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

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."

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

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 - 2007).

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 http://www.hycom.org

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

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 2002. 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.

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

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

with assimilation (GLBa0.08-60.4)

without assimilation (GLBa0.08-05.8)

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

Eddy Kinetic Energy Comparison EKE at ~700 m in the Gulf Stream Observations from Schmitz (1996) NCOM - 2004 HYCOM - 2004

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

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

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)

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

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