A parsimonious approach to stochastic multisite modelling and disaggregation of daily rainfall

Daily rainfalls are simulated through a two station model at a key station and satellite stations whilst maintaining the first three moments and relevant correlations. Wet and dry runs of the occurrence process of daily rainfall are assumed to have a geometric distribution. Disaggegration of daily rainfalls into hourly values is made through dimensionless accumulated hourly amounts generated by a beta distribution. It is postulated that the occurrence process of hourly rainfall has also a geometric distribution but it is conditioned on the total daily rainfall. Application is made to the Tevere (Tiber) basin in central Italy. The simple reduced parameter approach is seen to reproduce satisfactorily extremes and other statistical properties of daily and hourly rainfalls.