SECT. 2] LARGE-SCALE INTERACTIONS 273 



two fluids is possible. Furthermore, very small changes in the sea may have 

 vast consequences upon air circulations, of which instability is the outstanding 

 feature, as we have seen. The possibility, therefore, exists that an alteration in 

 air circulation could, if it persists, modify the surface waters in such a way as 

 to maintain itself or even to amplify with time. 



Unfortunately, this is one of the most difficult areas in geophysics to study 

 in terms of well-formulated physical laws or under controlled conditions, or 

 even quantitatively in any manner at all. One always has the uncomfortable 

 feeling that the openness of the boundaries and the processes of necessity 

 omitted may contribute so largely and nonlinearly as to invalidate almost any 

 conclusion drawn. To estabhsh any theory with real confidence, first, three- 

 dimensional data are necessary over huge regions, long periods and in both sea 

 and air together. These data range in scope from solar output throughout its 

 spectrum, down to vertical ocean motions, of the orders of meters per year 

 through the thermocline ! Such data do not exist today in a quality or quantity 

 even approaching in order of magnitude the necessary bare minimum. Nor are 

 they likely to do so in the foreseeable future. Secondly, as we can now see from 

 the restricted budget studies of carefully selected situations presented here, the 

 terms in the equations needed to examine long-period changes are the smallest 

 ones ; they are very tiny differences between the dominant terms. We are over- 

 joyed if we can evaluate these latter to within 25%. 



Occasionally, however, even if the cautions we have raised are ignored, a 

 broad sweep at an overly large phase of the interaction problem can by bold 

 intuitive hypothesis suggest what specific phases may be worth isolating later. 

 This will thus serve as an inspiration and a challenge for the necessary pains- 

 taking and far less spectacular labors required for their proper establishment 

 or rejection. We shall conclude this chapter by brief discussion of two such 

 courageous efforts concerning long-period variations, each by a man whose 

 outstanding experience-acquired intention in geophysics suggests that his 

 visions are worth careful consideration and pursuit. 



a. Interacting anomalies of several months persistence 



Until the mid-1950's, serious studies of long-period sea-air interactions had 

 more or less been abandoned since their vigorous pursuit by Helland-Hansen 

 and Nansen (1920) early in the century. Recently, renewed interest has been 

 stirred up, with impetus added by some rather obvious ocean-temperature 

 anomalies. In particular, a fairly sudden warming (up to 4°F) in the eastern 

 Pacific (Fig. 85) was noted, which began in the summer of 1957 and persisted 

 for more than a year. Among others, this caught the curiosity of Namias (1959), 

 whose experience in laying the foundations for long-range weather forecasting 

 had led to recognition of anomalous air-circulation patterns which maintain 

 themselves over similar intervals of space and time. 



His study is based on the premise that an average air-circulation picture over 

 a decade or two is a meaningful climatological "normal" which can be related 



10— s. I 



