MODELING EXTREMES OF THE AREAL RAINFALL PROCESS

Risk assessment for many hydrological structures requires an estimate of the extremal behaviour of the rainfall regime within a specified ca tchment region. In most cases it is the spatially aggregated rainfall which is the key process, though in practice only pointwise rainfall m easurements from a network of sites over the region are available. In this paper we address the problem of making inferences about the extre mal properties of the aggregated process from the pointwise data. Work ing within the usual extreme value paradigm, a model is derived in whi ch the resulting distribution is determined by the marginal tail behav iour and spatial dependence at extreme levels of the process. Data col lected from a region in the south-west of England are used to illustra te the procedure.