The OCARINA platform (Ocean Coupled with Atmosphere, Interface Research on Annexed Vessels) is a naval surface drone developed specifically to carry out measurements of turbulent and radiative exchanges at the ocean/atmosphere interface.
Designed and built at LATMOS in 2009, the initial version of OCARINA has evolved over the course of campaigns and collaborations with DT-INSU, Ifremer, LOCEAN and IRPHE.
Night-time deployment of the trimaran OCARINA, from the aft gantry of the Atalante (Genavir/Ifremer), in 2012
The onboard instruments include an inertial unit, a GPS, a sonic anemometer, a probe for measuring upward and downward radiative fluxes in the infrared and visible wavelengths, a CT-type underwater probe and a meteorological station.
The OCARINA platform is used as a drifting buoy, located by SPOT beacon or Iridium modem. It is deployed for ten-hour periods from a zodiac or from the aft gantry of an oceanographic vessel. The data is stored on an SD card.
OCARINA has been implemented in several campaigns, including FROMVAR 2011 (L. Marié, Ifremer), STRASSE 2012 (G. Reverdin), AMOP 2014 (B. Dewitte), and BBWAVES 2015 and 2016 (F. Ardhuin).
OCARINA complements the measurement masts on the bow of oceanographic vessels. Its advantage is that it causes very little disturbance to its environment and provides an estimate of the sea state, as the platform follows the movement of the waves. Its disadvantages are its limited autonomy (10 hours) and the fact that it cannot cope with strong sea states. To date, we have obtained measurements in conditions of up to 12 m/s wind and 3.5 m swell.
The level 2 data supplied are :
- location, speed, course set and route taken
- the height and significant period of waves longer than two metres
- water temperature (SST) at a depth of 30 cm
- surface salinity (SSS)
- meteorological variables (wind modulus and direction, temperature, humidity and pressure) at a height of one metre.
- upward and downward solar and infrared fluxes
- bulk turbulent flows (u*, Hs and LE), and the Monin-Obukhov ratio (z/L)
- u* and Hsv (the turbulent buoyancy flux) estimated by the inertial-dissipative method
- u* and Hsv estimated by the covariance method
References
- Bourras, D., Cambra, R., Marié, L., Bouin, M.-N., Baggio, L., Branger, H., et al. (2019). Air-sea turbulent fluxes from a wave-following platform during six experiments at sea. Journal of Geophysical Research: Oceans, 124, 4290-4321. https://doi.org/10.1029/2018JC014803
- Sentchev, A., M. Yaremchuk, D. Bourras, I. Pairaud, and P. Fraunié, 2023: Estimation of the Eddy Viscosity Profile in the Sea Surface Boundary Layer from Underway ADCP Observations. J. Atmos. Oceanic Technol, 40, 1291-1305, https://doi.org/10.1175/JTECH-D-22-0083.1.
- Bourras, D., H. Branger, G. Reverdin, L. Marié, R. Cambra, L. Baggio, C. Caudoux, G. Caudal, S. Morisset, N. Geyskens, D. Hauser, A. Weill, D. Hauser, 2014. A new platform for the determination of Air-Sea Fluxes (OCARINA): overview and first results. J. Atmos. Oceanic Technol. 31, 1043-1062. doi : http://dx.doi.org/10.1175/JTECH-D-13-00055.1.
- Cambra, R., Study of turbulent flows at the air-sea interface using data from the OCARINA platform. PhD thesis from the University of Versaille Saint-Quentin-en-Yvelines, 320 pages, defended on 4 December 2015.