US East Coast ROMS/TOMS Projects
North Atlantic Basin (NATL)
Northeast North American shelf (NENA)
NSF CoOP Buoyancy driven flow (LaTTE)
CBLAST-Low
Northeast Observing System (NEOS)
John Wilkin
H. Arango, K. Fennel, L. Lanerolle, J. Levin
Institute of Marine and Coastal Sciences
Rutgers University
John Wilkin
[email protected]
North Atlantic
Climatological
heat/freshwater fluxes
3-day average NCEP winds
John Wilkin
[email protected]
Northeast North Atlantic (NENA) embedded within NATL
3-day average open boundary values from NATL
7-component NPZD ecosystem
Temperature
John Wilkin
[email protected]
Chlorophyll
Lagrangian Transport and
Transformation Experiment (LaTTE)
• Dye release in Hudson River plume
• 4D-var assimilation with ROMS
• Coupled bio-optical modeling with EcoSim
John Wilkin
[email protected]
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.
John Wilkin
[email protected]
CBLAST-Low Observing System:
MVCO
Aircraft
ASIT
K
Nantucket SODAR
ASIMET moorings with
ocean T(z) and ADCP
3-D
Moorin
g
Remote
Sensing
John Wilkin
[email protected]
Solar, IR, rain, U, T, Q
Heat, mass &
momentum flux, ε
U, T, Q
Heat, mass &
mom. flux, ε
Waves
23m
Irradiance
15m
John Wilkin
[email protected]
Irradiance
Waves
T, S
Heat, mass
mom. flux, ε
COAMPS CBLAST, 3km, 91x91
ROMS CBLAST configuration
1 km horizontal resolution
20 s-levels (stretched toward surface)
9 km
27 km, 151x121x30
M2 displacement ellipses from ADCIRC
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, v
Climatology, tides [9], radiation (gh)
on  and depth average u,v
John Wilkin
[email protected]
160 x 380 x 20 grid requires
approximately 2 CPU mins per model day
on 16-processor HP/Compaq
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
[email protected]
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).
John Wilkin
[email protected]
3-day composite SST for 30-Aug-2002
John Wilkin
[email protected]
Tidal mixing
generates a region of
perpetually cold SST
on the eastern flank
of the Nantucket
Shoals
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.
July
2002
John Wilkin
[email protected]
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.
John Wilkin
[email protected]
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.
CTD temperature section between ASIT and mooring-A, late July 2001.
Observed
John Wilkin
[email protected]
Modeled
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.
John Wilkin
[email protected]
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.
John Wilkin
[email protected]
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
John Wilkin
[email protected]
Northeast Observing System (NEOS)
John Wilkin
[email protected]
Northeast Observing System (NEOS)
John Wilkin
[email protected]
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 …)
John Wilkin
[email protected]
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
John Wilkin
[email protected]