erly or easterly winds of lower speed and with 

 a higher sea-air vapor pressure difference as, 

 for example, during February 1964. 



A relative difference in the heat of evapora- 

 tion, possibly 20 percent, due to the difference 

 in processing methods can cause a much larger 

 relative error in the net heat exchange, whose 

 absolute value ranges from to 200 cal. cmr^ 

 day-'. This effect is apparent in figure 4, where 

 the net heat exchange across the sea surface 

 has been plotted by using the three methods of 

 computation described for the heat of evapora- 

 tion, in the area lat. 25° to 29° N., long. 140° to 

 144° W. The 2-year average of Q(N|) is -32 cal. 

 cmT^day"' and that of Q(N2) is 7 cal. cm.'^day"'. 

 In the trade wind zone such differences in the 

 ocean heat budget are significant. 



Comparison with Other Results 

 in the North Pacific 



It remains to compare the results of table B 

 with other heat exchange values for the North 

 Pacific. Most suitable for comparison are the 

 monthly charts of the heat of evaporation and 

 the net heat exchange across the sea surface 

 prepared by Wyrtki (1966). His charts are based 

 on 1947 to 1960 averages of marine surface 

 meteorological data. He calculated the heat ex- 

 change processes with the same empirical for- 

 mulas as were used here except for minor dif- 

 ferences in the coefficients and for his use of 

 constant drag coefficient in the evaporation 

 equation. The comparison, therefore, primarily 

 shows the differences between the monthly ex- 

 change processes of individual years and those 



200 





-300 



1963 



SONDIJ FMAMJ 



N D I , 



F M A M 



1964 



I96S 



Figure 4. — Monthly net heat exchange across the sea surface 

 (cal. cm. "^day"'^) lat. 25° to 29° N. , long. 140° to 144° W. , 

 July 1963 to June 1963. Q(N), mean net heat exchange based 

 on computations made for each set of meteorological obser- 

 vations, Q(Ni), mean net heat exchange based on daily mean 

 meteorological properties, and Q(N2), mean net heat exchange 

 based on monthly mean meteorological properties. 



13 



