272 MALKUS [chap. 4 



1 meal cm"" 2 sec ^ if the conservative value of 50 g cm i sec~' for the coefficient 

 of turbulent mass exchange is placed in the heat diffusion equation (12). As the 

 airplane gives the net heat flow in the atmosphere, it is apparent that a down- 

 ward flux should be obtained from its records, as indeed it was. Thus the strong 

 mean subsidence behind the front, which unfortunately could not be estimated, 

 preserved the great stability and resulted in large downward flow of heat by 

 advection and diffusion even under conditions of slight turbulence and a great 

 sea-air temperature difference. The lowest air is heated by the ocean, becomes 

 unstable and rises in small buoyant "thermals" which penetrate a short 

 distance into the stable air. The heat transport by this convection jDrocess was, 

 in this case, small compared to the downward flows ; this air-mass was heated 

 more by warm stable air aloft than by the warm ocean. 



It is interesting to note that this wave cyclone did not deepen further : the 

 inhibition of exchange by dynamic factors may have played a role in this 

 failure, a subject interesting to speculate upon if it leads to specific questions 

 for future research. This work was a small part of an extensive aircraft program 

 led by Bunker and his colleagues to study the effects of exchange in air-mass 

 modification over the ocean ; like all worth-while pioneering efforts it proceeds 

 at the expense of painstaking labor in the face of obstacles which fall just short 

 of being insuperable. 



B. Long- Period Variations in Sea- Air Interaction 



At the very beginning of this chapter we purposely set to one side long-period 

 circulation anomalies in air and sea and their effects upon each other. For the 

 purpose of making the climatological exchange picture meaningful, for develop- 

 ing physical and analytical models of transfer processes and their consequences, 

 it was assumed that, in the broad scale average, one winter or summer was just 

 like any other in both media. In order to use the energy budget equations as a 

 foundation for our models, such an assumption is both necessary and justifiable ; 

 for example, secular heat storage in the sea over several years is clearly both a 

 negligible and non-computable term in a joint budget study of the Caribbean 

 in two particular winter months. 



This assumption is tacitly based on carrying to an extreme the knowledge 

 that, compared to the fickle atmosphere, the ocean is a high inertia, infinite 

 reservoir of heat and water, and that its circulation patterns respond to the in- 

 put of solar heat and wind stress in such a way that its temperature structure 

 shows only a seasonal cycle in a given region. Then it would be true that ex- 

 change fluctuations are regulated by the sun and atmosphere and, when 

 averaged over the seasonal cycle, exert an invariant effect upon the sea. It is 

 clearly at this last point that the assumption breaks down. Because the upper 

 layers of the ocean are somewhat decoupled from the abyss, so that the shallow 

 strata above the thermocline may be moved about by the winds, or their 

 thickness altered with little effect upon the deeper waters, and because it is the 

 surface layers to which the atmosphere responds, a coupled instability of the 



