The Navy’s Application of Ocean Forecasting to Decision Support

Abstract : The Naval Oceanographic Office (NAVOCEANO) provides daily operational global, regional, and coastal ocean model forecasts and their associated prediction products. The models utilized include three-dimensional circulation, wave and ice forecasting systems that have been developed to meet Navy requirements; the models are forced by Navy atmospheric models and constrained by Navy-developed bottom topography. In addition, NAVOCEANO acquires, quality controls, and delivers real-time ocean observations from both in situ and remote-sensing resources for assimilation by the ocean models. These observations are also used to assess model skill and develop ocean climatologies. A major supercomputing capacity is needed to run this ocean modeling suite, as well as a uniquely skilled model operations team that keeps the systems running. Dedicated ocean forecasters interpret the predictions and apply the information to Navy operations. The path from requirements to development to operations demonstrates the close links between research and development production, and operational Navy applications. This path also provides innovative future ocean modeling plans directed to improve oceanographic support to the Navy.

these models.This article summarizes the main elements of NAVOCEANO's operational modeling systems in 2014.

SUMMARY OF OCEAN MODELS USED BY NAVOCEANO
Ocean modeling at NAVOCEANO takes a serial approach, starting each daily cycle with global prediction and scaling down to higher resolution regional and coastal domains (Figure 1).These ocean models, most of which were developed at the Naval Research Laboratory (NRL), output global, regional, and nearshore two-and three-dimensional ocean dynamic and thermodynamic properties and two-dimensional regional and coastal wave properties.NAVOCEANO ensures that these ocean models run on schedule, data are delivered in a timely fashion to Navy users, and interpretations of the information are provided, similar to the mission of the US National Oceanic and Atmospheric Administration's National Weather Service.Summaries of the ocean models used by NAVOCEANO follow.

Global Circulation Model
The HYbrid Coordinate Ocean Model (HYCOM), which was delivered from NRL as the Global Ocean Forecast System 3.0 (GOFS 3.0), is a fourdimensional ocean forecasting system that daily predicts the structure of ocean temperature, salinity, currents, and elevation through the next seven days, or 168 hours (Metzger et al., 2014, in this issue).Products include a two-dimensional global surface file and 18 three-dimensional regional data sets of all properties at three-hour intervals.Forty depth levels are output, expanding from a 1 m thickness at the surface to 1,000 m layers at deep ocean depths.The Fleet Numerical Meteorology and Oceanography Center (FLENUMMETOCCEN) half-degree NAVy Global Environmental Model (NAVGEM) provides the atmospheric forcing (Hogan et al., 2014, in  for data files.

Regional Circulation Model
The Navy Coastal Ocean Model (NCOM) is a four-dimensional ocean forecasting system that daily predicts the structure of ocean temperature, salinity, currents, and elevation for the length of the atmospheric forecast, which is currently four days (96 hours).
This model was developed at NRL as the Relocatable NCOM system (Rowley and Mask, 2014, in this issue).
In specific areas of Navy interest, a Regional NCOM (RNCOM) is run at a horizontal resolution higher than that sets, which cover United States coastal areas, are delivered like HYCOM output to NOAA's websites in real time.

Ice Forecasts
NAVOCEANO runs the NRL-developed Arctic Cap Nowcast/Forecast System (ACNFS), which encompasses all ice covered seas from 40°N-90°N latitude.
A number of output fields, including ice coverage, thickness, drift, temperature, salinity, and currents, are delivered to the National Ice Center (NIC) to provide guidance to forecasters.NCEP also receives this model guidance for service to National Weather Service users and the public.In the near future, ACNFS will be discontinued as an independent model, and CICE will be coupled within the global HYCOM system for both the Arctic and Antarctic regions.

Regional Coupled Modeling
In 2012, initial implementation of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) was completed at NAVOCEANO.COAMPS couples the separate ocean and atmosphere models by exchanging variables between them as they run to provide a single virtual model containing both environments (Figure 2).NRL is finalizing inclusion of the wave model component in COAMPS (Allard et al., 2014, in

Bottom Topography for Ocean Models
The accuracy of an ocean model depends on a proper definition of the "basin" in which the water resides.The shape, composition, and frictional characteristics

Atmospheric Forcing
A primary driving factor for all of NAVOCEANO models is the effect that the atmosphere has on the ocean surface.As noted earlier, NAVOCEANO relies on output data from NAVGEM for global HYCOM and from COAMPS to The second step is the main NCODA system.This system can run in a standalone version that supplies the background fields for NCODA OceanQC, or it can run as a pre-processing step in the ocean models (Metzger et al., 2014, andRowley andMask, 2014, both

DoD'S SUPERCOMPUTING RESOURCE CENTER
Operational ocean models require a major commitment in computational

HOW OCEAN MODEL PRODUCTS SUPPORT NAV Y APPLICATIONS
A  The Navy is often first on scene to assist with disasters such as typhoons, earthquakes, lost people and gear, or oil spills.NAVOCEANO has specialized capabilities to respond quickly to these events, either alone or in cooperation with national partners such as NOAA and the US Coast Guard as well as with international partners.These capabilities include probabilistic and deterministic forecasts for drifting objects (Figure 5) and oil dispersion, as well as forecasts of high seas and storm surge when tropical weather systems make landfall.

