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Improvements to the modelling of British rainfall using a modified Random Parameter Bartlett-Lewis Rectangular Pulse Model

1994; Elsevier BV; Volume: 157; Issue: 1-4 Linguagem: Inglês

10.1016/0022-1694(94)90104-x

1879-2707

Christian Onof, H. S. Wheater,

Hydrology and Watershed Management Studies

The Random Parameter Bartlett-Lewis Rectangular Pulse Model (RPBLRPM) was shown in a previous paper to provide generally good results when applied to a 38.5 year record of hourly rainfall from the Elmdon raingauge, Birmingham, UK: second-order properties of the depth and the interevent time distributions and the proportion of dry periods for different time-scales were on the whole well reproduced by the optimized parameters. However, two main problems arose, namely an overestimation of the autocorrelations for daily data in particular, and relatively poor performance in reproducing the extreme values of the depth distribution. The first of these problems is here addressed by superposition of a jitter process on the rectangular pulse, thus providing a more realistic representation of the continuous time process. Applying the jitter to each rainfall cell appears more effective than applying it to the instantaneous rainfall depth and enables a more satisfactory reproduction of the autocorrelations. The use of a gamma variable to replace the exponential distribution of the cell intensity provides a good reproduction of the extreme rainfall depths at different time-scales. Moreover, the values of the parameters providing an optimal reproduction of the extreme values of the depth distribution are in most cases close to those obtained by optimizing on the interevent time features, which provides a method for estimation and ensures that the two objectives do not conflict.