Edson James B.

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Edson

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James B.

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0000-0002-8777-031X

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Air-sea gas transfer : its dependence on wind stress, small-scale roughness, and surface films

(American Geophysical Union, 2004-08-21) Frew, Nelson M. ; Bock, Erik J. ; Schimpf, Uwe ; Hara, Tetsu ; Haußecker, Horst ; Edson, James B. ; McGillis, Wade R. ; Nelson, Robert K. ; McKenna, Sean P. ; Uz, B. Mete ; Jahne, B.

The influence of wind stress, small-scale waves, and surface films on air-sea gas exchange at low to moderate wind speeds (<10 m s−1) is examined. Coincident observations of wind stress, heat transfer velocity, surface wave slope, and surface film enrichments were made in coastal and offshore waters south of Cape Cod, New England, in July 1997 as part of the NSF-CoOP Coastal Air-Sea Chemical Fluxes study. Gas transfer velocities have been extrapolated from aqueous heat transfer velocities derived from infrared imagery and direct covariance and bulk heat flux estimates. Gas transfer velocity is found to follow a quadratic relationship with wind speed, which accounts for ~75–77% of the variance but which overpredicts transfer velocity in the presence of surface films. The dependence on wind stress as represented by the friction velocity is also nonlinear, reflecting a wave field-dependent transition between limiting transport regimes. In contrast, the dependence on mean square slope computed for the wave number range of 40–800 rad m−1 is found to be linear and in agreement with results from previous laboratory wind wave studies. The slope spectrum of the small-scale waves and the gas transfer velocity are attenuated in the presence of surface films. Observations over large-scale gradients of biological productivity and dissolved organic matter show that the reduction in slope and transfer velocity are more clearly correlated with surface film enrichments than with bulk organic matter concentrations. The mean square slope parameterization explains ~89–95% of the observed variance in the data and does not overpredict transfer velocities where films are present. While the specific relationships between gas transfer velocity and wind speed or mean square slope vary slightly with the choice of Schmidt number exponent used to scale the heat transfer velocities to gas transfer velocities, the correlation of heat or gas transfer velocity with mean square slope is consistently better than with wind speed.
Measurements of momentum and heat transfer across the air–sea interface

(American Meteorological Society, 2008-05) Gerbi, Gregory P. ; Trowbridge, John H. ; Edson, James B. ; Plueddemann, Albert J. ; Terray, Eugene A. ; Fredericks, Janet J.

This study makes direct measurements of turbulent fluxes in the mixed layer in order to close heat and momentum budgets across the air–sea interface and to assess the ability of rigid-boundary turbulence models to predict mean vertical gradients beneath the ocean’s wavy surface. Observations were made at 20 Hz at nominal depths of 2.2 and 1.7 m in 16 m of water. A new method is developed to estimate the fluxes and the length scales of dominant flux-carrying eddies from cospectra at frequencies below the wave band. The results are compared to independent estimates of those quantities, with good agreement between the two sets of estimates. The observed temperature gradients were smaller than predicted by standard rigid-boundary closure models, consistent with the suggestion that wave breaking and Langmuir circulation increase turbulent diffusivity in the upper ocean. Similarly, the Monin–Obukhov stability function ϕh was smaller in the authors’ measurements than the stability functions used in rigid-boundary applications of the Monin–Obukhov similarity theory. The dominant horizontal length scales of flux-carrying turbulent eddies were found to be consistent with observations in the bottom boundary layer of the atmosphere and from laboratory experiments in three ways: 1) in statically unstable conditions, the eddy sizes scaled linearly with distance to the boundary; 2) in statically stable conditions, length scales decreased with increasing downward buoyancy flux; and 3) downwind length scales were larger than crosswind length scales.
A Ka-band wind Geophysical Model Function using doppler scatterometer measurements from the Air-Sea Interaction Tower experiment

(MDPI, 2022-04-26) Polverari, Federica ; Wineteer, Alexander ; Rodríguez, Ernesto ; Perkovic-Martin, Dragana ; Siqueira, Paul ; Farrar, J. Thomas ; Adam, Max ; Closa Tarrés, Marc ; Edson, James B.

