Journal of the Japanese Society of Snow and Ice

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There are some experimental reports on electrostatic charge measurements of blowing-snow particles in the field and wind tunnel. While there were qualitatively consistent in the sign; negative, there were gaps quantitatively between them. A reason of the gaps speculated widely is due to differences of the collision frequency of particles to the snow surface. The purpose of this experiment is to measure the charge of blowing-snow particles focusing on the collision frequency and clarify the relationship between them. Experiments were carried out in a cryogenic wind tunnel using spherical and dendritical snow particles under the following conditions: hard snow surface, air temperature in the range －20 to －5℃. The collision frequency of particle was controlled by changing the wind velocity (4.5 to 7ms-1) under the fixed fetch (12m). Blowing-snow particles tend to accumulate negative charges with increase of collision frequency to the snow surface. As a result, it is demonstrated that the gaps between the field values and the wind tunnel ones were due to difference of the collision frequency of snow particles.

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Winter road conditions pose a serious problem to the traffic in the cold regions. We developed a new system to detect freezing as well as snow cover on roads. This system determines road conditions by measuring the microwave radiation emitted by a road and surface road temperature. The system also checks for the changes in the road microwave/surface temperature pattern and in possible road conditions. The standard range of microwave radiation for various road conditions was obtained for the experimental road surface. The proposed system was installed at the Sekihoku Pass in the Taisetsu Mountains, and it monitored the winter road conditions for one complete winter season. The data obtained by the system at the Sekihoku Pass was used to define standard ranges to distinguish between various road conditions. The accuracy of the sensor and the analyzing system in detecting the correct road conditions for an uniform road condition was more than 90 ％.

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