Preparation and Evaluation of a Dutch-German Radar Composite to Enhance Precipitation Information in Border Areas

The Dutch weather radars in De Bilt and Den Helder have only limited coverage in the Dutch-German border area in the north-eastern part of the Netherlands, whereas the German radar in Emden is just across the border. For many years, local water authorities have been looking for a better quantitative precipitation estimate(QPE) for this region. Recently, a German water-management consultancy: hydro & meteo and a Dutch one: HydroLogic have jointly taken up the challenge to develop a completely new precipitation radar composite for this part of the Netherlands. The new composite uses the basic polar radar products (volume data) of the two national weather bureaux. The composite should be able to meet precipitation-information requirements of operational water managers; in other words it should be able to provide QPE in real time. The present case study of an interesting rainfall event demonstrates the capabilities of the new composite tool. The rainfall event was used to evaluate various filtering and correction algorithms. QPE results were verified against independent rain-gauge data. On average, the results of the new composite were found to be similar to the Dutch weather bureau's QPE for the entire Netherlands. However, the new composite yielded a much better QPE for the north-eastern part of the country, as a result of the addition of the Emden radar data. The algorithms we developed are ready to be applied in operational water-management by water boards and municipalities in the northeastern part of the Netherlands.