降雨の時間分布の統計的構造に関する研究-雨量配分率の分布特性-

Abstract

As a method to research for statistical structure of time distribution of rainfall, the authorhas studied theoretically and empirically on probability distributions of several kinds ofdistribution rate of rainfall, because of application purpose such as more effective use offorecasted rainfall amount in flood control or examination of safety of design rainfallamount in water planning against floods.In this paper, the following items, which were not examined or not sufficiently done inthe former studies, are examined mainly through analyses of 12-hour-rainfall data of rec-ording unit 1 hour observed at 6 points in the Kinki District: (1) Degrees of difference ofprobability distributions or averages of the maximum distribution rate (a) to 1 hour and(b) to any sub-period of integer hours by observation points, (2) the same by classes ofrainfall magnitude. (3) Statistical characteristics of time distribution in the sub-periods towhich the maximum rainfall is distributed. (4) Degrees of difference between averages ofthe maximum distribution rates to any sub-period which can be estimated from rainfall dataof recording unit 1 hour and those which would be obtained from instantaneous rainfallrecords.The results corresponding to the above items are roughly as follows: (1) The maximumdifference is 11% about averages of (a) and 6% about those of (b). (2) The same is 20%and 9 %, respectively. (3) Degree of concentration into short time is considerably less thanthe case of pure random process. (4) Ratio of the latter to the former will be 1.1～1.2 forsub-period of 1 hour, but become nearly equal to 1.0 when the sub-period is longer than3～4 hours.