35 research outputs found
The annual cycle of air-sea fluxes in the northwest tropical Atlantic
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bigorre, S. P., & Plueddemann, A. J. The annual cycle of air-sea fluxes in the northwest tropical Atlantic. Frontiers in Marine Science, 7, (2021): 612842, https://doi.org/10.3389/fmars.2020.612842.In this article we analyze 11 years of near-surface meteorology using observations from an open-ocean surface mooring located in the Northwestern Tropical Atlantic (51°W, 15°N). Air-sea fluxes of heat, freshwater, and momentum are derived from these observations using the Coupled Ocean–Atmosphere Response Experiment (COARE) bulk parameterization. Using this dataset, we compute a climatology of the annual cycle of near-surface meteorological conditions and air-sea fluxes. These in situ data are then compared with three reanalyses: the National Centers for Environmental Prediction-Department of Energy [NCEP-DOE (hereafter referred to as NCEP-2)], the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim and the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalyses. Products from the Clouds and the Earth’s Radiant Energy System (CERES) and the Tropical Rainfall Measuring Mission (TRMM) are also used for comparison. We identify the agreements and characterize the discrepancies in the annual cycles of meteorological variables and the different components of air-sea heat fluxes (latent, sensible, shortwave, and longwave radiation). Recomputing the reanalyses fluxes by applying the COARE algorithm to the reanalyses meteorological variables results in better agreement with the in situ fluxes than using the reanalyses fluxes directly. However, the radiative fluxes (longwave and shortwave) from some of the reanalyses show significant discrepancies when compared with the in situ measurements. Longwave radiation from MERRA-2 is biased high (too much oceanic heat loss), and NCEP-2 longwave does not correlate to in situ observations and other reanalyses. Shortwave radiation from NCEP-2 is biased low in winter and does not track the observed variability in summer. The discrepancies in radiative fluxes versus in situ fluxes are explored, and the potential regional implications are discussed using maps of satellite and reanalyses products, including radiation and cloud cover.The NTAS project was funded by the Global Ocean Monitoring and Observing Program of the National Oceanic and Atmospheric Administration (CPO FundRef number 100007298), through the Cooperative Institute for the North Atlantic Region (CINAR) under Cooperative Agreement NA14OAR4320158
NTAS 16 sixteenth setting of the NTAS Ocean Reference Station cruise on board RV Endeavor January 21 - February 8, 2017 Narragansett, Rhode Island - San Juan, Puerto Rico
The Northwest Tropical Atlantic Station (NTAS) was established to address the need for
accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface
temperature anomalies and the likelihood of significant local air–sea interaction on inter-annual
to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological
and oceanographic measurements at a site near 15N, 51W by successive mooring turnarounds.
These observations are used to investigate air–sea interaction processes related to climate
variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National
Oceanic and Atmospheric Administration’s (NOAA) Ocean Observing and Monitoring Division.
This report documents recovery of the NTAS-15 mooring and deployment of the NTAS-16
mooring. Both moorings used Surlyn foam buoys as the surface element. These buoys were
outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each system measures,
records, and transmits via Argos satellite the surface meteorological variables necessary to
compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the mooring line
were outfitted with oceanographic sensors for the measurement of temperature, salinity and
velocity.
The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole
Oceanographic Institution (WHOI), onboard R/V Endeavor (cruise EN590). The cruise took
place between January 21 and February 8 2017. The NTAS-16 mooring was deployed on
January 30, and the NTAS-15 mooring was recovered on January 31. A 24-hour intercomparison
period was conducted on January 29 in front of the NTAS 15 buoy, and again on
February 1 in front of the NTAS 16 buoy. During the inter-comparisons, data from
instrumentation on the buoys, telemetered through Argos satellite system, and the ship’s
meteorological and oceanographic measurements were monitored while the ship was stationed
0.2 nm downwind of the buoys. This report describes these operations, as well as other work
done on the cruise and some of the pre-cruise buoy preparations.
Other operations during EN590 consisted in the recovery and deployment of the Meridional
Overturning Variability Experiment (MOVE) Pressure Inverted Echo Sounders (PIES) at two
MOVE arrays (MOVE 1 in the east, and MOVE 3 in the west near Guadeloupe). Acoustic
downloads of data from (PIES) and subsurface mooring (MOVE1, 3 and 4) were also conducted.
MOVE is designed to monitor the integrated deep meridional flow in the tropical North Atlantic.Funding was provided by the National Oceanic and Atmospheric Administration
under Grant No. NA14OAR4320158
The thermocline and current structure in subtropical/subpolar basins
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1984Part one of this thesis discusses the structure of the thermocline and the
current pattern within a two-layer model. The corresponding flow field is
explored as the amount of water in the upper layer is gradually reduced (or as
the wind stress is gradually increased).