Physical understanding and modeling of Ka-band ocean surface backscatter is challenging due to a lack of measurements. In the framework of the NASA Earth Ventures Suborbital-3 Submesoscale Ocean Dynamics Experiment (S-MODE) mission, a Ka-Band Ocean continuous wave Doppler Scatterometer (KaBODS) built by the University of Massachusetts, Amherst (UMass) was installed on the Woods Hole Oceanographic Institution (WHOI) Air-Sea Interaction Tower. Together with ASIT anemometers, a new data set of Ka-band ocean surface backscatter measurements along with surface wind/wave and weather parameters was collected. In this work, we present the KaBODS instrument and an empirical Ka-band wind Geophysical Model Function (GMF), the so-called ASIT GMF, based on the KaBODS data collected over a period of three months, from October 2019 to January 2020, for incidence angles ranging between 40° and 68°. The ASIT GMF results are compared with an existing Ka-band wind GMF developed from data collected during a tower experiment conducted over the Black Sea. The two GMFs show differences in terms of wind speed and wind direction sensitivity. However, they are consistent in the values of the standard deviation of the model residuals. This suggests an intrinsic geophysical variability characterizing the Ka-band surface backscatter. The observed variability does not significantly change when filtering out swell-dominated data, indicating that the long-wave induced backscatter modulation is not the primary source of the KaBODS backscatter variability. We observe evidence of wave breaking events, which increase the skewness of the backscatter distribution in linear space, consistent with previous studies. Interestingly, a better agreement is seen between the GMFs and the actual data at an incidence angle of 60° for both GMFs, and the statistical analysis of the model residuals shows a reduced backscatter variability at this incidence angle. This study shows that the ASIT data set is a valuable reference for studies of Ka-band backscatter. Further investigations are on-going to fully characterize the observed variability and its implication in the wind GMF development.
Air-sea CO2 exchange in the equatorial Pacific

(American Geophysical Union, 2004-08-28) McGillis, Wade R. ; Edson, James B. ; Zappa, Christopher J. ; Ware, Jonathan D. ; McKenna, Sean P. ; Terray, Eugene A. ; Hare, Jeffrey E. ; Fairall, Christopher W. ; Drennan, William M. ; Donelan, Mark A. ; DeGrandpre, Michael D. ; Wanninkhof, Rik ; Feely, Richard A.

GasEx-2001, a 15-day air-sea carbon dioxide (CO2) exchange study conducted in the equatorial Pacific, used a combination of ships, buoys, and drifters equipped with ocean and atmospheric sensors to assess variability and surface mechanisms controlling air-sea CO2 fluxes. Direct covariance and profile method air-sea CO2 fluxes were measured together with the surface ocean and marine boundary layer processes. The study took place in February 2001 near 125°W, 3°S in a region of high CO2. The diurnal variation in the air-sea CO2 difference was 2.5%, driven predominantly by temperature effects on surface solubility. The wind speed was 6.0 ± 1.3 m s−1, and the atmospheric boundary layer was unstable with conditions over the range −1 < z/L < 0. Diurnal heat fluxes generated daytime surface ocean stratification and subsequent large nighttime buoyancy fluxes. The average CO2 flux from the ocean to the atmosphere was determined to be 3.9 mol m−2 yr−1, with nighttime CO2 fluxes increasing by 40% over daytime values because of a strong nighttime increase in (vertical) convective velocities. The 15 days of air-sea flux measurements taken during GasEx-2001 demonstrate some of the systematic environmental trends of the eastern equatorial Pacific Ocean. The fact that other physical processes, in addition to wind, were observed to control the rate of CO2 transfer from the ocean to the atmosphere indicates that these processes need to be taken into account in local and global biogeochemical models. These local processes can vary on regional and global scales. The GasEx-2001 results show a weak wind dependence but a strong variability in processes governed by the diurnal heating cycle. This implies that any changes in the incident radiation, including atmospheric cloud dynamics, phytoplankton biomass, and surface ocean stratification may have significant feedbacks on the amount and variability of air-sea gas exchange. This is in sharp contrast with previous field studies of air-sea gas exchange, which showed that wind was the dominating forcing function. The results suggest that gas transfer parameterizations that rely solely on wind will be insufficient for regions with low to intermediate winds and strong insolation.
Corrigendum : On the exchange of momentum over the open ocean

