554
2.1
Martha’s Vineyard coastal observatory and CBLASTLow
The inner continental shelf of southeastern New England south of Cape
Cod, Massachusetts, encompasses a variety of circulation regimes delineated
by the geography of the region. The waters of Nantucket Sound are shallow
and relatively sheltered by the islands of Martha’s Vineyard and Nantucket.
Tidal mixing on the Nantucket Shoals vertically mixes the water column
throughout the year, while the waters south of Martha’s Vineyard undergo a
seasonal cycle of stratification and mixing. The Martha’s Vineyard Coastal
Observatory (MVCO) is a permanently cabled site, like LEO, that sits 3 km
from the southern shore of Martha’s Vineyard. The MVCO includes a
meteorological mast on land, an undersea node at a depth of 12 m, and, in
waters 15 m deep, an offshore air-sea interaction tower (ASIT) that spans the
water column and extends 20 m into the atmosphere. Routinely obtained
MVCO measurements now include wind velocity, air temperature, and solar
radiation at the meteorological mast, near-bottom temperature and salinity at
the undersea node, velocities throughout the water column from an ADCP at
the undersea node, and estimates of Reynolds stress from an array of
acoustic Doppler velocimeters (ADVs) near the bottom at the ASIT.
The CBLAST-Low program is a study of air-sea interaction at low wind
speeds – a regime for which atmosphere and ocean boundary layer processes
are modulated significantly by thermal forcing. In addition to the fixed
instrumentation at MVCO and ASIT, additional instruments were deployed
in the environs of MVCO during CBLAST Intensive Observing Periods in
the summers of 2001, 2002 and 2003 (Hutto et al. 2003). In the most
comprehensive field season, 2003, the first set of atmosphere and ocean flux
observations from the ASIT became available, an array of 6 ‘heavy’
moorings south of ASIT measured meteorological boundary layer properties
(winds, temperature, humidity and radiation) at the surface buoy plus ocean
temperature and velocity profiles to the seafloor, a further 9 ‘light’ moorings
observed sub-surface temperature profiles, surface currents were measured
from a CODAR site on Nantucket, research aircraft profiled the marine
boundary layer, and vertical thermistor strings were towed by ship through
thermal features evident in satellite and aircraft imagery. The U.S. Navy
operated the COAMPS (Coupled Ocean Atmosphere Mesoscale Prediction
System) model in a multiply-nested configuration; the 27-km resolution
West Atlantic operational product (Hodur et al. 2002) was refined through a
9-km resolution intermediate mesh to a very high (3-km) resolution
experimental forecast specifically for the CBLAST-Low study (Wang 2004).
Observations from the fixed ASIT tower are being used to quantify the
vertical fluxes of turbulent kinetic energy, momentum, mass, and heat in the
oceanic mixed-layer and atmospheric boundary layer. With coincident local
measurements of radiative fluxes, the independent air-side and water-side
flux estimates can be compared to those derived from the bulk formulae
JOHN L. WILKIN AND LYON LANEROLLE
2.1
Martha’s Vineyard coastal observatory and CBLASTLow
The inner continental shelf of southeastern New England south of Cape
Cod, Massachusetts, encompasses a variety of circulation regimes delineated
by the geography of the region. The waters of Nantucket Sound are shallow
and relatively sheltered by the islands of Martha’s Vineyard and Nantucket.
Tidal mixing on the Nantucket Shoals vertically mixes the water column
throughout the year, while the waters south of Martha’s Vineyard undergo a
seasonal cycle of stratification and mixing. The Martha’s Vineyard Coastal
Observatory (MVCO) is a permanently cabled site, like LEO, that sits 3 km
from the southern shore of Martha’s Vineyard. The MVCO includes a
meteorological mast on land, an undersea node at a depth of 12 m, and, in
waters 15 m deep, an offshore air-sea interaction tower (ASIT) that spans the
water column and extends 20 m into the atmosphere. Routinely obtained
MVCO measurements now include wind velocity, air temperature, and solar
radiation at the meteorological mast, near-bottom temperature and salinity at
the undersea node, velocities throughout the water column from an ADCP at
the undersea node, and estimates of Reynolds stress from an array of
acoustic Doppler velocimeters (ADVs) near the bottom at the ASIT.
The CBLAST-Low program is a study of air-sea interaction at low wind
speeds – a regime for which atmosphere and ocean boundary layer processes
are modulated significantly by thermal forcing. In addition to the fixed
instrumentation at MVCO and ASIT, additional instruments were deployed
in the environs of MVCO during CBLAST Intensive Observing Periods in
the summers of 2001, 2002 and 2003 (Hutto et al. 2003). In the most
comprehensive field season, 2003, the first set of atmosphere and ocean flux
observations from the ASIT became available, an array of 6 ‘heavy’
moorings south of ASIT measured meteorological boundary layer properties
(winds, temperature, humidity and radiation) at the surface buoy plus ocean
temperature and velocity profiles to the seafloor, a further 9 ‘light’ moorings
observed sub-surface temperature profiles, surface currents were measured
from a CODAR site on Nantucket, research aircraft profiled the marine
boundary layer, and vertical thermistor strings were towed by ship through
thermal features evident in satellite and aircraft imagery. The U.S. Navy
operated the COAMPS (Coupled Ocean Atmosphere Mesoscale Prediction
System) model in a multiply-nested configuration; the 27-km resolution
West Atlantic operational product (Hodur et al. 2002) was refined through a
9-km resolution intermediate mesh to a very high (3-km) resolution
experimental forecast specifically for the CBLAST-Low study (Wang 2004).
Observations from the fixed ASIT tower are being used to quantify the
vertical fluxes of turbulent kinetic energy, momentum, mass, and heat in the
oceanic mixed-layer and atmospheric boundary layer. With coincident local
measurements of radiative fluxes, the independent air-side and water-side
flux estimates can be compared to those derived from the bulk formulae
JOHN L. WILKIN AND LYON LANEROLLE