| To clarify the meteorological conditions for occurrence of wet snow avalanches in Hokkaido, located in the northern part of Japan, data analysis have been carried out using wet snow avalanche examples occurred on roadside slopes in the past 11 years. The 100 wet snow avalanche cases, including of 53 full-depth avalanches and 47 surface avalanches, were used in this study. The cumulated air temperature above 0 oC, precipitation amount and snow depth used in this analysis were obtained from the nearest observational station at avalanche site. The results revealed that the meteorological conditions for occurrence of wet snow avalanches differed in the period of earlier and later winter season. In January, air temperature is commonly subfreezing and snow depth is not yet its maximum, wet snow avalanche tends to be accompanied with rainfall but increase in the air temperature was not remarkable. In March, snowpack will start to be melted, most of wet snow avalanches were associated with the increasing air temperature above 0 oC and occurred as full-depth avalanches. In February, have commonly the minimum of air temperature and the maximum of snow depth in the winter season in Hokkaido, both the rainfall and the increase in air temperature caused the wet snow avalanche, but rainfall induced mainly surface avalanches when snow depth exceed about 1.5 m. This seasonal change in meteorological conditions for occurrence of wet snow avalanche would be affected to seasonal changes in snowpack properties. |