(American Meteorological Society, 2014-09) Edson, James B. ; Jampana, Venkata ; Weller, Robert A. ; Bigorre, Sebastien P. ; Plueddemann, Albert J. ; Fairall, Christopher W. ; Miller, Scott D. ; Mahrt, Larry ; Vickers, Dean ; Hersbach, Hans
Biases in the air-sea flux of CO2 resulting from ocean surface temperature gradients

(American Geophysical Union, 2004-06-30) Ward, Brian ; Wanninkhof, Rik ; McGillis, Wade R. ; Jessup, Andrew T. ; DeGrandpre, Michael D. ; Hare, Jeffrey E. ; Edson, James B.

The difference in the fugacities of CO2 across the diffusive sublayer at the ocean surface is the driving force behind the air-sea flux of CO2. Bulk seawater fugacity is normally measured several meters below the surface, while the fugacity at the water surface, assumed to be in equilibrium with the atmosphere, is measured several meters above the surface. Implied in these measurements is that the fugacity values are the same as those across the diffusive boundary layer. However, temperature gradients exist at the interface due to molecular transfer processes, resulting in a cool surface temperature, known as the skin effect. A warm layer from solar radiation can also result in a heterogeneous temperature profile within the upper few meters of the ocean. Here we describe measurements carried out during a 14-day study in the equatorial Pacific Ocean (GasEx-2001) aimed at estimating the gradients of CO2 near the surface and resulting flux anomalies. The fugacity measurements were corrected for temperature effects using data from the ship's thermosalinograph, a high-resolution profiler (SkinDeEP), an infrared radiometer (CIRIMS), and several point measurements at different depths on various platforms. Results from SkinDeEP show that the largest cool skin and warm layer biases occur at low winds, with maximum biases of −4% and +4%, respectively. Time series ship data show an average CO2 flux cool skin retardation of about 2%. Ship and drifter data show significant CO2 flux enhancement due to the warm layer, with maximums occurring in the afternoon. Temperature measurements were compared to predictions based on available cool skin parameterizations to predict the skin-bulk temperature difference, along with a warm layer model.
A surface mooring for air–sea interaction research in the Gulf Stream. Part I : mooring design and instrumentation

(American Meteorological Society, 2012-09) Weller, Robert A. ; Bigorre, Sebastien P. ; Lord, Jeffrey ; Ware, Jonathan D. ; Edson, James B.

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.
Sea-to-air fluxes from measurements of the atmospheric gradient of dimethylsulfide and comparison with simultaneous relaxed eddy accumulation measurements

(American Geophysical Union, 2004-01-30) Hintsa, Eric J. ; Dacey, John W. H. ; McGillis, Wade R. ; Edson, James B. ; Zappa, Christopher J. ; Zemmelink, Hendrik J.

We measured vertical profiles of dimethylsulfide (DMS) in the atmospheric marine boundary layer from R/P FLIP during the 2000 FAIRS cruise. Applying Monin-Obukhov similarity theory to the DMS gradients and simultaneous micrometeorological data, we calculated sea-to-air DMS fluxes for 34 profiles. From the fluxes and measured seawater DMS concentrations, we calculated the waterside gas transfer velocity, kw. Gas transfer velocities from the gradient flux approach are within the range of previous commonly used parameterizations of kw as a function of wind speed but are a factor of 2 smaller than simultaneous determinations of transfer velocity using the relaxed eddy accumulation technique. This is the first field comparison of these different techniques for measuring DMS flux from the ocean; the accuracy of the techniques and possible reasons for the discrepancy are discussed.
Scalar flux profile relationships over the open ocean

(American Geophysical Union, 2004-08-14) Edson, James B. ; Zappa, Christopher J. ; Ware, J. A. ; McGillis, Wade R. ; Hare, Jeffrey E.

