Air‐sea exchange of water vapor and sensible heat: The Humidity Exchange Over the Sea (HEXOS) results

DeCosmo, Janice; Katsaros, Kristina B.; Smith, Stuart D.; Anderson, R.J.; Oost, W.A.; Bumke, Karl; Chadwick, Helen M.

doi:10.1029/95jc03796

Cited by 238 publications

(202 citation statements)

References 67 publications

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“…Andreas (2004) by Sahlée et al (2007), showed that the expected contribution of spray to the flux of sensible heat in this wind speed range is only 5-10%. This finding is also in general agreement with the conclusions from the HEXOS experiment, Decosmo et al (1996); cf. also Andreas and DeCosmo (2002).…”

Section: Introductionsupporting

confidence: 82%

Critical re‐evaluation of the bulk transfer coefficient for sensible heat over the ocean during unstable and neutral conditions

Smedman

Erik

Johansson

2007

Quart J Royal Meteoro Soc

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ABSTRACT:A new analysis of the neutral heat transfer coefficient C HN on data fromÖstergarnsholm is presented, which is primarily based on a limited set of measurements with the very accurate MIUU (Meteorological Institute of the University of Uppsala) instrument, but with additional information from an extensive set of measurements with Solent sonic R2. Sonic data are, however, used with great caution, since for wind speed U above 10 m s −1 , a strongly windspeed-dependent correction is shown to be required. This error is roughly proportional to (U − 10) for sea-air temperature differences less than 4-5 K. For a larger temperature difference, no correction appears to be necessary in the wind speed range 10-15 m s −1 .We infer from our data that for conditions when unstable and near-neutral conditions prevail, measurements of the sea surface -air temperature difference are accurate to within 0.1 K at our site. This means that data for a range of relatively small temperature differences (0.5-1.5 K) which were often rejected in previous studies could be retained. It is observed that a rapid increase of C H and C HN occurs in that range.For wind speed above 10 m s −1 , C HN is observed to increase rapidly with U 10 . During those conditions, the wave field at the site is known to have characteristics very similar to those in deep-sea conditions. In a previous analysis of data fromÖstergarnsholm, it was speculated that observed high C HN values could be due to spray. Calculations with a spray model showed, however, conclusively that for wind speeds less than 14 m s −1 , the spray effect on the sensible heat flux is expected to be small. The high C HN values must instead be due to dynamic effects.It is demonstrated that when the Obukhov length L is less than about −150 m a regime with very specific characteristics ensues. This regime is dominated by surface-layer scale eddies, which cause Monin-Obukhov relations for the exchange of sensible heat to break down. The characteristics of this surface-layer regime are treated in detail in the companion paper.The rise of C HN with wind speed is shown to be closely related to a corresponding increase of z 0T with roughness Reynolds number for winds above 10 m s −1 . This means that during those conditions, traditional surface renewal theory for heat is no longer valid. It is suggested that this, in turn, is a result of increasing importance of wave-breaking with increasing wind and with a possible link to processes in near-surface atmospheric layers in the regime with −L > 150 m.

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Section: Introductionsupporting

confidence: 82%

Critical re‐evaluation of the bulk transfer coefficient for sensible heat over the ocean during unstable and neutral conditions

Smedman

Erik

Johansson

2007

Quart J Royal Meteoro Soc

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“…It was found that the often used bulk transfer coefficients for sensible heat of Large and Pond (1982) or of Smith (1988) lead to a considerable underestimation of sensible heat fluxes under the conditions experienced over the Labrador Sea in winter, that is, large air-sea temperature differences and high wind speeds. Parameterizations according to Isemer and Hasse (1987), Anderson and Smith (1981), DeCosmo et al (1996), and Anderson (1993) give reasonable results for an area like the Labrador Sea during wintertime.…”

Section: Discussionmentioning

confidence: 98%

“…Compared with dissipation sensible heat fluxes, the Bunker parameterization overestimates fluxes by 13%. Parameterizations according to Anderson and Smith (1981), DeCosmo et al (1996), and Anderson (1993) underestimate the measured fluxes by approximately 10%; those of Large and Pond (1982) and Smith (1988) underestimate sensible heat fluxes by more than 18% and 34% compared to estimates based on the inertial dissipation method.…”

