John Wilkin Modeling the Heat Budget of Southeast New England Shelf Waters for CBLAST-Low John Wilkin H. Arango, K. Fennel, L. Lanerolle, J. Levin Institute of Marine and Coastal Sciences Rutgers, The State University of New Jersey NSF CoOP Buoyancy driven flow (LATTE) Northeast Observing System (NEOS) Northeast North American shelf (NENA) North Atlantic Basin (NATL)

John Wilkin 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. 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. 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. Modeling complements the interpretation of the field observations by quantifying unobserved lateral transport and mixing of heat. 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.

Low Winds Improve Flux Parameterizations  =  C D  U 2 Research Question: What physical processes are responsible for this enhancement?

John Wilkin Irradiance 23m 15m U, T, Q Heat, mass & mom. flux, ε Waves Waves T, S Heat, mass mom. flux, ε Solar, IR, rain, U, T, Q Heat, mass & momentum flux, ε

John Wilkin MVCO K ASIT CBLAST-Low Observing System 2002: Nantucket SODAR IR Aircraft 3-D mooring Flux Aircraft RemoteSensing ASIMET moorings with ocean T(z) and ADCP

John Wilkin The Regional Ocean Modeling System (ROMS/TOMS) has been configured for a region of the southeastern New England shelf encompassing the CBLAST observation area Purpose: Obtain model hind-cast of summertime ocean conditions that captures the essential features of the ocean heat budget on diurnal to several day time-scales, and spatial scales of order 1 km

John Wilkin The Regional Ocean Modeling System (ROMS/TOMS) has been configured for a region of the southeastern New England shelf encompassing the CBLAST observation area Motivation (1) Model evaluation: Compare model heat budget to observations: Evaluate heat budget sensitivity to vertical turbulent closures in ROMS Evaluate heat budget sensitivity to vertical turbulent closures in ROMS Evaluate heat budget sensitivity to air-sea flux bulk formulae Evaluate heat budget sensitivity to air-sea flux bulk formulae Evaluate contribution to hind-cast skill of meteorological model (COAMPS) compared to using observed marine boundary layer conditions Evaluate contribution to hind-cast skill of meteorological model (COAMPS) compared to using observed marine boundary layer conditions

John Wilkin Motivation (2) Observational data analysis: Horizontal mixing and advection are largely unobserved by the CBLAST field instrumentation. This affects closure of the observed heat budget, especially: Advection of vertically mixed waters originating on the Nantucket Shoals Advection of vertically mixed waters originating on the Nantucket Shoals Advection past the CBLAST tower of tidally generated eddies transporting Vineyard Sound water through Muskeget channel Advection past the CBLAST tower of tidally generated eddies transporting Vineyard Sound water through Muskeget channel To what extent does wind-driven upwelling maintain stratification, and contribute to local heat budgets?

John Wilkin ROMS CBLAST domain 1 km grid resolution 20 vertical levels (stretched) Surface forcing: Observed ASIT/MVCO and modeled (COAMPS) mairne boundary conditions Observed ASIT/MVCO and modeled (COAMPS) mairne boundary conditions Initial and inflow/outflow boundary conditions from bi-monthly climatology Tides

John Wilkin COAMPS CBLAST, 3km, 91x91 9 km 27 km, 151x121x30 Surface forcing: Heat and momentum fluxes from bulk formulae model SST model SST T air, p air, rel. humidity, U 10, V 10, and short- wave radiation from 3km resolution nested COAMPS hr forecast T air, p air, rel. humidity, U 10, V 10, and short- wave radiation from 3km resolution nested COAMPS hr forecast observed downward long-wave at MVCO or net long-wave from COAMPS observed downward long-wave at MVCO or net long-wave from COAMPS Courtesy S. Wang and Q. Wang, NRL

