Experimental validation of WPL correction for CO2 flux by eddy covariance technique over the asphalt surface

Abstract

We experimentally validated the density correction (called WPL or Webb correction) over the dry asphalt surface by simultaneously measuring CO 2 fluxes by closed-path eddy covariance and closedchamber techniques, which is inescapable for evaluating the surface CO 2 flux by the open-path eddy covariance technique. The total CO 2 flux with WPL correction by the open-path eddy covariance technique was evaluated as a systematically small upward flux, which was consistent with that of our previous study. The instrumental error of the sonic anemometers and the additional heating correction for the open-path gas analyzer were not potential sources of total upward CO 2 fluxes. The CO 2 flux by the closed-chamber technique was also an upward flux; however, it was three orders of magnitude smaller than the total CO 2 flux by the open-path eddy covariance technique. The CO 2 flux calculated from the CO 2 mixing ratio by the closed-path eddy covariance technique was almost zero. Our results suggest the possible upward overestimation of the total CO 2 flux with the WPL correction by the open-path eddy covariance technique.

Surface energy flux measurements in a flooded and an aerobic rice field using a single eddy-covariance system

“…Paddy Water Environ PEC software is fundamentally based on the methodology described in Kondo and Tsukamoto (2012), implementing only the corrections that in most situations show to exert the greater influence in the determination of turbulent fluxes, that are the two proposed, respectively, by Webb et al (1980) andvan Dijk et al (2003), and described in Masseroni et al (2013). Using the PEC software, only halfhourly data are required to calculate turbulent fluxes.…”