This paper aims at classification of seasonal snowcover depth patterns which comprise the daily accumulation, deposition, and melting of snow. Investigation about 1000 patterns taken from a wide area in Japan, five simplified fundamental models are proposed. The models are defined in accordance with meteorological, topographical and geographical factors, and with the time of the occurrence of the maximum depth of snowcover during the season. To evaluate the presented models, the mechanism of occurrence is discussed and the regional characteristics are explained. On the basis of case studies, it is found that snow disasters tend to appear with a few limited patterns which are made above the average depth of snowcover at each station, particularly in times when an extraordinarily heavy snow falls. The five models classified here are the typical of all kinds of seasonal snowcover depths except in permanent snow fields. The same models defined in this paper may be applied to the classification in other regions.

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To investigate the impact pressure of snow avalanches, it is necessary to study the collisions of individual snow blocks, because snow avalanches include many small snow masses. The author therefore made measurements of the impact pressures of snow blocks onto a small plate and investigated the difference in wave form of impact pressure caused by the difference of properties of snow and the condition of collisions. Cubical or Cylindrical snow blocks were dropped from a height of about 7 m onto a small circular iron plate 10 cm in diameter. Time sequence of impact pressures was measured with a strain-gauge-type load cell and a data recorder. To examine how the snow block breaks, it was photographed by a strobocamera at the instant of collision with the plate. Peak values of impact pressure were analysed in terms of the initial density of snow samples, the value of hardness obtained from Kinosita's hardness gauge and the velocity at the initiation of impact. Assuming that the peak value of impact pressure P is given by P=K · ρ · V², where ρ is the density and V is the velocity, then the constant K ranges from 1.0 to 5.0, with a mean value of 3.0. The impact pressure of harder snow blocks depended considerably on the value of hardness obtained from Kinosita's hardness gauge.

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The present paper reports that the landslide in the snowmelt period in Niigata prefecture (1950-1974) depends mainly on the snowmelt, as follows :
(1) The longest period in every year in which snowmelt water covers the ground surface, ND, is denoted approximately by the uninterrupted number of decreasing days of snowcover depth at Nagaoka city, Niigata prefecture. In defining N_D, the small suspension of decreasing in snow depth (less than two days) is of little significance to water saturation underground, therefore, it is omitted.
(2) The frequency of landslides in the maximum snowmelt period (usually in March and April, and in some cases continuing into May) N_S, by using the above mentioned N_D, is given as N_S=10.2+0.91N_D, where the largest observed values where N_S=52 times and N_D=45 days. The correlation coefficient between N_S and N_D is obtained as 0.70.

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The main part of annual accumulation of the glaciers in Nepal is due to precipitation during the summer monsoon season. Since such glaciers which have more accumulation in summer than winter are distributed widely in Asia, they can be called the 'summer-accumulation type' and relations between their mass balance and meteorological conditions are studied in the case of Glacier AX010 (area : 0.57 km²) in the Shorong Himal. Since accumulation and ablation on such glaciers occur simultaneously in the same season, separate measurements of those amounts are difficult. Therefore, accumulation (amount of solid precipitation, c_h in cm) and ablation (a_h in cm) during each half month are calculated from mean air temperature (T_h°C) and precipitation (P_h cm) during the same period by the following equations. c_h=P_h (0. 85-0.24 T_h) for ·0.6≤T_h≤3. 5, a_h=-0. 15 (T_h+ 3. 0) ^3.2 for ·3.0≤T_h. From values of T_h and P_h through a year and the lapse rate of 0.6°C/100 m for T_h, the patterns of annual variations of accumulation, ablation and balance for the whole area of the glacier are obtained. Then the dependence of these variations on air temperature is discussed. Through winter, accumulation and ablation are small and the balance is near equilibrium. On the other hand, mass exchange is active in summer. Balance during summer varies between the positive and the negative sensitively depending on change in summer air temperature. It is pointed out from the above characteristics that the 'stratigraphic system' for the mass balance term is not suitable for the summer-accumulation type.

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In a previous report, glaciers which have more accumulation in summer than winter were called the'summer-accumulation type'. The mass balance of Glacier AX010 in east Nepal was studied as a model case of such a type. In that study, accumulation, ablation and balance during each half month were calculated from mean air temperature (T_h) and precipitation (P_h) during the same period. By the use of the above formulas, various annual values of mass balance elements are calculated in the present study, giving values of T_h and P_h through the year for various cases of annual mean air temperature and annual precipitation. The altitudinal profiles of mass balance of glaciers in various places in Nepal, where summer precipitation decreases from east to west, are shown from the calculated results. It can be seen in those profiles that the increase of annual ablation is more at the lower warmer part and annual balance shows larger altitudinal difference than annual ablation due to the decrease of accumulation in solid precipitation on the lower part. The amounts of annual exchange of the glaciers in Nepal are compared with those of glaciers elsewhere in the world and relatively small amounts are obtained for the summer-accumulation type. However, their 'activity indexes'are relatively high, since the dependence of balance on air temperature, which changes with altitude, is high. By the use of'Regimen Degrees'which are defined with the combinations of total mass, annual exchange and annual balance of a whole glacier, the glaciers of the summer-accumulation type are compared with glaciers elsewhere in the world.

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