A Micrometeorological Facility for Eddy Flux Measurements of CO2 and H2O

F. Chahuneau Dépt. de Biométrie, Institut National de Recherche Agronomique, Jouy-en-Josas, France

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R. L. Desjardins Land Resource Research Centre, Research Branch, Agriculture Canada, Ottawa, Canada

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R. Verdon Land Resource Research Centre, Research Branch, Agriculture Canada, Ottawa, Canada

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E. Brach Engineering and Statistical Research Centre, Research Branch, Agriculture Canada, Ottawa, Canada

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Abstract

A ground-based eddy flux system which is used to measure the CO2 and H2O exchange between the atmosphere and the biosphere is described. Fluctuations of CO2, H2O, air temperature and atmospheric turbulence are sampled at frequencies up to 50 Hz. A microcomputer-based data acquisition system is used to calculate in real time, using standard hardware, the raw and corrected flux of CO2, latent and sensible heat and momentum. Flux density data taking into account all known sources of energy exchange in a maize crop are presented as an example of the strategy employed to control the quality of the data in measuring eddy fluxes under field conditions and to demonstrate the sources of errors and the degree of accuracy which we can obtain CO2 and H2O flux density measurements with modern equipment.

Abstract

A ground-based eddy flux system which is used to measure the CO2 and H2O exchange between the atmosphere and the biosphere is described. Fluctuations of CO2, H2O, air temperature and atmospheric turbulence are sampled at frequencies up to 50 Hz. A microcomputer-based data acquisition system is used to calculate in real time, using standard hardware, the raw and corrected flux of CO2, latent and sensible heat and momentum. Flux density data taking into account all known sources of energy exchange in a maize crop are presented as an example of the strategy employed to control the quality of the data in measuring eddy fluxes under field conditions and to demonstrate the sources of errors and the degree of accuracy which we can obtain CO2 and H2O flux density measurements with modern equipment.

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