Storm Surge Network ForumVenice, November 2013 Storm Surge modelling in Venice and the Mediterranean Sea: Improving the forecast tuning ECMWF wind fields Marco Bajo (1), Stefano Zecchetto (2), Georg Umgiesser (1), Francesco De Biasio (2) (1) - ISMAR-CNR, Venezia (2) - ISAC-CNR, Padova

Storm Surge Network ForumVenice, November 2013 Operational SHYFEM-based systems Storm surge + total sea level inside the Venice lagoon: - ICPSM model (since 2003) : neural network post- processing - ISPRA model (since 2011): data assimilation (4D-PSAS) with data from 9 stations Total sea level + waves on Mediterranean and Black Sea: - Kassandra (since 2010)

Storm Surge Network ForumVenice, November 2013 Storm Surge Forecast System for the Mediterranean Sea The models is operational from May Information, results and forecasts can be found under:

Storm Surge Network ForumVenice, November nodes elements Resolution: open sea km coast 5 km Italian coast 1 km

Storm Surge Network ForumVenice, November 2013 eSurge Venice eSurge-Venice (ESA Storm Surge for Venice) is a project funded by the European Space Agency, part of its Data User Element (DUE) programme. It aims to increase the usage of Earth Observation (EO) satellite data, from both ESA and other spacecraft, within the storm surge community. Introduction

Storm Surge Network ForumVenice, November 2013 Storm surges in Venice Introduction Sea levelFlooded pavement ratio 190 cm88% 140 cm59% 130 cm46% 120 cm28% 110 cm12% 100 cm5%

Storm Surge Network ForumVenice, November 2013 Satellite data ALTIMETER DATA: to improve the initial state of the storm surge model, using data assimilation techniques or other methods. SCATTEROMETER DATA: to improve the wind forcing of the storm surge model, looking for a tuning of the modelled wind. Introduction

Storm Surge Network ForumVenice, November 2013 Correction of the wind fields w c = w e + ( Δ w/w s ) w e θ c = θ e + Δθ ECMWF wind speed (w e ) was tuned using scatterometer data (w s ): (w s -w e )/w s, averaged over a specific time window around each SEV. A similar method was used to obtain a field Δθ, for the directions: Methods

Storm Surge Network ForumVenice, November 2013 SEV list 12 SEVs recorded in Venice from 2010 to 2012 were considered. Methods SEV SEV SEV SEV SEV SEV SEV SEV SEV SEV SEV SEV Venice Acqua Alta Platform

Storm Surge Network ForumVenice, November 2013 Methods Wind forcing From the degree wind and pressure fields, 0.25 and 0.5 degree fields were sub-sampled, in order to investigate the importance of the resolution. For each SEV the original and the tuned fields were tested. A total of 6 simulations were carried on for each SEV. First 10 days are considered spin-up time.

Storm Surge Network ForumVenice, November 2013 The model uses the wind stress (Liu et al., 1979), which was computed using the ECMWF air density fields, the wind fields and the drag coefficient C d fields. These depend also on the wind correction. Hydrodynamic model A finite element model, solving the shallow water equations (SHYFEM) was used to run the hydrodynamic simulations. This model runs operationally every day at the storm surge forecasting and warning Centre in Venice (ICPSM). Methods

Storm Surge Network ForumVenice, November 2013 Methods Computational grid used by the model: - open boundary in the Gibraltar Strait; - only wind and pressure forcings; - sea level in the Acqua Alta Platform are used to run a second simulation inside the Venice Lagoon. Acqua Alta Platform Mediterranean Sea

Storm Surge Network ForumVenice, November 2013 CASE 1: SEV Results

Storm Surge Network ForumVenice, November 2013 Normalised bias Δ w/w scat between ASCAT and ECMWF related to a selected SEV for the Mediterranean Sea. Quickscat vs ECMWF Results SEV

Storm Surge Network ForumVenice, November 2013 Statistics of the tuned data shows more directionality and higher wind speeds. SpeedDirection Results SEV Quickscat vs ECMWF

Storm Surge Network ForumVenice, November 2013 Results SEV Original Tuned

Storm Surge Network ForumVenice, November 2013 Results CASE 2: SEV

Storm Surge Network ForumVenice, November 2013 Results SEV Original Tuned

Storm Surge Network ForumVenice, November 2013 Results Statistics Original Tuned Errors on maximum peaks

Storm Surge Network ForumVenice, November 2013 Skew surge Observed Original Tuned

Storm Surge Network ForumVenice, November 2013 Results Average statistics Resolution RMSE [m]CorrelationPeak error [m] Original data Tuned data

Storm Surge Network ForumVenice, November 2013 Conclusions Spatial wind resolution seems to have a low importance in the storm surge forecast in the Adriatic Sea. Until 0.5 degree grid size the performances are similar. Tuned wind fields improve statistics What about temporal resolution? Better reproduction of the storm surge peaks. The improvement is higher with storm conditions.

Storm Surge Network ForumVenice, November 2013 Thank you for your attention!