融雪流出の研究 (II)
融雪に関する試験
1964 年 1964 巻 8 号 p. 22-29
詳細
1964 年 1964 巻 8 号 p. 22-29
The quantity of snow melt (as the transmission water through snow layers) was measured with transmission gauges (dia. 80 cm) set on the ground, at a plot located in low mountainous area in the south-west part of Aomori prefecture, in the melting season of 1957-1961.
Determination of the snow melt indicated that air temperature during a short melting period can be considered as an index of the integrated effect of radiation, and sensible heat exchange. Thus, the mean daily temperature and the air temperatures determined by using different base temperatures, such as degree-day, degree-hour, and effective mean daily temperature (daily mean of integrated value of air temperature above a base temperature) were introduced for comparison of the effect upon daily snow melt.
Results are summarised as follows:
1) The snow melt by conduction from the underlying soil is 0.2-4.0 mm·day-1.
2) Melt water finds its way downward along the lines of the least resistance and the channels, capable of carrying gravity water through the snow layers, which are developed along the crevices in ice planks and are filled with granular snow. The velocity of melt water through the snow layers is 20-90 cm·hr-1.
3) The daily variation of snow melting can be expressed by the lognormal distribution of Eq.(2), and it is graphically shown in Fig. 3.
4) The effective mean daily temperature determined by using a base temperature of 0°C is the most important and representative factor which causes daily snow melt. The relations are expressed by Eq.(2)-Eq.(6), depending on the type of weather condition.
5) Snow can retain a part of rainfall. Assuming the residual water content of snow is 6.0mm on rainy days, the correlation of the effective mean daily temperature to the daily snow melt becomes most close, and the relation can be expressed by Eq.(7).
6) The accumulated values of the daily snow melt (adjusted for rainfall, if any) plotted against the accumulated values of the effective mean daily temperature for the daily readings and an estimated line of best fit to the points are shown in Fig. 6. The gradient of this line is called snow melt coefficient. The snow melt coefficient is 1.2-2.7 (mm·cm-2·deg-1·day-1) in the early melting season, and 3.2-4.5 in the active melting season.
