The distribution of depth hoar in Honshu, Japan

Abstract

Akitaya and Endo (1980, 1982) developed a calculating expression for deciding whether depth hoar grew in the snow cover in Hokkaido, using averages of snow depth and air temperature during January and February in individual districts. As for Honshu, Japan's largest island, to the south of Hokkaido, almost no record of depth hoar in the snow cover is available. Thus, we applied this expression there, using meteorological data, from which it followed that depth hoar was likely to develop in the snow cover in several districts of Honshu. By actually surveying the snow cover in eight of these districts, we confirmed the development of fragile depth hoar in the lower part of the snow cover. As a result, this expression proved to be applicable in Honshu, as well.
Then, we examined the meteorological data of all Japan except Hokkaido, with a finding of more than 40 districts where depth hoar developed in the snow cover in more than two of the recent ten winters, almost all of them being in Honshu, not other islands. They are on the Pacific Ocean side of the backbone ranges of Honshu, having a little snow and low temperature in winter. They distribute in the southeastern part of Aomori Prefecture and almost all parts of Iwate Prefecture, both of northern Honshu, as well as, in central Honshu in such districts as highlands and the eastern side of mountain ranges or high mountains forming terrain obstacle to the northwesterly monsoon.