1. Fixed Vertical Coordinates POM SWAFS NCOM POP Lagrangian Vertical Coordinate NLOM Hybrid Vertical Coordinate HYCOM Lagrangian Vertical Coordinate

2. NCOM NRL (or Navy) Coastal Ocean Model Primary contacts: Paul Martin (NRLSSC), Julie Pullen (NRLMRY) NCOM Version 1.0 (Martin 2000) is based primarily on POM and the sigma/z-level Model developed by Paul Martin at NRL. A 1/8° global version has been running in real-time data- assimilative mode at NRL since Oct. 2001. It is expected to transition to NAVO by the end of 2002. (Rhodes et al. 2002) Regional versions are being evaluated. The plan is to use NCOM both globally, for the upper ocean boundary layer and to provide initial and boundary conditions to finer resolution models, and regionally for coastal applications and for coupling with the atmospheric model in COAMPS TM.

3. NCOM is a free surface primitive equation model based on POM and the sigma/z model which allows for a hybrid vertical coordinate. It includes a turbulence closure model for parameterization of vertical mixing (Martin 2000). NCOM http://www7320.nrlssc.navy.mil/global_ncom/ http://www.ocean.nrlssc.navy.mil/global_ncom/ http://www7320.nrlssc.navy.mil/global_ncom/ http://www.ocean.nrlssc.navy.mil/global_ncom/

4. Physics Primitive equation Hydrostatic Implicit free surface –This differs from POM which uses an explicit time step for the free surface. Embedded turbulence closure model for vertical mixing

5. Domain Global, including Arctic, being run at NRL, to be transitioned to NAVO Other regions run for testing, evaluation, and research –Mediterranean –Chesapeake Bay outflow region Allows for easy nesting

6. Grid and Coordinate System Hybrid vertical coordinate system –  -coordinates for upper layers At least 1  level is needed at the top to allow the free surface to move –z-levels for lower layers Bathymetry is truncated to the nearest model z-level Shallowest z level must be deeper than lowest expected sea level –User specifies depth at which transition between the 2 coordinate systems occurs There are a number of options for the horizontal grid type Global domain has bipolar grid with poles over land at 47  N in North America and Asia

7. Different ways the sigma/z-level grid can be set up From Martin, 2000

8. NCOM Vertical Grid ( Adriatic ) Courtesy of Julie Pullen (NRLMRY)  highest resolution in surface and bottom boundary layers  enhanced resolution in the shallow northern Adriatic waters using terrain- following coordinates  pressure gradient errors associated with  -levels are avoided in the deeper southern Adriatic by employing z-levels there

9. Global grid Northern Hemisphere Courtesy of John Harding (NRLSSC)

10. Spatial Resolution Nominally 1/8  for global domain Global domain has 40 levels in the vertical (19  and 21 z) Nested coastal domains with increasingly finer resolution are being used in research and validation mode

11. NCOM Modeling Nesting with feedback: 9 Km MED 3 km ADRIATIC 3 km ALBORAN GYRE SSH 5 cm intervals 2 year run 5 days/frame Climatological forcing SSH 5 cm contour interval Nesting with feedback: 9 km MED 3 km ADRIATIC 3 km ALBORAN GYRE Courtesy of Paul Martin (NRLSSC)

12. 6 km 2 km 0.2 km 0.6 km Courtesy of Paul Martin (NRLSSC) NCOM Modeling Pullen, Signell, Martin, Harris

13. Temporal resolution Since NCOM uses an implicit scheme for the free surface, it can use a longer time step than a model with an explicit free surface (like POM), and so would not resolve fast gravity waves as well. Tides or wind-driven setup with time scales of hours or more should be well represented however. A typical time step for horizontal grid resolution of 1 km would be about 250 seconds.

14. Boundary Conditions Realistic topography including continental shelves to 5 m depth

15. Forcing Wind stress and surface heat flux –3-hourly NOGAPS for global domain –hourly COAMPS TM for Mediterranean There is option to calculate fluxes from bulk formulae instead of using fluxes directly from atmospheric model River inflow is included Can include tidal forcing, but at present it is not included in either the global or Mediterranean implementations

16. Initialization 1/8° global NCOM was initialized from MODAS annual mean T and S climatology. Run for 6 yrs with Hellerman-Rosenstein wind forcing and relaxation to MODAS monthly climate SST and SSS Switched to real-time NOGAPS atmospheric forcing and data assimilation on Oct 1, 2000 and then run up to present time.

