| OCR Text |
Show snow density: 0.24; air temperature: - 1.6° C. Wind exerts a great influence on snowcover temperature by penetrating the snow and bringing its temperature close to that of air. During cloudy weather the snow surface temperature is near air temperature. During unvarying freezing weather, with no abrupt changes in air temperature, snowcover temperatures gradually increase from the snow surface to the ground, where it remains near 0° C all winter. The variations in air temperature which markedly affect the upper layers in the absence of wind are slow to be felt in the deep layers. This is why the middle layers may for a time maintain a lower temperature than the upper ones as warming takes place. With the beginning of thaw, a temperature of 0° C is established throughout the cover. An average temperature for the lower layers, computed from 28 observations during the winter of 1938- 39, is as follows: ground surface: - 1.3°; 10 cm above ground: - 2.2°; 20 cm above ground: - 3.4°; 30 cm above ground; - 4.7°; 40 cm above ground: - 5.9° C. The corresponding water vapor pressures were 5.5 mb, 5.1 mb, 4.6 mb, 4.1 mb, and 3.7 mb, respectively. au- 60 50 UO 30 20 10 0 <" L i / y / t i '/ f 1 1 / / / • * 1' > ' A ,--• r1 ^~ -^"" 0 - 2 - 4 - 6 - 8 - 10 - 12 - Ik - 16 - 18 0 temperature Fig. 5. Snowcover Temperature Figure 5 shows the curves characteristic of snow cover temperature with variations in air temperature. The continuous curve corresponds to warming; the broken curve, to cooling; and the thin, broken curve, to steady freezing weather. On mountain tops the snow temperature at the surface of the ground under cover of the same thickness is slightly lower than in the valleys. This can be explained not only by the lower average air temperature but by the more frequent winds. P. F. Semerov has discovered pockets of permanent frost on Mount Ukspor in the vicinity of Hackmann Pass ( Gorge). In low, wet spots under heavy snowcover, the ground remains unfrozen all through the winter. - 26- |
