Investigating discrepancies in heat, CO2 fluxes and O3 deposition velocity over maize as measured by the eddy-covariance and the aerodynamic gradient methods

The eddy covariance (EC) method is widely considered as the reference method for heat and trace gas exchange flux measurements. However, for some species of interest, the aerodynamic gradient method (AG) is still a valuable method. Furthermore, some useful datasets are based on the AG method. In this study we compare the EC and the AG methods for latent (LE) and sensible (H) heat, carbon dioxide (Fc) fluxes and ozone deposition velocity (Vd O3) over a maize field near Paris. The AG method gave roughly 15% smaller Fc and LE, similar H, and 40% larger Vd O3 than the EC method. The differences between the two methods are discussed. In particular, the effects of the displacement height and heights of measurements on the AG fluxes are explored and the similarity among heat, CO2, H2O and O3 is tested. Furthermore, the vertical divergence of the flux above the canopy is estimated with the AG method.