Boundary-Layer Meteorology

, Volume 53, Issue 1, pp 63-76

First online:

Eddy-covariance CO2 flux measurements using open- and closed-path CO2 analysers: Corrections for analyser water vapour sensitivity and damping of fluctuations in air sampling tubes

  • R. LeuningAffiliated withCSIRO Division of Forestry and Forest Products
  • , J. MoncrieffAffiliated withDepartment of Forestry and Natural Resources, University of Edinburgh

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Methods of calibrating infrared CO2 analysers for sensitivity to CO2 and water vapour are described. Equations to correct eddy covariance CO2 flux measurements are presented for: (i) analyser cross-sensitivity to water vapour and the effects of density fluctuations arising from atmospheric fluxes of water vapour and sensible heat, (ii) flux losses caused by signal processing and limited instrument frequency response for open- and closed-path CO2 analysers, and (iii) flux losses resulting from damping of concentration fluctuations in a tube used to sample air for closed-path CO2 analysers. Examples of flux corrections required for typical instruments are presented.