Fairall Christopher W.

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Fairall

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Christopher W.

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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
Overview of the Arctic Sea state and boundary layer physics program

(American Geophysical Union, 2018-04-16) Thomson, Jim ; Ackley, Stephen ; Girard-Ardhuin, Fanny ; Ardhuin, Fabrice ; Babanin, Alexander ; Boutin, Guillaume ; Brozena, John ; Cheng, Sukun ; Collins, Clarence ; Doble, Martin ; Fairall, Christopher W. ; Guest, Peter ; Gebhardt, Claus ; Gemmrich, Johannes ; Graber, Hans C. ; Holt, Benjamin ; Lehner, Susanne ; Lund, Björn ; Meylan, Michael ; Maksym, Ted ; Montiel, Fabien ; Perrie, Will ; Persson, Ola ; Rainville, Luc ; Rogers, W. Erick ; Shen, Hui ; Shen, Hayley ; Squire, Vernon ; Stammerjohn, Sharon E. ; Stopa, Justin ; Smith, Madison M. ; Sutherland, Peter ; Wadhams, Peter

A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and wave events drive episodic advances and retreats of the ice edge, with associated variations in sea ice formation types (e.g., pancakes, nilas). This variability becomes imprinted on the winter ice cover, which in turn affects the melt season the following year.
Emerging trends in the sea state of the Beaufort and Chukchi seas

(Elsevier, 2016-07-06) Thomson, James M. ; Fan, Yalin ; Stammerjohn, Sharon E. ; Stopa, Justin ; Rogers, W. Erick ; Girard-Ardhuin, Fanny ; Ardhuin, Fabrice ; Shen, Hayley ; Perrie, Will ; Shen, Hui ; Ackley, Stephen ; Babanin, Alexander ; Liu, Qingxiang ; Guest, Peter ; Maksym, Ted ; Wadhams, Peter ; Fairall, Christopher W. ; Persson, Ola ; Doble, Martin J. ; Graber, Hans C. ; Lund, Bjoern ; Squire, Vernon ; Gemmrich, Johannes ; Lehner, Susanne ; Holt, Benjamin ; Meylan, Michael ; Brozena, John ; Bidlot, Jean-Raymond

The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing, independent of changes in the wind forcing. Wave model hindcasts from four selected years spanning recent conditions are consistent with this expectation. In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally longer. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance. However, trends in the amount of wave energy impinging on the ice-edge are inconclusive, and the associated processes, especially in the autumn period of new ice formation, have yet to be well-described by in situ observations. There is an implicit trend and evidence for increasing wave energy along the coast of northern Alaska, and this coastal signal is corroborated by satellite altimeter estimates of wave energy.
Measurements from the RV Ronald H. Brown and related platforms as part of the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC)

(Copernicus Publications, 2021-04-29) Quinn, Patricia K. ; Thompson, Elizabeth ; Coffman, Derek J. ; Baidar, Sunil ; Bariteau, Ludovic ; Bates, Timothy S. ; Bigorre, Sebastien P. ; Brewer, Alan ; de Boer, Gijs ; de Szoeke, Simon P. ; Drushka, Kyla ; Foltz, Gregory R. ; Intrieri, Janet ; Iyer, Suneil ; Fairall, Christopher W. ; Gaston, Cassandra J. ; Jansen, Friedhelm ; Johnson, James E. ; Krüger, Ovid O. ; Marchbanks, Richard D. ; Moran, Kenneth P. ; Noone, David ; Pezoa, Sergio ; Pincus, Robert ; Plueddemann, Albert J. ; Pöhlker, Mira L. ; Pöschl, Ulrich ; Quinones Melendez, Estefania ; Royer, Haley M. ; Szczodrak, Malgorzata ; Thomson, Jim ; Upchurch, Lucia M. ; Zhang, Chidong ; Zhang, Dongxiao ; Zuidema, Paquita

The Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) took place from 7 January to 11 July 2020 in the tropical North Atlantic between the eastern edge of Barbados and 51∘ W, the longitude of the Northwest Tropical Atlantic Station (NTAS) mooring. Measurements were made to gather information on shallow atmospheric convection, the effects of aerosols and clouds on the ocean surface energy budget, and mesoscale oceanic processes. Multiple platforms were deployed during ATOMIC including the NOAA RV Ronald H. Brown (RHB) (7 January to 13 February) and WP-3D Orion (P-3) aircraft (17 January to 10 February), the University of Colorado's Robust Autonomous Aerial Vehicle-Endurant Nimble (RAAVEN) uncrewed aerial system (UAS) (24 January to 15 February), NOAA- and NASA-sponsored Saildrones (12 January to 11 July), and Surface Velocity Program Salinity (SVPS) surface ocean drifters (23 January to 29 April). The RV Ronald H. Brown conducted in situ and remote sensing measurements of oceanic and atmospheric properties with an emphasis on mesoscale oceanic–atmospheric coupling and aerosol–cloud interactions. In addition, the ship served as a launching pad for Wave Gliders, Surface Wave Instrument Floats with Tracking (SWIFTs), and radiosondes. Details of measurements made from the RV Ronald H. Brown, ship-deployed assets, and other platforms closely coordinated with the ship during ATOMIC are provided here. These platforms include Saildrone 1064 and the RAAVEN UAS as well as the Barbados Cloud Observatory (BCO) and Barbados Atmospheric Chemistry Observatory (BACO). Inter-platform comparisons are presented to assess consistency in the data sets. Data sets from the RV Ronald H. Brown and deployed assets have been quality controlled and are publicly available at NOAA's National Centers for Environmental Information (NCEI) data archive (https://www.ncei.noaa.gov/archive/accession/ATOMIC-2020, last access: 2 April 2021). Point-of-contact information and links to individual data sets with digital object identifiers (DOIs) are provided herein.
Stratus Ocean Reference Station (20˚S, 85˚W), mooring recovery and deployment cruise R/V Revelle cruise dana 03, November 10 - November 26, 2003

(Woods Hole Oceanographic Institution, 2004-03) Hutto, Lara ; Weller, Robert A. ; Lord, Jeffrey ; Smith, Jason C. ; Ryder, James R. ; Galbraith, Nancy R. ; Fairall, Christopher W. ; Stalin, Scott ; Andueza, Juan Carlos ; Tomlinson, Jason

The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile and Peru is being maintained to provide ongoing, climate-quality records of surface meteorology, of air-sea fluxes of heat, freshwater, and momentum, and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station, hereafter ORS Stratus, is supported by the National Oceanic and Atmospheric Administrations (NOAA) Climate Observation Program. It is recovered and redeployed annually, with cruises that have come in October or November. During the November 2003 cruise of Scripps Institution of Oceanography's R/V Roger Revelle to the ORS Stratus site, the primary activities where the recovery of the WHOI surface mooring that had been deployed in October 2002, the deployment of a new WHOI surface mooring at that site, the in-situ calibration of the buoy meteorological sensors by comparison with instrumentation put on board by Chris Fairall of the NOAA Environmental Technology Laboratory (ETL), and observations of the stratus clouds and lower atmosphere by NOAA ETL and Jason Tomlinson from Texas A&M. The ORS Stratus buoys are equipped with two Improved Meteorological systems, which provide surface wind speed and direction, air temperature, relative humidity, barometric pressure, incoming shortwave radiation, incoming longwave radiation, precipitation rate, and sea surface temperature. The IMET data are made available in near real time using satellite telemetry. The mooring line carries instruments to measure ocean salinity, temperature, and currents. On some deployments, additional instrumentation is attached to the mooring to measure rainfall and bio-optical variability. The ETL instrumentation used during the 2003 cruise included a cloud radar, radiosonde balloons, and sensors for mean and turbulent surface meteorology. In addition to this work, buoy work was done in support of the Ecuadorian Navy Institute of Oceanography (INOCAR) and of the Chilean Navy Hydrographic and Oceanographic Service (SHOA). The surface buoy, oceanographic instrumentation, and upper 500 m of an INOCAR surface mooring at 2°S, 84°W that had been vandalized were recovered and transferred to the Ecuadorian Navy vessel B. A. E. Calicuchima. A tsunami warning mooring was installed at 75°W, 20°S for SHOA. SHOA personnel onboard were trained during the cruise by staff from the NOAA Pacific Marine Environmental Laboratory (PMEL) and National Data Buoy Center (NDBC). The cruise hosted two teachers participating in NOAA's Teacher at Sea Program, Deb Brice from San Marcos, California and Viviana Zamorano from Arica, Chile.
Stratus Ocean Reference Station (20˚S, 85˚W), mooring recovery and deployment cruise, R/V Ron Brown cruise 04-11, December 5 - December 24, 2004

(Woods Hole Oceanographic Institution, 2005-05) Colbo, Keir ; Weller, Robert A. ; Lord, Jeffrey ; Smith, Jason C. ; Bouchard, Paul R. ; Fairall, Christopher W. ; Bradley, Frank ; Wolfe, Dan ; Serpetzoglou, Efthymios ; Tomlinson, Jason ; Tisandie, Alvaro Gustave Vera ; Bustos, Juan Francisco Santibanez

