Atmospheric Turbulence and Wave Measurements with a Small Spar Buoy

A small and easily deployable flux sampling system (Marine-Air-Sea-Flux system, MASFlux), based on a small 19" spar buoy has been developed by the Meteorology Department of the Naval Postgraduate School. This system measures mean wind and thermodynamic profiles in the lowest 3.5 m of the atmospheric surface above sea and turbulence perturbations at the highest level using a sonic anemometer, as well as ocean water temperature down to 0.5 m depth. Miniature motion sensors for measurement of buoy acceleration and angular rotation are used to correct the fast wind data for the motion effect of the buoy. The same motion data are also used to estimate the two dimensional wave spectrum.

About ten deployments of four to seven hours duration each have taken place in Monterey Bay during 2012 (initial test deployments) and offshore Virginia Beach during Trident Warrior 2013 field experiment. Turbulent spectra of data before and after buoy motion correction demonstrated the effectiveness of motion correction. The comparison of wave spectra and derived parameters with a commercial wave buoy (Datawell DWR-G4) showed the good response of the buoy to wave motion and its ability to measure accurately wave spectra. The simultaneous fast measurement of wind turbulence and wave parameters permits the estimation of the wave-induced part of wind turbulence and, thus, the study of the wave effect on momentum fluxes. Initial results from the data collected so far under various atmospheric and wind sea or swell conditions are presented. Future work including more data will focus on development of wave parameterizations of roughness length and more generally in the study of air-sea wave interaction.