Presentation by Firmijn Zijl, Deltares, at the Delft3D - User Days (Day 2: Hydrodynamics), during Delft Software Days - Edition 2019. Tuesday, 12 November 2019, Delft.

1. D e l t a r e s – D e l f t S o f t w a r e D a y s – 1 2 N o v e m b e r 2 0 1 9
Firmijn Zijl, Julien Groenenboom and Stendert Laan
3D model of the North Sea using Delft3D FM

2. Contents
• Background
• Model setup
• Results
• Ongoing developments
o Current validation
o Extension with Baltic Sea
3DmodeloftheNorthSeausingDelft3DFM
2/25

3. Background - ‘Sea Level Science’
• Models used for official Dutch water level forecasts
• Accurate, real-time water level forecasting important for informed discussion on movable barrier closure
• D-Flow FM module of the Delft3D Flexible Mesh Suite (Delft3D FM) now available
➢ New model to take advantage of new possibilities: DCSM-FM (DCSM = Dutch Continental Shelf Model)
3/25
3DmodeloftheNorthSeausingDelft3DFM

4. Background – ‘Environmental Hydrodynamics’
Outside world (e.g. CMEMS):
• Increased spatial extent
• Higher horizontal resolution
• Higher vertical resolution
➢Upgrade required
Difference in approach for:
• Environmental Hydrodynamics
(with 3D transport models)
• Sea Level Science
(with 2D tide-surge models)
Solution: borrow schematization, barotropic forcing and
calibration effort from existing 2D models
3D ZUNO(-DD) model
4/25
3DmodeloftheNorthSeausingDelft3DFM

5. Background – Proposed DCSM-FM schematisations
5/25
DCSM-FM 0.5nm
DCSM-FM 100m
2D
3D (+S/T)
2D
Ensemble Prediction
System (EPS)
Deterministic water level
forecasts
Water levels (incl. MDT)
Geodetic applications
Currents and transport
Water quality and ecology
3D boundary conditions
Oil dispersal
SAR
MetOcean
3DmodeloftheNorthSeausingDelft3DFM

6. Model setup – Network and bathymetry
6/25
Yellow: 1/10° x 1/15° ~ 4 nm x 4 nm
Green: 1/20° x 1/30° ~ 2 nm x 2 nm
Blue: 1/40° x 1/60° ~ 1 nm x 1 nm
Red: 0.75’ x 0.5’ ~ 0.5 nm x 0.5 nm
→ 800 m isobath
→ 50 m isobath
→ 200 m isobath
3DmodeloftheNorthSeausingDelft3DFM

7. Model setup – Network optimization
• Transitions in resolution (triangles) outside locations with high flow velocities → more cells, but faster
7/25
3DmodeloftheNorthSeausingDelft3DFM

8. Model setup – Barotropic forcing
Open boundary forcing
• Water level elevation imposed at 205 sections:
• Tide (from FES2012; 33 constituents)
• Storm surge (Inverse Barometer Correction)
Surface forcing
• Wind speed and air pressure from:
• HIRLAM7.2 →Arome-Harmonie
• ERA-Interim →ERA5
• ECMWF IFS
• Charnock relation for sea surface roughness (consistent with
meteo model), except:
• Surface current speed taken into account in wind drag relation
Also included
• Tidal potential
• Energy dissipation through generation of internal waves
• Barrier operations (closing of 8 storm surge barriers)
8/25
3DmodeloftheNorthSeausingDelft3DFM

9. Model setup – 3D baroclinic model
• 20 equidistant σ-layers (→51 z-layers)
• k-ε turbulence closure model
• Lateral forcing:
• Temperature and salinity from World Ocean Atlas (WOA13)
(As climatological mean monthly fields (0.25° grid, 107 depth levels, steps of 5 m at surface)
• Steric water level contribution
• Heat fluxes computed based on:
• Dew point temperature, air temperature and cloud cover (and wind speed)
• Fresh water discharges (~900):
• Climatology derived from EHYPE
Monthly means derived from 2001-2013
• 7 most important Dutch rivers
• 3 most important German rivers (Ems, Weser, Elbe)
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3DmodeloftheNorthSeausingDelft3DFM

