Assessing the sensitivity of storm surge simulation to the atmospheric forcing resolutions across the estuary-sea continuum

Abstract. Estuaries are particularly vulnerable to flooding from extreme events such as storm surges, and this vulnerability can be exacerbated by climate change. Numerical models are valuable tools for supporting flood prevention and planning in these regions. However, despite recent improvements in storm surge modeling, most models use atmospheric forcing data with spatial resolutions of several tens of kilometers and temporal resolutions of a few hours, hence much coarser than their own resolution. This discrepancy may have an impact on the overall model accuracy. Here, we evaluate the impact of atmospheric forcing data’s spatial and temporal resolution on storm surge modeling within the Scheldt river-estuary-North Sea sea continuum. Atmospheric forcings were incorporated at spatial resolutions ranging from 2 km to 30 km and at temporal resolutions from 15 minutes to 6 hours. Using an unstructured-mesh multiscale hydrodynamic model, we assessed how these variations influenced the accuracy of storm surge simulations. Our findings indicate that increasing spatial resolution significantly improves the accuracy of peak surge predictions in estuarine areas, while higher temporal resolution further enhances model performance only at the finest spatial resolution. The effect of the temporal resolution diminishes as spatial resolution becomes coarser, suggesting that spatial resolution is more critical for improving storm surge forecasts in estuaries like the Scheldt. The timing of peak surges remained consistent across all configurations. The best results are obtained with 2 km and 15 min atmospheric forcing resolution. This study underscores the importance of aligning atmospheric forcing resolution with the hydrodynamic model's spatial scale to achieve optimal accuracy in storm surge predictions for estuaries.