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Marco Bajo (1) , Stefano Zecchetto (2) , Georg Umgiesser (1) , Francesco De Biasio (2)

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. Operational SHYFEM-based systems.

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Marco Bajo (1) , Stefano Zecchetto (2) , Georg Umgiesser (1) , Francesco De Biasio (2)

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  1. 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

  2. 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)

  3. Kassandra Storm Surge Forecast System for the Mediterranean Sea • The models is operational from May 2010. Information, results and forecasts can be found under: http://www.ismar.cnr.it/kassandra

  4. Kassandra 80002 nodes 143286 elements Resolution: • open sea 15-20 km • coast 5 km • Italian coast 1 km

  5. Introduction eSurge Venice www.esurge-venice.eu 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.

  6. Sealevel Floodedpavement ratio 190 cm 88% 140 cm 59% 130 cm 46% 120 cm 28% 110 cm 12% 100 cm 5% Introduction Storm surges in Venice

  7. Introduction 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.

  8. Methods Correction of the wind fields ECMWF wind speed (we) was tuned using scatterometer data (ws): (ws-we)/ws, averaged over a specific time window around each SEV. A similar method was used to obtain a field Δθ, for the directions: wc= we + (Δw/ws)we θc= θe+ Δθ

  9. Venice Acqua Alta Platform Methods SEV list 12 SEVs recorded in Venice from 2010 to 2012 were considered. SEV 2010-02-28 SEV 2010-11-10 SEV 2010-11-19 SEV 2010-11-21 SEV 2010-11-26 SEV 2010-12-23 SEV 2011-02-16 SEV 2012-10-27 SEV 2012-10-31 SEV 2012-11-02 SEV 2012-11-11 SEV 2012-11-28

  10. Methods Wind forcing From the 0.125 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.

  11. Methods 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). 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 Cd fields. These depend also on the wind correction.

  12. Acqua Alta Platform Mediterranean Sea 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.

  13. Results CASE 1: SEV 2010-11-26

  14. Results SEV 2010-11-26 Quickscat vs ECMWF Normalised bias Δw/wscat between ASCAT and ECMWF related to a selected SEV for the Mediterranean Sea.

  15. Results SEV 2010-11-26 Quickscat vs ECMWF Statistics of the tuned data shows more directionality and higher wind speeds. Speed Direction

  16. Original Tuned Results SEV 2010-11-26

  17. Results CASE 2: SEV 2012-11-11

  18. Original Tuned Results SEV 2012-11-11

  19. Original Tuned Errors on maximum peaks Results Statistics

  20. Observed Original Tuned Skew surge

  21. Results Average statistics

  22. 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. What about temporal resolution? Tuned wind fields improve statistics Better reproduction of the storm surge peaks. The improvement is higher with storm conditions.

  23. Thank you for your attention!

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