17. Data Assimilation Global NCOM uses –1/16 o NLOM SSH –1/8 o MODAS 2D SST –MODAS synthetic T and S profiles Mediterranean NCOM uses Ocean MVOI for data assimilation

18. MVOI NCOM 96h forecast Cold Start:  First-guess: GDEM or long-term spin-up  QC observations  MVOI (z-levels)  Initialization  5-day spin-up Warm Start:  First-guess: NCOM 12 h forecast  QC observations  MVOI (z-levels)  Increments added to first-guess  Initialization Atmospheric Stresses and Fluxes 12h MVOI NCOM 96h forecast Atmospheric Stresses and Fluxes Data Assimilation MVOI-NCOM Interface Courtesy Hodur, Cummings, and Pullen, NRL Monterey

19. Implementation Efficient scalable, portable code Designed to fit with code structure of COAMPS TM to enable ocean-atmosphere model coupling

20. Output Not being run operationally yet. Following is example output from NRL Click below to get to most recent output –SSH, SSS, and SST for the globe and for 14 predefined regions.SSH, SSS, and SST for the globe and for 14 predefined regions The following link opens a quicktime movie (it may take a while to load ) –View animation of the North AtlanticView animation of the North Atlantic

21. Japan / East Sea

22. NCOM Response to Kursk Disaster in Barents Sea 8-12-2000Russian Oscar II Kursk sinks in Barents Sea 8-14-2000Russia admits Kursk down; US, UK offer assistance 8-16-2000NAVOCEANO requests NRL assistance, results from global NCOM, PIPS to support Oscar II SAR Russia requests assistance from UK and Norway 8-17-2000Begin providing NCOM nowcasts/forecasts. Continue 2 weeks. 9-06-2000Received BRAVO ZULU from CAPT McGee, Commanding Officer of NAVOCEANO, for response including retrieving NCOM from R&D to provide support 00Z, SFC.00Z, 50m Courtesy of John Harding (NRLSSC)

23. Domain Configuration 6 km NCOM 27 km 81 km COAMPS TM Momentum, Heat fluxes 36 km 12 km COAMPS TM 4 km 2 km NCOM Momentum, Heat fluxes Initial conditions and lateral boundary forcing Courtesy of J. Pullen (NRLMRY)

24. NCOM Specifications Features Mediterranean: Adriatic:  ocean model based on POM, C-grid, hybrid sigma-z vertical coordinate (Paul Martin, NRL-Stennis)  forced by hourly COAMPS TM momentum and heat fluxes  6 km, 40 levels (15 sigma levels)  grid size: 576x288  starting from multi-year spin- up beginning 1999  climatological river discharge from 54 major rivers  2 km, 50 levels (36 sigma levels)  grid size: 136x376  initialized from Med 6 km NCOM  lateral boundary values taken from Med grid at 12 hr frequency  daily Po River discharge from river gauge Courtesy of J. Pullen (NRLMRY)

25. Ocean Model Validation  ONR EuroSTRATAFORM PI Andrea Ogston (University of Washington) and NRL-SSC scientist Hank Perkins maintained ADCP instruments in the northern Adriatic during the overlapping time period 28 January – 4 June 2001 (125 days). The sites were separated by ~ 125 km.  The model represents the increased variability at the UW site relative to the NRL site and the mean currents aligned along local isobaths at both sites. Courtesy of J. Pullen (NRLMRY)

26. Ocean Model Validation: Time Series Courtesy of J. Pullen (NRLMRY)

27. References Rhodes, R.C., H.E. Hurlburt, A.J. Wallcraft, C.N. Barron, P.J. Martin, E.J. Metzger, J.F. Shriver, D.S. Ko, O.M. Smedstad, S.L. Cross, and A.B. Kara, Navy Real-time Global Modeling Systems, Oceanography, 15, 29-43, 2002 Martin, P.J., Description of the Navy Coastal Ocean Model Version 1.0, Naval Research Laboratory, Stennis Space Center, MS, 2000

28. Fixed Vertical Coordinates POM SWAFS NCOM POP Lagrangian Vertical Coordinate NLOM Hybrid Vertical Coordinate HYCOM Lagrangian Vertical Coordinate

29. NLOM NRL Layered Ocean Model Primary contacts: Robert Rhodes and Harley Hurlburt (NRLSSC) NLOM is a descendent of the earlier layered primitive equation ocean model of Hurlburt and Thompson, with substantial enhancements in processing and capability from Wallcraft (references in Rhodes et al. 2002) NAVO has been running it real-time since Oct. 2000; it has been an operational product since Sept. 2001.