The Ocean Reference Station at 20° S, 85° W under the stratus clouds west of northern Chile and Peru is being maintained to provide ongoing, climate-quality records of surface meteorology, of air-sea fluxes of heat, freshwater, and momentum, and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. It is recovered and redeployed annually, with cruises that have come between October and December. During the December 2004 cruise of NOAA's R/V Ronald H. Brown to the ORS Stratus site, the primary activities where the recovery of the WHOI surface mooring that had been deployed in November 2003, the deployment of a new WHOI surface mooring at that site, the in-situ calibration of the buoy meteorological sensors by comparison with instrumentation put on board by staff of the NOAA Environmental Technology Laboratory (ETL), and observations of the stratus clouds and lower atmosphere by NOAA ETL and Jason Tomlinson from Texas A&M. The ORS Stratus buoys are equipped with two Improved Meteorological systems, which provide surface wind speed and direction, air temperature, relative humidity, barometric pressure, incoming shortwave radiation, incoming longwave radiation, precipitation rate, and sea surface temperature. The IMET data are made available in near real time using satellite telemetry. The mooring line carries instruments to measure ocean salinity, temperature, and currents. The ETL instrumentation used during the 2004 cruise included cloud radar, radiosonde balloons, and sensors for mean and turbulent surface meteorology. The atmospheric observations also benefited from the C-Band radar mounted on the R/V Ronald H. Brown. In addition to this work, buoy work was done in support of the Chilean Navy Hydrographic and Oceanographic Service (SHOA). A tsunami warning mooring was reinstalled at 75°W, 20°S for SHOA, after the previous buoy installed last year failed. SHOA personnel were onboard to direct the deployment and to gain experience. Four students from the University of Concepcion collected hydrographic data and water samples. One other Chilean student from the University of Chile was involved in the atmospheric sampling program, with a particular focus on the near coast jet. Finally, the cruise hosted a teacher participating in NOAA's Teacher at Sea Program, Mary Esther Cook, who used her experience to develop lessons for her class back in Arkansas.
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.
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-6 2009 mooring turnaround cruise report

(Woods Hole Oceanographic Institution, 2010-02) Whelan, Sean P. ; Santiago-Mandujano, Fernando ; Bradley, Frank ; Plueddemann, Albert J. ; Barista, Ludovic ; Ryder, James R. ; Lukas, Roger ; Lethaby, Paul ; Snyder, Jefrey ; Sabine, Christopher L. ; Stanitski, Diane ; Rapp, Anita D. ; Fairall, Christopher W. ; Pezoa, Sergio ; Galbraith, Nancy R. ; Lord, Jeffrey ; Bahr, Frank B.

The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the Hawaiian Ocean Timeseries (HOT) program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. The first WHOTS mooring (WHOTS-1) was deployed in August 2004. Turnaround cruises for successive moorings (WHOTS-2 through WHOTS-5) have typically been in either June or July. This report documents recovery of the WHOTS-5 mooring and deployment of the sixth mooring (WHOTS-6). The moorings utilize Surlyn foam buoys as the surface element and are outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET 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 155 m of the mooring is outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii (UH). A pCO2 system is installed on the buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. Dr. Frank Bradley, CSIRO, Australia, assisted with meteorological sensor comparisons. A NOAA “Teacher at Sea” and a NOAA “Teacher in the Lab” participated in the cruise. The WHOTS mooring turnaround was done on the University of Hawaii research vessel Kilo Moana, Cruise KM-09-16, by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution in cooperation with UH and NOAA’s Earth System Research Laboratory, Physical Sciences Division (ESRL/PSD). The cruise took place between 9 and 17 July 2009. Operations began with deployment of the WHOTS-6 mooring on 10 July at approximately 22°40.0'N, 157°57.0'W in 4758 m of water. This was followed by meteorological intercomparisons and CTDs at the WHOTS-6 and WHOTS-5 sites. The WHOTS-5 mooring was recovered on 15 July 2009. The Kilo Moana then moved to the HOT central site (22°45.0'N, 158°00.0'W) for CTD casts. This report describes the cruise operations in more detail, as well as some of the in-port operations and pre-cruise buoy preparations.
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.
Stratus 9/VOCALS ninth setting of the Stratus Ocean Reference Station & VOCALS Regional Experiment

(Woods Hole Oceanographic Institution, 2009-04) Whelan, Sean P. ; Lord, Jeffrey ; Galbraith, Nancy R. ; Weller, Robert A. ; Farrar, J. Thomas ; Grant, David ; Grados, Carmen ; de Szoeke, Simon P. ; Moffat, Carlos F. ; Zappa, Christopher J. ; Yang, Mingxi ; Straneo, Fiamma ; Fairall, Christopher W. ; Zuidema, Paquita ; Wolfe, Dan ; Miller, Matthew ; Covert, David

