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Storm Surge Network Forum Venice, 18-20 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 Forum Venice, 18-20 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 Forum Venice, 18-20 November 2013
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
Storm Surge Network Forum Venice, 18-20 November 2013
80002 nodes143286 elements
Resolution:• open sea 15-20 km• coast 5 km• Italian coast 1 km
Storm Surge Network Forum Venice, 18-20 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.
www.esurge-venice.eu
Introduction
Storm Surge Network Forum Venice, 18-20 November 2013
Storm surges in Venice
Introduction
Sea level Flooded pavement ratio
190 cm 88%
140 cm 59%
130 cm 46%
120 cm 28%
110 cm 12%
100 cm 5%
Storm Surge Network Forum Venice, 18-20 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 Forum Venice, 18-20 November 2013
Correction of the wind fields
wc = we + (Δw/ws) we
θc = θe + Δθ
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:
Methods
Storm Surge Network Forum Venice, 18-20 November 2013
SEV list12 SEVs recorded in Venice from 2010 to 2012 were considered.
Methods
SEV 2010-02-28SEV 2010-11-10SEV 2010-11-19SEV 2010-11-21SEV 2010-11-26SEV 2010-12-23
SEV 2011-02-16
SEV 2012-10-27SEV 2012-10-31SEV 2012-11-02SEV 2012-11-11SEV 2012-11-28
Venice
Acqua AltaPlatform
Storm Surge Network Forum Venice, 18-20 November 2013
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.
Storm Surge Network Forum Venice, 18-20 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 Forum Venice, 18-20 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 AltaPlatform
Mediterranean Sea
Storm Surge Network Forum Venice, 18-20 November 2013
CASE 1: SEV 2010-11-26Results
Storm Surge Network Forum Venice, 18-20 November 2013
Normalised bias Δw/wscat between ASCAT and ECMWF related to a selected SEV for the Mediterranean Sea.
Quickscat vs ECMWF
Results
SEV 2010-11-26
Storm Surge Network Forum Venice, 18-20 November 2013
Statistics of the tuned data shows more directionality and higher wind speeds.
Speed Direction
Results
SEV 2010-11-26Quickscat vs ECMWF
Storm Surge Network Forum Venice, 18-20 November 2013
Results
SEV 2010-11-26
OriginalTuned
Storm Surge Network Forum Venice, 18-20 November 2013
Results
CASE 2: SEV 2012-11-11
Storm Surge Network Forum Venice, 18-20 November 2013
Results
SEV 2012-11-11
OriginalTuned
Storm Surge Network Forum Venice, 18-20 November 2013
Results
Statistics
OriginalTuned
Errors on maximum peaks
Storm Surge Network Forum Venice, 18-20 November 2013
Skew surge
ObservedOriginalTuned
Storm Surge Network Forum Venice, 18-20 November 2013
Results
Average statistics
Resolution RMSE [m] Correlation Peak error [m]
Original data
0.125 0.072 0.908 -0.102
0.25 0.072 0.906 -0.102
0.5 0.073 0.904 -0.104
Tuned data
0.125 0.066 0.918 -0.062
0.25 0.066 0.917 -0.063
0.5 0.067 0.915 -0.067
Storm Surge Network Forum Venice, 18-20 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 Forum Venice, 18-20 November 2013
Thank you for your attention!