抄録
A year is diveded into two half seasons: summer half and winter half. The former involves 7 months from April to October and the latter remaining 5 months from November to March. Such division of a year is a customary one on the stand point of plant ecology and bioclimatology. The ratio of the total precipitation during summer half to that of winter half is calculated for the observed value at various meteorological stations in Japan, and the distribution of the ratio is shown in the maps.
