SECT. 2] LARGE-SCALE INTERACTIONS 101 



ways, the one using overall energy and mass budget requirements, the other 

 based upon the so-called "exchange formulas" which, via the laws of small- 

 scale molecular and turbulent transfer, give the exchange as a function of the 

 air-sea property difference and the wind speed. The budget method, to be 

 described first, is only suitable for arriving at averages over rather large 

 regions ( ~ 5° latitude) and long periods (monthly or longer) since it depends on 

 radiation figures which are only computable for these intervals. The scale of 

 applicability of the transfer formulas, discussed secondly, is dependent on the 

 observations used ; they appear to give satisfactory results from the climato- 

 logical scale down to periods of one hour and to resolve meso-scale variations if 

 desired. 



A. Energy Budget Method of Air-Sea Flux Computation 



Let us consider the heat-energy budget of a deep ocean column of unit area 

 in order to arrive at the transfers across its surface. Of the total impinging 

 solar radiation, some is reflected and some is reradiated back to space in long 

 wave lengths. That which is radiated to the atmosphere and reradiated back 

 to the sea, due to the "greenhouse eflFect", does not directly enter the budget 

 equations as a net gain or loss for the ocean column, although it is obviously of 

 major indirect importance in governing the temperatures, radiation balances 

 and other features of the air-sea system and its parts. The net amount absorbed, 

 called the "radiation balance" of the surface, is used in three ways : it may raise 

 the temperature of the ocean column, be carried away by sea transports, or be 

 supplied to the atmosphere in latent and/or sensible form. 



The law of energy conservation is used to express this heat balance quantita- 

 tively, as follows : 



R = Qs + Qe+S + Qvo, (1) 



where the units of each term are heat energy per unit area per unit time, 

 commonly cal cm~2 sec~i. Qs plus Qe is the heat energy supplied by the sea to 

 the atmosphere in sensible, Qs, plus latent, Qe, form. The latter may be written 

 as LE, where L is the latent heat of vaporization in cal g~i and E is evaporation 

 in g cm~2 or in cm of water per cm^ ; the ocean recognizes the sum of these 

 as a sensible heat loss. S is the ocean storage, jDositive for increased heat content 

 of the column ; it is assumed zero in the climatological calculations of annual 

 budgets (assumption (6), p. 92), although its maximum seasonal values may 

 exceed one-third Qe. Shorter term storage fluctuations are generally unknown 

 and pose great difficulty in smaller scale budget analyses. Qvo is the flux di- 

 vergence of oceanic heat transports, assumed for large areas to be due to 

 advective currents although for restricted regions lateral eddy fluxes might 

 require inclusion. Omitted from equation (1) are heat sources due to dissipation 

 of kinetic energy of air and ocean, and that due to radioactive decay in the 

 earth's interior transmitted through the ocean bottom. The former may, in the 

 extreme, amount to 1% of the dominant terms or 3 cal/cm^ per day, while 