In the model, when the amount of water in the upper layer is less than a
first critical value, the lower layer outcrops near the middle of the western
boundary. A dynamically consistent picture includes a whole loop of boundary
currents, which surround the outcropping zone completely and have quite
different structures. In addition to the boundary currents found in previous
models, there is an isolated western boundary current (i.e. bounded on one
side by the wall and on the other by a streamline along which the upper layer
thickness vanishes), an internal boundary current and possibly isolated
northern/southern boundary currents. Within the limitations of the two-layer
model, the isolated western boundary current appears to represent the Labrador
Current while the internal boundary current may represent the North Atlantic
Current. A first baroclinic mode of water mass exchange occurs across the ZWCL
(zero-wind-curl-line).
When the amount of water in the upper layer is less than a second critical
value, the upper layer separates from the eastern wall and becomes a warm
water pool in the south-west corner of the basin. Under this warm water pool
is the ventilated lower layer.
The sea surface density distribution is not specified; it is determined
from a consistent dynamical and mass balance. Implicit in this model is the
assumption that advection dominates in the mixed layer.
The subtropical gyre and the subpolar gyre combine asymmetrically with
respect to the ZWCL.
Chapter I discusses the case when the lower layer depth is infinite.
Chapter II discusses the case when the lower layer depth is finite. In the
Addendum the climatological meaning of this two-layer model is discussed.
Part two of this thesis concerns the use of a continuously stratified
model to represent the thermocline and current structures in
subtropical/subpolar basins. The ideal fluid thermocline equation system Is a
nonlinear, non-strict hyperbolic system. In an Addendum to Chapter III the
mathematical properties of this equation system are studied and a proper way
of formulating boundary value problems is discussed. Although the equations
are not of standard type, so that no firm conclusions about the existence and
uniqueness of solutions have been drawn, some possible approaches to properly
posed boundary value problem are suggested. Chapter III presents some simple
numerical solutions of the ideal fluid thermocline equation for a subtropical
gyre and a subtropical/subpolar basin using one of these approaches. Our model
predicts the continuous three dimensional thermocline and current structures
in a continuously stratified wind-driven ocean. The upper surface density and
Ekman pumping velocity are specified as input data; in addition, the
functional form of the potential vorticity is specified.
The present model emphasizes the idea that the ideal fluid thermocline
model is incomplete. The potential vorticity distribution can not be
determined within this idealized model. This suggests that the diffusion and
upwelling/downwelling within the western boundary current and the outcropping
zone in the north-west corner are important parts of the entire circulation
system.This work was supported by NSF Grant 80-19260-0CE
Eastern Pacific oxygen time series from the Stratus mooring and from floats
In the tropical eastern South Pacific the Stratus Ocean Reference Station (~20°S, 85°W) is located in the transition zone between the oxygen minimum zone (OMZ) and the well oxygenated subtropical gyre. This region is also known for its high eddy frequency [Chaigneau et al., 2008]. From 6 April 2011 to 29 May 2012 oxygen was measured in the mooring from 9 oxygen optodes located between 45 m and 601 m depth at the southern boundary of the oxygen minimum zone. The oxygen time series describe the passage of several eddies, including a strong anticyclonic mode water eddy in February/March 2012 with oxygen decreasing by up to 200 mol/L and an available oxygen deficit of 10.5x1016 mol in comparison to its surrounding water. The eddy observed at the mooring was formed 11 months earlier off the coast of northern Chile. During its westward propagation one float was located for 3 months in this eddy and provided hydrographic and oxygen measurements along the path of the eddy. Several other floats were placed in eddies in the region, but did not stay continuously inside these eddies. The continuous oxygen measurements in the mooring and floats indicate high oxygen variability caused by eddies with enhanced oxygen in cyclonic eddies and reduced oxygen in anticyclonic eddies. Hence, oxygen trends determined from a few measurements might be biased by eddy processes. Finally, gliders with oxygen sensors may provide better eddy surveys than floats
The Northwest Tropical Atlantic Station (NTAS) : NTAS-15 Mooring Turnaround Cruise Report cruise on board RV Endeavor January 25 - February 13, 2016 Narragansett RI, USA - San Juan, Puerto Rico
The Northwest Tropical Atlantic Station (NTAS) was established to address the need for
accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface
temperature anomalies and the likelihood of significant local air–sea interaction on interannual to
decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological
and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds.
These observations are used to investigate air–sea interaction processes related to climate
variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National
Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program.
This report documents recovery of the NTAS-14 mooring and deployment of the NTAS-15
mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These
buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each
system measures, records, and transmits via Argos satellite the surface meteorological variables
necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the
mooring line were outfitted with oceanographic sensors for the measurement of temperature,
salinity and velocity.