30. NLOM is a primitive equation, hydrodynamic, layered model. It is used as an eddy-resolving large-scale (global or basin), rather than regional coastal, model. The Navy is using it primarily to provide SSH and front and eddy forecasting capabilities. NLOM http://www.ocean.nrlssc.navy.mil/global_nlom http://www.ocean.nrlssc.navy.mil/global_nlom

31. NAVO frontal analysis from satellite SST overlain on NLOM SSH. SSH can reveal subsurface eddies not visible in SST; SSH isn’t limited to cloud-free conditions as satellite SST is.

32. Physics Primitive equation model Free surface Horizontally and temporally varying density (includes thermodynamics) Includes a mixed layer model Includes density relaxation to climatology within a layer below the mixed layer –This does not damp anomalies because most of the information about the anomalies is in the layer thickness variation; e.g. NLOM with thermodynamics maintained an El Nino- generated oceanic disturbance for more than a decade (Jacobs et al., 1994, Nature)

33. Domain Nearly global 72°S – 65°N for water depths > 200 m, plus selected straits and all resolved deep straits

34. Grid and Coordinate System Vertical coordinate is density Uses layers, which allow it to work well with lower vertical resolution –A layered model can have many layers but doesn’t need as many as a z or σ model The lowest layer is active (unlike in some layered models) so there is flow – topography interaction Spherical coordinate system (not curvilinear)

35. Spatial Resolution 1/16  at mid-latitudes –1/16  latitude x 45/512  longitude 6 layers in the vertical plus embedded mixed layer which is not confined to the top layer Layer depths vary in space and time Layer # Average depth range 1 0-65 m surface layer 2 65-240 mundercurrent layer 3 240-500 mstratified thermocline 4 500-900 mto intermediate 5 900-1500 mwater layers 6 1500-bottomabyssal layer

36. Research has shown 3.5–7 km (1/32–1/16 °) horizontal resolution is needed at mid- latitude for proper representation of flow/topography interactions in basin and global scale models, as well as to resolve fronts and represent straits and islands (Rhodes et al. 2002) NLOM Drifter Climatological Flow (after Flament, 1997) Eddy kinetic energy in color red> 40cm/s rms blue >20cm/s rms purple<20 cm/s rms Courtesy of John Harding (NRLSSC) 1/16 1/8

37. Boundary Conditions When topography is incorporated (as it is in global version running at NAVO), it is confined to the lowest layer, forcing the flow to follow f/h contours.

38. Forcing NOGAPS wind stress and heat flux –Latent and sensible heat flux are calculated using the Kara et al. (2002) formulation with NOGAPS and NLOM SST

39. Initialization Spun-up 1990 – 2000 using: –combination of climatological and NOGAPS wind forcing –European Centre for Medium-Range Weather Forecasts thermal forcing (1990-1997) –NOGAPS thermal forcing (1998-2000) Data assimilation began –1997 for SSH –1998 for SST

40. Data Assimilation Assimilation cycle goes back 3 days in time. During these 3 days: Satellite SSH is assimilated daily using an optimum interpolation method –Model first guess is used in SSH analysis –Incremental insertion is used to reduce generation of inertial oscillations SST is assimilated by relaxing the NLOM SST to the MODAS global SST analysis (which is updated daily)

41. Forecasts NAVO produces 4-day forecast once a day, except 1 day / week, 30-day forecast is produced –The forecast atmospheric forcing only goes out 5 days and reverts toward climatology after that “During the forecast period, SST is relaxed to climatologically corrected persistence of the nowcast SST”. Relaxation time is ¼ that of the forecast length. (Rhodes et al. 2002)

