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Nested Interdisciplinary Modeling along the U.S. East Coast

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Nested Interdisciplinary Modeling along the U.S. East Coast

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  1. US East Coast ROMS/TOMS ProjectsNorth Atlantic Basin (NATL) Northeast North American shelf (NENA)NSF CoOP Buoyancy driven flow (LaTTE)CBLAST-LowNortheast Observing System (NEOS)John WilkinH. Arango, K. Fennel, L. Lanerolle, J. LevinInstitute of Marine and Coastal SciencesRutgers University

  2. Nested Interdisciplinary Modeling along the U.S. East Coast John Wilkin (http://marine.rutgers.edu/~wilkin) Katja Fennel

  3. Northeast Observing System (NEOS)

  4. NEOS • Assimilate regional CODAR with 4D-Var • Use tangent linear and adjoint to develop AUV deployment stategies • Apply multiple-scale nesting in support of subregion studies (LaTTE, CBLAST …)

  5. CBLAST: Coupled Boundary Layers and Air-Sea Transfer The ONR CBLAST-Low program focuses on air-sea interaction and coupled atmosphere/ocean boundary layer dynamics at low wind speeds where processes are strongly modulated by thermal forcing. • Precise observations of air-sea fluxes and turbulent mixing from CBLAST are ideal for evaluating the suite of ocean model vertical turbulence closure schemes implemented in ROMS. • This comparison will be possible provided the model captures the essential features of the ocean heat budget on diurnal to several day time-scales, and spatial scales of order 1 km. • Modeling complements the interpretation of the field observations by quantifying unobserved lateral transport and mixing of heat.

  6. MVCO Aircraft ASIT K Nantucket SODAR ASIMET moorings with ocean T(z) and ADCP 3-D Mooring Remote Sensing CBLAST-Low Observing System:

  7. Lagrangian Transport and Transformation Experiment (LaTTE) • Dye release in Hudson River plume • 4D-var assimilation with ROMS • Coupled bio-optical modeling with EcoSim

  8. North Atlantic Simulation. • Resolution: 1/10 deg. Grid is 1000x1000x30; • Disk space for input datasets: 15.7 Gb • Monthly climatology (12 records 250 Mb each) • Wind forcing (7 years of daily records 4.8 Mb each) • Surface fluxes (12 records 32 Mb each) • Disk space for model output: 280 Gb • 3 day averages for 7 years (854 records 325 Mb each) • Simulation runs on 32 processors of SGI Origin 3000 • Total memory 11 Gb • One day of simulation take 46 CPU hours • Wall clock time to run 7 years of simulation: 153 days.

  9. 14 months of simulation, starting Jan 1993Temperature at 100 m depth.

  10. Need open boundary conditions from an assimilative North Atlantic model • Though the MAB shelf is somewhat isolated from remote forcing, the salinity of the Scotian Shelf inflow plays a significant role in interannual variability of the MAB and preconditions water masses and stratification inshore from the shelf-slope front. • Present NENA solutions have a weak, or reversed, Maine Coastal Current because of inadequate salinity open boundary conditions on the Scotian Shelf. • Accordingly, we wish to move beyond nesting within a climatologically forced model to 1-way nesting of NENA within the HYCOM data assimilating North Atlantic model. This development will apply inter-annual variability to the a priori inflow open boundary conditions of the NENA/NEOS models. • Gulf Stream variability at Cape Hatteras influences the exchange of shelf and slope waters at the terminus of the southwestward MAB coastal current, so the open boundary model must achieve a realistic GS separation • We are also developing 1-way nesting of NENA within the approximately 7-km resolution European Mercator North Atlantic operational 14-day forecast system.

  11. Summary • Hierarchy of modeling studies from basin to coastal using ROMS/TOMS tools • Processes: CO2 cycling, buoyancy-driven flow, wind-driven upwelling, air-sea interaction, coastal bio-optics and sediment transport • Integrated observational/modeling studies • CBLAST: air-sea interaction, waves, mixing • LaTTE: intensive observing systems • NEOS: prototype modern, relocatable, observing network • Adjoint, tangent linear codes feature in most projects • Developing coastal prediction systems • using new observing system capabilities, adaptive sampling design, 4D-Var

  12. U.S. East Coast oceanography and open boundary conditions • Gulf of Maine: Surface inflow of relatively fresh water from the Scotian Shelf and onshore flow of dense slope water at depth via deep channels produce an estuarine-like circulation. This fosters shelf/deep-ocean exchange strongly steered by bathymetry.

  13. Mid-Atlantic Bight: GoM waters exit around Cape Cod and feed a southwestward mean flow on the broad (100-200 km) and shallow (100-200 m) MAB shelf. The shelf-slope front separates fresh/cool shelf waters from saltier/warmer slope water, isolating the shelf from deep ocean influences and admitting a greater forcing role for riverine buoyancy input than is typical of, e.g., the US West Coast shelf. • Water mass properties and drifter trajectories in the MAB reveal increasing exchange of shelf waters with the adjacent deep ocean as the southwestward mean flow approaches Cape Hatteras.

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