The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing climate-quality records of surface meteorology; air-sea fluxes of heat, freshwater, and momentum; and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. It is recovered and redeployed annually, with cruises that have come between October and December. During the 2008 cruise on the NOAA ship Ronald H. Brown to the ORS Stratus site, the primary activities were recovery of the Stratus 8 WHOI surface mooring that had been deployed in October 2007, deployment of a new (Stratus 9) WHOI surface mooring at that site; in-situ calibration of the buoy meteorological sensors by comparison with instrumentation put on board by staff of the NOAA Earth System Research Laboratory (ESRL); and observations of the stratus clouds and lower atmosphere by NOAA ESRL. A buoy for the Pacific tsunami warning system was also serviced in collaboration with the Hydrographic and Oceanographic Service of the Chilean Navy (SHOA). The DART (Deep-Ocean Assessment and Reporting of Tsunami) carries IMET sensors and subsurface oceanographic instruments. A DART II buoy was deployed north of the STRATUS buoy, by personnel from the National Data Buoy Center (NDBC) Argo floats and drifters were launched, and CTD casts carried out during the cruise. The ORS Stratus buoys are equipped with two Improved Meteorological (IMET) systems, which provide surface wind speed and direction, air temperature, relative humidity, barometric pressure, incoming shortwave radiation, incoming longwave radiation, precipitation rate, and sea surface temperature. Additionally, the Stratus 8 buoy received a partial CO2 detector from the Pacific Marine Environmental Laboratory (PMEL). IMET data are made available in near real time using satellite telemetry. The mooring line carries instruments to measure ocean salinity, temperature, and currents. The ESRL instrumentation used during the 2008 cruise included cloud radar, radiosonde balloons, and sensors for mean and turbulent surface meteorology. Finally, the cruise hosted a teacher participating in NOAA’s Teacher at Sea Program.
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.
Climatology of surface meteorology, surface fluxes, cloud fraction, and radiative forcing over the southeast Pacific from buoy observations

(American Meteorological Society, 2009-10-15) Ghate, Virendra P. ; Albrecht, Bruce A. ; Fairall, Christopher W. ; Weller, Robert A.

A 5-yr climatology of the meteorology, including boundary layer cloudiness, for the southeast Pacific region is presented using observations from a buoy located at 20°S, 85°W. The sea surface temperature and surface air temperature exhibit a sinusoidal seasonal cycle that is negatively correlated with surface pressure. The relative humidity, wind speed, and wind direction show little seasonal variability. But the advection of cold and dry air from the southeast varies seasonally and is highly correlated with the latent heat flux variations. A simple model was used to estimate the monthly cloud fraction using the observed surface downwelling longwave radiative flux and surface meteorological parameters. The annual cycle of cloud fraction is highly correlated to that of S. A. Klein: lower-tropospheric stability parameter (0.87), latent heat flux (−0.59), and temperature and moisture advection (0.60). The derived cloud fraction compares poorly with the International Satellite Cloud Climatology Project (ISCCP)-derived low-cloud cover but compares well (0.86 correlation) with ISCCP low- plus middle-cloud cover. The monthly averaged diurnal variations in cloud fraction show marked seasonal variability in the amplitude and temporal structure. The mean annual cloud fraction is lower than the mean annual nighttime cloud fraction by about 9%. Annual and diurnal cycles of surface longwave and shortwave cloud radiative forcing were also estimated. The longwave cloud radiative forcing is about 45 W m−2 year-round, but, because of highly negative shortwave cloud radiative forcing, the net cloud radiative forcing is always negative with an annual mean of −50 W m−2.
Stratus Ocean Reference Station (20˚S, 85˚W), mooring recovery and deployment cruise R/V Ronald H. Brown cruise 05-05, September 26, 2005–October 21, 2005

(Woods Hole Oceanographic Institution, 2006-02) Hutto, Lara ; Weller, Robert A. ; Lord, Jeffrey ; Smith, Jason C. ; Bouchard, Paul R. ; Fairall, Christopher W. ; Pezoa, Sergio ; Bariteau, Ludovic ; Lundquist, Jessica ; Ghate, Virendra P. ; Castro, Rodrigo ; Cisternas, Carolina

The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing, climate-quality records of surface meteorology, of air-sea fluxes of heat, freshwater, and momentum, and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. It is recovered and redeployed annually, with cruises that have come between October and December. During the October 2005 cruise of NOAA’s R/V Ronald H. Brown to the ORS Stratus site, the primary activities were recovery of the WHOI surface mooring that had been deployed in December 2004, deployment of a new WHOI surface mooring at that site, in-situ calibration of the buoy meteorological sensors by comparison with instrumentation put on board by staff of the NOAA Environmental Technology Laboratory (ETL), and observations of the stratus clouds and lower atmosphere by NOAA ETL. The ORS Stratus buoys are equipped with two Improved Meteorological (IMET) systems, which provide surface wind speed and direction, air temperature, relative humidity, barometric pressure, incoming shortwave radiation, incoming longwave radiation, precipitation rate, and sea surface temperature. The IMET data are made available in near real time using satellite telemetry. The mooring line carries instruments to measure ocean salinity, temperature, and currents. The ETL instrumentation used during the 2005 cruise included cloud radar, radiosonde ballons, and sensors for mean and turbulent surface meteorology. In addition, two technicians from the University of Concepcion collected water samples for chemical analysis. Finally, the cruise hosted a teacher participating in NOAA’s Teacher at Sea Program.
Surface cloud forcing in the East Pacific stratus deck/cold tongue/ITCZ complex

