Smith 



In addition to the eddies reported here, cyclonic and anticyclonic 

 eddies, 50 to 100 miles in diameter, have been reported on the lee- 

 ward side of the island chain during all seasons of the year (McGary, 

 1955, and Sechel, 1955). Some of the eddies migrated and some were 

 stationary during the periods of observation. Eddies of about this 

 same size have been observed northeast of Oahu during the winter 

 months (Sechel, 1955). 



CONCLUSION 



The oceanographic environment on the leeward side of the Hawai- 

 ian Islands is highly variable because of eddies. The eddies are 

 present consistently and to maintain individual eddy histories would 

 require a formidable number of observations. Therefore, any reli- 

 able long-term prediction of underwater sound-propagation param- 

 eters in this area is unlikely at the present time. 



The region discussed here is used as an exercise area by sur- 

 face and subsurface vessels of the U. S. Navy. Environmental par- 

 ameters such as spreading, adsorption, and reflection must be known 

 for reliable and efficient operation of advanced sonar systems. 

 Since each of these variables can be density- dependent, predictions 

 made in an area of migrating eddies might be valid for short periods 

 only. 



In view of the environmental variability of the area and the tech- 

 nological requirements of advanced underwater sound systems, it 

 is the opinion of the author that another area, perhaps east of the 

 Hawaiian Islands, should be considered for initial testing and evalu- 

 ation of such systems. After reliable operation is achieved in a 

 stable and more predictable environment, the island wake area 

 could be used. 



REFERENCES 



Barkley, R. A. and staff, 1965, "Progress in 1962-63, " U. S. 

 Bureau of Commercial Fisheries, Hawaii Area Biological Labora- 

 tory, Circular 206. 



Christensen, N. , 1966, "Determination of Currents From Instru- 

 ments Attached to the NEL Thermistor Chain, " U. S. NEL Tech- 

 Memo. No. 974, pp 15. 



Ekman, V. W. , 1905, "On the Influence of the Earth's Rotation on 

 Ocean Currents, " Akr. Mat. Astr. Fys. , 2, 11:52 pp. 



Lamb, H. , 1945, Hydrodynamics, Dover Publications. 



Long, R. R. , 1952, "The Flow of a Fluid Past a Barrier in a Rota- 

 ting Spherical Shell, " Jour, of Meteorology, Vol. 9, No. 3, pp. 

 187-199. 



413 