OCEAN FORECAST SKILL
A continuing challenge for ocean modeling is to demonstrate that the forecast is reliable or that it has skill.COAMPS® is a registered trademark of the Naval Research Laboratory.
this issue).HYCOM runs without tides, but barotropic tidal data from the Oregon State University Tidal Inversion Software (OTIS) are added after the model completes its run.A number of HYCOM data sets are delivered to the National Oceanic and Atmospheric Administration (NOAA) in real time.NOAA's National Centers for Environmental Prediction (NCEP) INTRODUCTION Most of us rely each day on National Weather Service forecasts to plan our daily schedules.These forecasts are derived from a combination of numerical models and observations.Similarly, the US Navy requires ocean forecasts to support naval operations, including environmental information on ocean currents, waves, tides, sound speed, water temperature, salinity, and visibility.The Naval Oceanographic Office (NAVOCEANO) generates these ocean forecasts, and they are used by trained Navy oceanographers and forecasters to provide useful "ocean weather" information to the Navy's decision makers, allowing them to plan and operate more safely, efficiently, and effectively.Other papers in this special issue of Oceanography describe the research behind the development of ABSTR ACT.The Naval Oceanographic Office (NAVOCEANO) provides daily operational global, regional, and coastal ocean model forecasts and their associated prediction products.The models utilized include three-dimensional circulation, wave, and ice forecasting systems that have been developed to meet Navy requirements; the models are forced by Navy atmospheric models and constrained by Navy-developed bottom topography.In addition, NAVOCEANO acquires, quality controls, and delivers real-time ocean observations from both in situ and remote-sensing resources for assimilation by the ocean models.These observations are also used to assess model skill and develop ocean climatologies.A major supercomputing capacity is needed to run this ocean modeling suite, as well as a uniquely skilled model operations team that keeps the systems running.Dedicated ocean forecasters interpret the predictions and apply the information to Navy operations.The path from requirements to development to operations demonstrates the close links between research and development, production, and operational Navy applications.This path also provides innovative future ocean modeling plans directed to improve oceanographic support to the Navy.provides public access to the model data via its Ocean Prediction Center (OPC) website for graphics or the National Operational Model Archive and Distribution System (NOMADS) Figure 1.System flow diagram of ocean and wave models from global to coastal scales run daily at the Naval Oceanographic Office (NAVOCEANO).» HYCOM = HYbrid Coordinate Ocean Model » WW3 = WAVEWATCH III » RNCOM = Regional Navy Coastal Ocean Model » CNCOM = Coastal Navy Coastal Ocean Model » PCTides = Two-dimensional barotropic tidal model » HYDROMAP = A commercial threedimensional, PC-based, globally relocatable model » Delft3D = A commercial coastal and estuarine circulation model » SWAN = Simulating WAves Nearshore » NSSM = Navy Standard Surf Model See text for descriptions of these models.
this issue) and will then add an ice model component to the system.The core models are COAMPS for the atmosphere, NCOM for the ocean, WAVEWATCH III (WW3) or Simulating WAves Nearshore (SWAN) for waves, and CICE for ice forecasting.Note that even though the name states it is coupled, COAMPS was first developed as a stand-alone, uncoupled atmospheric model, and its recent evolution is producing a fully coupled solution.COAMPS currently uses 3D Variational (3DVAR) data assimilation and will soon be upgraded to use 4D Variational (4DVAR) data assimilation.An advantage of 4DVAR is that observations will have larger impacts on the predictions as the system dynamics propagate the information through space and time.The exchanges of relevant field variables between COAMPS system components are conducted via ESMF software, and the added feedback physics contribute to an improved forecast for each environment.While the components are all contained in COAMPS, any single component will be able to run with externally provided inputs from the others, if desired.One by one, NAVOCEANO plans to replace regional and coastal stand-alone NCOM domains with COAMPS.In the next few years, what is learned via COAMPS implementation will be applied to a global coupled modeling system, the Earth System Prediction Capability (ESPC; Burnettet al., 2014, in this issue).

