Development and validation of a storm surge forecasting/hindcasting modelling system for the extensive Río de la Plata Estuary and its adjacent Continental Shelf

Abstract

The Río de la Plata (RdP) Estuary is affected by significant surges several times per year. This phenomenon has historically caused catastrophic water-level enlargements of up to 4.44 m, threatening and claiming human lives and producing major economic and material damages. The negative surges are less frequent, but when they do occur, inhibit the access to the principal harbors and waterways and disable the drinking water intakes of the Metropolitan Area of Buenos Aires (the Capital City of Argentina) with a population of more and 16 million people. Recent works suggest that the number and strength of the surge events have been increasing with time. Nevertheless, a state-of-the-art system for the forecast of those events is not available yet. In this work, the implementation of a numerical modelling system for the forecast/hindcast of storm surges and the associated currents in the RdP and the adjacent continental shelf are presented and validated. This pre-operational system is based on an adaptation of the CROCO community ocean model to solve the dynamics associated with the surge. The model was implemented using a set of routines written in open-source programming language (Linux and Python) to be cheap and efficient and to ensure an easy future transfer to the services responsible for the alerts. For a better representation of the regional atmospheric dynamics, wind speed and sea-level pressure used to force the simulations were corrected using direct observations collected at an oceanographic buoy anchored at the estuary. The model system performance in hindcast mode was quantified by comparison with observations from tidal gauges and current meters at several locations of the estuary and the adjacent shelf. Percent errors for water level over the whole estuary and currents in the intermediate and exterior estuary drove to average results of 8 and 13%, respectively. The skill scores resulted, on average, of 0.90 and 0.80, respectively. The model performance in both hindcast and forecast modes was evaluated during historical extreme storm surges. Results support the good performance of the model to simulate even extreme events with average skill scores of 0.97 and 0.92, respectively. Results are encouraging, particularly taking into account the limitations in the atmospheric forcing for the region, where only a relatively small number of direct observations are assimilated by the reanalysis and forecast models.

Development and evaluation of an ensemble forecast/hindcast system for storm surges in the Río de la Plata Estuary

“…To capture a large number of surge events, the quality of the EHS was assessed for the long time period between 2000 and 2010. This period was chosen because (a) it is a recent period which is properly represented by ERA5 (Dinápoli et al ., 2014b), (b) during this period the ten most extreme storm surge of the last two decades took place, (c) the numerical model was validated for this period and showed a good ability to reproduce these ten extreme events (Dinápoli et al ., 2020c), and (d) wind speed (OB) and water level (Palermo station) time series are available, which are long enough to obtain statistically robust results. Firstly, wind speed from ERA5 was compared to observations in order to determine whether the reanalysis represents the forcing uncertainties.…”

“…It should be noted that Dinápoli et al . (2020c) have shown that surface wind is spatially homogeneous (in both timing and amplitude) over the RdP; thus, OB is representative of the region. In addition, the time‐scale of the surge is from hours to days and, therefore, 1 year of hourly data is enough to obtain statistically significant conclusions.…”

“…Tide gauge water level observations at the Palermo (square in Figure 1) station, located close to Buenos Aires City Harbour, were provided by the SHN. Even though there are several tidal gauges inside the RdP (e.g., Dinápoli et al ., 2020c), Palermo is the only coastal station at the RdP with storm surge and extreme event thresholds and where a large continuous record of observations (from 1905 to the present) is available. It must be taken into account that Palermo is located at the uppermost and narrowest part of the estuary where the storm surge amplitudes (Simionato et al ., 2004) as well as the nonlinear tide–surge interactions (Dinápoli et al ., 2020b) and the nonlinear tide–river and surge–river interactions (Dinápoli et al ., 2020d) maximize.…”

“…In addition, in domain B the atmospheric forcings are corrected using an empirical function developed by Dinápoli et al . (2020c). The wind speed is adjusted using where w and are the ERA5 and the calibrated wind speed, respectively.…”

“…Nonetheless, when they do occur, the associated surge inhibits access to the principal harbours, waterways and drinking water intakes of one of the most important cities of southern South America (Campetella et al ., 2007). As an example of the strength of those events, in 2010 a negative extreme surge decreased the water level to −2.40 m below the Tidal Datum (Dinápoli et al ., 2020c). Even though positive and negative storm surges are not always so extreme, they occur several times per year; moreover, observations suggest that the number and strength of the events have been increasing with time (D'Onofrio et al ., 2008; Meccia et al ., 2009).…”