The sensitivity of WRF extreme precipitation simulations over the Henan Province to different topography and reanalysis data

The ability to simulate and forecast extreme precipitation events has become increasingly important due to their significant impacts on society. From 29 July to 31 July 2023, Henan province was hit by extreme rainfall, which led to widespread flooding and significant economic losses (this event is referred to as "23·7"). The research assessed the model's sensitivity to topography data (USGS and SRTM), initial and boundary conditions - IBC (FNL and ERA), and model initial times. Results indicated that while all experiments could capture the general rainfall pattern, their performance varied significantly. The model showed greater sensitivity to IBC than to topography. FNL IBC experiments initialized on 29 July better replicated the spatial distribution of precipitation, whereas ERA IBC experiments more accurately simulated its temporal evolution and heavy rain extent. While the use of SRTM topography demonstrates improvement in almost all FNL IBC experiments, it exhibits a decline in simulation performance for the ERA IBC experiments initialized on 28 July. The choice of initial time also significantly influenced the results. These results will be helpful in understanding how the combination of different topography data and IBC affects rainfall prediction in the WRF model and improves the forecast skills for heavy rainfall over the study region.