Journal of the Japanese Society of Snow and Ice

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Dependence of seasonal frost depth of ground on meteorological conditions and ground surface parameters was investigated with one-dimensional models. We used meteorological data of northeastern districts of China where seasonally frozen ground developed. For the case of bare surface, it is shown that the air temperature controls the frost depth and the increase of wind speed gives a slight decrease in the frost depth. The frost depth depends slightly on the soil water content except when the water content is less than 0.1, and it also depends slightly on the dry soil density. For the case of snow cover, the frost depth is seriously influenced by the thermal property of snow as well as the snow depth. For the vegetated surface, the frost depth is almost independent of forest density. A universal method to estimate the frost depth in the snow-covered ground is derived from a semi-theoretical solution of temperature profile in the snow cover. However, this method needs further elaboration.

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Catch ratios of three gauges (RT-1, RT-3 and RT-4) which have been conventionally used in Japan were evaluated for solid precipitation in the Hokuriku region over two winters. The true precipitation was determined according to the recommendations of WMO International Organizing Committee for the Intercomparison. Catch ratios decreased with increasing wind speed and were about 60% at the speed of 4ms^-1. The gauge RT-4 gave the best catch ratios, then followed RT-1 and RT-3. Snow adhering on the reference gauge (Double Fence Intercomparison Reference) was sometimes observed. It seems that the recommended method by the committee is not necessarily suited to the precipitation measurement in the Hokuriku region where heavy and wet snowfalls take place.

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