Advanced real-time precipitation components for urban hydrological applications as part of a digital twin for the city of Hanover

Overview & Synopsis

In the joint project « ZwillE », funded by the German Federal Ministry of Education and Research (BMBF), a digital twin for the city of Hanover is being developed, with the aim of creating a virtual image of the drainage system, and, based on this, providing measures and recommendations for action in the case of extreme rain events. We present the work and first results in the project topic “precipitation measurement and forecasting”. We describe and evaluate advances regarding the real-time preparation of radar-based precipitation estimates and nowcasts based on radar and rain gauge data provided by the German Weather Service. These include an increased spatial resolution of the polar radar scans from 1 km x 1 ° to currently 250 m x 1°. A new, flexible radar-rain gauge adjustment routine has been developed, optimized for the application in real-time systems. Further developments are an automatic rain gauge check based on both rain gauge and radar data and the production of nowcasts at an increased spatial resolution. Together with the generation of ensemble nowcasts and a blending procedure to combine nowcasts and the ensemble numerical weather forecasts ICON-D2-EPS, the new procedures will be used to provide input for real-time hydrological applications such as the simulation and control of sewer systems. Further research work will address the development of a short-term flooding forecast.