278 MALKUS [chap. 4 



changes as too small to contribute significantly. His final tentative conclusion 

 was that the long period of warm water off the California coast resulted from a 

 combination of atmospherically induced factors : the summer and early fall 

 warmth associated with diminished upwelling and evaporation, with a slight 

 contribution from increased solar radiation (fewer stratus clouds than normal) ; 

 and the late fall and winter warmth mainly associated with surface advection 

 of warmer water and somewhat reduced upwelling. 



A fascinating feature of the study was the continuity and seasonal migrations 

 of the anomalous patterns in both sea and air, which, while remaining strong 

 and identifiable, moved eastward from the summer through fall and winter. 

 As summer goes into fall, two climatological phenomena are highly probable : 

 (i) the westerlies over the Pacific increase in strength, and (ii) the trough along 

 the east coast of Asia becomes established. These phenomena are associated 

 with increased cyclonic activity off the Asiatic coast, incident to the monsoon 

 outbursts we have described previously. The cyclones forming in the intense 

 thermal gradients of this region travel toward the Aleutians as they develop. 

 Thus the trough off Korea becomes "locked" into this position with the ap- 

 proach of winter. The increasing westerlies then require a dynamic readjustment 

 in the planetary wave pattern (Rossby, 1939) to move the next downstream 

 trough farther away or toward the east. If such a hypothesis contains a germ 

 of truth, one is led to the most important resulting question, namely, why did 

 the anomaly centers and mean troughs have such long lifetimes? 



Namias suggests a coupled feed-back mechanism between air and sea. In the 

 first place, the abnormally warm water in the eastern Pacific provides an 

 enhanced source of both heat and moisture to aid cyclonic development by 

 imposed convective ascent, as suggested by Winston's work. The longitudinal 

 water contrast, by enhancing horizontal temperature gradients in the over- 

 lying air-masses, may also assist cyclonic developments, which draw heavily on 

 the stored potential energy in sharp thermal contrasts or fronts. In other words, 

 incipient cyclones moving over these abnormal waters could feed on the in- 

 creased moisture, sensible heat and temperature contrast imparted to the air, 

 so that a more or less geographically fixed area favors cyclogenesis and pre- 

 vailingly negative anomalies. However, the area of influence would also be 

 affected by climatic conditions involving the general atmospheric circulations 

 (as indicated above) and thus might move with time. That is, the air circulation 

 responsible for the underlying temperature variations might change because of 

 factors more potent than those produced solely by water anomalies. In fact, 

 the shift of the latter, apparently in response to seasonal changes in air patterns, 

 suggests that the upper ocean layers respond rather rapidly to atmospheric 

 variations and that their anomalies have less inertia than previously suspected. 

 Their persistence thus may signify a balance between rather rapid growth and 

 destruction governed by dynamic processes rather than the existence of inert 

 "puddles" of warm and cold water. 



An exciting support of this last suggestion, which has significant practical 

 consequences, arises when we learn that 1957-58 was a catastrophic "El Nino" 