Figure 2 .
Figure 2. Flow diagram of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) in its atmosphere-ocean-waves configuration.The atmosphere core model highlighted in orange, the ocean core model in blue, and the wave core model in purple.» CAGIPS = Come And Get It Product Service » ESMF = Earth System Modeling Framework » GOFS = Global Ocean Forecast System.» NAVGEM = NAVy Global Environmental Model » NCODA = Navy Coupled Atmosphere/Ocean Data Assimilation » NCOM =Navy Coastal Ocean Model » NAVDAS = NRL Atmospheric Variational Data Assimilation System, the atmospheric equivalent to NCODA modeling tasks for the Navy, with FLENUMMETOCCEN's WW3 covering large basin areas and NAVOCEANO's SWAN providing coastal wave and surf predictions(Rogers et al., 2014, in this   issue).NAVOCEANO also runs a global multigrid WW3 to provide spectral boundary conditions for regional and coastal SWAN domains.WW3 is a third-generation spectral wave model developed at NOAA's NCEP, and the operational version was transitioned by NRL to NAVOCEANO.NAVOCEANO runs a large number of SWAN domains to forecast various wave parameters ranging from significant wave and swell height to wave steepness.Resolutions range from ~ 1/12 degree or six and a half kilometers for regional domains to 10 m for very nearshore coastal domains, depending on requirements and the availability of high-resolution gridded bottom topography.SWAN is a third-generation, phase-averaged wave model developed at the Delft University of Technology.Although it is part of the Delft3D modeling package, it is currently implemented as a stand-alone model at NAVOCEANO.SWAN is also linked with the Navy Standard Surf Model to generate surf forecasts at individual beach locations.NAVOCEANO OCEAN MODEL SETUP, ATMOSPHERIC FORCING , AND DATA ASSIMIL ATION To model the ocean properly, certain environmental data are needed, including an accurate representation of the ocean bottom and the coastline, real-time energy exchanges at the surface due to atmospheric forcing, and observations for assimilation.FLENUMMETOCCEN supplies all atmospheric information, as mentioned earlier, and NAVOCEANO supplies all oceanic information.
(b) Speed vs. Height (Pt2 at 0 ft; 36.9302°N,75.9649°W) of the bottom to some degree affect mass conservation, momentum and heat transports, tidal elevation, and current structure.This dependency is especially true in the coastal regions where the prediction of currents, wave steepening, surf characteristics, or storm surge and inundation require accurate and consistent information about the bottom from deepwater regions, across the shelf, over the beach, and into the foreshore.For the past two centuries, NAVOCEANO and its predecessors have been leaders in the collection, analysis, and delivery of bottom topography and geology data for many Navy and national applications, including ocean modeling efforts.A fleet of survey ships, lidar-equipped aircraft, high-resolution multispectral satellites, and specialized on-scene collection teams gather highly accurate data.Data extracted from NAVOCEANO's massive global bottom topography holdings are provided to the ocean modelers, ensuring that they are working with the best available bottom structure.