10. Model setup – Computational times
• Maximum allowed numerical time step increasing from 120s to 200 s
• With the upgraded flexible resolution grid and increased time step, the model is 4 times faster
Model
Resolution
Comp. time
(min/day)*
Comp. time
(hr/yr)*
Avg. time step
(s)
# nodes
DCSMv6 (WAQUA) 1nm 1.6 10.0 120 859,217
DCSM-FM (1nm ) 4nm-1nm 0.4 2.5 199 373,522
DCSM-FM (0.5nm) 4nm-0.5nm 1.2 7.5 118 629,187
3D DCSM-FM (0.5nm) 4nm-0.5nm 13.0 79 111 629,187
*On 20 CPU cores
(3D ZUNO-DD: ~5 days/year)
Possibilities:
• 2D: Ensemble with 50 members
• 3D: Decadal scale 3D computations
• 3D: Real-time forecasting computations
Combining 2D/3D in one schematization is feasible:
• more resolution,
• much larger domain,
• more vertical resolution
• less computational cost!
10/25
3DmodeloftheNorthSeausingDelft3DFM

11. Model results – Water levels
Goodness-of-Fit (in cm) for the year 2014
11/25
RMSE tide (cm) RMSE surge (cm) RMSE total (cm)
ZUNO-DD DCSM-FM % ZUNO-DD DCSM-FM % ZUNO-DD DCSM-FM %
Cadzand 30.5 4.8 -84% 13.1 4.4 -66% 33.2 6.5 -80%
Westkapelle 27.0 5.1 -81% 12.7 4.4 -65% 29.9 6.7 -78%
Haringvliet 10 21.1 4.8 -77% 11.9 4.7 -61% 24.3 6.7 -72%
Hoek van Holland 17.1 5.9 -65% 11.8 5.1 -57% 20.7 7.8 -62%
Scheveningen 19.5 5.2 -73% 12.0 4.8 -60% 22.9 7.1 -69%
IJmuiden Buitenhav. 18.7 5.9 -68% 12.2 5.1 -58% 22.4 7.8 -65%
Average 22.3 5.3 -76% 12.3 4.8 -61% 25.6 7.1 -72%
Huge improvement in skill
3DmodeloftheNorthSeausingDelft3DFM

12. Model results – Surface salinity and temperature
12/25
3DmodeloftheNorthSeausingDelft3DFM
Salinity Temperature

13. Model results – Surface salinity and temperature
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3DmodeloftheNorthSeausingDelft3DFM
Salinity Temperature

14. Model results – Temperature (stratification)
Measurement
Simulation
Stratification (surface minus bottom)
14/25
Sea Surface Temperature
3DmodeloftheNorthSeausingDelft3DFM

15. Model results – Current velocity (2D vs. 3D)
15/25
3DmodeloftheNorthSeausingDelft3DFM
3D (surface)2D

16. Model results – Current velocity (2D vs. 3D)
16/25
3DmodeloftheNorthSeausingDelft3DFM
2D 3D (surface)

17. Current validation
17/25
TNW
HKZ
HKNHKW
3DmodeloftheNorthSeausingDelft3DFM
ADCP current profiles
Preliminary results

18. Baltic Sea – Network and bathymetry
18/25
3DmodeloftheNorthSeausingDelft3DFM
Green: 1/20° x 1/30° ~ 2 nm x 2 nm
Blue: 1/40° x 1/60° ~ 1 nm x 1 nm
Red: 0.75’ x 0.5’ ~ 0.5 nm x 0.5 nm
→ 100 m isobath
→ 50 m isobath

19. Baltic Sea – Salinity and temperature (preliminary)
3DmodeloftheNorthSeausingDelft3DFM
19/25
Salinity Temperature

20. Baltic Sea – Salinity and temperature (preliminary)
3DmodeloftheNorthSeausingDelft3DFM
20/25
TemperatureSalinity

21. Baltic Sea – Water levels
3DmodeloftheNorthSeausingDelft3DFM
21/25

22. Baltic Sea – Water levels (impact on DCSM-FM)
3DmodeloftheNorthSeausingDelft3DFM
22/25
No significant impact on water levels in Skagerrak/Kattegat
DCSM-FM + Baltic DCSM-FM only

23. Baltic Sea – Salinity in 3D DCSM-FM
3DmodeloftheNorthSeausingDelft3DFM
23/25DCSM-FM only

24. Baltic Sea – Salinity (exchange with Kattegat)
• Impact on salinity
3DmodeloftheNorthSeausingDelft3DFM
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25. Baltic Sea – Salinity (exchange with Kattegat)
• Impact on salinity
3DmodeloftheNorthSeausingDelft3DFM
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26. D e l t a r e s – D e l f t S o f t w a r e D a y s – 1 2 N o v e m b e r 2 0 1 9
Firmijn Zijl, Julien Groenenboom and Stendert Laan
3D model of the North Sea using Delft3D FM