Technical description of the KNMI Rainfall Generators for the Rhine and Meuse basins

This report gives a technical description of what is briefly known as the KNMI Rainfall (or Weather) Generators for the Rhine and Meuse basins. These rainfall generators form part of the GRADE system for respectively the rivers Rhine and Meuse. GRADE stands for Generator of Rainfall and Discharge Extremes and is a collective development of Rijkswaterstaat, Deltares and KNMI. The KNMI rainfall generators are not single programs but are sets of programs that altogether form what we call ‘the rainfall generators’. They contain programs that are considered as the core of the rainfall generators (and that are essentially the same for both rainfall generators) but also programs for pre-processing the historical meteorological data that serve as basis for the weather generators and programs for post-processing the synthetic data produced by the weather generators. This report describes all these programs and the steps that are needed to run these programs to generate the (current) reference Rainfall Generator (RG) simulations for the Rhine and Meuse basins, to perform an uncertainty analysis for both Rainfall Generators, to convert the Rainfall Generator output to the data-format suitable for the GRADE-FEWS1 system, and to update the Rainfall Generators in the future by incorporating more recent historical meteorological data.

Most of the information in this report was already published; in KNMI Publications 186-I to 186-VII for the RG for the Rhine basin and in Publications 196-I to 196-VI for the RG for the Meuse basin. While these reports present the Rainfall Generator developments in historical order this report gives a systematic overview of the components of the latest versions of the Rainfall Generators and of the similarities and differences between them. The focus in this report is thus on the application and the updating (in the future) of the Rainfall Generators. In this respect it can also be regarded as an application manual of the KNMI Rainfall Generators.

An important goal of this report is therefore to give sufficient details (together with references to earlier work) about how to reproduce the current Rainfall Generator results and how to produce updated Rainfall Generator results in the future. This document describes the status of the Rainfall Generators at the end of 2013/early 2014. These are the Rainfall Generators that were used to generate the 50,000-year reference simulations for the Rhine and the Meuse basins which are used in the version of GRADE (version 2.0) provided to WTI20172 in 2014, and of which the results are described in detail in the GRADE Final Report (Hegnauer et al., 2014).