[1] The FETCH campaign was for a large part devoted to the measurement and analysis of turbulent fluxes in fetch-limited conditions. Turbulent measurements were performed on board the R/V L'Atalante, on an ASIS spar buoy and on aircraft. On the R/V L'Atalante, turbulent data were obtained from a sonic anemometer and from a microwave refractometer. The main focus of this paper is to present results of momentum and heat fluxes obtained from the R/V L'Atalante, using the inertial-dissipation method and taking into account flow distortion effects. Numerical simulations of airflow distortion caused by the ship structure have been performed to correct the wind measurements on the R/V L'Atalante during the FETCH experiment. These simulations include different configurations of inlet velocities and six relative wind directions. The impact of airflow distortion on turbulent flux parameterizations is presented in detail. The results show a very large dependence on azimuth angle. When the ship is heading into the wind (relative wind direction within ±38°of the bow), the airflow distortion leads to an overestimation of the drag coefficient, associated with a wind speed reduction at the sensor location. For relative wind directions of more than ±38°from the bow, flow distortion causes the wind to accelerate at the sensor location, which leads to an underestimate of the drag coefficient. The vertical displacement of the flow streamlines could not be fully established by numerical simulation, but the results are in qualitative agreement with those inferred from the data by prescribing the consistency of momentum flux as a function of azimuth angle. Both show that the vertical elevation of the flow can be considered as constant (1.21 m from numerical simulations) only within about ±20°from bow axis. Values of vertical displacements up to 5 m are found from the data for high wind speeds and beam-on flows. Our study also shows that the relative contributions of the streamline vertical displacement and the mean wind speed underestimate or overestimate vary significantly with relative wind direction. The relative contribution due to vertical streamline displacement is higher for heat flux than for momentum flux. The consistency of our correction for airflow distortion is assessed by the fact that the correction reduces the standard deviation of the drag coefficient: only if this correction is taken into account, do the curves of the drag coefficient versus wind speed become similar for data corresponding to wind in the bow direction and from the side. When the complete numerical airflow correction is applied to the data set limited to relative wind directions at ±30°from the bow axis, the drag coefficient formula is C D10N Â 1000 = 0.56 + 0.063 U 10N , for U 10N > 6 m s À1 . This formula provides C D10N values comparable to the ones found from the ASIS buoy data for wind speeds of about 13 m s À1 . They are however smaller by 9% at higher winds (>15 m s À1 ). This formula is also similar, within a few percent, to the parameterizati...

An accurate determination of turbulent exchanges between the ocean and the atmosphere is a prerequisite to identify and assess the mechanisms of interaction that control part of the variability in the two media over a wide range of spatial and temporal scales. An extended dataset for estimating air-sea fluxes (representing nearly 5700 h of turbulence measurements) has been collected since 1992 during six dedicated experiments performed in the Atlantic Ocean and the Mediterranean Sea. This paper presents the methodology used through the successive experiments to progress in this field. The major developments concern (i) flux instrumentation, with the deployment of a microwave refractometer to get the latent heat flux in most meteorological conditions; (ii) the analysis of airflow distortion effects around the ship structure and sensors through both computational fluid dynamics and physical simulations in a water tank, then the derivation of correction for these effects; (iii) the application of both inertial dissipation and eddy-correlation methods from the various experiments, allowing the authors to assess and discuss flux-determination methods on ships, and particularly bulk parameterization; (iv) the validation and analysis of mesoscale surface flux fields from models and satellites by using ship data, showing some deficiencies in operational model fields from ECMWF, the need of high-quality fluxes to interpret oceanatmosphere exchanges, and the potential advantage of satellite retrieval methods. Further analysis of these datasets is being performed in a unique database (the ALBATROS project, open to the international scientific community). It will include refinement of airflow distortion correction and reprocessing of earlier datasets, the investigation of fluxes under specific conditions (low wind), and the effect of sea state among others. It will also contribute to further validation and improvements of satellite retrievals in various climatic/meteorological conditions.

