For the purpose of numerically studying sahelian storm rainfields, a family of random functions is described with a characterization of its finite dimensional law. Some problems appearing when fitting its functional parameters are put forward and two solutions to bypass those problems are provided, according to the regularity properties of the marginal cumulative distribution function. An illustration of this method is implemented on a set of sahelian rainfields of event accumulation displaying a strong spatial intermittency. Keywords : geostatistic, Gaussian random functions, anamorphosis, intermittency, discontinuous c.d.f, valid covariance, internal consistency. 1 Introduction 1.1 Scale problems in hydrologic modelling in the Sahel It is generally admitted that water balance modelling requires rainfall data as input to hydrologic models at fine scale. This need is particularly strong in the sahelian region. Indeed, rainfall being mainly of convective origin, rainfall fields are hi...