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Boundary-Layer Meteorology

, Volume 97, Issue 3, pp 487–511 | Cite as

Correction Of Eddy-Covariance Measurements Incorporating Both Advective Effects And Density Fluxes

  • Kyaw Tha Paw U
  • Dennis D. Baldocchi
  • Tilden P. Meyers
  • Kell B. Wilson
Article

Abstract

Equations are presented to correct eddy-covariancemeasurements for both fluctuations in density andnon-zero mean advection, induced by convergence ordivergence of flow, and spatial source/sinkinhomogeneity, under steady-state and transientconditions. This correction collapses to theWebb–Pearman–Leuning expression ifthe mean vertical velocity is zero, and formally addsthe Webb–Pearman–Leuning expression to the correctionssuggested by Lee for conditions ofnon-zero vertical velocity and source/sink and meanscalar horizontal homogeneity. The equation requiresmeasurement of the mean vertical gradients of thescalar concentration of interest (air temperature,humidity, CO2) as well as an accurateestimation of the mean vertical velocity, in additionto the vertical eddy covariance of the scalar. Simplemethods for the approximation of sensor tilt andcomplex terrain flow angle are presented, to allowestimation of non-zero mean vertical velocities. Theequations are applied to data from a maize crop and aforest to give examples of when the correction issignificant. In addition, a term for thethermodynamic expansion energy associated with watervapour flux is derived, which implies that the sonictemperature derived sensible heat flux will accuratelyinclude this contribution.

Advection Carbon dioxide Density correction Eddy covariance 

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Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Kyaw Tha Paw U
    • 1
  • Dennis D. Baldocchi
    • 2
  • Tilden P. Meyers
    • 3
  • Kell B. Wilson
    • 3
  1. 1.Atmospheric ScienceUniversity of CaliforniaDavisU.S.A.
  2. 2.Department of Environmental Science, Policy and ManagementUniversity of CaliforniaBerkeleyU.S.A.
  3. 3.Atmospheric Turbulence and Diffusion Division, Environmental Research LaboratoryNational Oceanic and Atmospheric AdministrationOak RidgeU.S.A.

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