Figure 3 .
Figure 3. Example products from Delft3D for the Chesapeake Bay.(a) Surface current magnitude in knots with directional vectors overlaid, (b) tidal currents over time showing magnitude in knots (black line) and tidal height in feet (blue line) at the location denoted by a purple star in (a), and (c) time versus depth plot of current magnitude at the same location.
Navy DSRC computational and storage assets at Stennis Space Center are designated for Navy modeling operations.While other DSRCs deliver high performance computational capabilities to both the DoD science and technology and test and evaluation communities, the state-of-the-art supercomputers at Stennis are managed with a concern for full-time operational support.The Navy DSRC systems are configcenter at NAVOCEANO routinely prepares and delivers to Fleet users a large set of products that includes ocean model output files and graphics from circulation, and daily wave models over their full prediction cycle.This capability is the responsibility of the Model Operations Team, which maintains schedules, monitors daily progress, finds and repairs issues, responds to requests for services, and manages changes in systems, software, and requirements.This effort requires a dedicated group of people with a wide range of skills that include conducting operations on various computational platforms (from supercomputers to Windows and LINUX desktops), creating and managing ocean models, scripting model processing, and troubleshooting problemskeep track of events, maintain schedules, allow quick progress evaluations via Web pages, provide alerts when issues occur, and suggest solutions to common problems.Other functions include acquisition and preparation of atmospheric forcing, process monitoring, control of the submission and setup for wave models, post-processing of data and graphic outputs for all ocean models, and delivery of forecast products internally and externally.ROAMER is the backbone that makes everything work together as an operational system.The Model Operations Team maintains a close relationship with NRL developers to resolve issues, establish requirements, suggest improvements, and help transition new capabilities or upgrades from the research machines into the operational run stream.This team also works with Navy customers to quickly supply data or graphics to support their operations.THE OCEAN FORECASTERS To help the Navy customer understand, synthesize, and better utilize ocean model data, a cadre of civilian ocean forecasters has been drawn together at NAVOCEANO.With varied academic backgrounds, these forecasters provide a broad skill set that forms the backbone for ocean forecasting at NAVOCEANO as they study the full water column, concentrating on how Navy ships and " THIS EFFORT REQUIRES A DEDICATED GROUP OF PEOPLE WITH A WIDE RANGE OF SKILLS THAT INCLUDE CONDUCTING OPERATIONS ON VARIOUS COMPUTATIONAL PLATFORMS (FROM SUPERCOMPUTERS TO WINDOWS AND LINUX DESKTOPS), CREATING AND MANAGING OCEAN MODELS, SCRIPTING MODEL PROCESSING, AND TROUBLESHOOTING PROBLEMS." sensors interact with this environment.They develop skills in physical oceanography, ocean modeling, meteorology, ocean acoustics, ocean sensors, data assimilation, data analysis, and computer science.Each ocean forecaster specializes in a geographical area and/or a forecaster function such as a specific model or tool.While a request for support may be funneled to the person with the highest related expertise, open discussions among team members help to maintain a broad base of knowledge among them so that most requests can be filled by any member of the team, ensuring that all requests are completed quickly and fully.OCEAN CLIMATOLOGY Ocean forecasters are often asked what will the ocean environment be beyond the current modeling predictions.Presently, ocean model predictions go out to seven days, but the Fleet needs to know what the ocean environment will be weeks, months, and years in advance when planning operations.To provide this information, NAVOCEANO creates climatology products from its ocean observation and model archives, as well as from the scientific literature, in order to estimate and describe typical regional ocean parameters and their variability in the context of future operational situations.A new source of historical data for building Navy ocean climatologies is NRL's HYCOM re-analyses, a historical, global model run going back to 1992, using the best atmospheric forcing and observation data sources available.Ocean climatology products may include statistics of current flows derived from multiple years of model current fields combined with historical observations.Products available for Fleet use include historical drift probability maps and statistics overlaid on speed and direction at multiple depths.These drift plots are used to determine where an object may drift to at a given time, or inversely, where a found object may have originated.Another example of a Navy ocean climatology product is the Generalized Digital Environmental Model (GDEM) database developed by NRL and NAVOCEANO.GDEM is a global, monthly, full-depth, 78-vertical level, gridded climatology of the means and standard deviations of temperature and salinity.These data provide ranges of values to estimate variability, in order to quality control observations for model assimilation and to evaluate model forecasts.

"eddies.
The file is followed by in-depth discussion of how the information presented could affect operations in the dynamically evolving ocean at scales from hours to days.Estimates of uncertainty and, in some cases, recommendations for best use of the environment or alternate approaches may be added.The TOFA may also include answers to specific questions based on the synthesis of historical or climatological data at NAVOCEANO.In many cases, cooperative exchange of ideas with the Navy personnel afloat is necessary to ensure forecast products provide the best possible operational support.

For
NAVOCEANO circulation models (HYCOM/NCOM), various ocean field variables, such as currents, temperature, and salinity and their vertical gradients at selected depths, are compared to available observations and historical studies to determine the skill of their output.Ocean model output is evaluated by comparison to appropriate measurements acquired from the varied sources discussed in the "Ocean Observations Acquisition" section above.Specific mesoscale ocean features, such as eddies, are also identified in these remote measurements and compared to the same features predicted by the models.In some modeled areas, where ocean measurements are sparse or unavailable, comparisons are made to trends found in the literature, to climatology, or to output from other models set up in the same or a similar region.Many of these comparisons are qualitative in nature, but NAVOCEANO also has tools to quantitatively compare observations to models.Recent comparisons indicate a relatively slow decay in ocean forecast skill for both HYCOM and NCOM as the forecast period increases, reassuring users that these ocean prediction fields can be used with confidence throughout the four-to seven-day forecast period.

Figure 4 .
Figure 4. (a) An example Tactical Ocean Feature Assessment (TOFA) overview slide.Surface elevation is shown using a hillshade effect, with currents shown as black vectors.Anticyclonic eddies are denoted as solid red lines (relatively higher sea surface height) and anticyclonic circulations of importance are denoted by dashed red lines.Cyclonic eddies are solid turquoise lines and cyclonic circulations of importance are denoted by dashed turquoise lines.The green line shows the extent of the vertical cross-section graphic (b) that displays the vertical temperature structure across several features.

Figure
Figure 5.A comparison of the Western Pacific RNCOM average currents (March 29-April 5, 2014) in knots to a surface drifter track for March 25 to April 8, 2014.These qualitative results show that the model is accurately predicting this eddy.
large suite of up-to-date ocean model graphics and data is posted daily for Fleet users via a DoD-only Web portal.