Ensemble Flood Forecasting Using Transposition of NWP Rainfall Fields Considering Orographic Rainfall

Abstract

The use of meteorological ensembles to produce sets of hydrological predictions has increased the ability to issue flood warnings. However, the spatial scale of a hydrological domain is still much finer than that of a meteorological model, and Numerical Weather Prediction (NWP) models have challenges with misplacement. This study assesses the transposition method with consideration of a spatial shift of ensemble NWP rainfall fields with the separation of orographic and non-orographic rainfall, in order to improve the accuracy improvement of the ensemble flood forecasting. The analysis shows that transposition of ensemble NWP rainfall fields improved the accuracy of the mean value and best value compared with original ensemble flood forecasting.