John Wilkin Split-explicit, free-surface, hydrostatic, primitive equation model Generalized, terrain-following vertical coordinates Orthogonal curvilinear, horizontal coordinates, Arakawa C-grid 3 rd - and 4 th -order advection and time-stepping; weighted temporal averaging; reduced pressure gradient and mode-splitting error Simultaneous conservation and constancy preservation for tracer equations in combination with evolving coordinate system due to free-surface Continuous, monotonic reconstruction of vertical gradients to maintain high-order accuracy ROMS/TOMS MPI shared and distributed memory f90 code netCDF I/O ROMS model attributes Split-explicit, free-surface, hydrostatic, primitive equation model Generalized, terrain-following vertical coordinates Orthogonal curvilinear, horizontal coordinates, Arakawa C-grid 3 rd - and 4 th -order advection and time-stepping; weighted temporal averaging; reduced pressure gradient and mode-splitting error Simultaneous conservation and constancy preservation for tracer equations in combination with evolving coordinate system due to free-surface Continuous, monotonic reconstruction of vertical gradients to maintain high-order accuracy ROMS/TOMS MPI shared and distributed memory f90 code netCDF I/O

John Wilkin Mellor-Yamada level 2.5 Mellor-Yamada level 2.5 Non-local, k-profile parameterization (KPP) surface and bottom closure scheme Non-local, k-profile parameterization (KPP) surface and bottom closure scheme surface boundary layer (KPP; Large et al., 1994) surface boundary layer (KPP; Large et al., 1994) bottom boundary layer (inverted KPP; Durski et al., 2001) bottom boundary layer (inverted KPP; Durski et al., 2001) Generalized Ocean Turbulence Model Generalized Ocean Turbulence Model Eddy viscosity and diffusivity product of a non-dimensional stability function, normalized TKE, and macro length scale Eddy viscosity and diffusivity product of a non-dimensional stability function, normalized TKE, and macro length scale The stability functions are the result of various second-moment closures. TKE and the length scales are calculated by dynamic equations (as in k-epsilon or Mellor-Yamada models) or algebraic formulations. The stability functions are the result of various second-moment closures. TKE and the length scales are calculated by dynamic equations (as in k-epsilon or Mellor-Yamada models) or algebraic formulations. ROMS Vertical Turbulence Closure options Umlauf, L. and H. Burchard. A generic length-scale equation for geophysical turbulence models J. Mar. Res., 2003 Warner, J.C., Sherwood, C.R., Butman, B., Arango, H.G., and Signell, R.P., Implementation of a generic length scale turbulence closure in a 3D oceanographic model." Ocean Modeling, 2003.

John Wilkin

Circulation around Nantucket Shoals is augmented by tidal rectified anti- cyclonic flow that carries water into Vineyard Sound through Muskeget Channel

John Wilkin 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). 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. Southwest of Martha’s Vineyard, and within Vineyard Sound, winds drive eastward depth averaged flow. July 2002 mean

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

John Wilkin Air-sea flux (Q net ) 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. July 2002

John Wilkin MVCO The time mean advection cools the box at, on average, 200 W/m 2. The net “eddy” divergence (u’T’) warms the MVCO region at about 50 W/m 2. 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.

John Wilkin CTD temperature section between ASIT and mooring-A, late July ObservedModeled 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.

John Wilkin 2003

COAMPS 72-hour forecast was generated every 12 hours at ARL.HPC.mil and transferred to IMCS where ROMS ran for the same forecast cycle. Operational forecasts were generated for July 21 through September 3, 2003

John Wilkin

Raw CTD data acquired via Iridium from a Slocum Glider transiting between ASIT and ASIMET mooring-A.