Section: Sensible Heat Fluxmentioning

confidence: 99%

“…The measured sensible heat fluxes have also been compared with parameterized fluxes using bulk transfer coefficients from Smith (1988), Bunker (1976), DeCosmo et al (1996) using drag coefficients according to Smith (1980), Anderson and Smith (1981), and Anderson (1993). Summarized results are given in Table 1.…”

Section: Sensible Heat Fluxmentioning

confidence: 99%

“…These estimated fluxes can be used to validate the results of numerical models (Renfrew et al 2002) or to check whether existing bulk parameterizations (e.g., Bunker 1976;Smith 1980;Large andPond 1981, 1982;Anderson and Smith 1981;Isemer and Hasse 1987;Smith 1988;Smith et al 1992;Anderson 1993;DeCosmo et al 1996) are valid for conditions as observed over the Labrador Sea during wintertime. Therefore, the main goal of the present paper is to analyze measurements of the turbulent fluxes of momentum and sensible heat and to check the validity of existing parameterizations under such conditions.…”

Section: Introductionmentioning

confidence: 99%

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Measurements of Turbulent Fluxes of Momentum and Sensible Heat over the Labrador Sea

2002

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Turbulent fluxes of momentum and sensible heat were estimated from sonic anemometer measurements gathered over the Labrador Sea during a winter cruise of the R/V Knorr. The inertial dissipation method was used to calculate turbulent fluxes of momentum. The resulting drag coefficients agree well with earlier findings. Sensible heat fluxes were computed using both cross-correlation and inertial dissipation techniques. There is good agreement between results from both methods, although there is more scatter in the correlation fluxes than the dissipation fluxes. The inertial dissipation method gives reasonable results even under conditions of high wind speeds and low air temperatures, which combined with the relatively warm sea surface temperatures lead to sensible heat fluxes of several hundred watts per square meter. Sensible heat fluxes obtained from the sonic anemometer measurements agree well with bulk turbulent fluxes according to the formulation of Isemer and Hasse.

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Direct measurements of wind stress over the surf zone

Shabani

Nielsen

Baldock

2014

J. Geophys. Res. Oceans

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Field data of the wind stress over surf zone waves are presented from an open ocean beach on the East Australian Coast. Two ultrasonic anemometers were deployed at nominal heights of 5 and 10 m above the water surface in the intertidal and inner surf zones, with concurrent measurements of water levels and offshore wave parameters. Following a rigorous quality control procedure, the wind stress was determined by the eddy correlation technique. A constant stress layer was observed between 5 and 10 m elevation. Considering nearneutral conditions only, the wind drag coefficients were found to systematically change with the wind angle of approach relative to the shoreline and are much smaller for longshore wind than during onshore wind. The concept of an apparent wave steepness changing with wind direction is suggested to explain this behavior. The drag coefficients over the surf zone during onshore wind and near-neutral conditions were determined to be almost twice the values expected at the same wind speed and open ocean conditions. The observed Charnock coefficient was similarly an order of magnitude larger than open ocean values. A wave celerity of the order of that expected in the inner surf zone is required to explain the observed large roughness and drag coefficients using existing wave age-dependent parameterizations. This suggests that the slower wave celerity in the surf zone is an important contributor to the increased wind stress, in addition to the sawtooth wave shape.

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Air‐sea exchange of water vapor and sensible heat: The Humidity Exchange Over the Sea (HEXOS) results

Cited by 238 publications

References 67 publications

Critical re‐evaluation of the bulk transfer coefficient for sensible heat over the ocean during unstable and neutral conditions

Critical re‐evaluation of the bulk transfer coefficient for sensible heat over the ocean during unstable and neutral conditions

Measurements of Turbulent Fluxes of Momentum and Sensible Heat over the Labrador Sea

Direct measurements of wind stress over the surf zone

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