Abstract
In order to obtain a preliminary information about the artificial acceleration of snow-melting, daily meteorological data at Takada (37°06′N, 138°15′E) for the period from 20 January to 27 March in 1962 were processed on the basis of the heat balance method. The heat balance equation at the snow surface in a melting season may be approximated by Eq. (2). The following methods were adopted to determine the daily amount of each heat balance item.
In determining the absorbed short-wave radiation, Rs(1-a), the value of albedo, a, was assumed to be 0.8 for a fresh snow surface and 0.5 for a granular snow surface. Effective long-wave radiation Re, was calculated from Eq. (3). Using Eqs. (6) and (7), sensible heat flux, L, and latent heat flux, lE, were determined from a sensible and latent heat transfer coefficients and the differences in temperature and water vapor pressure between the snow surface and the standard height (1.5m). Eq. (8) was used to get the value of sensible heat transfer coefficient. Table 1 shows the comparison of the wind dependences of sensible heat transfer coefficient calculated from Eqs. (8) and (9).
Figs. 1 and 2 present the seasonal change in quantities relating to the heat balance and meteorological conditions during the snow melting season. The characteristic in heat balance at the snow surface on days with the snow melting converted to water depth over 10mm per day is shown in Table 2. This table indicates that the contribution of net radiation, S, to a snow melting is large in comparison with other items and that the contribution decreases from about 100per cent for the early stage of a snow melting to about 50per cent for the latter stage. On the other hand, the contribution of heat (L+lE) transferred from air layer to the surface was found to increase somewhat in the latter stage (see Table 2).