John Wilkin Long-range CODAR at ’Siasconset Nantucket

John Wilkin CBLAST: CBLAST: Lessons for ocean modeling: Differing vertical turbulence parameterizations lead to different 3-dimensional coastal mesoscale flowsDiffering vertical turbulence parameterizations lead to different 3-dimensional coastal mesoscale flows CBLAST data suited to turbulence closure evaluation:CBLAST data suited to turbulence closure evaluation: –Combination of direct air-sea flux and vertical turbulence observations, and in situ oceanic conditions for validation Spatially variable atmospheric forcing (COAMPS) is importantSpatially variable atmospheric forcing (COAMPS) is important Heat budget requires further analysis of horizontal/vertical circulations: overturning/upwelling vs. depth-average flow contributions, especially at moorings and ASITHeat budget requires further analysis of horizontal/vertical circulations: overturning/upwelling vs. depth-average flow contributions, especially at moorings and ASIT

John Wilkin CBLAST: Lessons for data analysis: Tides affect the circulation and heat budget through residual mean currents and vertical mixingTides affect the circulation and heat budget through residual mean currents and vertical mixing Wind-driven upwelling circulation contributes to the heat budget southwest of Martha’s VineyardWind-driven upwelling circulation contributes to the heat budget southwest of Martha’s Vineyard 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 budgetsLateral 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 Vineyard Sound, Nantucket Shoals, MVCO, shows differing heat balances in July meanVineyard Sound, Nantucket Shoals, MVCO, shows differing heat balances in July mean Modeling shows a 1-D heat balance occurs near the B-A-C ASIMET mooring sites, which suggests vertical turbulence closures can be evaluated locally thereModeling shows a 1-D heat balance occurs near the B-A-C ASIMET mooring sites, which suggests vertical turbulence closures can be evaluated locally there

John Wilkin Nested Grids 1) NENA 2) NEOS 3) CBLAST 4) LATTE 5) NY/NJ Bight 6) Caribbean

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

John Wilkin Northeast North Atlantic (NENA) embedded in NATL 3-day average open boundary values from NATL 10-component NPZD ecosystem: NO 3, NH4, chl-a, phytoplankton, zooplankton, small/large detritus, TIC, alkalinity, oxygen TemperatureChlorophyll

John Wilkin CO 2 flux (mol m- 2 yr -1 ) Day of year Air-sea CO2-flux: - simulated (above and top right) - observed (bottom right; Boehme et al., Mar. Chem. 1998)

John Wilkin NEOS NENA Salinity at 20 m Initialized 01-Jan-1993 Northeast Observing System (NEOS)

John Wilkin Assimilate regional CODAR with 4D- variational method Assimilate regional CODAR with 4D- variational method Develop AUV deployment strategies; tangent linear and adjoint give singular vectors of model showing regions of most rapid perturbation growth Develop AUV deployment strategies; tangent linear and adjoint give singular vectors of model showing regions of most rapid perturbation growth Multiple-scale nesting in support of sub-region studies (LaTTE, CBLAST) Multiple-scale nesting in support of sub-region studies (LaTTE, CBLAST) Northeast Observing System (NEOS)

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

John Wilkin Hierarchy of integrated observational/modeling studies from basin to coastal using ROMS/TOMS tools Hierarchy of integrated observational/modeling studies from basin to coastal using ROMS/TOMS tools Processes: coastal bio-optics, sediment transport, CO 2 cycling, buoyancy-driven flow, wind-driven upwelling, air-sea interaction Processes: coastal bio-optics, sediment transport, CO 2 cycling, buoyancy-driven flow, wind-driven upwelling, air-sea interaction Adjoint, tangent linear, variational assimilation codes feature in projects Adjoint, tangent linear, variational assimilation codes feature in projects Objectives ( ) for coastal prediction system development: Objectives ( ) for coastal prediction system development: turbulence closure: evaluate with CBLAST-Low data turbulence closure: evaluate with CBLAST-Low data air-sea fluxes, coupling to atmospheric models (COAMPS, WRF) air-sea fluxes, coupling to atmospheric models (COAMPS, WRF) 4D-variational assimilation 4D-variational assimilation new observing system technologies (CODAR, gliders) new observing system technologies (CODAR, gliders) use adjoint for sampling design and predictability studies use adjoint for sampling design and predictability studies Summary