The aim of this study is to explore the appropriate coupling scale of the coupled atmospheric–hydrologic modeling system, which is established by the Weather Research and Forecasting (WRF) model and the gridded Hebei model with different sizes. The results show that the flood simulation results may not always be improved with higher-dimension precision and a more complicated system, and the grid size selection has a strong relationship with the rainfall evenness.

Both radar reflectivity and GTS data are good choices for assimilation in improving high-resolution rainfall of the NWP systems, which always fails in providing satisfactory rainfall products for hydrological use. Simultaneously assimilating GTS and radar data always performs better than assimilating radar data alone. The assimilation efficiency of the GTS data is higher than both radar reflectivity and radial velocity considering the number of data assimilated and its effect.

Accurately simulating and predicting the precipitation by numerical weather prediction is a difficult task for medium-sized catchments in semi-humid regions. This study shows that using multiphysics ensembles is a good method to reduce the uncertainties of rainfall simulation. This paper provides more guidance for choosing the physical parameterizations for accurate rainfall simulations of different storm types in semi-humid regions.