(American Meteorological Society, 2006-02-01) Cronin, Meghan F. ; Bond, Nicholas A. ; Fairall, Christopher W. ; Weller, Robert A.

Data from the Eastern Pacific Investigation of Climate Studies (EPIC) mooring array are used to evaluate the annual cycle of surface cloud forcing in the far eastern Pacific stratus cloud deck/cold tongue/intertropical convergence zone complex. Data include downwelling surface solar and longwave radiation from 10 EPIC-enhanced Tropical Atmosphere Ocean (TAO) moorings from 8°S, 95°W to 12°N, 95°W, and the Woods Hole Improved Meteorology (IMET) mooring in the stratus cloud deck region at 20°S, 85°W. Surface cloud forcing is defined as the observed downwelling radiation at the surface minus the clear-sky value. Solar cloud forcing and longwave cloud forcing are anticorrelated at all latitudes from 12°N to 20°S: clouds tended to reduce the downward solar radiation and to a lesser extent increase the downward longwave radiation at the surface. The relative amount of solar radiation reduction and longwave increase depends upon cloud type and varies with latitude. A statistical relationship between solar and longwave surface cloud forcing is developed for rainy and dry periods and for the full record length in six latitudinal regions: northeast tropical warm pool, ITCZ, frontal zone, cold tongue, southern, and stratus deck regions. The buoy cloud forcing observations and empirical relations are compared with the International Satellite Cloud Climatology Project (ISCCP) radiative flux data (FD) dataset and are used as benchmarks to evaluate surface cloud forcing in the NCEP Reanalysis 2 (NCEP2) and 40-yr ECMWF Re-Analysis (ERA-40). ERA-40 and NCEP2 cloud forcing (both solar and longwave) showed large discrepancies with observations, being too large in the ITCZ and equatorial regions and too weak under the stratus deck at 20°S and north to the equator during the cool season from July to December. In particular the NCEP2 cloud forcing at the equator was nearly identical to the ITCZ region and thus had significantly larger solar cloud forcing and smaller longwave cloud forcing than observed. The net result of the solar and longwave cloud forcing deviations is that there is too little radiative warming in the ITCZ and southward to 8°S during the warm season and too much radiative warming under the stratus deck at 20°S and northward to the equator during the cold season.
Air-sea fluxes with a focus on heat and momentum

(Frontiers Media, 2019-07-31) Cronin, Meghan F. ; Gentemann, Chelle L. ; Edson, James B. ; Ueki, Iwao ; Bourassa, Mark A. ; Brown, Shannon ; Clayson, Carol A. ; Fairall, Christopher W. ; Farrar, J. Thomas ; Gille, Sarah T. ; Gulev, Sergey ; Josey, Simon A. ; Kato, Seiji ; Katsumata, Masaki ; Kent, Elizabeth ; Krug, Marjolaine ; Minnett, Peter J. ; Parfitt, Rhys ; Pinker, Rachel T. ; Stackhouse, Paul W., Jr. ; Swart, Sebastiaan ; Tomita, Hiroyuki ; Vandemark, Douglas ; Weller, Robert A. ; Yoneyama, Kunio ; Yu, Lisan ; Zhang, Dongxiao

Turbulent and radiative exchanges of heat between the ocean and atmosphere (hereafter heat fluxes), ocean surface wind stress, and state variables used to estimate them, are Essential Ocean Variables (EOVs) and Essential Climate Variables (ECVs) influencing weather and climate. This paper describes an observational strategy for producing 3-hourly, 25-km (and an aspirational goal of hourly at 10-km) heat flux and wind stress fields over the global, ice-free ocean with breakthrough 1-day random uncertainty of 15 W m–2 and a bias of less than 5 W m–2. At present this accuracy target is met only for OceanSITES reference station moorings and research vessels (RVs) that follow best practices. To meet these targets globally, in the next decade, satellite-based observations must be optimized for boundary layer measurements of air temperature, humidity, sea surface temperature, and ocean wind stress. In order to tune and validate these satellite measurements, a complementary global in situ flux array, built around an expanded OceanSITES network of time series reference station moorings, is also needed. The array would include 500–1000 measurement platforms, including autonomous surface vehicles, moored and drifting buoys, RVs, the existing OceanSITES network of 22 flux sites, and new OceanSITES expanded in 19 key regions. This array would be globally distributed, with 1–3 measurement platforms in each nominal 10° by 10° box. These improved moisture and temperature profiles and surface data, if assimilated into Numerical Weather Prediction (NWP) models, would lead to better representation of cloud formation processes, improving state variables and surface radiative and turbulent fluxes from these models. The in situ flux array provides globally distributed measurements and metrics for satellite algorithm development, product validation, and for improving satellite-based, NWP and blended flux products. In addition, some of these flux platforms will also measure direct turbulent fluxes, which can be used to improve algorithms for computation of air-sea exchange of heat and momentum in flux products and models. With these improved air-sea fluxes, the ocean’s influence on the atmosphere will be better quantified and lead to improved long-term weather forecasts, seasonal-interannual-decadal climate predictions, and regional climate projections.
Ocean–cloud–atmosphere–land interactions in the southeastern Pacific : the VOCALS Program

