392 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



10° 



15° 



20° 

 NORTH LATITUDE 



FiGtTRE 18.— Mean meridional profile (150° W.-180°) for 

 the Hawaiian survey region of the net heat exchange and 

 its equivalent change of surface temperature during June 

 and December. 



crops would show small seasonal variations) 

 whereas on the other side these seasonal variations 

 would increase toward higher latitudes. 

 B. Evaporation Minus Precipitation 



The term in the salt budget (equation 7) which 

 would be equivalent to the heat exchange in the 

 heat budget (equation 6) is the freshwater ex- 

 change across the sea surface or the evaporation 

 minus precipitation {E—P). Evaporation has 

 the effect of increasing the surface salinity and 

 precipitation of decreasing it. Although the 

 salinity data in part I are inadequate for salt 

 budget computations, they are sufficient to war- 



rant a brief discussion of the evaporation minus 

 precipitation. 



Albrecht (1951), in connection with the water 

 budget of the Indo-Pacific, computed the precipi- 

 tation. His work was based on a revision of 

 Schott's (1935) mean annual precipitation charts, 

 McDonald's (1938) charts of frequency of precipi- 

 tation, and precipitation data from island and 

 coastal stations. Figure 19 shows the seasonal, 

 meridional distribution of evaporation minus 

 precipitation at 160° W., based on the revised 

 charts of Albrecht (1951), received in a personal 

 communication. 



The northward progression of the maximum 

 {E—P) with time is apparent. At 15° N. it 

 occurs during December, at 20° N. in April and 

 May, and at 28° N. during October. Maximum 

 {E—P) is centered about 20° N. and the months 

 about July, when it is higher than 10 cm. per 

 month. Maximum and minimum {E—P) at 10° 

 to 15° N. coincides with minimum and maximum 



JAN MAR MAY JUL SEP NOV JAN 



Figure 19. — Seasonal evaporation minus precipitation 

 along 160° W. in cm. mos."'. 



