A Micrometeorological Facility for Eddy Flux Measurements of CO2and H2O

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.