A New Platform for the Determination of Air–Sea Fluxes (OCARINA): Overview and First Results

Abstract

The present paper describes a new type of floating platform that was specifically designed for estimating air-sea fluxes, investigating turbulence characteristics in the atmospheric surface boundary layer, and studying wind-wave interactions. With its design, it can be deployed in the open ocean or in shallow water areas. The system is designed to be used from a research vessel. It can operate for ~10 hours as a drifting wave rider and three hours under power. Turbulence and meteorological instrument packages are placed at a low altitude (1-1.5 m). It was deployed for validation purposes during the FROMVAR 2011 experiment off the west coast of Brittany (France). Wind friction velocity and surface turbulent buoyancy flux were estimated using eddy-covariance, spectral, bulk and profile methods. The comparisons of the four methods show a reasonable agreement except for the spectral buoyancy flux. This suggests that the platform design is correct. Also the wind measured at a fixed height above the sea shows spectral coherence with wave heights, such that wind and swell are in phase, with largest wind values on top of swell crests. This result in qualitative agreement with current model predictions supports the capability of OCARINA to investigate wind-swell interactions. 3 IntroductionAir-sea fluxes of momentum and heat, atmospheric turbulence in the surface atmospheric boundary layer, and wind-wave interactions are key characteristics that are needed to validate and improve dynamical models of the atmosphere, the upper ocean and waves.

Surface Salinity in the North Atlantic Subtropical Gyre During the STRASSE/SPURS Summer 2012 Cruise

“…In particular, are they similar to what was found in areas of higher mesoscale activity/energy (Mahadevan and Tandon, 2006)? Does wind play a role in cross-frontal transport (e.g., Thomas and INSTRUMENTATION Air-sea fluxes were estimated by combining data from the different meteorological packages on R/V Thalassa with ship-mast winds that were corrected by comparing those data with nearby wind measurements recorded during deployments of the autonomous instrumented platform Ocarina (Bourras et al, 2014). Comparison of humidity measurements from three instruments indicated absolute accuracy of corrected relative humidity on the order of 1%.…”

Air‐Sea Turbulent Fluxes From a Wave‐Following Platform During Six Experiments at Sea

“…We analyzed data from a novel‐drifting and wave‐following platform that was already described in Bourras et al (). It was deployed in four regions during six experiments from 2011 to 2017.…”

“…In this paper, we take advantage of data collected over 7 years with a novel wave‐following platform dedicated to air‐sea flux measurements (Bourras et al, , B14 hereafter) to contribute to surface flux parameterization, with the following specificities: our data were collected in the open sea, mostly in conditions of swell, with significant wave heights hsw averaging to 1.5 m, and in light to moderate wind conditions, that is, 2 ≤ U ≤ 10 m/s. The turbulence measurements were performed at a 1.5‐m height, which is in a part of the atmospheric layer influenced by the presence sea waves (e.g., B14; Hara & Sullivan, ).…”

Identification of Eddy Viscosity in the Unsteady Marine Ekman Layer Flow

“…A new in situ experiment was started in 2015-2018, offshore the Toulon -Hyères bays, involving HF radars, floating buoys and instrumented drifted structures [12,13], oceanographic research vessel cruises and a fixed ADCP profiler.…”

“…Among the collected data [12], vertical profiles of horizontal velocity in the marine upper layer (0-10m), as shown in Fig 1, exhibit both deepening and rotation of the Ekman layer, following the unsteady Ekman solution [14]. The vertical profiles in a fixed point exhibit both effects of Ekman layer deepening and inertial rotation that can be moreover affected by stratification.…”