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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



associated with certain physical processes. Or, 

 if the space and time distribution of surface vari- 

 ables is known, then one should be able to obtain 

 some information about the physical processes. 

 To be more specific, one can formulate a heat 

 budget and say that the rate of change of heat 

 content in the surface water (approximately pro- 

 portional to the surface temperature) must depend 

 on the rate at which heat enters or leaves across 

 the sea surface, the diffusion (a change of concen- 

 tration due to mixing), and advection (a change 

 of concentration due to currents introducing 

 water with different properties). Similarly, one 

 should be able to formulate salt budgets in which 

 evaporation and precipitation at the surface must 

 be considered and, possibly, momentunt budgets in 

 which the surface wind stress must be considered. 



Such an approach has been described in the 

 chapter on the Theory of Distribution of Vari- 

 ables in the Sea, bj' Sverdrup et al. (1942). In 

 practice, of course, the formulae presented there 

 must be simplified before application. However, 

 the equations state that whenever physical proc- 

 esses are to be related to the distribution of vari- 

 ables, such as temperature, salinity, momentum, 

 oxygen, and phosphate, the following data must 

 be available about the variable in question: 

 (1) the local-time rate of change and (2) the three- 

 dimensional space distribution. This require- 

 ment, as it concerns the heat budget of the surface 

 water in the Hawaiian Islands region, can be 

 satisfied by using all the available data mentioned. 



In weather analysis, the seasonal changes in 

 temperature at any location are explained in 

 terms of solar energy received and in terms of 

 the motions of high- and low-pressure systems. 

 In central North America, for example, the cold, 

 dry, winter weather is associated with the south- 

 ward motion of the polar high pressure system. 

 In summer, as this system's boundaries move 

 northward, the cold, dry air is replaced by the 

 maritime-tropical air moving inland through the 

 Gulf of Mexico producing warm and highly 

 humid weather. This type of weather analysis 

 is called climatology and, therefore, by analogy, 

 the investigation to be described here can be 

 called "climatic oceanography." 



In order to study the oceanographic climate of 

 the Hawaiian Islands, the results of previous 

 surveys (McGary, 1955; Seckel, 1955) made it 

 evident that an area larger than the immediate 



vicinity of the main Hawaiian Islands must be 

 chosen. Natural boundaries for this area, to be 

 referred to as the Hawaiian region, are the vicin- 

 ity of the northern edge of the equatorial counter- 

 current, or 10° N., and the vicinity of the salinity 

 maximum, or 30° N. In the west, the 180th 

 meridian was chosen, and in the east, lack of 

 data limited the area to 150° W. 



For this region, then, the climatic study will 

 be divided into two parts. First, the distribu- 

 tion of surface parameters, such as the depth of 

 mixed layer, temperature, salinity, and geopo- 

 tential topography, will be described essentially 

 without interpretation. Second, the processes 

 with which these parameters are associated will be 

 investigated. Because adequate salinity and cur- 

 rent data are lacking, the present paper will pri- 

 marily be concerned with the processes of heat 

 exchange across the sea surface and heat advec- 

 tion as they are related to the distribution and 

 rate of change of temperature throughout the 

 region. 



In the course of the analysis, "characteristic 

 advection diagrams," "characteristic heating 

 curves," and "intrinsic temperatures" will be 

 defined. It will tlien be shown how these can be 

 used to interpret continuous surface temperature 

 data, such as are obtained at the Koko Head 

 monitoring station on Oahu. 



The final portion of the analysis will consist of 

 an integrated account of the. oceanographic 

 climate of the Hawaiian Islands region. Here 

 features of interest described in part I will, as far 

 as is possible, be explained by the processes de- 

 scribed in part II. Readers who are primarily 

 interested in the results of the study can proceed 

 directly to part III, and turn to parts I and II for 

 details of the analysis. 



The sources of data will be indicated in the 

 Appendix, with an account of the manner in 

 which they were treated. 



Finally, the aims of the study have been 

 achieved. Despite the fact that the data used do 

 not readily lend themselves to an analysis of 

 processes because they were collected for other 

 purposes, over a period of years, at unrelated 

 times and places, and in an area where their 

 seasonal and annual variations are of the same 

 order of magnitude, a gross picture of the oceano- 

 graphic climate in the vicinity of Hawaii has been 

 developed. 