The most commonly used flux-profile relationships are based on Monin-Obukhov (MO) similarity theory. These flux-profile relationships are required in indirect methods such as the bulk aerodynamic, profile, and inertial dissipation methods to estimate the fluxes over the ocean. These relationships are almost exclusively derived from previous field experiments conducted over land. However, the use of overland measurements to infer surface fluxes over the ocean remains questionable, particularly close to the ocean surface where wave-induced forcing can affect the flow. This study investigates the flux profile relationships over the open ocean using measurements made during the 2000 Fluxes, Air-Sea Interaction, and Remote Sensing (FAIRS) and 2001 GasEx experiments. These experiments provide direct measurement of the atmospheric fluxes along with profiles of water vapor and temperature. The specific humidity data are used to determine parameterizations of the dimensionless gradients using functional forms of two commonly used relationships. The best fit to the Businger-Dyer relationship [ Businger, 1988 ] is found using an empirical constant of a q = 13.4 ± 1.7. The best fit to a formulation that has the correct form in the limit of local free convection [e.g., Wyngaard, 1973 ] is found using a q = 29.8 ± 4.6. These values are in good agreement with the consensus values from previous overland experiments and the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.0 bulk algorithm [ Fairall et al., 2003 ]; e.g., the COARE algorithm uses empirical constants of 15 and 34.2 for the Businger-Dyer and convective forms, respectively. Although the flux measurements were made at a single elevation and local similarity scaling is applied, the good agreement implies that MO similarity is valid within the marine atmospheric surface layer above the wave boundary layer.
A surface mooring for air–sea interaction research in the Gulf Stream. Part II : analysis of the observations and their accuracies

(American Meteorological Society, 2013-03) Bigorre, Sebastien P. ; Weller, Robert A. ; Edson, James B. ; Ware, Jonathan D.

A surface mooring was deployed in the Gulf Stream for 15 months to investigate the role of air–sea interaction in mode water formation and other processes. The accuracies of the near-surface meteorological and oceanographic measurements are investigated. In addition, the impacts of these measurement errors on the estimation and study of the air–sea fluxes in the Gulf Stream are discussed. Pre- and postdeployment calibrations together with in situ comparison between shipboard and moored sensors supported the identification of biases due to sensor drifts, sensor electronics, and calibration errors. A postdeployment field study was used to further investigate the performance of the wind sensors. The use of redundant sensor sets not only supported the filling of data gaps but also allowed an examination of the contribution of random errors. Air–sea fluxes were also analyzed and computed from both Coupled Ocean–Atmosphere Response Experiment (COARE) bulk parameterization and using direct covariance measurements. The basic conclusion is that the surface buoy deployed in the Gulf Stream to support air–sea interaction research was successful, providing an improved 15-month record of surface meteorology, upper-ocean variability, and air–sea fluxes with known accuracies. At the same time, the coincident deployment of mean meteorological and turbulent flux sensors proved to be a successful strategy to certify the validity of the bulk formula fluxes over the midrange of wind speeds and to support further work to address the present shortcomings of the bulk formula methods at the low and high wind speeds.
Sensors for physical fluxes at the sea surface : energy, heat, water, salt

(Copernicus Publications on behalf of the European Geosciences Union, 2008-12-10) Weller, Robert A. ; Bradley, E. F. ; Edson, James B. ; Fairall, Christopher W. ; Brooks, Ian M. ; Yelland, Margaret J. ; Pascal, Robin W.

