The purpose of this paper is to explain the distinctive features of the maximum snow depths in NIIGATA prefecture. The maximum snow depth data for the 'cold half' years from 1891 to 1987 were collected from the NIIGATA Local Meteorogical Observatory. The number of observatories keeping data is 60.
Concluding remarks are as follows :
(1) The deepest disturibution of maximum snow depth is determined by the difference in the height of the eastside or southside mountain chains. (Figs.1, 2, 3, 4)
(2) The shallowest disturibution of maximum snow depth is closely proportional to the height of each observatory. (Figs.1, 5)
(3) The heavy snow's patterns in NIIGATA prefecture are classified into two types : 1945 yr. and 1963yr. (Figs.6, 7, 8, 9)
(4) The upper limit of maximum snow depth which is estimated relative to an observatoty's height is shown by the following formula. (The upper limit line is designated "N-Line", Fig.10)
Hs=200 logH+75
Hs : the upper limit of maximum snow depth (cm)
H : the height of the observatory (m)
However, the maximum snow depths of two observatories, TAKADA and TOCHIOMATA, were over the N-Line.
(5) Taking into account the changes in the maximum snow depths after the latter term of the Meiji era, there seems to be two cycles of snowfalls : a cycle where there is a relatively little snowfall followed by a period of heavy snowfall and then repeating. (Fig.11)
(6) In the UONUMA area which has a heavy snowfall for NIIGATA prefecture, there are cycles of mild winters from 5-8 years. All mild winters are not the same as in El Nino years, but there is a possibility that a big El Nino brings a mild to average winter (relatively mild snowfall) to the UONUMA area. (Fig. 12)
