TABLE 7. INDEX OF REFLECTION 



i° 90 80 70 60 50 40 30 20 10 



r" 48.3 47.3 44.5 40.3 34.9 28.7 21.9 14.8 7.4 



^i/^o 



100.0 35.0 13.5 6.0 3.5 2.5 2.2 2.1 2.1 



The surface of the sea, however, is not only illuminated by direct solar rays, but also by 

 scattered radiation, i.e. , by rays falling onto it from all directions and partially reflected in all 

 directions . 



The concept of "albedo" is introduced to take account of the energy thus reflected, by albedo 

 we understand the ratio of the reflected to the scattered energy incident on the given surface ex- 

 pressed in percent or, in other words, the coefficient of reflection. 



The concept of albedo should be expanded for such semi-transparent media as water and ice. 

 Actually, as Kalitin pointed out, the albedo of the sea includes, first, solar radiation reflected and 

 scattered by the sea surface, second, radiation sent by the sea into the atmosphere and caused by 

 molecular scattering of the water mass itself and the particles suspended in it. 



The purer and more transparent the ocean water, the lower the albedo and the closer it 

 approaches the one derived from table 7. 



Employing this table, we find that even for direct solar radiation at solar altitudes greater 

 than 25°, the albedo of the sea is less than 9 per cent; in other words, the ocean albedo is small in 

 comparison with that of all other forms of the earth's surface. The albedo of old, settled snow, on 

 the other hand, varies between 30 and 50 percent, while it reaches 70 to 90 per cent for the white 

 smooth surface of freshly fallen snow. Thus, of all the natural surfaces of the earth, the ocean is 

 the most absorptive of solar energy, while snow and ice are the most reflective. 



Due to the high albedo of the snow cover, illumination even in the middle latitudes is maxi- 

 mum in spring (when the air is most transparent), in presence of a snow cover not yet affected by 

 thawing (high albedo) and in presence of slight cloudiness and during a light snowstorm (great 

 scattered radiation) . 



LITERATURE: 62, 73, 81. 



Section 11. Absorption and Scattering of Solar Energy 



The stream of solar energy, on passing through the layers of water and being absorbed in 

 part, loses some energy on heating the sea. 



Investigations have shown: 



1. The values of the absorption coefficients, even for slightly differing wavelengths of solar 

 energy, fluctuate within very wide limits. Thus, the absorption of solar energy by water is an 

 extremely selective process. 



2. The absorption coefficients are maximum in the infrared, absorption is considerably less 

 in the ultraviolet and least in the visible spectrum. 



3. The long waves are absorbed more intensively in the visible spectrum. 



20 