The current status of meteorological sensors used aboard ships and buoys to measure the air-sea fluxes of momentum, heat, and freshwater is reviewed. Methods of flux measurement by the bulk aerodynamic, inertial dissipation and eddy-correlation methods are considered; and areas are identified where improvements are needed in measurement of the basic variables. In some cases, what is required is the transition from emergent to operational technology, in others new technologies are needed. Uncertainties in measured winds caused by flow distortion over the ship are discussed; and the possible role of computational fluid mechanics models to obtain corrections is considered. Basic studies are also needed on the influence of waves and rain on the fluxes. The issues involved in the specification of sea surface temperature are described, and the relative merits of the available sensors are discussed. The improved capability of buoy-mounted systems will depend on the emergence of low-power instruments, and/or new means of increasing the available power capacity. Other issues covered include the continuing uncertainty about the performance of rain gauges and short-wave radiometers. Also, the requirements for new instruments to extend the range of observations to extreme wind conditions are outlined, and the latest developments in the measurement of aerosol fluxes by eddy-correlation are presented.
Comparison of direct covariance flux measurements from an offshore tower and a buoy

(American Meteorological Society, 2016-04-20) Flügge, Martin ; Bakhoday Paskyabi, Mostafa ; Reuder, Joachim ; Edson, James B. ; Plueddemann, Albert J.

Direct covariance flux (DCF) measurements taken from floating platforms are contaminated by wave-induced platform motions that need to be removed before computation of the turbulent fluxes. Several correction algorithms have been developed and successfully applied in earlier studies from research vessels and, most recently, by the use of moored buoys. The validation of those correction algorithms has so far been limited to short-duration comparisons against other floating platforms. Although these comparisons show in general a good agreement, there is still a lack of a rigorous validation of the method, required to understand the strengths and weaknesses of the existing motion-correction algorithms. This paper attempts to provide such a validation by a comparison of flux estimates from two DCF systems, one mounted on a moored buoy and one on the Air–Sea Interaction Tower (ASIT) at the Martha’s Vineyard Coastal Observatory, Massachusetts. The ASIT was specifically designed to minimize flow distortion over a wide range of wind directions from the open ocean for flux measurements. The flow measurements from the buoy system are corrected for wave-induced platform motions before computation of the turbulent heat and momentum fluxes. Flux estimates and cospectra of the corrected buoy data are found to be in very good agreement with those obtained from the ASIT. The comparison is also used to optimize the filter constants used in the motion-correction algorithm. The quantitative agreement between the buoy data and the ASIT demonstrates that the DCF method is applicable for turbulence measurements from small moving platforms, such as buoys.
On estimating the surface wind stress over the sea

(American Meteorological Society, 2018-07-10) Mahrt, Larry ; Miller, Scott ; Hristov, Tihomir ; Edson, James B.

Our study analyzes measurements primarily from two Floating Instrument Platform (FLIP) field programs and from the Air–Sea Interaction Tower (ASIT) site to examine the relationship between the wind and sea surface stress for contrasting conditions. The direct relationship of the surface momentum flux to U2 is found to be better posed than the relationship between and U, where U is the wind speed and is the friction velocity. Our datasets indicate that the stress magnitude often decreases significantly with height near the surface due to thin marine boundary layers and/or enhanced stress divergence close to the sea surface. Our study attempts to correct the surface stress estimated from traditional observational levels by using multiple observational levels near the surface and extrapolating to the surface. The effect of stability on the surface stress appears to be generally smaller than errors due to the stress divergence. Definite conclusions require more extensive measurements close to the sea surface.
Effects of rainfall on the atmosphere and the ocean during spurs-2

(Oceanography Society, 2019-06-14) Clayson, Carol A. ; Edson, James B. ; Paget, Aaron ; Graham, Raymond ; Greenwood, Benjamin

The salinity variability of the upper ocean is influenced by surface heat, momentum, and freshwater fluxes, which are in turn affected by atmospheric conditions. It is necessary to accurately measure these surface fluxes within their atmospheric environment to understand the linkages between rain events and the resulting upper-ocean salinity balance that occurs at cloud scales. We describe a comprehensive set of atmospheric and oceanic data collected during the second Salinity Processes in the Upper-ocean Regional Study (SPURS-2) experiment in the tropical eastern Pacific Ocean. These measurements included direct estimates of heat, moisture, and momentum fluxes using direct covariance flux systems on R/V Roger Revelle and a 3 m discus buoy. These are the first successful direct measurements of evaporation from a buoy over an extended period. The atmospheric moisture budget is estimated from a combination of data, including measured freshwater fluxes, upper air sounding data, and satellite data. This analysis reconfirms the important role of moisture convergence beneath the Intertropical Convergence Zone in this region. We perform an analysis of the near-surface vertical salinity structure and its relationship to these surface fluxes, highlighting the roles of stabilization by solar insolation and precipitation and the effects of rainfall on mixing of the upper ocean.
Novel and flexible approach to access the open ocean: Uses of sailing research vessel Lady Amber during SPURS-2.

