降水量にみられる長期的変動について

Abstract

The outlines of periodic variations, in this paper, in the time series of annual sum andannual maximum of daily amounts of precipitation St 19 gauging stations in Japan were describ-ed from a view-point of engineering. It was found that the variations of T ~鯖0 and T ~・9in years, which were separated from these series by the helps of periodogram analysis and over-lapping moving average have the following characteristics:For the annual sum : (1) The trends of periodic variations of T~・19 are similar to oneanother, generally, and of T-45-60 are remarkable except Hokkaido. (2) Considering thetrends of variations of I0週<18 the several regions, in which the trends are similar, areclassified in Japan.For the annual maximum: (1) The variations of T.・9 seem to be no-significant in thesense of statistics and negligible in the sense of engineering in most of locations. (2) Thetrends of the variations of I 0週粛 8 are not always similar even in a region.It was concluded from the above results that the long-periodic variations in the hydrologicamounts of short duration are almost negligible from a viex~-point of engineering and seemto be much stochastic, although the ones for long duration have similar trends to one anotherin a region and or generally. The detailed method of application of these results to waterwoska were suspended in this paper, because the several problems to be discussed has, , beenremained unsolved.