Evaporation from the Surface of the Sea and the Water Budget of the Earth 223 



3. Meridional Distribution of Evaporation over the Whole Ocean and its Determination 

 from Energy Considerations 



The mean values of the true evaporation for different parts of the ocean which can 

 be regarded as the direct result of observations have been used by Wiist 

 to give values for latitude zones of 10° width in the Atlantic and for the total 

 ocean. These depend on interpolation and in part on extrapolation and can thus be 

 considered only as a first approximation. The values recalculated with a correction 

 factor k = 0-53 are given in Table 85. The zonal variations in evaporation, with 

 pronounced maxima in the trade wind regions and a low value in the doldrums, are 

 less pronounced in the figures for the total ocean than in those for the Atlantic alone. 

 Due to the relatively large proportion of the Polar Sea with a low evaporation the mean 

 value for the Atlantic is less than that for the total ocean. The mean evaporation for 

 the total ocean found in this way is 93 cm/year or 2-54 mm/day. The limits of error for 

 this mean value and for the zonal values are about ±12%. 



Table 85. Zonal distribution of evaporation 



in the Atlantic and for the total ocean 

 (According to Wiist. (Correction factor k = 0-53.)) 



The mean evaporation of the total ocean can also be determined by another method, 

 suggested by Schmidt (1915). It has already been shown in Chapter III/ 1 (see p. 88), 

 in discussing the heat budget, that evaporation is one of the most important items 

 (loss) in the heat budget of the sea. From a comparison of the amounts of heat in- 

 volved in the heat budget for the world ocean the maximum heat amount available 

 for evaporation can be estimated. 



Denoting the mean annual energy gain of the total ocean surface due to sun and 

 sky radiation by Qs, the energy loss due to outgoing radiation from the ocean to the 