(Oceanography Society, 2019-06-14) Rainville, Luc ; Centurioni, Luca R. ; Asher, William E. ; Clayson, Carol A. ; Drushka, Kyla ; Edson, James B. ; Hodges, Benjamin A. ; Hormann, Verena ; Farrar, J. Thomas ; Schanze, Julian J. ; Shcherbina, Andrey Y.

SPURS-2 (Salinity Processes in the Upper-ocean Regional Study 2) used the schooner Lady Amber, a small sailing research vessel, to deploy, service, maintain, and recover a variety of oceanographic and meteorological instruments in the eastern Pacific Ocean. Low operational costs allowed us to frequently deploy floats and drifters to collect data necessary for resolving the regional circulation of the eastern tropical Pacific. The small charter gave us the opportunity to deploy drifters in locations chosen according to current conditions, to recover and deploy various autonomous instruments in a targeted and adaptive manner, and to collect additional near-surface and atmospheric measurements in the remote SPURS-2 region.
The CLIMODE field campaign : observing the cycle of convection and restratification over the Gulf Stream

(American Meteorological Society, 2009-09) Marshall, John C. ; Ferrari, Raffaele ; Forget, Gael ; Andersson, A. ; Bates, Nicholas R. ; Dewar, William K. ; Doney, Scott C. ; Fratantoni, David M. ; Joyce, Terrence M. ; Straneo, Fiamma ; Toole, John M. ; Weller, Robert A. ; Edson, James B. ; Gregg, M. C. ; Kelly, Kathryn A. ; Lozier, M. Susan ; Palter, Jaime B. ; Lumpkin, Rick ; Samelson, Roger M. ; Skyllingstad, Eric D. ; Silverthorne, Katherine E. ; Talley, Lynne D. ; Thomas, Leif N.

A major oceanographic field experiment is described, which is designed to observe, quantify, and understand the creation and dispersal of weakly stratified fluid known as “mode water” in the region of the Gulf Stream. Formed in the wintertime by convection driven by the most intense air–sea fluxes observed anywhere over the globe, the role of mode waters in the general circulation of the subtropical gyre and its biogeo-chemical cycles is also addressed. The experiment is known as the CLIVAR Mode Water Dynamic Experiment (CLIMODE). Here we review the scientific objectives of the experiment and present some preliminary results.
Air-Sea trace gas fluxes: direct and indirect measurements

(Frontiers Media, 2022-07-29) Fairall, Christopher W. ; Yang, Mingxi ; Brumer, Sophia E. ; Blomquist, Byron ; Edson, James B. ; Zappa, Christopher J. ; Bariteau, Ludovic ; Pezoa, Sergio ; Bell, Tom G. ; Saltzman, Eric

The past decade has seen significant technological advance in the observation of trace gas fluxes over the open ocean, most notably CO2, but also an impressive list of other gases. Here we will emphasize flux observations from the air-side of the interface including both turbulent covariance (direct) and surface-layer similarity-based (indirect) bulk transfer velocity methods. Most applications of direct covariance observations have been from ships but recently work has intensified on buoy-based implementation. The principal use of direct methods is to quantify empirical coefficients in bulk estimates of the gas transfer velocity. Advances in direct measurements and some recent field programs that capture a considerable range of conditions with wind speeds exceeding 20 ms-1 are discussed. We use coincident direct flux measurements of CO2 and dimethylsulfide (DMS) to infer the scaling of interfacial viscous and bubble-mediated (whitecap driven) gas transfer mechanisms. This analysis suggests modest chemical enhancement of CO2 flux at low wind speed. We include some updates to the theoretical structure of bulk parameterizations (including chemical enhancement) as framed in the COAREG gas transfer algorithm.
Coastal mixing and optics experiment moored array data report

(Woods Hole Oceanographic Institution, 1999-12) Galbraith, Nancy R. ; Plueddemann, Albert J. ; Lentz, Steven J. ; Anderson, Steven P. ; Baumgartner, Mark F. ; Edson, James B.

