Regional Rainfall Frequency Analysis via Stochastic Storm Transposition

In a previous study, Foufoula-Georgiou (1989a) investigated a stochastic storm transposition (SST) approach as a possible methodology of assessing the probability of exceedance of extreme precipitation depths over a catchment. The purpose of this paper is to report further methodological advances on the SST approach and present the results of a pilot implementation study in the Midwest. Under the assumptions of an elliptical storm shape and spread function of a given functional form, extreme storms have been described by the joint probability distribution of seven storm parameters (five specifying the magnitude, orientation, shape, and within-storm spatial variability, and two specifying the location of the storm center). A nonhomogeneous spatial multivariate point process model has been postulated for the joint probability distribution of the storm center depth and storm location and it has been fitted to 65 extreme storms in the nine-state mid-western region. The method has been used to estimate the tails of the probability distribution of the average catchment depths over several hypothetical catchments in the Midwest and to describe the spatial variability of the estimates over the studied region.