Operational wave forecasts in the southern North Sea

1. Caroline Gautier and Sofia Caires
June 30th, 2015
Operational Wave Forecasts in the
Southern North Sea
IAHR special session: Coasts at Threat in Europe

2. 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
2

3. SWAN-North Sea for operational wave forecasts
June 30th, 2015 3

4. Model set up SWAN-North Sea
June 30th, 2015 4
SWAN-DCSM
Rectangular
Area:
1500 km x 1700 km
Cell size:
3.6 km x 3.6 km
SWAN-ZUNO
Curvilinear
Area:
770 km x 750 km
Cell size:
200 m - 2 km x
200 m - 2 km

5. 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 hr
Wind:
KNMI’s HIRLAM11-v7.2 model 0:00 6:00 12:00 18:00…
dt = 1hr
Water levels:
WAQUA DCSMv6 0:00 6:00 12:00 18:00…
dt = 1hr
Currents (SWAN-ZUNO only):
WAQUA DCSMv6 0:00 6:00 12:00 18:00…
dt = 1hr
Bathymetry:
based on WAQUA DCSMv6 and ZUNOv4 (before calibration)
June 30th, 2015 5

6. Model set up SWAN-North Sea
June 30th, 2015 6
every 6 hour, a new SWAN run is started
6 hours hindcast + 48 hours forecast
time step: 1 hr

7. Model calibration SWAN-North Sea
June 30th, 2015 7
1. WEO
2. AZB12
3. ELD
4. K13
5. IJMUN
6. EPL
freq [Hz]
E[m2/Hz]
0.0 0.1 0.2 0.3 0.4 0.5
HE10, Hm0, Tm-1,0

8. Model calibration SWAN-North Sea
June 30th, 2015 8
Observation
Komen; =0
Cfric=0.038
(SWAN North Sea)
Westhuysen
Komen; =1
(presently default in
SWAN)
Hm0[m]HE10[m]Tm-1,0[s]U10[m/s]
Westhuysen,
Cfric=0.048
Komen; =0
Cfric=0.028
Komen; =0.5
Cfric=0.028

9. Model calibration SWAN-North Sea
June 30th, 2015 9
• 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 [%]

10. Model calibration SWAN-North Sea
June 30th, 2015 10
0.5 < HE10 < 1.5 [%] Hm0 [%] Tm-1,0 [%]

11. Conclusions SWAN-North Sea
June 30th, 2015 11
• 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-ZUNO
SWAN-ZUNO
SWAN-ZUNO