Air-sea carbon-dioxide flux estimated by eddy covariance method from a buoy observation

Precise measurements of the CO₂ gas transfer across the air-sea interface provide a better understanding of the global carbon cycle. The air-sea CO₂ fluxes are obtained by the eddy covariance method and the bulk method from a buoy observation in the northern Huanghai sea. The effects of buoy motion on flux calculated by the eddy covariance method are demonstrated. The research shows that a motion correction can improve the correlation coefficient between the CO₂ fluxes estimated from two different levels. Without the CO₂-H₂O cross-correlation correction which is termed as PKT correction, the air-sea CO₂ fluxes estimated by eddy covariance method using the motion corrected data are nearly an order of magnitude larger than those estimated by the bulk method. After the CO₂-H₂O cross-correlation correction, some eddy covariance CO₂ fluxes indeed become closer to the bulk CO₂ flux, whereas some are overcorrected which are in response to small water vapor flux.