Tower-based flux measurement using the eddy covariance method at Ieodo Ocean Research Station

Abstract

Surface energy and CO 2 fluxes have been measured over an ocean at Ieodo Ocean Research Station of KORDI since May 2003. Eddy covariance technique, which is a direct flux measurement, is used to quantitatively understand the interaction between the ocean surface and the atmospheric boundary layer. Although fluxes were continuously measured during the period from May 2003 to February 2004, the quality control of these data yielded <20% of data retrieval. The atmospheric stability did not show any distinct diurnal patterns and remained near-neutral to stable from May to June but mostly unstable during fall and winter in 2003. Sensible heat flux showed a good correlation with the difference between the seawater temperature and the air temperature. The maximum fluxes of sensible heat and latent heat were 120 Wm -2 and 350 Wm -2 respectively, with an averaged Bowen ratio of 0.2. The ocean around the tower absorbed CO 2 from the atmosphere and the uptake rates showed seasonal variations. Based our preliminary results, the daytime CO 2 flux was steady with an average of -0.1 mgCO 2 m -2 s -1 in summer and increased in winter. The nighttime CO 2 uptake was greater and fluctuating, reaching up to -1.0 mgCO 2 m -2 s -1 but these data require further examination due to weak turbulent mixing at nighttime. The magnitude of CO 2 flux was positively correlated with the half hourly changes in horizontal mean wind speed. Due to the paucity of quality data, further data collection is needed for more detailed analyses and interpretation.