42. Implementation Efficient scalable, portable code ( Wallcraft and Moore 1997)

43. Output Through NAVO –SSH and surface current series 0-96 hrs at 24 hr intervals –All domains have SSH graphic, some (like Sea of Japan) also have surface currents Through NRL –Most recent nowcast and forecast SSH, SST, and surface currents for various regions –30-day forecasts –Hindcast animations various regions http://www7320.nrlssc.navy.mil/global_nlom/globalnlom/skill.html

44. NLOM Speed (m/s)

45. UNCLASSIFIED Location: Sea of Japan Type: NLOM Description: Sea Surface Height Series (U) POC: NAVO - NLOM Library Custodian COMM: 228-688-5176 DSN: 828-5176 or E-mail Us Update Cycle: 24 hour(s) Typical File Size: 77(K) Level-of-Confidence: This product has been validated and is recommended for support unless otherwise stated. Current File Statistics: i.jah00.gif Size: 296 (Kbytes) Last Update: 19-Jul-15:50 CDT (U) ii.jah24.gif Size: 296 (Kbytes) Last Update: 19-Jul-15:50 CDT (U) iii.jah48.gif Size: 296 (Kbytes) Last Update: 19-Jul-15:50 CDT (U) iv.jah72.gif Size: 296 (Kbytes) Last Update: 19-Jul-15:50 CDT (U) v.jah96.gif Size: 296 (Kbytes) Last Update: 19-Jul-15:50 CDT (U) Additional Information: i.Initial Posting on Tue Sep 19 14:39:10 2000 (CST) (U) ii.Additional Information on Sea Surface Height (U)

48. Oman Coastal Filaments During Spring Intermonsoon Comparison of SeaWIFS and NRL Real Time Models Anticycl. Eddy Cyclonic Eddy Anticycl. Eddy 1/8 0 NCOM: 19 Apr. 20011/16 0 NLOM: 19 Apr. 2001 SeaWIFS: 19 Apr. 01 Cyclonic Eddy Filament Model SST and Surface CurrentsChlorophyll from SeaWIFS Courtesy Rhodes and Hurlburt (NRLSSC)

49. Real-time 1/16º Global NLOM - Kuroshio Region NLOM SSH analysis January 3, 2001 15-day NLOM SSH forecast valid January 18, 2001 NLOM SSH analysis valid January 18, 2001 30-day NLOM SSH forecast valid February 2, 2001 NLOM SSH analysis valid February 2, 2001 Courtesy of John Harding (NRLSSC)

50. Real-time 1/16º Global NLOM - Kuroshio Region MODAS 3-D synthetic T,S calculated from NLOM analysis SSH and SST for January 3, 2001 15-day forecast T,S from NLOM SSH,SST valid January 18, 2001 30-day forecast T,S from NLOM SSH,SST valid February 2, 2001 T,S from NLOM analysis SSH, SST for January 18, 2001 T,S from NLOM analysis SSH, SST for February 2, 2001 Courtesy of John Harding (NRLSSC)

51. References Rhodes, R.C., H.E. Hurlburt, A.J. Wallcraft, C.N. Barron, P.J. Martin, E.J. Metzger, J.F. Shriver, D.S. Ko, O.M. Smedstad, S.L. Cross, and A.B. Kara, Navy Real-time Global Modeling Systems, Oceanography, 15, 29-43, 2002

52. Relationship between NLOM and NCOM Since it is not currently affordable to run a global model with both the desired vertical and horizontal resolution, NAVO’s current strategy is to run NLOM at a nominal horizontal resolution of 1/16° and use the resulting SSH fields to construct MODAS synthetic T and S profiles for assimilation into NCOM, with nominal horizontal resolution of 1/8°, but much better vertical resolution than NLOM. NCOM would then be used for upper ocean boundary layer applications and as boundary and initial conditions for finer resolution coastal models. (Rhodes et al. 2002)

53. Global Ocean Prediction Baseline 1/16 0 Global NLOM 1/8 0 Global MODAS 1/8 0 Global NCOM 15-30 Day Front, Eddy & SSH Forecast 2D SSH SSTSSH 3D T&S 5 Day 3D T,S,U,V Forecast NOGAPS Heat & Momentum Fluxes 15-30 Day Mesoscale T,S, U,V Forecast T,S 3D T,S Nowcast synthetics AMOP 9; 1/8/01 Courtesy of John Harding (NRLSSC)