A simple scaling model for extreme rainfall

The simple scaling hypothesis is applied to the intensity-duration-frequenc y (IDF) description of rainfall. It is shown that the cumulative distributi on function for the annual maximum series of mean rainfall intensity has a simple scaling property over the range 30 min to 24 hours and in some insta nces to 48 hours. This behavior is demonstrated through an examination of t he scaling properties of the moments and the scaling of the parameters of a n extreme value distribution fitted to the data. A simple analytical formul a for the IDF relationship is proposed, which embodies the scaling behavior . Once the scaling parameter has been obtained for a gauge or set of gauges in a region, this formula enables the calculation of rainfall amounts, of a chosen return period and duration shorter than a day, directly from the i nformation obtained from the analysis of daily data.