[1] In this paper, we present the results obtained with the eddy correlation method applied to data acquired during the Flux, Etat de mer et Télédetection en Condition de Fetch variable experiment onboard the R/V L'Atalante. We discuss the corrections made to account for platform motion and for the effects of mean airflow distortion. The data are compared to those obtained from a moored Air-Sea Interaction Spar (ASIS) buoy and from the L'Atalante using the inertial dissipation method (IDM). The main results from eddy correlation method on L'Atalante are that the momentum flux in-line with the mean wind, Àhu 0 w 0 i, is overestimated by 18%, likely due to turbulent flow distortion around the ship. In contrast, the results for heat flux do not appear to be contaminated by turbulent flow distortion. Indeed, heat fluxes obtained using the sonic temperature on the L'Atalante and the ASIS buoy are very similar. The eddy correlation latent heat fluxes obtained on the L'Atalante using a refractometer are significantly higher than those obtained from the same sensor using the IDM.

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S U M M A R YCATCH (Couplage avec I' Atmosphsre en Conditions Hivernales) was the oceanic component of FASTEX (Fronts and Atlantic Storm-Track Experiment). It took place in January and February 1997, in the Newfoundland Basin near 47"N. 40°W, a region characterized by the presence of the warm North Atlantic Current and cold surrounding waters. CATCH was devoted to the study of the parametrization of surface turbulent fluxes in strong winds and changing directions, the surface-flux variability related to the passage of atmospheric fronts and the influence on fluxes of the strong sea surface temperature gradients associated with the North Atlantic Current. This paper presents first results of ship data analysis. A large range of wind and stratification conditions were experienced: 5%of measured winds were higher than 20 m s-I; 30% of unstable stratification (air-sea temperature differences lower than -5 degC) and 30% of very dry conditions (air-sea moisture differences lower than -2.5 g kg-') were sampled. Surface turbulent heat and momentum fluxes were obtained using the inertiakiissipative method from which a bulk algorithm was derived. A significant increase of latent-heat and momentum-transfer coefficients with increasing wind is obtained. This parametrization is compared to others published using the CATCH dataset. For high winds and unstable stratifications. differences between schemes reach 200 W mP2 for latent-heat flux values of 600 W m-'. Radiative and turbulent ship-measured fluxes are compared with modelled fluxes from the European Centre for Medium-Range Forecasts (ECMWF) along the ship's trajectory: each component of the net heat budget is higher in the ECMWF model, consequently the heat loss of the ocean is 35% higher in the model. Finally, the effect of sea surface temperature fronts on surface turbulent fluxes is analysed by evaluating the contribution of the various terms in the flux variations, showing a significant impact of the surface temperature change in all unperturbed cases. KEY WORDS: Air-sea flux measurement Air-sea flux parametrization FASTEX Inertial dissipation method Sea surface temperature * Corresponding author: M t t t o France, CNRM, 42 av. G. Coriolis, 3 1057 Toulouse Cedex, France. 3566L. EYMARD et al. 0 Meteorological sensors, some mounted on a I 1 m mast (16 m above the sea surface) located on the foredeck, and others on the upper deck: temperature, moisture (HMP35D from Vaisala) and wind (WIND MONITOR AQ from Young); incoming short-wave (CM3 RDV IS0 9060 from Kipp and Zonen) and long-wave radiation (CGI from Kipp and Zonen) sensors were located at the top of the foredeck mast as well as a sonic anemometer (Gill Solent symmetric instrument) and a refractometer (developed at CETP) for turbulence measurements. A laser telemeter (from IMPULSPHY SIK) measured the cloud base, an optical precipitation gauge (ORGIOO from SCIENTIFIC TECHNOLOGY INC.) and a two-channel upward-looking microwave radiometer (developed at CETP (Eymard 1999), to monitor the integrated water vapour and clou...