Improving Estuarine Hydrodynamic Forecasts Through Numerical Model Ensembles

Abstract

Numerical models are essential tools for the study and analysis of the hydrodynamics of estuarine systems. However, the model results contain uncertainties, which need to be minimized to increase the accuracy of predictions. In this work, the ensemble technique is proposed as a solution to improve hydrodynamic forecasts for estuarine regions. Two numerical models, openTELEMAC-MASCARET and Delft3D, were considered for the application of this technique to two Portuguese estuaries. Superensembles for three scenarios (summer, winter, and extreme event) were built to assess the effectiveness of the technique in improving water level prediction. Various weighing techniques were tested in the construction of the ensembles. Weighing techniques that consider the previous performance of each model alone outperformed other techniques. This was observed for all scenarios considered, at all sampling points and in both studied estuaries. The effect of the ensemble size was also analyzed. It was found that the size of the set is directly related to the prediction accuracy, with the best results provided by the superensembles with the highest number of elements. It is concluded that the combined use of several hydrodynamic models reduces the uncertainty of the results and increases the reliability and consistency of predictions for estuarine regions.

Hydrodynamic Model Ensembles for Climate Change Projections in Estuarine Regions

“…Two different estuarine areas were considered in this study: the Douro and Minho estuaries (Figure 1). Despite the fact that these estuaries are separated by a distance of less than 100 km and present similar seasonal flow regimes, their river flow average and peak discharges, as well as their morphology, bathymetry, banks configuration, extension, and level of urbanization, are completely different, which is reflected in distinct dynamics and environmental conditions [2,28]. Therefore, separate studies were carried out to represent the local effects of climate change conditions and extreme events.…”

“…Given the need for accurate forecasts, finding and implementing new solutions that avoid or mitigate errors is crucial. In this context, ensemble modeling is considered one of the best solutions because it can minimize the combined uncertainty in input data, model parameters, and model structure, improving the performance of the models [25][26][27][28]. An ensemble uses statistical methods to combine several numerical model simulations.…”

“…This is a widely applied technique in atmospheric, climatic, and hydrological sciences [4,26,27,29,30]. Previous application of this technique to estuarine regions by Iglesias et al [28] revealed that an adequate ensemble effectively improves the forecasting results of the individual models, even for the scenarios that were more difficult to forecast by single models. However, the ensemble technique, successfully applied in estuarine hydrodynamics [25,28], has not been fully developed to forecast future hydrodynamic patterns in estuarine regions considering climate change scenarios [4].…”

“…Previous application of this technique to estuarine regions by Iglesias et al [28] revealed that an adequate ensemble effectively improves the forecasting results of the individual models, even for the scenarios that were more difficult to forecast by single models. However, the ensemble technique, successfully applied in estuarine hydrodynamics [25,28], has not been fully developed to forecast future hydrodynamic patterns in estuarine regions considering climate change scenarios [4]. The objective of this work was to address this issue and apply the ensemble technique previously developed and implemented by Iglesias et al [28] to forecast future scenarios for two different estuarine regions under climate change conditions.…”

“…However, the ensemble technique, successfully applied in estuarine hydrodynamics [25,28], has not been fully developed to forecast future hydrodynamic patterns in estuarine regions considering climate change scenarios [4]. The objective of this work was to address this issue and apply the ensemble technique previously developed and implemented by Iglesias et al [28] to forecast future scenarios for two different estuarine regions under climate change conditions.…”