(American Meteorological Society, 2014-03) Mechoso, C. R. ; Wood, R. ; Weller, Robert A. ; Bretherton, Christopher S. ; Clarke, A. D. ; Coe, Hugh ; Fairall, Christopher W. ; Farrar, J. Thomas ; Feingold, Graham ; Garreaud, R. ; Grados, Carmen ; McWilliams, James C. ; de Szoeke, Simon P. ; Yuter, Sandra ; Zuidema, Paquita

The present paper describes the Variability of the American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study (VOCALS), an international research program focused on the improved understanding and modeling of the southeastern Pacific (SEP) climate system on diurnal to interannual time scales. In the framework of the SEP climate, VOCALS has two fundamental objectives: 1) improved simulations by coupled atmosphere–ocean general circulation models (CGCMs), with an emphasis on reducing systematic errors in the region; and 2) improved estimates of the indirect effects of aerosols on low clouds and climate, with an emphasis on the more precise quantification of those effects. VOCALS major scientific activities are outlined, and selected achievements are highlighted. Activities described include monitoring in the region, a large international field campaign (the VOCALS Regional Experiment), and two model assessments. The program has already produced significant advances in the understanding of major issues in the SEP: the coastal circulation and the diurnal cycle, the ocean heat budget, factors controlling precipitation and formation of pockets of open cells in stratocumulus decks, aerosol impacts on clouds, and estimation of the first aerosol indirect effect. The paper concludes with a brief presentation on VOCALS contributions to community capacity building before a summary of scientific findings and remaining questions.
On the exchange of momentum over the open ocean

(American Meteorological Society, 2013-08) 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 ; Zhao, F.

This study investigates the exchange of momentum between the atmosphere and ocean using data collected from four oceanic field experiments. Direct covariance estimates of momentum fluxes were collected in all four experiments and wind profiles were collected during three of them. The objective of the investigation is to improve parameterizations of the surface roughness and drag coefficient used to estimate the surface stress from bulk formulas. Specifically, the Coupled Ocean–Atmosphere Response Experiment (COARE) 3.0 bulk flux algorithm is refined to create COARE 3.5. Oversea measurements of dimensionless shear are used to investigate the stability function under stable and convective conditions. The behavior of surface roughness is then investigated over a wider range of wind speeds (up to 25 m s−1) and wave conditions than have been available from previous oversea field studies. The wind speed dependence of the Charnock coefficient α in the COARE algorithm is modified to , where m = 0.017 m−1 s and b = −0.005. When combined with a parameterization for smooth flow, this formulation gives better agreement with the stress estimates from all of the field programs at all winds speeds with significant improvement for wind speeds over 13 m s−1. Wave age– and wave slope–dependent parameterizations of the surface roughness are also investigated, but the COARE 3.5 wind speed–dependent formulation matches the observations well without any wave information. The available data provide a simple reason for why wind speed–, wave age–, and wave slope–dependent formulations give similar results—the inverse wave age varies nearly linearly with wind speed in long-fetch conditions for wind speeds up to 25 m s−1.
EUREC4A

