✦ LIBER ✦

Effects of heat and water vapor transport on eddy covariance measurement of CO2fluxes

✍ Scribed by R. Leuning; O. T. Denmead; A. R. G. Lang; E. Ohtaki

Publisher: Springer
Year: 1982
Tongue: English
Weight: 889 KB
Volume: 23
Category: Article
ISSN: 0006-8314
DOI: 10.1007/bf00123298

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✦ Synopsis

Flux densities of carbon dioxide were measured over an arid, vegetation-free surface by eddy covariance techniques and by a heat budget-profile method, in which CO* concentration gradients were specified in terms ofmixing ratios. This method showed negligible fluxes ofCO,, consistent with the bareness ofthe experimental site, whereas the eddy covariance measurements indicated large downward fluxes ofC0,. These apparently conflicting observations are in quantitative agreement with the results of a recent theory which predicts that whenever there are vertical fluxes of sensible or latent heat, a mean vertical velocity is developed. This velocity causes a mean vertical convective mass flux ( = ir;W for CO,, in standard notam. The eddy covariance technique neglects this mean convective flux and measures only the turbulent flux p:, ~8'. Thus, when the net flux ofC0, is zero, the eddyzriance method indicates an apparent flux which is equal and opposite to the mean convective flux, i.e., pie ---pew. Corrections for the mean convective flux are -particularly significant for CO* because y,w and p: w' are often of similar magnitude. The correct measurement of the net CO, flux by eddy covariance techniques requires that the fluxes of sensible and latent heat be measured as well.

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