

Figure 3-5. — Visibility. 



VISIBILITY IN THE ARCTIC 



The problem of visibility in the Arctic is extremely complex. 

 The air is very transparent. The records of many travelers are 

 replete with accounts of the extreme range of visibility. It is 

 not uncommon to see dark mountains 100 miles distant. On the 

 other hand, the lack of contrast, particularly where all surface 

 objects are covered with new snow, results in the inability to 

 distinguish objects close at hand. The traveler may easily fall 

 into a crevasse which he is unable to see in midday. The black 

 nose and claws of a polar bear may be seen clearly before it is 

 possible to see any outline of the animal, because the yellowish 

 white of the fur blends with snow-covered background. 



The frequent well-marked temperature inversions of the arctic 

 region explain the many accounts of mirages. Objects that are 

 known to be below the horizon are not infrequently visible as 

 mirages ; and the periods of daytime and twilight are lengthened 

 as the normal index of refraction is altered. The inversions may 

 also interfere with the identification of landmarks through dis- 

 tortion, and the estimation of vertical distances is made much 

 more difficult. 



In winter the poorest visibility is indicated in the vicinity of 

 Cape Chelyuskin. Improved visibility conditions are to be found 

 to the west in the neighborhood of Murmansk, and to the east in 

 the neighborhood of Uelen and Anadyr. Visibility conditions are 

 better in the spring, particularly over inland stations. The sec- 

 tion with the poorest visibility continues to be the Kara Sea. Dur- 



111 



