Storm surge modelling in the Storm surge modelling in the Mediterranean Sea with focus on Mediterranean Sea with focus on

the Italian coastthe Italian coast

Christian Ferrarin1.2. Georg Umgiesser1. Andrea Cucco2. Marco Bajo1

1. ISMAR-CNR. Venice. Italy. 2. IAMC-CNR. Oristano. Italy.

Christian Ferrarin : c.ferrarin@ismar.cnr.it

The goal of this research is to describe/predict the storm surge in the Mediterranean Sea with focus on the Italian coast, through the application of high resolution numerical models.

ObjectiveObjective

The TOTAL WATER LEVEL is given by:• Tidal Oscillation• Meteorological Surge• Wave set-up / set-down

Finite element tide-surge-wave modelling system

Meteorological Model

HydrodynamicModel

SpectralWave Model

STORM SURGE

MO

DEL F

RA

MEW

OR

K

i

iy z

vkτ

SHYFEM ModelShallow water HYdrodynamic Finite Element Model

SHYFEM ModelShallow water HYdrodynamic Finite Element Model

xgH

xgH

H

F

y

U

x

UA

x

p

x

ζgHfV

y

Uv

x

Uu

t

U xh

sx

bx

a

2

2

2

2111

ygH

ygH

H

F

y

V

x

VA

y

p

y

ζgHfU

y

Vv

x

Vu

t

V yh

sy

by

a

2

2

2

2111

0

y

V

x

U

t

= water levelH = water depthg = gravityf = Coriolis parameterU.,V = velocitiesAh = hor. diff. coeff.pa = atm. pressureη = equilibrium tideα = Love numberβ = loading factor

Potentialtide

Loadingtide

WaveRadiation

stress

Windstress

Pressuregradient

Bottomstress

Charnockg

uz

BankeSmithuC

uC

s

wd

wdas

2*

0

3

2

&10)066.063.0(

1/62

22

=

=

HkCC

gc

H

vuuc

sb

bb

Operator Splitting Methods (OSM) 1st and 2nd Step – Spectral part

2nd Step – Geographical space

3rd Step – Integration of the source terms

*

*000; on 0,t

Nc N N N t

t

***

** ** *** **00 ; on 0,x y t t t

Nc N c N N N t

t x y

****

**** ***,** 0; on 0,totN t t t

NS N N t

t

**

* ** *00; on 0,t t t

Nc N N N t

t

Finite element wave model WWM

totalyx S

NCNC

y

NC

x

NC

t

N

)()()()(

Finite element wave model based on the spectral action balance equation (Hsu et al. 2005):

N = wave action density S = source term

Model domainModel domain

646218 nodes117714 elements

Resolution:• open sea 15-20 km• coast 5 km• Italian coast 1.5 km

Model set upModel set up

FORCING:• ECMWF wind & pressure• FES2004 tide at Gibraltar Strait• Body + earth + load tides

• 4 diurnal (K1, O1, P1, Q1)

• 4 semidiurnal (M2, S2, N2, K2)

• 3 long term (Mf, Mm, Ssa)

Hydrodynamic:• 2D borotropic• Smith & Banke formulation• Time step: 300 s (adaptive)

Wave:• 18 directions• 18 frequency [0.05 ... 0.5]• Time step = 600 s

Model results 1: tideModel results 1: tide

Amp Pha Amp Pha Amp Pha Amp Pha Amp Pha Amp Pha Amp Pha Amp Pha-0,21 -1,06 -0,10 -4,33 -0,15 1,27 -0,20 3,28 0,34 2,03 0,44 -0,40 0,25 19,79 -0,06 -6,510,83 6,81 0,35 8,25 0,25 8,29 0,34 9,93 0,42 69,92 0,59 18,27 0,30 23,39 0,16 14,23

K1 O1 P1 Q1

AverageRMSE

M2 S2 N2 K2

1,07 0,65 1,19 0,811,62 1,09 1,54 0,39Tsimplis

D(cm) M2 S2 K1 O1

SHYFEM

0

5

10

15

20

25

0 5 10 15 20 25

Mo

delle

d A

mp

litu

de

(cm

)

Observed Amplitude (cm)

M2

K1

0

30

60

90

120

150

180

210

240

270

300

330

360

0 30 60 90 120 150 180 210 240 270 300 330 360

Mo

delle

d P

ha

se (d

eg

)

Observed Phase (deg)

M2

K1

Model results 2: Model results 2: Residual Residual differencesdifferences

StationRMSE [cm] CORR BIAS [cm] SI

ID Name1 Trieste 0.11 0.70 -0.02 1.072 Venezia 0.12 0.76 -0.07 0.983 Ravenna 0.09 0.75 0.00 0.864 Ancona 0.12 0.78 0.09 1.355 Ortona 0.15 0.72 0.12 1.616 Vieste 0.19 0.64 0.17 1.917 Bari 0.22 0.67 0.20 2.028 Otranto 0.30 0.57 0.29 2.349 Taranto 0.26 0.56 0.25 2.27

10Crotone 0.24 0.49 0.22 2.2211Reggio Cal. 0.25 0.55 0.24 2.3012Palinuro 0.17 0.56 0.16 2.0613Salerno 0.19 0.53 0.18 2.1514Napoli 0.16 0.55 0.15 2.0115Civitav 0.10 0.57 0.07 1.5816Livorno 0.09 0.65 0.06 1.3917Genova 0.07 0.68 -0.04 1.0218 Imperia 0.06 0.67 -0.01 0.9219Messina 0.11 0.59 0.09 1.7420Palermo 0.08 0.59 -0.06 1.1921Porto Emp. 0.10 0.48 0.08 1.7922Catania 0.06 0.66 0.01 1.0523Lampedusa 0.08 0.50 -0.04 1.2424Cagliari 0.16 0.53 -0.14 1.8025Carloforte 0.13 0.57 -0.11 1.6226Porto Torres 0.12 0.60 -0.11 1.46

  AVERAGE 0.14 0.61 0.07 1.61

Model results 2: Model results 2: Residual Residual differencesdifferences

Line = medianBox = 25th to 75th percentileWisker = 1.5 * IQRStar = average value