Characteristics of Snow Cover in Japan*

Abstract

In Japan a fairly detailed snow cover chart is made based on the observations at meteorological observatories and climatological stations (Central Meteorological Observa-tory, 1949). However, due to the limitation of networks in the mountainous regions, the distribution of snow cover in those regions shown in the charts has less reliability. Several methods have been presented to overcome this handicap. Among them a coaxial method (Ishihara, Fukui, 1959) and aerial photographic analysis technique (Takasaki, Seto and Iozawa, 1964) are worthy of special attention. The former, primarily through taking orographical factors into account gives fairly good result, while as to the latter although it can not help involving a certain error at present status it has a bright future. Now looking from another point of view, from the standpoint of water resource utility, the equivalent water of snow cover is a great problem. Snow surveys have been carried out actively in Japan for a while (Ishihara, 1957). However a method to estimate the equivalent water of snow cover from the density and depth of snow cover is under study recently. For the estimation of the density of snow cover, the theory developed by Kojim