A daily rainfall disaggregation model

Abstract

Short-time-intensity rainfall is often required in experimental and predictive studies of runoff, erosion and pollutant transport. While daily rainfall records of up to 100 years duration are commonly available in Australia, few short-time-intensity records of even 25 years duration have been maintained. In this paper, we describe and test a model that allows disaggregation of measured daily rainfall into short-time-intensity data. Parameters are derived from a relatively short, measured time-intensity record. The model simulates number of events on a rain day, and starting time, duration, rainfall amount, time to peak intensity and peak intensity of each event. A double exponential is used to generate internal intensity for each event. The model is relatively simple and can be parametrised with a measured time-intensity record as short as three years. The model adequately reproduced characteristics of rainfall from four locations in Australia with contrasting climates. The disaggregation model has application with simulation or experimental studies where information about the time distribution of rainfall is required. The model would be suitable for incorporation into cropping system and other models.