| OCR Text |
Show On the other hand, penetration of dry snow by the wind extends crystallization and increases settling. Figure 4 shows the settling rate per hour for a layer of loose, fine granular snow 50 cm in thickness and density 0.12- 0.20. Eight cm of fresh snow of 0.10- 0.12 density lay on the receptacle. The upper curves show air temperature; the lower curves, settling rate. **-- N 5 to a H • P set 1.0 0,8 0.6 OM Q2 0.0 H 6v 12v 18* March Ik March 16 March 17 Fig. 4. Settling Rate of Snowcover Under Varying Weather Conditions. Weather conditions for the days in question were as follows. March 14: low cloudcover, some wind; March 16: gusty wind up to 9 m/ sec at night, some overground blowing ( During the day, the wind slackened, the sky cleared, and the sun showed.); March 17: little wind, clear sunny weather. During these 3 days the temperature gradually dropped from - 4° to - 22° C. There was no precipitation. As shown by the curve for March 16, penetration of the snow by a medium wind speeded the settling rate to 10- 20 times ( rise in curve) that occurring during still weather. Repeated observations showed that dir rate even when the temperature remained we was measured at 6- hour intervals, one can compared with cloudy days or at night. In first stage of recrystallization, the ques tion of the recrystallization process is d The effect of sunlight on settling rate is 17 in Figure 4, Here, when the sun was 21 tling was 15 times greater than for March ect sunlight increased the settling 11 below 0° C. Even where settling see the increase in rate on sunny as observations of loose snow in the tion arises of whether the accelera-ue to the effect of sunlight or heat. clearly shown by the curve for March 0 above the horizon for 13 hours, set- 14, a cloudy day. An abrupt sinking often occurs in snowcover during gradual settling. Collapse of an entire layer will result in acceleration of the settling of superimposed layers for days afterwards. Such an abrupt settling is recorded by a portion of the lower curve in Figure 4 corresponding to the 98th day of observation ( March 14). Here the snow slipped 1 mm at one time. Later on, settling - 24- |
