1. U.S. GODAE: Global Ocean Prediction with
Community Effort: NRL, FSU, U. of Miami, NASA-GISS, NOAA/NCEP, NOAA/AOML, NOAA/PMEL, PSI, FNMOC, NAVOCEANO, SHOM, LEGI, OPeNDAP, UNC, Rutgers, USF, Fugro-GEOS, Orbimage, Shell, ExxonMobil

2. Global Ocean Data Assimilation Experiment (GODAE)
The vision:
"A global system of observations, communications, modeling and assimilation, that will deliver regular, comprehensive information on the state of the oceans in a way that will promote and engender wide utility and availability of this resource for maximum benefit to society."

3. GODAE Modeling/Assimilation Centers
Australia : (BLUELINK): Regional Australian seas to Global Ocean
Japan : N. Pacific to Global Ocean
US (HYCOM-US and ECCO projects): N. Atlantic to Global Ocean
Europe (Mersea/MyOcean Consortium)
Italy (MFS) : Mediterranean Sea
France (MERCATOR) : N. Atlantic and Mediterranean Sea to Global Ocean
Norway (TOPAZ) : North Atlantic to Arctic
UK (FOAM) : N. Atlantic / Global ocean

4. Objectives and Goals
A broad partnership of institutions that collaborate in developing and demonstrating the performance and application of eddy-resolving, real-time global and basin-scale ocean prediction systems using HYCOM.
Transition for operational use by the U.S. Navy at NAVOCEANO (2008) and by NOAA at NCEP (N. Atlantic ).

5. Objectives and Goals
Strong participation of the coastal ocean modeling community in using and evaluating boundary conditions from the global and basin-scale ocean modeling prediction systems
Efficient data distribution (100 Terabytes Storage Area Network)
The data are available to the community at large within 24 hours via Live Access Server (LAS), ftp, and OPeNDAP at

6. The hybrid coordinate in HYCOM is one that is isopycnal in the open, stratified ocean, but smoothly reverts to a terrain-following coordinate in shallow coastal regions, and to pressure coordinate in the mixed layer and/or unstratified seas
1/25° East Asian Seas HYCOM
(nested inside 1/6° Pacific HYCOM)
North-south velocity cross-section along 124.5°E, upper 400 m
Snapshot on 14 October
density front
associated with
sharp topographic feature
(cannot be easily resolved with
fixed z- or sigma- coordinates)
East China
Sea
Yellow Sea flow
reversal with depth
Isopycnals over
shelf region
z-levels and sigma-levels
over shelf and in mixed layer
Snapshot on 12 April
Yellow
Note the sharp feature in the bottom topography near 25°N. It is shallow, rising to about 125m, and is only a few grid points wide. It could not be accurately represented by sigma coordinates. However, in the top panel it is associated with a sharp density front (sharp rise in isopycnal depth above the lip topography) and the location of the Kuroshio.
This provides a good example of all three vertical coordinates within HYCOM: z-levels in the mixed layer, isopycnals in the deeper ocean but also over the shelf, and sigma coordinates in the shallow water. Note the adaptive vertical coordinate that changes from isopycnal in shallow water in October to sigma and z levels in April when the water is less stratified.
blue=westward flow
red=eastward flow

7. Present nowcast/forecast
systems
1/12º Atlantic near real-time system
- Running once a week since July 2002
- Assimilation: gridded surface observations only
- 10 day hindcast, 14 day forecast
1/12º Global real time system
- Running daily since December 2006
- Assimilation: NCODA
- 5 day hindcast, 5 day forecast
1/25º Gulf of Mexico real time system
- Running daily since November 2006
- 5 day hindcast, 7 day forecast
Present near real-time system, Atlantic Ocean, run since July of Only gridded full field surface observations are assimilated in this system.
Running on kraken on 28 nodes, 224 cpus. Results on the hycom consortium web page and there is a LAS server where the data can be obtained.

