228 INTERACTION BETWEEN THE ATMOSPHERE AND THE OCEANS 



of the air, and p is the atmospheric pressure. The total energy lost by 

 the water is therefore 



g. = a + Q. = He. - O (l + 0.64^^^^^) 



w. 



The numerical values of the constant k depend upon the units em- 

 ployed and upon the heights above the sea surface at which the vapor 

 pressure in the air and the wind velocity are measured. The constant 

 can be determined on a semi-theoretical basis, or, when average values of 

 observed differences and wind velocities are introduced, it can also be 

 derived by requiring that the computed annual energy loss from the 

 the oceans must equal the total radiation surplus (p. 67). 



The latter method was adopted by Jacobs, who based his investi- 

 gations on the climatological charts of the oceans, published by the 

 U. S. Weather Bureau. These charts contain the average wind velocities 

 in the four seasons for all oceans and for the North Atlantic and the 

 North Pacific; they also contain charts for seasons of the temperature 

 difference {i^w — ^a), for values of the sea surface temperature, and for 

 the wet-bulb depression. Thus, the necessary data are available for 

 carrying out the computations for the two oceans. 



Figs. 64 and 65 show Jacobs' charts for the total amount of energy 

 given off from the sea surface in summer and winter, expressed in g 

 cal/cm^/day. The charts clearly demonstrate that in the Tropics nearly 

 the same amounts of heat are given off in the two seasons, whereas in 

 middle and higher latitudes the atmosphere receives very little energy 

 from the oceans in summer but great quantities in winter. It is also 

 seen that in winter by far the greater amounts of energy are transferred to 

 the air off the east coasts of the continents, in the Atlantic Ocean from 

 the Gulf Stream system, and in the Pacific Ocean from the Kuroshio 

 system. 



The importance of the ocean currents to the localization of the areas 

 in which energy is given off to the atmosphere is further illustrated by 

 figs. 66 and 67. Fig. 66 shows the net annual surplus of radiation that 

 the water receives. It has been computed by correcting Kimball's 

 charts of the incoming radiation from the sun and sky for reflection loss 

 at the sea surface and by subtracting the net back radiation to the atmos- 

 phere as derived from the sea surface temperature, the humidity of the air 

 over the oceans, and the cloudiness (p. 59). During the yesir the oceans 

 in all latitudes receive a surplus of radiation, but north of latitude 25°N 

 the surplus decreases with increasing distance from the Equator. In 

 latitudes 10°N to 45°N it is smaller off the east coast of the continents 

 than off the west coasts because of the difference in cloudiness. 



If the oceans were at rest and if the mean annual temperature re- 

 mained constant, the annual radiation surplus in every locality would 



