Symposium Next Generation Hydro Software (NGHS)

1. Delft Software Days, November 5th 2014
Global tide and storm-surge model
with Delft3D Flexible Mesh
Martin.verlaan@deltares.nl

2. DSD November 5th 2014
Outline
• Motivation
• Grid development
• Required physical processes
• Calibration
• Some results
• Ongoing work and challenges

3. New surge & tide model – DCSMv6
DCSM-v5 DCSM-v6
1/8º x 1/12º 1/40º x 1/60º
3
Includes tidal potential
Zijl et. Al. 2013 & Slobbe et. al. 2013

4. Effect of sealevel rise on tides
Effect of 2 meter rise of MSL on M2 amplitude
4
Pickering et. al. 2013
OTIS-MPI

5. Existing global tide models
DSD November 5th 2014
M2

6. First attempt of grid in Delft3D
→ Lack of resolution near coasts.
DSD November 5th 2014

7. Grid in Dflow-FM
Unstructured approach - step 1: grid thinning at high latitudes
DSD November 5th 2014

8. Unstructured approach - step 2: grid refinement in shallow areas
8
Grid in Dflow-FM
This Dflow-FM grid uses triangles and rectangles
for local grid refinement. Resolution is based on Courant number.

9. First results in Dflow-FM

10. Necessary improvements
• Self attraction and loading
• Tides modify the gravity potential as well
• Computation is very time-consuming
• Start wit simple approximation
• Internal tides
• Tides create internal tide
where there is stratification
and steep bathymetry
• This creates dissipation
(roughly ¼ of total tidal
dissipation on global scale)
∂ρ
∂ z Depends on stratification
DSD November 5th 2014
f x=β g ∂ h
∂ x
N=√−g
ρ0

11. Modified equations
Gravity potential
DSD November 5th 2014
r
α
Re
R
Conservation of momentum
∂u
+u ∂u
+v ∂ u
+g ∂h−ζ−βh
∂t
∂ x
∂ y
∂ x
−f v+ gu √u2+v2
C2 H
+ α κ N d2 √ω2−f 2
2ω H
u=0
∂ v
∂t
+u ∂ v
∂ x
+v ∂ v
∂ y
+ g ∂ h−ζ−βh
∂ y
+f u+ g v √u2+v2
C2 H
+ α κ N d2 √ω2−f 2
2ω H
v=0
ζ
1. tidal forcing
2. SAL
3. dissipation by internal tides

12. Calibration of the Model
FES2012
DSD November 5th 2014
Altimeter observations:
- assimilated FES2012 gridded data
- very accurate on deep water
Automated calibration:
- 21 parameters
- deep water series Jan2007
Calibration parameters:
- Depth & Friction
- 7 regions

13. Calibration results for deep water
Region Before After
Arctic 5.1 cm 3.2 cm
N. Atlantic 9.4 7.4
S. Atlantic 12.1 8.4
N. Pacific 8.1 6.2
S. Pacific 11.2 7.3
Indian Ocean 11.7 8.2
S. Ocean 12.4 10.2
Total 10.2 7.4
DSD November 5th 2014

14. Sample deep water station
DSD November 5th 2014
Before calibration

15. Sample deep water station
DSD November 5th 2014
After calibration

16. Sample coastal time-series
Cordova Honolulu
Tide
Surge
DSD November 5th 2014

17. Ongoing work and challenges
• Ongoing work:
• Operational global storm-surge model (ID-Lab)
• Climate impact studies (cooperation with VU and EU-RISES)
• Modeling Self-Attraction and Loading
• Challenges:
• Further improve dissipation by internal tides
• Improve computational performance with parallel computing
• Link to real-time observations
• Hurricane forecasts
• Improve open-boundary conditions for regional models
DSD November 5th 2014

18. Questions?

19. Grid Arctic

20. Grid North America

21. Grid South-East Asia

22. Grid Northern Europe