Spectral analysis of ship-based eddy covariance data

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Rui, Zhang
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Because of complications associated with ship motion and airflow distortion, eddy covariance (EC) from ships has not seen widespread application. In 2011, high frequency (10 Hz) measurements of three-dimensional wind velocity, temperature, CO2 and humidity and slow response sensors recording air temperature, humidity, wind speed/direction, surface temperature were deployed on a tower installed on the foredeck of the research ice breaker CCGS Amundsen to characterize the surface fluxes within the Canadian Arctic Archipelago. The ensemble averaged co-spectra for wind, temperature and CO2 showed general agreements evaluated against theoretical curves (Kaimal et al. 1972). Port- and starboard-side co-spectra appear to follow the theoretical curves while an over-estimation was seen at high frequencies for winds coming over the bow. Fluxes were also compared against modern parameterizations for CO¬2, heat and momentum exchange for open water environments. The range of EC momentum and sensible fluxes looks reasonable while CO2 flux exhibits uncertainties.
Eddy covariance, Spectral analysis, Motion correction, Flow distortion