The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole
Oceanographic Institution (WHOI), onboard R/V Endeavor, Cruise EN573. The cruise took
place between January 25 and February 13 2016. The NTAS-15 mooring was deployed on
February 2, and the NTAS-14 mooring was recovered on February 4. A 24-hour intercomparison
period was conducted on February 5, during which data from the buoy, telemetered
through Argos satellite system, and the ship’s meteorological and oceanographic data were
monitored while the ship was stationed 0.2 nm downwind of NTAS-15 buoy. A similar
procedure was done at NTAS-14 but for only about 10 hours on the morning of February 4. This
report describes these operations, as well as other work done on the cruise and some of the precruise
buoy preparations.
Other operations during EN573 consisted in the recovery and deployment of the Meridional
Overturning Variability Experiment (MOVE) subsurface moorings array (MOVE 1 in the east,
and MOVE 3 and 4 in the west near Guadeloupe). Acoustic download of data from Pressure
Inverted Echo Sounders (PIES) was also conducted. MOVE is designed to monitor the integrated
deep meridional flow in the tropical North Atlantic.Funding was provided by the National Oceanic and Atmospheric Administration
under Grant No. NA14OAR4320158
The Northwest Tropical Atlantic Station (NTAS) : NTAS-14 mooring turnaround cruise report
The Northwest Tropical Atlantic Station (NTAS) was established to address the need for
accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface
temperature anomalies and the likelihood of significant local air-sea interaction on interannual to
decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological
and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds.
These observations are used to investigate air-sea interaction processes related to climate
variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National
Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program.
This report documents recovery of the NTAS-13 mooring and deployment of the NTAS-14
mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These
buoys were outfitted with two Air-Sea Interaction Meteorology (ASIMET) systems. Each
system measures, records, and transmits via Argos satellite the surface meteorological variables
necessary to compute air-sea fluxes of heat, moisture and momentum. The upper 160 m of the
mooring line were outfitted with oceanographic sensors for the measurement of temperature,
salinity and velocity.
The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole
Oceanographic Institution (WHOI), onboard R/V Endeavor, Cruise EN549. The cruise took
place between December 5 and 21 December 2014. The NTAS-14 mooring was deployed on
December 13, and immediately followed by a 36-hour intercomparison period during which data
from the buoy, telemetered through Argos satellite system, and the ship’s meteorological and
oceanographic data were monitored. The NTAS-13 buoy had parted on September 23 and was
recovered on October 28 while drifting freely near Martinique. The rest of the mooring, which
had fallen to the seafloor was recovered during EN549, on December 17. This report describes
these operations, as well as other work done on the cruise and some of the pre-cruise buoy
preparations.
Other operations during EN549 consisted in the recovery and deployment of Pressure Inverted
Echo Sounders (PIES) and the acoustic download of data from PIES and subsurface moorings
that are part of the Meridional Overturning Variability Experiment (MOVE) array. MOVE is
designed to monitor the integrated deep meridional flow in the tropical North Atlantic. Two
Argo floats were also deployed during the cruise on behalf of the Argo group at WHOI.Funding was provided by the National Oceanic and Atmospheric Administration
under Grant No. NA14OAR4320158
The Northwest Tropical Atlantic Station (NTAS) : NTAS-17 mooring turnaround cruise report cruise on board FV Pisces May 30 – June 21, 2018 Mayport, FL, USA – Morehead City, NC, USA
The Northwest Tropical Atlantic Station (NTAS) was established to address the need for
accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface
temperature anomalies and the likelihood of significant local air–sea interaction on interannual to
decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological
and oceanographic measurements at a site near 15N, 51W by successive mooring turnarounds.
These observations are used to investigate air–sea interaction processes related to climate
variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National
Oceanic and Atmospheric Administration’s (NOAA) Ocean Observing and Monitoring Division.
This report documents recovery of the NTAS-16 mooring and deployment of the NTAS-17
mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These
buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each
system measures, records, and transmits via Argos satellite the surface meteorological variables
necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the
mooring line were outfitted with oceanographic sensors for the measurement of temperature,
salinity and velocity.
The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole
Oceanographic Institution (WHOI), onboard F/V Pisces, Cruise PC-18-03. The cruise took place
between May 30 and June 21 2018. The NTAS-17 mooring was deployed on June 10, and the
NTAS-16 mooring was recovered on June 12. No inter-comparison between ship and buoys was
performed on this cruise. This report describes these operations, as well as other work done on
the cruise and some of the pre-cruise buoy preparations.
