Temperature profile and its change with time in a snow surface layer cooling through nocturnal radiation is measured by thermometers of minute thermistor elements (fig. 1). Thermal diffusivity is calculated from the change with time of temparature profile by Takahashi's graphical method of solution for the problems of heat conduction (fig. 3), and the value of 0.00276cm²/sec is obtained (measured snow density is 0.15). The lowest temperature is observed at a depth of about 0.7cm under the surface (fig. 5). This feature of the profile is attributable to semi-transparency of snow layer, and is also demonstrated theoretically, assuming that radiation takes place in the snow layer down to a certain depth (fig. 7). In the case when heat transfer between snow and air is small due to weak turbulence of air the surface of snow is kept at the lowest temperature. As to the compensation for the remarkable temperature fall of the snow surface layer (fig. 8) will be discussed later.

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The variation of the equivalent reflection coefficient (ρ_e) is one of the most important factors which determine the properties of K-Type Fading at microwave propagation over snow-covered terrain. And ρ_e's physical meaning is somewhat complicated by the reason that it contains many factors (surface deposited snow's dielectric properties, radio meteorology, etc.). So we observed ρ_e's daily variation at the model propagation test (at very short distance 100m, 4000) and annexed the radio meteorological condition's measurements.
This paper shows the method of this experiments and the analytic results on the radio meteorological M-curve (M-profile lies on the very low layer near upon the model test's reflection point). The vertical profiles of measured atmospheric temperature and M-curve are represented in Fig. 4 and ΔM (M-inversion) in Fig. 6 respectively.
In general, the variation of ΔM is smaller than over the land and sea, especially at night time. So it is found that the dielectric properties of deposited snow at reflection surface had probably a pretty large influence on the variation of ρ_e.

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