Caroline Gautier and Sofia CairesJune 30th, 2015

Operational Wave Forecasts in theSouthern North SeaIAHR special session: Coasts at Threat in Europe

June 30th, 2015

Coasts at Threat in Europe

SWAN-North Sea for operational wave forecasts- Waves during extreme storm surges- Waves effecting vessel operations in approach channel

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SWAN-North Sea for operational wave forecasts

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Model set up SWAN-North Sea

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SWAN-DCSMRectangularArea:1500 km x 1700 kmCell size:3.6 km x 3.6 km

SWAN-ZUNOCurvilinearArea:770 km x 750 kmCell size:200 m - 2 km x200 m - 2 km

Model set up SWAN-North Sea

Wave boundary conditions for SWAN-DCSM:WAM model by ECMWF (30 freq x 24 dir) 0:00 6:00 12:00 18:00…

dt = 6 hrWind:KNMI’s HIRLAM11-v7.2 model 0:00 6:00 12:00 18:00…

dt = 1hrWater levels:WAQUA DCSMv6 0:00 6:00 12:00 18:00…

dt = 1hrCurrents (SWAN-ZUNO only):WAQUA DCSMv6 0:00 6:00 12:00 18:00…

dt = 1hrBathymetry:based on WAQUA DCSMv6 and ZUNOv4 (before calibration)

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Model set up SWAN-North Sea

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every 6 hour, a new SWAN run is started

6 hours hindcast + 48 hours forecasttime step: 1 hr

Model calibration SWAN-North Sea

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1. WEO2. AZB123. ELD4. K135. IJMUN6. EPL

freq [Hz]

E[m

2/H

z]

0.0 0.1 0.2 0.3 0.4 0.5

HE10, Hm0, Tm-1,0

Model calibration SWAN-North Sea

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Observation

Komen; =0Cfric=0.038(SWAN North Sea)

Westhuysen

Komen; =1(presently default inSWAN)

Hm

0[m

]H

E10

[m]

T m-1

,0[s

]U

10[m

/s]

Westhuysen,Cfric=0.048

Komen; =0Cfric=0.028

Komen; =0.5Cfric=0.028

Model calibration SWAN-North Sea

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• Reducing bottom friction (from 0.038 to 0.028) improves the bias of HE10

• Westhuysen whitecaping gives smallest bias• Komen whitecapping ( =0) gives least scatter in HE10

0.5 < HE10 < 1.5 [%] Hm0 [%] Tm-1,0 [%] 0.5 < HE10 < 1.5 [%] Hm0 [%] Tm-1,0 [%]

Model calibration SWAN-North Sea

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0.5 < HE10 < 1.5 [%] Hm0 [%] Tm-1,0 [%]

Conclusions SWAN-North Sea

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• SWAN-North Sea consists of:SWAN-DCSM and the nested SWAN-ZUNO

• Input comes from: - HIRLAM wind fields- ECMWF-WAM off shore waves- WAQUA water levels and currents

• HE10 is a sensitive parameter, especially for whitecapping formulation

• Improved settings: HE10 bias= -8% scatter= 33%Hm0 bias= 4% scatter= 16%Tm-1,0 bias= -11% scatter= 9%

HE10 Hm0 Tm-1,0

observations observations observations

SWAN

-ZU

NO

SWAN

-ZU

NO

SWAN

-ZU

NO