Other operations during PC-18-03 consisted in the recovery and deployment of the Meridional
Overturning Variability Experiment (MOVE) subsurface moorings array (MOVE 1 in the east,
and MOVE 3 and 4 in the west near Guadeloupe). Acoustic download of data from Pressure
Inverted Echo Sounders (PIES) was also conducted. MOVE is designed to monitor the integrated
deep meridional flow in the tropical North Atlantic.Funding was provided by the National Oceanic and Atmospheric Administration
under Grant No. NA14OAR432015
The Northwest Tropical Atlantic Station (NTAS): NTAS-18 Mooring Turnaround Cruise Report Cruise On Board RV Ronald H. Brown January 6 –26, 2020 Bridgetown, Barbados – Bridgetown, Barbados
The Northwest Tropical Atlantic Station (NTAS) was established to address the need for
accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface
temperature anomalies and the likelihood of significant local air–sea interaction on interannual to
decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological
and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds.
These observations are used to investigate air–sea interaction processes related to climate
variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National
Oceanic and Atmospheric Administration’s (NOAA) Global Ocean Monitoring and Observing
(GOMO) Program (formerly Ocean Observing and Monitoring Division).
This report documents recovery of the NTAS-17 mooring and deployment of the NTAS-18
mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These
buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each
system measures, records, and transmits via satellite the surface meteorological variables
necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the
mooring line were outfitted with oceanographic sensors for the measurement of temperature,
salinity and velocity.
The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole
Oceanographic Institution (WHOI), onboard R/V Ron Brown, Cruise RB-20-01. The cruise took
place between January 6 and 26 2020. The NTAS-18 mooring was deployed on January 10, and
the NTAS-17 mooring was recovered on January 15. Inter-comparison between ship and buoys
were performed on this cruise. This report describes these operations, as well as other work done
on the cruise and some of the pre-cruise buoy preparations.
Other operations during RB-20-01 consisted in the acoustic communications with the Meridional
Overturning Variability Experiment (MOVE) subsurface mooring array MOVE 1-13 and
acoustic downloads of data from Pressure Inverted Echo Sounders (PIES) was also conducted at
MOVE 1. MOVE is designed to monitor the integrated deep meridional flow in the tropical
North Atlantic. Two ARGO floats were also deployed on behalf of the WHOI ARGO group.
During the cruise, atmospheric measurements of aerosols, as well as radar, Lidar, radiosondes
were made as part of the ATOMIC campaign.
3Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA14OAR432015
A surface mooring for air–sea interaction research in the Gulf Stream. Part I : mooring design and instrumentation
Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 29 (2012): 1363–1376, doi:10.1175/JTECH-D-12-00060.1.The design of a surface mooring for deployment in the Gulf Stream in the Mid-Atlantic Bight is described. The authors' goals were to observe the surface meteorology; upper-ocean variability; and air–sea exchanges of heat, freshwater, and momentum in and near the Gulf Stream during two successive 1-yr deployments. Of particular interest was quantifying these air–sea fluxes during wintertime events that carry cold, dry air from the land over the Gulf Stream. Historical current data and information about the surface waves were used to guide the design of the surface mooring. The surface buoy provided the platform for both bulk meteorological sensors and a direct covariance flux system. Redundancy in the meteorological sensors proved to be a largely successful strategy to obtain complete time series. Oceanographic instrumentation was limited in size by considerations of drag; and two current meters, three temperature–salinity recorders, and 15 temperature recorders were deployed. Deployment from a single-screw vessel in the Gulf Stream required a controlled-drift stern first over the anchor sites. The first deployment lasted the planned full year. The second deployment ended after 3 months when the mooring was cut by unknown means at a depth of about 3000 m. The mooring was at times in the core of the Gulf Stream, and a peak surface current of over 2.7 m s−1 was observed. The 15-month records of surface meteorology and air–sea fluxes captured the seasonal variability as well as several cold-air outbreaks; the peak observed heat loss was in excess of 1400 W m−2.This work was funded by the National
Science Foundation Grant OCE04-24536 as part
of the CLIVAR Mode Water Dynamics Experiment
(CLIMODE). The Vetlesen Foundation is also acknowledged
for the early support of SB.2013-03-0
Accuracy of wind observations from open-ocean buoys: Correction for flow distortion
The comparison of equivalent neutral winds obtained from (a) four WHOI buoys in the subtropics and (b) scatterometer estimates at those locations reveals a root-mean-square (RMS) difference of 0.56-0.76 m/s. To investigate this RMS difference, different buoy wind error sources were examined. These buoys are particularly well suited to examine two important sources of buoy wind errors because: (1) redundant anemometers and a comparison with numerical flow simulations allow us to quantitatively assess flow distortion errors, and (2) one-minute sampling at the buoys allows us to examine the sensitivity of buoy temporal sampling/averaging in the buoy-scatterometer comparisons. The inter-anemometer difference varies as a function of wind direction relative to the buoy wind vane and is consistent with the effects of flow distortion expected based on numerical flow simulations. Comparison between the anemometers and scatterometer winds supports the interpretation that the inter-anemometer disagreement, which can be up to 5% of the wind speed, is due to flow distortion. These insights motivate an empirical correction to the individual anemometer records and subsequent comparison with scatterometer estimates show good agreement