Abstract
The present author gives results of statistics on the duration of rainfall observed at the Nagano Meteorological Station. Results are shown in 4 tables. (p.) The first table contains frequencies of rainfall which set in A. M. (and which set) in P. M. The second table contains the result of summation of rains beginning between Oh-6h, between 6h-12h, between 12h-18h and between 18h-24h.
In these tables, monthly values for April to October are shown. These data are taken from the records of a selfregistering raingauge. In winter pluviograph is not generally in good working order, so that results for November to March are not given here. In these tables the small figures in bracket are numbers of thunderstorms in corresponding monthes. Small figures at right foot are numbers of rainfall, amount of which is less than 0.1mm.
The third table gives the frequency of the period of breaking of rainfall. The author observed the time between the beginning of a rain and its next breaking epoch, or between two epochs of breaking, and numbers of events corresponding to 0-5 min., 5-10 min., …… are given. To get rid of the ambiguity of determination of such breakiug epoch, the author compares these results with the smoothed values obtained by a method of mean 1/5(a/2+b+2c+d+e/2). For example, in the second column for April corresponding to 25, 30, 35, 40 and 45 min. (in the first column), numbers 1, 8, 4, 15 and 7 are given. From these numbers a value 1/5(1/2×1+8+2×4+15+1/2×7)=7 is shown as a smoothed value in the third column to correspond to 35min. Fat figures in this table are maximum values which are greater than cousecutive ones before and after.
In the forth table, data about heavy raius and relation between its intensity i and duration t are shown. Most of product i√t=n (Köppens, Das Wetter P. 169) lies between 2 and 3 which is very near to Wussow's1)value √5. But in case of shorter duration the products are much greater than this value √5, this case resembles Fassig's2) result observed in America3).
