14 Jan 08 1 UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Navy Operational Assimilative Global Ocean Modeling Dr. Charlie Barron Naval Research Laboratory Stennis Space Center

14 Jan 08 2 UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Navy Global Ocean Modeling The Naval Research Laboratory has developed and transitioned the global ocean modeling system now operational at the Naval Oceanographic Office: Present system Key products Evaluate performance Future plans

14 Jan 08 3 UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Regional models NCOM/NCODA Global models NCOM, HYCOM Ocean Analysis NCODA, ISOP Ocean Prediction acoustics/currents Operational Navy Assimilative Ocean Modeling

14 Jan 08 4 UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Global NCOM: configuration and references ~14 km average spacing 41 vertical σ–z levels stretched logarithmically to 5500 m 1 m upper layer rest thickness CICE 3.0 Arctic ice model NOGAPS wind stress, bulk heat flux NCODA assimilation of in situ observations Global NCOM Key references: Barron et al., JGR Oceans, 2007.drifter evaluation Barron et al., Ocean Modelling, 2006.model formulation Kara et al., Ocean Modelling, 2006.general evaluation Barron et al., J. Atm. Oceanic Techn., 2004.SSH evaluation

14 Jan 08 5 UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Key Products Key operational products supported by global Navy ocean models include: Sound speed for acoustic calculations in anti submarine warfare Boundary conditions for nested ocean models and coupled atmospheric models Currents for buoy drift, mine drift, search and recovery Ice products such as ice edge, thickness Model validation studies focus on these operational products. New transitions must in some way improve information for key operational products.

6 RMS Range error:0.5 km Max Range error:1.3 km Assimilating synthetics into global NCOM: Dynamics produce a relatively deep mixed layer Smaller errors in predicting transmission loss Impact of ocean models on sound speed prediction 0600Hz at 20m depth RMS Range error:1.7 km Max Range error:4.1 km Present operational synthetic based on SSH, SST: Fails to represent surface sonic layers Significant errors in predicting transmission loss GNCOM Observed Synthetic

7 Validate model attributes that are relevant to key products Evaluate hydrographic proxies to indicate expected acoustic fidelity: Mixed Layer Depth (MLD) Kara et al. (2000) density threshold equivalent to ΔT=0.8°C Below-Layer Gradient (BLG) Fit a line to sound speed points between SLD and SLD+100m BLG is the slope*100 with units ms -1 /100m Negative BLG↔ downward refraction Positive BLG↔ upward refraction speed(z) ≈ speed(SLD) + BLG*(z-SLD)/100 Sonic Layer Depth (SLD) Helber et al. (submitted) near surface sound speed maximum appropriate for frequency range

8 For MLD, where is MLD-modified GNCOM better than a standard synthetic (MODAS) ? Evaluate NCOM assimilating MLD-modified synthetic vs. synthetic 11 m GNCOM median improvement GNCOM better in 80% of the regions. (shown in red and yellow) Statistics based on 43,474 T,S profiles from 2006.

9 10 m GNCOM median improvement GNCOM better in 83% of the regions. (shown in red and yellow) For MLD, where is MLD-modified GNCOM better than a standard synthetic (MODAS) ? Evaluate NCOM assimilating MLD-modified synthetic vs. synthetic Statistics based on 6,942 unassimilated T,S profiles from 2006.

10 Median statistics relative to 43,474 T,S profiles over the global ocean. Case MLD bias (m) SLD bias (m) BLG bias (ms -1 /100m) Climatology (MODAS) Synthetic (MODAS) Standard GNCOM GNCOM assimilating MLD-modified synthetics Median observed value (not bias) MLD 41 SLD 47 BLG Statistics based on 43,474 T,S profiles from Profiles are compared with nearest climatology, synthetic, and GNCOM nowcasts. None of the products here assimilate profiles. Validate model attributes that are relevant to key products

11 Median statistics relative to 6,942 T,S profiles over the Western North Pacific. Case MLD bias (m) SLD bias (m) BLG bias (ms -1 /100m) Climatology (MODAS) Synthetic (MODAS) Standard GNCOM GNCOM assimilating MLD-modified synthetics Median observed value (not bias) MLD 39 SLD 44 BLG Statistics based on 6,942 T,S profiles from Profiles are compared with nearest climatology, synthetic, and GNCOM nowcasts. None of the products here assimilate profiles. Validate model attributes that are relevant to key products

14 Jan UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Product example: currents for search and recovery Adam Air flight 574 crashed in the Java Sea on 1 January USNS Mary Sears assisted in search and recovery, locating black boxes on 21 January. initial crash debris Pinger Locations NTSB location Reverse 10-day trajectories starting from debris field Forward 10-day trajectories starting around crash site EAS NCOM results (nested within global NCOM) guided the search by predicting sources of debris that washed ashore ten days after the crash and evaluating debris distributions from potential crash sites.

Region Persist (km) V2.0 (km) V2.5 (km) V2.0a (km) V2.5a (km) Clim (km)  V (cm s -1 ) n pairs Celtic-Biscay-North Sea Iberia Region Humboldt Current Eastern North Pacific Brazil Malvinas Gulf of Alaska Benguela Current Black Sea Australia - New Zealand Central Pacific Gulf of Guinea Equatorial Atlantic North Atlantic Pacific Islands Japan/East Sea South China Sea Tehuantepec Equatorial Pacific Indian Ocean Java Sea Intra Americas Seas Agulhas East Asian Pacific Madagascar Kuroshio Taiwan North Brazil Current Arabian Sea Gulf of Mexico Gulf Stream Top0.00% 60.00%26.67%16.67%3.33% In top 20.00% 86.67%43.33%60.00%10.00% RMS separation (km) after one day between observed and simulated drifter trajectories for experiments in Regions sorted by increasing  V. Best results are highlighted in green, second- place in grey. 200,000 + comparisons see Barron et al., J. Geophys Res., 2007.

14 Jan UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Assessment Summary RMS drifter separation after one day prior operational V2.0 and new V2.5 (1/16° to 1/32° NLOM, no mean correction) RMS error is linearly proportional to σ V. 8% reduction in prediction uncertainty 15% reduction in predicted search area

14 Jan UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Future Plans Similar metrics are being applied to planned upgrades. Upgrades will transition to operations if they demonstrate improved performance. Global HYCOM ~6.5 km avg. spacing 32 hybrid layers Cycling NCODA assimilation ESMF-coupled CICE ISOP New covariances, EOF models to estimate synthetic profiles

14 Jan UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Operational Navy Assimilative Ocean Modeling Summary Identify key products Focus on relevant metrics Establish performance of present system Demonstrate benefit of potential upgrades

14 Jan UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Backup slides

14 Jan UNCLASSIFIED Ocean Modeling Workshop NCEP, Camp Springs, MD January 2008 Most Important Navy Product: Sound Speed Objective: Develop next-generation methods to estimate ocean sound speed. NAVOCEANO uses climatologies, observations and models … … to estimate sound speed … … used in acoustic tactical decision aids by the fleet.