Global tide surge mode

1. GLOSSIS: a global storm surge
forecasting and information system
martin.verlaan@deltares.nl
lora.buckman@deltares.nl
simone.dekleermaeker@detlares.nl

2. Why? – Need for an
operational
Global Tide Surge Model

3. Cyclone Patricia October 2015

4. GLOSSIS for Patricia October 2015
Mexico

5. Existing global (tide) models
Empirical tide
GOT4.7 Most accurate tides, relies on
altimeter
EOT11
Spectral tide
FES2012 Only for tides, data-assimilation
available
TPXO7.2 (OTIS)
DTU10 Based on FES
Timestepping tide/surge
T-UGO/MOG2D Eg satellite inv baro correction
OMCT
Tropical cyclones
Hyflux2 Regional approach

6. How? - Development of
Global Tide Surge Model

7. step 1: grid thinning at high latitudes
step 2: grid refinement in shallow areas, with triangles and rectangles for local grid refinement. Resolution is based on Courant number.
Resulting grid resolution varies from 5 km (1/20°) at the coast to 50 km (1/2°) in open oceans, with nearly 1 million cells in total
Grid in Dflow-FM – unstructured grid

8. Parallel performance
1 2 4 8 16 32 64 128 256
0
100
200
300
400
500
600
700
800
900
Parallel speedup on E3 cluster
sec/day
Number of cores
Computationtimepersimulationday[s]
1 2 4 8 16 32 64
0
10
20
30
40
50
60
70
Speed up
Counting nodes instead of cores
Speedup
Ideal speedup
Number of nodes
Speedup

9. How well? - Reanalysis of
extreme sea- levels

10. Validation (1980-2011)
Surge errors with ERA-interim forcing (0.75 degree)
472 stations from University of Hawaii Sea-Level Center (UHSLC) dataset.
Work of: Sanne Muis

11. Validation – return periods
GTSM generally underestimates the maximum of a storm
Work of: Sanne Muis

12. Extreme sea levels
1/10 year high-waters along the coast
Work of: Sanne Muis

13. Cyclones are underestimated by coarse NWP

14. Delft Software Days 2015
Coarse ERA-interim winds
GTSM high-resolution winds
Without coastal refinement
Dietrich et al 2009

15. What for? - GLOSSIS
operational information
system

16. Nasa: aug 30
GLOSSIS – operational information system
NOAA GFS 0.25 degree
Real-time observations from IOC
Work of: Lora Buckman

17. Guidance - Warning thresholds

18. What’s next? –
Model improvements and
dissemination

19. Internal tides and SAL, calibration fine model
τ IT =CρNκ−1
(∇ h2
)u
Internal tides: simplified formulation
Work of: Shobhit Jain
Full SAL equations
Work of: Camille le Coz

20. Dissemination
Dissemination of results via website
•Automated web reports & web viewer
•Services such boundary conditions for regional models

21. Why?Why?
Need for a global tide surge modelNeed for a global tide surge model
How?How?
Development of Global Tide Surge ModelDevelopment of Global Tide Surge Model
How well?How well?
Reanalysis of extreme sea levelsReanalysis of extreme sea levels
What for?What for?
GLOSSIS operational forecasting and information systemGLOSSIS operational forecasting and information system
What’s next?What’s next?
Model improvements and disseminationModel improvements and dissemination
Contact: martin.verlaan@deltares.nl
Questions?

22. Backup slides

23. GLOSSIS – operational information system
Operational model, run 4 times per day
•Boundary conditions for regional models
•Guidance for area’s without regional model

24. Additional physical processes
Self attraction and loading
• gravitational potential of moving water masses (tide) and their
capability of modifying the Earth’s shape
• Start with simple approximation, proportional to the pressure gradient
Internal tidal wave drag
• Where there is stratification and
steep bathymetry
• Start with approximation: on global scale
roughly ¼ of total tidal dissipation
• Modeled as an additional linear friction
component
f x =βg
∂h
∂ x

25. Coast and Ports 2015
Automated calibration
FES2012
Altimeter observations:
- assimilated FES2012 gridded data
- very accurate on deep water
Calibration parameters:
- Depth & (bed and linear) Friction
- 7 regions
Automated calibration:
- 21 parameters
- deep water series Jan2007

26. 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
RMSE of tide on deep water

27. 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
Regional models – Operational use