(Copernicus Publications, 2021-08-25) Stevens, Bjorn ; Bony, Sandrine ; Farrell, David ; Ament, Felix ; Blyth, Alan ; Fairall, Christopher W. ; Karstensen, Johannes ; Quinn, Patricia K. ; Speich, Sabrina ; Acquistapace, Claudia ; Aemisegger, Franziska ; Albright, Anna Lea ; Bellenger, Hugo ; Bodenschatz, Eberhard ; Caesar, Kathy-Ann ; Chewitt-Lucas, Rebecca ; de Boer, Gijs ; Delanoë, Julien ; Denby, Leif ; Ewald, Florian ; Fildier, Benjamin ; Forde, Marvin ; George, Geet ; Gross, Silke ; Hagen, Martin ; Hausold, Andrea ; Heywood, Karen J. ; Hirsch, Lutz ; Jacob, Marek ; Jansen, Friedhelm ; Kinne, Stefan ; Klocke, Daniel ; Kölling, Tobias ; Konow, Heike ; Lothon, Marie ; Mohr, Wiebke ; Naumann, Ann Kristin ; Nuijens, Louise ; Olivier, Léa ; Pincus, Robert ; Pöhlker, Mira L. ; Reverdin, Gilles ; Roberts, Gregory ; Schnitt, Sabrina ; Schulz, Hauke ; Siebesma, Pier ; Stephan, Claudia Christine ; Sullivan, Peter P. ; Touzé-Peiffer, Ludovic ; Vial, Jessica ; Vogel, Raphaela ; Zuidema, Paquita ; Alexander, Nicola ; Alves, Lyndon ; Arixi, Sophian ; Asmath, Hamish ; Bagheri, Gholamhossein ; Baier, Katharina ; Bailey, Adriana ; Baranowski, Dariusz ; Baron, Alexandre ; Barrau, Sébastien ; Barrett, Paul A. ; Batier, Frédéric ; Behrendt, Andreas ; Bendinger, Arne ; Beucher, Florent ; Bigorre, Sebastien P. ; Blades, Edmund ; Blossey, Peter ; Bock, Olivier ; Böing, Steven ; Bosser, Pierre ; Bourras, Denis ; Bouruet-Aubertot, Pascale ; Bower, Keith ; Branellec, Pierre ; Branger, Hubert ; Brennek, Michal ; Brewer, Alan ; Brilouet, Pierre-Etienne ; Brügmann, Björn ; Buehler, Stefan A. ; Burke, Elmo ; Burton, Ralph ; Calmer, Radiance ; Canonici, Jean-Christophe ; Carton, Xavier ; Cato, Gregory, Jr. ; Charles, Jude Andre ; Chazette, Patrick ; Chen, Yanxu ; Chilinski, Michal T. ; Choularton, Thomas ; Chuang, Patrick ; Clarke, Shamal ; Coe, Hugh ; Cornet, Céline ; Coutris, Pierre ; Couvreux, Fleur ; Crewell, Susanne ; Cronin, Timothy W. ; Cui, Zhiqiang ; Cuypers, Yannis ; Daley, Alton ; Damerell, Gillian M. ; Dauhut, Thibaut ; Deneke, Hartwig ; Desbios, Jean-Philippe ; Dörner, Steffen ; Donner, Sebastian ; Douet, Vincent ; Drushka, Kyla ; Dütsch, Marina ; Ehrlich, André ; Emanuel, Kerry A. ; Emmanouilidis, Alexandros ; Etienne, Jean-Claude ; Etienne-Leblanc, Sheryl ; Faure, Ghislain ; Feingold, Graham ; Ferrero, Luca ; Fix, Andreas ; Flamant, Cyrille ; Flatau, Piotr Jacek ; Foltz, Gregory R. ; Forster, Linda ; Furtuna, Iulian ; Gadian, Alan ; Galewsky, Joseph ; Gallagher, Martin ; Gallimore, Peter ; Gaston, Cassandra J. ; Gentemann, Chelle L. ; Geyskens, Nicolas ; Giez, Andreas ; Gollop, John ; Gouirand, Isabelle ; Gourbeyre, Christophe ; de Graaf, Dörte ; de Graaf, Geiske E. ; Grosz, Robert ; Güttler, Johannes ; Gutleben, Manuel ; Hall, Kashawn ; Harris, George ; Helfer, Kevin C. ; Henze, Dean ; Herbert, Calvert ; Holanda, Bruna ; Ibanez-Landeta, Antonio ; Intrieri, Janet ; Iyer, Suneil ; Julien, Fabrice ; Kalesse, Heike ; Kazil, Jan ; Kellman, Alexander ; Kidane, Abiel T. ; Kirchner, Ulrike ; Klingebiel, Marcus ; Körner, Mareike ; Kremper, Leslie Ann ; Kretzschmar, Jan ; Krüger, Ovid O. ; Kumala, Wojciech ; Kurz, Armin ; L'Hégareta, Pierre ; Labaste, Matthieu ; Lachlan-Cope, Thomas ; Laing, Arlene ; Landschützer, Peter ; Lang, Theresa ; Lange, Diego ; Lange, Ingo ; Laplace, Clément ; Lavik, Gauke ; Laxenaire, Rémi ; Le Bihan, Caroline ; Leandro, Mason ; Lefevre, Nathalie ; Lena, Marius ; Lenschow, Donald ; Li, Qiang ; Lloyd, Gary ; Los, Sebastian ; Losi, Niccolò ; Lovell, Oscar ; Luneau, Christopher ; Makuch, Przemyslaw ; Malinowski, Szymon ; Manta, Gaston ; Marinou, Eleni ; Marsden, Nicholas ; Masson, Sebastien ; Maury, Nicolas ; Mayer, Bernhard ; Mayers-Als, Margarette ; Mazel, Christophe ; McGeary, Wayne ; McWilliams, James C. ; Mech, Mario ; Mehlmann, Melina ; Meroni, Agostino Niyonkuru ; Mieslinger, Theresa ; Minikin, Andreas ; Minnett, Peter J. ; Möller, Gregor ; Morfa Avalos, Yanmichel ; Muller, Caroline ; Musat, Ionela ; Napoli, Anna ; Neuberger, Almuth ; Noisel, Christophe ; Noone, David ; Nordsiek, Freja ; Nowak, Jakub L. ; Oswald, Lothar ; Parker, Douglas J. ; Peck, Carolyn ; Person, Renaud ; Philippi, Miriam ; Plueddemann, Albert J. ; Pöhlker, Christopher ; Pörtge, Veronika ; Pöschl, Ulrich ; Pologne, Lawrence ; Posyniak, Michał ; Prange, Marc ; Quinones Melendez, Estefania ; Radtke, Jule ; Ramage, Karim ; Reimann, Jens ; Renault, Lionel ; Reus, Klaus ; Reyes, Ashford ; Ribbe, Joachim ; Ringel, Maximilian ; Ritschel, Markus ; Rocha, Cesar B. ; Rochetin, Nicolas ; Röttenbacher, Johannes ; Rollo, Callum ; Royer, Haley M. ; Sadoulet, Pauline ; Saffin, Leo ; Sandiford, Sanola ; Sandu, Irina ; Schäfer, Michael ; Schemann, Vera ; Schirmacher, Imke ; Schlenczek, Oliver ; Schmidt, Jerome M. ; Schröder, Marcel ; Schwarzenboeck, Alfons ; Sealy, Andrea ; Senff, Christoph J. ; Serikov, Ilya ; Shohan, Samkeyat ; Siddle, Elizabeth ; Smirnov, Alexander ; Späth, Florian ; Spooner, Branden ; Stolla, M. Katharina ; Szkółka, Wojciech ; de Szoeke, Simon P. ; Tarot, Stéphane ; Tetoni, Eleni ; Thompson, Elizabeth ; Thomson, Jim ; Tomassini, Lorenzo ; Totems, Julien ; Ubele, Alma Anna ; Villiger, Leonie ; von Arx, Jan ; Wagner, Thomas ; Walther, Andi ; Webber, Ben ; Wendisch, Manfred ; Whitehall, Shanice ; Wiltshire, Anton ; Wing, Allison A. ; Wirth, Martin ; Wiskandt, Jonathan ; Wolf, Kevin ; Worbes, Ludwig ; Wright, Ethan ; Young, Shanea ; Zhang, Chidong ; Zhang, Dongxiao ; Ziemen, Florian ; Zinner, Tobias ; Zöger, Martin

