The prediction of short-duration storm rainfall intensity maxima

Abstract

The acquisition of rainfall intensity maxima data over very short durations (generally less than 15 min) for individual rainstorms remains a problem. Autographic gauges of a desirable accuracy are rarely available at low cost and other forms of measurement such as radar, also depend heavily upon intensive capital investment. Certain within-storm maximum intensity relationships can, however, be exploited to permit the estimation of shorter-period from longer-period values, where the instrumental base is poor or sparse. Statistically significant relationships emerge between short and longer duration maxima over a number of rain events at a site. The significance of these relationships increases as the durations correlated approach one another, due to interdependence of data. More usefully, however, curves of the form I t = kt − n , generally applied to intensity maxima over periods of the order of decades, can be equally well-fitted to observed intensity maxima over different durations in the same rain event. Examples of convectional storms and frontal disturbances are given and in each case the goodness of fit is excellent.