A Statistical Analysis of the Frequency Distribution of the Summer Rainfall in Japan

Abstract

It is important not only from the climatological but also from the agricultural and industrial point of view to ascertain the variability of summer precipitation (May to September) in Japan. Although many works have been undertaken, there is no fundamental guidance exactly to determine the coefficient of variability. Present work was intended to determine the variability of summer precipitation in Japan.
The results obtained are presented as follows:
(1) The standard deviation of frequency distribution of the summer precipitation for 53 meteorological stations hitherto since 40 years was calculated; it was found that the correlation between the standard deviation of frequency distribution above mentioned and the mean amount of summer precipitation was highly intimated, and the coefficient of correlation was as follows:
+0.938±0.011.
From this, we see that as the variability coefficient it could be cboosen the standard deviation already described. As numerical relation between the variability coefficient x and the mean amount of summer precipitation y (cm) we get x=0.0118y+0.1392
(2) The geographical distribution of the variability as represented on a map (Fig. 3) gives interesting results. The Pacific coast from southern Kyûsyû to Izu peninsula has greater variability than that of the other portion of Japan, and the variability decreases with increasing latitude. Hokkaido has lowest variability.
(3) The variability after Maurer's scheme was also calculated. It was found that the summer precipitation fluctuates within a wider range from year to year than that of annuals.