Of course, in general, the farther the water-adjacent atmosphere is from a state of saturation 

 the greater will be the evaporation rate. The latter is determined either by the moisture deficit (A) 

 or by the relative humidity (r) which can be determined from the formulas 



A=£ —e and 



r=IOO-, 

 E 



where E is the pressure of the vapor saturating the air at the given temperature, e is the pressure 

 of the vapor in the air at that same temperature. 



The saturation vapor pressure increases very rapidly with increasing temperature and, con- 

 sequently, the dryness of the air also increases. With a drop in temperature, the relative humidity 

 of the air increases and at a temperature called the dew point, when the moisture deficit is zero and 

 the relative humidity 100 percent, evaporation ceases and condensation begins, i.e. the formation 

 of fog and the precipitation of dew. 



The following are given in table 6: E^^ the saturation vapor pressure above water in mb, E^ 

 the saturation vapor pressure above ice in mb, q the water-vapor density above water in g/m^, g^ 

 the water-^fapor density above ice in g/m^. 



TABLE 6. THE PRESSURE AND DENSITY OF WATER VAPOR 

 ABOVE WATER AND ICE 



From the table it is evident that the saturation vapor pressure above ice is less than the vapor 

 pressure above supercooled water at the same temperature. Consequently, there cannot be equilib- 

 rium above water and ice at the same temperature: water vapor in the atmosphere above ice will 

 become ever denser until the entire liquid evaporates or until all the ice melts. Equilibrium be- 

 tween water and ice is even less feasible when there is a difference in temperature. 



LITERATURE: 62, 73. 



Section 10. Reflection and Refraction of Solar Energy 



A sun's ray falling on the surface of the sea in part is reflected into the atmosphere and in 

 part is refracted into the water. 



The coefficients of refraction in water for all wavelengths of the visible spectnim are approx- 

 imately 1. 34. They increase slightly with decreasing temperature and increasing salinity. 



Table 7 shows the angles of incidence (i) and of refraction (r) of an individual ray of light, 



and also the ratio between the reflected ( 7 . ) and incident ( j ) energy (index of reflection) . 



^ 



19 



