Climate and Dynamics

Estimates of net CO2 flux by application of equilibrium boundary layer concepts to CO2 and water vapor measurements from a tall tower

  1. Brent R. Helliker1,
  2. Joseph A. Berry1,
  3. Alan K. Betts2,
  4. Peter S. Bakwin3,
  5. Kenneth J. Davis4,
  6. A. Scott Denning5,
  7. James R. Ehleringer6,
  8. John B. Miller3,
  9. Martha P. Butler4,
  10. Daniel M. Ricciuto4

Article first published online: 19 OCT 2004

DOI: 10.1029/2004JD004532

Issue

Journal of Geophysical Research: Atmospheres (1984–2012)

Journal of Geophysical Research: Atmospheres (1984–2012)

Additional Information

How to Cite

Helliker, B. R., J. A. Berry, A. K. Betts, P. S. Bakwin, K. J. Davis, A. S. Denning, J. R. Ehleringer, J. B. Miller, M. P. Butler, and D. M. Ricciuto (2004), Estimates of net CO2 flux by application of equilibrium boundary layer concepts to CO2 and water vapor measurements from a tall tower, J. Geophys. Res., 109, D20106, doi:10.1029/2004JD004532.

Author Information

  1. 1

    Department of Global Ecology, Carnegie Institution of Washington, Stanford, California, USA

  2. 2

    Atmospheric Research, Pittsford, Vermont, USA

  3. 3

    Climate Monitoring and Diagnostics Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA

  4. 4

    Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania, USA

  5. 5

    Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA

  6. 6

    Department of Biology, University of Utah, Salt Lake City, Utah, USA

Publication History

  1. Issue published online: 19 OCT 2004
  2. Article first published online: 19 OCT 2004
  3. Manuscript Accepted: 21 JUL 2004
  4. Manuscript Revised: 2 JUL 2004
  5. Manuscript Received: 12 JAN 2004

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Keywords:

  • boundary layer;
  • CO2 exchange;
  • evapotranspiration

[1] Convective turbulence within the atmospheric boundary layer (ABL) and movement of the ABL over the surface results in a large spatial (104–105 km2) integration of surface fluxes that affects the CO2 and water vapor mixing ratios. We apply quasi-equilibrium concepts for the terrestrial ABL to measurements of CO2 and water vapor made within the ABL from a tall tower (396 m) in Wisconsin. We suppose that CO2 and water vapor mixing ratios in the ABL approach an equilibrium on timescales longer than a day: a balance between the surface fluxes and the exchange with the free troposphere above. By using monthly averaged ABL-to-free-tropospheric water vapor differences and surface water vapor flux, realistic estimates of vertical velocity exchange with the free troposphere can be obtained. We then estimated the net surface flux of CO2 on a monthly basis for the year of 2000, using ABL-to-free-tropospheric CO2 differences, and our flux difference estimate of the vertical exchange. These ABL-scale estimates of net CO2 flux gave close agreement with eddy covariance measurements. Considering the large surface area which affects scalars in the ABL over synoptic timescales, the flux difference approach presented here could potentially provide regional-scale estimates of net CO2 flux.

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