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North Atlantic Climatological heat/freshwater fluxes 3-day average NCEP winds

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North Atlantic Climatological heat/freshwater fluxes 3-day average NCEP winds

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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. North Atlantic Climatological heat/freshwater fluxes 3-day average NCEP winds

  3. Northeast North Atlantic (NENA) embedded within NATL 3-day average open boundary values from NATL7-component NPZD ecosystem Chlorophyll Temperature

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

  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. Solar, IR, rain, U, T, QHeat, mass & momentum flux, ε U, T, QHeat, mass & mom. flux, εWaves 23m WavesT, S Heat, mass mom. flux, ε Irradiance 15m Irradiance

  8. ROMS CBLAST configuration COAMPS CBLAST, 3km, 91x91 9 km 27 km, 151x121x30 M2 displacement ellipses from ADCIRC 1 km horizontal resolution20 s-levels (stretched toward surface) • Surface forcing: • Heat and momentum fluxes from bulk formulae [6] with model SST, observed downward long-wave at MVCO, and Tair, pair, rel. humidity, U10, V10, and short-wave radiation from 3 km resolution nested COAMPS 6--36 hr forecast • Open boundary conditions: • Inflow climatology [7] + outflow radiation [8] on T,S, u, vClimatology, tides [9], radiation (gh) on  and depth average u,v • 160 x 380 x 20 grid requires approximately 2 CPU mins per model day on 16-processor HP/Compaq

  9. July 2002 mean Mean circulation and heat budget The open boundary climatology imposes a south and westward flow from the Gulf of Maine, through Great South Channel and around Nantucket Shoals. Circulation around the Nantucket Shoals is augmented by strong tidal rectified cyclonic flow that carries water northward into Vineyard Sound through Muskegat Channel (between Nantucket and the Vineyard). Southwest of Martha’s Vineyard, and within Vineyard Sound, winds drive eastward depth averaged flow.

  10. 3-day composite SST for 30-Aug-2002 Tidal mixing generates a region of perpetually cold SST on the eastern flank of the Nantucket Shoals

  11. July 2002 Air-sea flux (Qnet) is greatest east of Vineyard Sound where SST is cold, but is largely balanced by divergence due to tidal mixing. Ocean temperature increase (storage) is largest south of The Islands, primarily due to surface heating. Horizontal divergence is small in the region of the B-C ASIMET moorings - indicating a region of approximate 1-D vertical heat balance suited to evaluating ROMS vertical turbulence closures.

  12. MVCO The time mean advection cools the box at, on average, 200 W/m2. The net “eddy” divergence (u’T’) warms the MVCO region at about 50 W/m2. Episodic positive divergence (cooling) events briefly arrest the warming trend. Time series of the heat budget in a box near MVCO shows half the air-sea flux goes to warming the water column, and half is removed by lateral divergence.

  13. CTD temperature section between ASIT and mooring-A, late July 2001. Observed Modeled Qualitative comparison to subsurface validation data (below) shows realistic vertical stratification and mixed layer depths. In 2003, an array of 5 subsurface moorings between ASIT and ASIMET mooring-A will enable validation of the modeled evolution of the diurnal mixed layer.

  14. Operational forecasts began July 8, 2003 COAMPS 72-hour forecast is generated every 12 hours at ARL.HPC.mil and transferred to IMCS where ROMS runs for the same forecast cycle. Real-time validation is available using CODAR on Nantucket (operational after July 7, 2003). ROMS forecasts will be factored into the deployment strategy for drifting instrument strings providing Lagrangian observations of evolving mixed-layer.

  15. CBLAST: Lessons for ocean modeling: • With sufficient realism in the model bathymetry and forcing, model vertical turbulence parameterizations can be critically evaluated by comparison to CBLAST observations • CBLAST observations ideal for evaluating turbulence closure • combination of direct air-sea flux observations, and in situ oceanic profile observations • Need to consider spatially variable atmospheric forcing (COAMPS) • Initial conditions are a source of uncertainty in the model configuration • A 1-D heat balance occurs near the B-A-C ASIMET mooring sites, and these data will be used for evaluation of model turbulent closures.

  16. Lessons for data analysis: • Model shows remote mixing and advection significantly influence the local heat budget at the SECNAV mooring site and CLAST tower • Tides significantly affect the mean circulation and heat budget. Lateral heat transport is large in much of the region, including near MVCO, and will need to be considered in the analysis of ASIT heat budgets. • Wind-driven upwelling circulation contributes to the heat budget southwest of Martha’s Vineyard. • Wind-driven upwelling contribution remains unquantified at this stage but is likely important in regions

  17. Northeast Observing System (NEOS)

  18. Northeast Observing System (NEOS)

  19. Northeast Observing System (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 …)

  20. 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

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