dsd-int 2014 - symposium next generation hydro software (nghs) - global tide model, martin verlaan,...
TRANSCRIPT
Delft Software Days, November 5th 2014
Global tide and storm-surge modelwith Delft3D Flexible Mesh
DSD November 5th 2014
Outline
• Motivation
• Grid development
• Required physical processes
• Calibration
• Some results
• Ongoing work and challenges
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New surge & tide model – DCSMv6
DCSM-v5 DCSM-v6
1/8º x 1/12º 1/40º x 1/60º
Includes tidal potential
Zijl et. Al. 2013 & Slobbe et. al. 2013
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Effect of sealevel rise on tides
Effect of 2 meter rise of MSL on M2 amplitude
Pickering et. al. 2013
OTIS-MPI
DSD November 5th 2014
Grid in Dflow-FM
Unstructured approach - step 1: grid thinning at high latitudes
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Grid in Dflow-FM
This Dflow-FM grid uses triangles and rectangles for local grid refinement. Resolution is based on Courant number.
Unstructured approach - step 2: grid refinement in shallow areas
DSD November 5th 2014
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 tidewhere there is stratificationand steep bathymetry
• This creates dissipation (roughly ¼ of total tidaldissipation on global scale)
f x=βg∂ h∂ x
N=√−gρ0
∂ρ
∂ zDepends on stratification
DSD November 5th 2014
Modified equations
r
αR
e
R
Conservation of momentum
∂u∂ t
+u∂u∂ x
+v∂ u∂ y
+g∂h−ζ−βh
∂ x−f v+
gu √u2+v2
C2 H+
α κ N d2 √ω2−f 2
2ω Hu=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 Hv=0
ζ
1. tidal forcing2. SAL3. dissipation by internal tides
Gravity potential
DSD November 5th 2014
Calibration of the Model
FES2012
Altimeter observations:- assimilated FES2012 gridded data- very accurate on deep water
Calibration parameters: - Depth & Friction- 7 regions
Automated calibration:- 21 parameters- deep water series Jan2007
DSD November 5th 2014
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
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