Abstract
In order to investigate the statistical and hydrological characteristics of rainfall in mountainous basins, we have installed a series of tipping bucket type-raingauges along the slopes of Mt. Yubari in the center of Hokkaido, Mt. Gozaisho in Suzuka Mountains and Owase in Mie prefecture, and the observations of rainfall were carried out from August to October, 1988-4993. From the observation, we could obtain rainfall intensity R(mm/min, mm/h, mm/day) for various observation time and total rainfall amount P(mm) for each rainfall events. The following knowledges concerning with rainfall characteristics in mountainous basins are obtained. (1) In Mountainous basins, total rainfall amount observed at each gauge sites increases linearly with their elevation, and its gradient also increases linearly with rainfall intensity (amount). (2) The relation between the total rainfall amount P(mm) and duration of a rainfall event D(hour) shows P∝Dn, n=0.3-0.8, and the relation between the maximum rainfall intensity Rmax(mm/h) and various observation time T(5-60 minutes) also shows R∝ T-m, m=0.2 or 0.5, which depend on meteorological classification of rainfall types (stratiform or convective). The exponents, n and m are different from the meteorological types of rainfall (typhoon, front and sunder storm). (3) We could obtain the expression to estimate the basin-averaged rainfall amount P, which shows 10-80% larger than the amount observed at the foot of the mountain.