To investigate vertical mixing processes influencing the evolution of the stratification over continental shelves a moored array was deployed on the New England shelf from August 1996 to June 1997 as part of the Office of Naval Research's Coastal Mixing and Optics program. The array consisted of four mid-shelf sites instrumented to measure oceanic (currents, temperature, salinity, pressure, and surface gravity wave spectra) and meteorological (winds, surface heat flux, precipitation) variables. This report presents a description of the moored array, a summary of the data processing, and statistics and time-series plots summarizing the data. A report on the mooring recovery cruise and a summary of shipboard CTD surveys taken during the mooring deployment are also included.
On assessing ERA5 and MERRA2 representations of cold-air outbreaks across the Gulf Stream

(American Geophysical Union, 2021-09-08) Chellappan, Seethala ; Zuidema, Paquita ; Edson, James B. ; Brunke, Michael ; Chen, Gao ; Li, Xiang-Yu ; Painemal, David ; Robinson, Claire ; Shingler, Taylor ; Shook, Michael ; Sorooshian, Armin ; Thornhill, Kenneth L. ; Tornow, Florian ; Wang, Hailong ; Zeng, Xubin ; Ziemba, Luke

The warm Gulf Stream sea surface temperatures strongly impact the evolution of winter clouds behind atmospheric cold fronts. Such cloud evolution remains challenging to model. The Gulf Stream is too wide within the ERA5 and MERRA2 reanalyses, affecting the turbulent surface fluxes. Known problems within the ERA5 boundary layer (too-dry and too-cool with too strong westerlies), ascertained primarily from ACTIVATE 2020 campaign aircraft dropsondes and secondarily from older buoy measurements, reinforce surface flux biases. In contrast, MERRA2 winter surface winds and air-sea temperature/humidity differences are slightly too weak, producing surface fluxes that are too low. Reanalyses boundary layer heights in the strongly forced winter cold-air-outbreak regime are realistic, whereas late-summer quiescent stable boundary layers are too shallow. Nevertheless, the reanalysis biases are small, and reanalyses adequately support their use for initializing higher-resolution cloud process modeling studies of cold-air outbreaks.
Evaluation of the National Oceanic and Atmospheric Administration/Coupled-Ocean Atmospheric Response Experiment (NOAA/COARE) air-sea gas transfer parameterization using GasEx data

(American Geophysical Union, 2004-07-16) Hare, Jeffrey E. ; Fairall, Christopher W. ; McGillis, Wade R. ; Edson, James B. ; Ward, Brian ; Wanninkhof, Rik

During the two recent GasEx field experiments, direct covariance measurements of air-sea carbon dioxide fluxes were obtained over the open ocean. Concurrently, the National Oceanic and Atmospheric Administration/Coupled-Ocean Atmospheric Response Experiment air-sea gas transfer parameterization was developed to predict gas transfer velocities from measurements of the bulk state of the sea surface and atmosphere. The model output is combined with measurements of the mean air and sea surface carbon dioxide fugacities to provide estimates of the air-sea CO2 flux, and the model is then tuned to the GasEx-1998 data set. Because of differences in the local environment and possibly because of weaknesses in the model, some discrepancies are observed between the predicted fluxes from the GasEx-1998 and GasEx-2001 cases. To provide an estimate of the contribution to the air-sea flux of gas due to wave-breaking processes, the whitecap and bubble parameterizations are removed from the model output. These results show that moderate (approximately 15 m s−1) wind speed breaking wave gas transfer processes account for a fourfold increase in the flux over the modeled interfacial processes.

Edson James B.

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