Improvements of storm surge forecasting in the Gulf of Venice exploiting the potential of satellite data: the ESA DUE eSurge-Venice project

Francesco De Biasio,Marco Bajo,Stefano Vignudelli,Georg Umgiesser,Stefano Zecchetto

doi:10.1080/22797254.2017.1350558

Francesco De Biasio, Marco Bajo + Show 3 more

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ABSTRACTThe northern Adriatic Sea is affected by storm surges, which often cause the flooding in Venice and the surrounding areas. We present the results of the eSurge-Venice project, funded by the European Space Agency (ESA) in the framework of its Data User Element programme: the project was aimed to demonstrate the potential of satellite data in improving storm surge forecasting, with focus on the Gulf of Venice. The satellite data used were scatterometer wind and altimeter sea level height. Hindcast experiments were conducted to assess the sensitivity of a storm surge model to a model wind forcing modified with scatterometer data and to altimeter retrievals assimilated with a dual 4D-Var system. The modified model wind forcing alone was responsible for a reduction of the mean difference between modelled and observed maximum surge peaks from −15.1 to −8.2 cm, while combining together scatterometer and altimeter data the mean difference further reduced to −6.0 cm. In terms of percent, the improvements in the reduction on the mean differences between modelled and observed surge peaks reaches 46% using only the scatterometer data, and 60% using both scatterometer and altimeter data.

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Storm surges are intense risings of the sea level, caused by severe meteorological conditions
Altimeter data were used in this experiment with the aim of improving the background surge level field of the first day of the SEV, and the schematic data flow is presented in the left panel of Figure 9: the outcome of the spin-up phase, the surge background state, is changed by the assimilation cycle into a new surge state called analysis state, which is used as starting point in the hindcast phase; (3) the SCATTALT hindcast experiment was set-up to assess the possible interaction between the mitigation technique and the assimilation procedure when applied together, and to quantify the performance of the storm surge model (SSM) using both scatterometer-mitigated NWP winds and altimeter Total Water Level Envelope (TWLE)* retrievals
−3.5 6.4 (Figure 10) confirming that the methodologies conceived for the ingestion of satellite data into the SSM were very well tolerated by the surge model, and did not alter significantly the correlation of the hindcast time series with respect to the control runs

Summary

Introduction

Storm surges are intense risings of the sea level, caused by severe meteorological conditions. They were designed to test the sensitivity of the SSM to the introduction of satellite data: (1) the SCATT experiment was performed substituting the standard ECMWF model wind forcing with the fields modified by the mitigation procedure with the scatterometer observations.

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