8. Global HYCOM configuration
Horizontal grid: 1/12° equatorial resolution
4500 x 3298 grid points, ~6.5 km spacing on average, ~3.5 km at pole, 5 m minimum depth
Mercator 79°S to 47°N, then Arctic dipole patch
32 σ2* vertical coordinate surfaces:
KPP mixed layer model
Thermodynamic sea-ice model (soon to be PIPS/CICE)
Surface forcing: wind stress, wind speed, thermal forcing, precipitation, weak relaxation to climatological SSS
Monthly river runoff (986 rivers)
Initialized from January climatology (GDEM3) T and S
Mainly climatological simulation so far. A couple of interannual forced cases.
216,000 CPU hrs/model year on 784 IBM Power 4+ CPUs
7.2 TB/model year for daily 3-D output

9. Data Assimilation via NCODA
(Cummings et al.)
Ocean obs
Sequential Incremental Update Cycle Analysis-Forecast-Analysis
SST: GAC/LAC MCSST, GOES, Ship, Buoy Profile: XBT, CTD, T & S profiling Floats (ARGO), Fixed Buoy, Drifting Buoy Altimeter SSHA SSM/I Sea Ice
Ocean data QC
Innovations
Ocean data
Analysis
3D MVOI &
Cooper-Haines
Increments
NCODA proof of concept working in global HYCOM. Multi variate optimal interpolation scheme, that can assimilate surface observations from satellite, altimetry, mcsst, and also profile data like xbts, palace floats. The forecast fields from HYCOM are used as a first guess for the NCODA analysis. These increments are then nudged into HYCOM.
Observations feed into NCODA that performs a QC check.
NCODA performs an ocean data analysis (MVOI of 5 ocean variables)
Provides increments to the model initial state (nudged in)
Model runs forward in time
Model forecast is used as a 1st guess for the next ocean data analysis
What gets assimilated? SSHA from altimeters, SST from various sources, profile data
Ocean model
HYCOM
Forecast Fields Prediction Errors
First Guess
MVOI - simultaneous analysis 5 ocean variables temperature, salinity, pressure, velocity (u,v)
29 June 2006

10. with assimilation (GLBa0.08-60.4)

11. without assimilation (GLBa0.08-05.8)

12. Overall increase in variability - largest changes occur in the western boundary currents

13. Eddy Kinetic Energy Comparison
EKE at ~700 m in the Gulf Stream
Observations from
Schmitz (1996)
NCOM
HYCOM

14. Forecast verification statistics
from .08 global HYCOM
1.0
0.9
0.8
0.7
World
Ocean
NW Arabian Sea and Gulf of Oman
Gulf Stream
Median SSH anomaly correlation
1.0
0.9
0.8
0.7
Equatorial
Pacific
Kuroshio
Gulf of Mexico
0.6 10 20 30
Forecast length (days)
4 Forecasts included in statistics

15. Product evaluation
Assessment of the outputs by comparison to independent observations
Comparison with other GODAE products (i.e. MERSEA collaboration)
Strong involvement of coastal ocean modeling groups to use and evaluate boundary conditions provided by the global and basin HYCOM real time prediction system outputs

16. West Florida Shelf Modeling
WFS ROMS SST and surface velocity is shown inside the dashed line and outside of this area is the North Atlantic HYCOM.
Warm water is detached from the Loop Current and transported northward as mesoscale eddies and filaments.
Barth et al. (USF)

17. Adding tidal capability to global HYCOM
Collaboration with Brian Arbic (U. Texas)
HYCOM with 8-component tide
vs tide gauge
HYCOM RMS errors for M2 tide vs satellite altimetry
.72 resolution
.08 resolution
.72 HYCOM tide
model tide gauge
Example with typical error:
89.6% of variance explained 5 10 15 20 25
RMS error = 9.9 cm
RMS error = 6.7 cm
Average RMS error over all 102 pelagic tide guages = 12.3 cm

18. Future Directions
1/25 global HYCOM prediction system with tides and wetting and drying
More advanced data assimilation
Nested coastal ocean prediction with grid resolution < 1 km
Range dependent acoustic prediction
Coupled atmosphere – ocean prediction
Bio – geo – chemical – optical and tracer/contaminant prediction
Ecosystem analysis and prediction
Earth system prediction: coupled atmosphere-ocean-ice-land