Model sensitivity during extreme positive and negative surges in the Río de la Plata estuary: highlighting the needs for an appropriate hindcast/forecast system

DINÁPOLI, MATÍAS G.; SIMIONATO, CLAUDIA G.; MOREIRA, DIEGO

WEATHER AND FORECASTING

AMER METEOROLOGICAL SOC

Lugar: Boston; Año: 2020

0882-8156

The large and fast-flowing Río de la Plata (RdP) estuary is affected by extreme storm-surges (above ±2 m respect to Tidal Datum), that have large impacts for the millions of inhabitants and for navigation. In this work the CROCO numerical model was modified and implemented as a set of regional one-way nested 2D applications for the hindcast/forecast of water level in the RdP. A sensitivity analysis (SA) was carried out to determine the impact on the numerical solutions of the uncertainties in the different modelling parameters-forcings and to highlight the needs for the construction of a modelling system that provides meaningful information to the potential users. The SA included the friction coefficients, the wind speed and direction, the atmospheric surface pressure and the continental discharge. Water level is most sensitive to uncertainties in the wind forcing; even small changes in this input can create large errors in the water level forecast/hindcast. Forcing with different analyses wind products yielded differences of up to 50% in the peak water levels. Results also showed that the modelling system requires a reasonable adjustment of the bottom friction parameters; that it is important to include the atmospheric surface pressure forcing; and that, from the point of view of water level forecast, it is not necessary to couple a hydrological model in spite of the enormous runoff of this estuary. Given the strong sensitivity to errors in the wind forcing, we believe it is important to provide estimates of uncertainty together with hindcast/forecast water level for these predictions to be of greatest quality and practical applicability.