2. One also notes that 



-— — and -r: are superunposed or in phase during 



Maj', as is also the case in area A2, indicating a 

 period of no advection during that month. 



In area A4, which extends from the northeast 

 corner of the region through the main island 

 group, the thi-ee pronounced advection peaks are 

 again apparent. The main peak of 1° C. mos."' 

 has shifted to July-August. There is no phase 

 shift in the October-November peak of 0.8° C. 

 mos."', and the Februarj''-March peak of area A3 

 is now more pronounced at 0.5° C. per month. 

 In addition, there appears a small peak during 

 April-May. Minimum advection of —0.7° C. 

 mos."' occurs in March-April. 



If one regards the advection pattern of area A, 

 as typical, then that of area A2 shows only a slight 

 change in shape, but no change in the time of 

 advection peaks. In areas A3 and A4, one notes 

 botli a ciiange in shape and phase shift of the 

 advection peaks, wliich may be due to the barrier 

 effects of the island cliain within a varving current 

 field. 



The characteiistic advection diagram of area B 

 shows an advection peak of 1° C. mos."' during 



