SECT. 2] LARGE-SCALE INTERACTIONS 141 



oceanic air in summer, and outflow of continental air over the seas in winter ; the 

 asymmetry in the hemispheres, shown in Table I, and the large cross-equatorial 

 flows are primarily the result of the enormous Asiatic monsoon, which domi- 

 nates the Indian Ocean region as shown in Fig. 17. Here, the regular form of the 

 annual radiation balance curve, with a summer maximum and a winter mini- 

 mum, is distorted by a rapid increase of cloudiness in summer during the period 

 of equatorial air-mass influx. An increase of cloudiness diminishes the total 

 radiation and radiation balance in midsummer so that a secondary autumn 

 maximum occurs. The turbulent heat emission Qs is insignificant in this region 

 during the entire year, the result of insignificant difference between water and 

 air temperatures. However, Qs increases somewhat during winter as is typical 

 for monsoon climates. Expenditure of heat for evaporation, Qe, in this region 

 changes during the year inversely to changes in radiation balance (this relation- 

 ship is typical for the major portion of the oceans). The winter maximum of 

 evaporation is, in this case, explained by advection of dry trade-wind air 

 masses, and is connected with a considerable increase in saturation deficit (19). 

 The summer Qe maximum is associated with a strong increase in wind speed 

 during the equatorial monsoon period. As a result of the considerable increase 

 of heat losses for evaporation in winter and summer, and of a diminished 

 radiation balance therewith, the heat flux between the sea surface and lower 

 water layers is directed upward {Qvo + S is negative) during these seasons, 

 although the absolute values are comparatively small. In contrast to this, in 

 spring and autumn great quantities of heat are transmitted from ocean surface 

 to deeper layers. Comparison of areas (approximately that between curve R 

 and curve Qe in Fig. 17 since Qs is so small) shows that the lower layers gain 

 more than they lose on an annual average and thus the net Qvo must be 

 positive, or represent an export of heat by the ocean from this region (see also 

 Fig. 11). 



We thus begin to see that, even in the tropical belt, the annual march of 

 energy transactions is vitally influenced by air and sea circulations, and is 

 diff'erent in areas having different circulation regimes. The modifications from 

 the mean latitudinal picture, or from that of an all-water world, are primarily 

 produced by the distribution of continents. Because of continental barriers, 

 the intense warm ocean currents are located at the western periphery of the 

 oceanic anticyclones (as is described elsewhere in this book). Among other 

 effects, this creates favorable conditions there for the largest values of Qs, the 

 turbulent heat emission from ocean to atmosphere. 



As an example, we shall next analyze the region near the island of Trinidad 

 (Southern Hemisphere, Atlantic Ocean, southeast of Brazilian Coast; to be 

 distinguished from British West Indian island of same name). The annual 

 march oiQe, Qs and R for this area is shown in Fig. 18. Radiation balance, under 

 these conditions, changes in accordance with the annual march of total radia- 

 tion, but expenditures of heat for evaporation have an o^Dposite pattern. The 

 turbulent heat emission grows in the winter months (for the Southern Hemi- 

 sphere) when the effect of the warm Brazilian current is strongest. At this time 



