Journal of the Japanese Society of Snow and Ice

The increased loads acting on a tree due to wet snow accretion and strong winds cause snow damage to trees, such as stem and branch breakage and uprooting. A structural analysis is employed to predict the initiation of snow damage due to snow accretion, thereby taking into account the loads caused by snow and wind. However, few studies have measured wind loads on trees, and the effect of snow accretion on the drag coefficient is unknown. In this study, wind tunnel testing was conducted to clarify the effect of snow accretion on the drag coefficient of Japanese cedar, which is a major forestry species in Japan. A model of cedar branches and leaves, made from actual material, was placed in a wind tunnel, and snow accretion was artificially generated by supplying wet snow into the wind tunnel while blowing air. The changes in the drag coefficient for different experimental conditions, such as wind speed and the amount of accreted snow, were measured. The results showed that snow accretion had three types of effects: (1) increasing the projection area due to the snow itself, (2) reducing drag force, and (3) inhibiting the decrease in projection area caused by the curvature of the branches and leaves due to wind action. These effects changed the drag coefficient.

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We conducted snow surveys and meteorological observations for three summer seasons on the Senjagaike perennial snow patch of Mt. Hakusan, located on the border of Ishikawa and Gifu prefectures. The characteristics of the surface heat balance in summer were assessed and the relationship between the snowmelt process and weather conditions was analyzed. Moreover, the influence of climatic conditions and heat balance characteristics on the annual change of the snow patch was examined. The 3-season average heat balance composition in summer was 447 W m^－2 net radiation (309 W m^－2 shortwave radiation and 138 W m^－2 longwave radiation), 140 W m^－2 sensible heat flux, 180 W m^－2 latent heat flux, and 39 W m^－2 rainfall heat flux. The 3-season average heat flux during rainfall ranged from 349 to 560 Wm^－2, and from 157 to 246 Wm^－2 during no rainfall, indicating that the snowmelt heat flux was larger than that during no rainfall. The net shortwave radiation contributed the most to the snowmelt in summer. However, the latent heat flux varied greatly depending on the frequency of severe weather events such as daily rainfall ≥ 50 mm and wind speed ≥7 m s^－1, which could result in differences in the accumulated snow height change in the summer season.

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