126 MALKUS [chap. 4 



The heat expenditure for evaporation, Qe, is seen to be one of the two major 

 ways the ocean gives off heat, the other being "back radiation", Qb [not shown 

 in the Table; very roughly equal to {Q-\-q) — K]. Qe and Qt are of comparable 

 size at all latitudes. Over the oceans, maximum values of evaporation and the 

 heat expenditure for it, Qe, are observed in the subtropical high pressure belts, 

 where the inflow of solar heat is especially great. In the proximity of the 

 equator, the evaporation from the ocean markedly diminishes. 



Turbulent heat emission from sea to air, Qs, is on an annual average compara- 

 tively small in all latitudes, averaging 13% oiQe. Its values increase somewhat 

 with higher latitude due to a growing significance of warm currents which heat 

 the air in the cold season, as does the ratio QsjQe, which averages 8% equator- 

 ward of 30° and 26% poleward. In constructing a planetary radiation budget, 

 Houghton (1954) obtained an average ratio QslQe of 43%. His global average 

 Qst was twice that of Budyko's but since it was found as residual in a radiation 

 balance, in which the uncertainties were comparable to the size of the residual, 

 it is likely that the independently tabulated Qs figures of Budyko are more 

 reliable. 



The results of this section have raised some vitally important questions to 

 marine scientists. Among these are questions concerning the relative im- 

 portance of poleward heat transport in ocean and atmosphere, the fate of the 

 water- vapor fuel and its use in driving the air circulations, the creation of wind 

 systems on various scales, and their role in exchange and in the maintenance of 

 ocean currents. The quantitative heat budget of the sea surface provides an 

 initial foundation for the pursuit of these questions, but to build it further we 

 must consider the mean annual heat budget of the joint air-sea system and, 

 briefly, that of the atmosphere itself. 



C. The Annual Heat and Water Budgets of the Ocean-Atmosphere System 



Using the material on the oceanic heat balance, we may now construct the 

 joint heat and water budgets of the ocean-atmosphere system to learn further 

 how its parts interact and affect each other. 



a. Heat energy budget of the system 



In order to analyze the joint annual heat budget, it is first necessary to 

 formulate a conservation law analogous to (1) for a column of unit area ex- 

 tending from the top of the atmosphere down into the ocean interior, namely, 



Rs = L{E-P)+Qro+Qva- (25) 



The same small terms have been neglected as previously, as well as storage 

 terms in sea and air. The latter are always negligible compared to the former, 

 which average out in an annual budget. P is precipitation in grams (or cm) 

 per cm2 per sec, E is evaporation in grams (or cm) per cm^ per sec. Thus the 

 term L{E — P) may be described equivalently either as the excess evaporation 