The science guiding the EUREC4A campaign and its measurements is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement.
Saildrone direct covariance wind stress in various wind and current regimes of the tropical Pacific

(American Meteorological Society, 2023-04-01) Reeves Eyre, J. E. Jack ; Cronin, Meghan F. ; Zhang, Dongxiao ; Thompson, Elizabeth J. ; Fairall, Christopher W. ; Edson, James B.

High-frequency wind measurements from Saildrone autonomous surface vehicles are used to calculate wind stress in the tropical east Pacific. Comparison between direct covariance (DC) and bulk wind stress estimates demonstrates very good agreement. Building on previous work that showed the bulk input data were reliable, our results lend credibility to the DC estimates. Wind flow distortion by Saildrones is comparable to or smaller than other platforms. Motion correction results in realistic wind spectra, albeit with signatures of swell-coherent wind fluctuations that may be unrealistically strong. Fractional differences between DC and bulk wind stress magnitude are largest at wind speeds below 4 m s −1 . The size of this effect, however, depends on choice of stress direction assumptions. Past work has shown the importance of using current-relative (instead of Earth-relative) winds to achieve accurate wind stress magnitude. We show that it is also important for wind stress direction. Significance Statement We use data from Saildrone uncrewed oceanographic research vehicles to investigate the horizontal forces applied to the surface of the ocean by the action of the wind. We compare two methods to calculate the forces: one uses several simplifying assumptions, and the other makes fewer assumptions but is error prone if the data are incorrectly processed. The two methods agree well, suggesting that Saildrone vehicles are suitable for both methods and that the data processing methods work. Our results show that it is important to consider ocean currents, as well as winds, in order to achieve accurate magnitude and direction of the surface forces.

Fairall Christopher W.

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