ing the summer are normal in these areas, and 20 to 25 days are 

 not uncommon. In adverse years 30 days with fog may be re- 

 corded. The frequency of the summer sea fogs diminishes rap- 

 idly from the coast line inland, and diminishes less rapidly over 

 the pack ice. 



It v^ill be noted from the data that the summer fogs are less 

 frequent over the Barents and Norwegian Seas. This is due to 

 the more turbulent nature of the lower atmosphere over these seas, 

 resulting in less fog and more low clouds. 



Little is known about the frequency of togs north of the main- 

 land of North America. It is probable that fog is only slightly 

 less frequent over the Beaufort Sea than over the Chukchi Sea. 

 ana that fog north of the Canadian archipelago and Greenland is 

 comparable to that over the central pack ice. In the summer the 

 advantages of inland terminals over coastal points exposed to the 

 sea fogs may be summed up in stating that fog is three to five 

 times more frequent over the open water of the Arctic than over 

 inland river ports, and many times more frequent than over in- 

 terior highland stations. 



Fogs are reported to occur in some localities when a sea breeze 

 carries moist air from the sea over the land. Such a condition 

 must be considered unusual, because the sea breezes are most 

 frequent in summer when the land is much warmer than the 

 ocean, and the turbulence in the cooled air passing over the warm 

 land results in the formation of strato-cumulus clouds. However, 

 there are days in the spring and fall when the land could be colder 

 than the open water of the neighboring sea, and fogs result from 

 the passage of moist air currents from the sea to land. The area 



Fisure 3-8. — Radiation Fogs. 



114 



