Advertisement

Boundary-Layer Meteorology

, Volume 107, Issue 1, pp 1–48 | Cite as

A Re-Evaluation of Long-Term Flux Measurement Techniques Part I: Averaging and Coordinate Rotation

  • J. J. Finnigan
  • R. Clement
  • Y. Malhi
  • R. Leuning
  • H.A. Cleugh
Article

Abstract

Experience of long term flux measurements over tall canopiesduring the last two decades has revealed that the eddy flux of sensible plus latentheat is typically 30% smaller than the available radiant energy flux. This failureto close the energy balance is less common close to the surface over short roughnessbut is still sometimes seen, especially in complex topography. These observationscast doubt on the results obtained from long term flux studies where daily and annualnet ecosystem exchange is usually the small difference between large positive andnegative fluxes over 24 h. In this paper we investigate this problem by examiningsome fundamental assumptions entailed in analysis of surface exchange by the eddyflux method.

In particular, we clarify the form and use of the scalar conservation equation thatunderlies this analysis and we examine the links between averaging period androtation of coordinates in the situation where coordinates are aligned with thewind vector. We show that rotating coordinates so that the x axis is alignedwith the mean wind vector has the effect of high pass filtering the scalar covariance,¯wc, such that contributions to the aerodynamic flux from atmosphericmotions with periods longer than the averaging period are lost while those of shorterperiod are distorted.

We compare the effect of computing surface exchange by averaging many shortperiods, in each of which the coordinates are rotated so that the mean verticalvelocity is zero (the method currently adopted in most long-term flux studies),with analysis in long-term coordinates and show a systematic underestimationof surface exchange in the former case. This is illustrated with data from threelong-term forest field sites where underestimations of sensible and latent heatfluxes of 10–15% averaged over many days are seen.Crucial factors determining the loss of flux are the averaging period T, themeasurement height and the content of the scalar cospectrum at periods longerthan T. The properties of this cospectrum over tall canopies in both homogeneousand complex terrain are illustrated by measurements at our three sites and we see thatover tall canopies on flat ground in convectiveconditions, or on hilly sites in near neutralflow, the scalar cospectra have much more low frequency contentthan classical surface-layerspectral forms would predict. We believe that the filtering of this low frequencycovariance by the averaging-rotation operations in common use is a large contributoryfactor to the failure to close the energy balance over tall canopies.

Atmospheric surface layer Eddy covariance Flux measurement Plant canopies Turbulent flux 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Aubinet, M., Grelle, A., Ibrom, A., Rannik, U., Moncrieff, J., Foken, T., Kowalski, A. S., Martin, P. H., Berbigier, P., Bernhofer, C., Clement, R., Elbers, J., Granier, A., Grunwald, T., Morgenstern, K., Pilegaard, K., Rebmann, C., Snijders,W., Valentini, R., and Vesala,T.: 2000, ‘Estimates of the Annual Net Carbon and Water Exchange of European Forests: The EUROFLUX Methodology’, Adv. Ecol. Res. 30, 113–175.Google Scholar
  2. Auble, D. and Meyers, T. P.: 1992, ‘An Open Path, Fast Response Infra-Red Absorption Gas Analyzer for H2O and CO2’, Boundary-Layer Meteorol. 59, 243–256.Google Scholar
  3. Baldocchi, D. D., Falge, E., Gu, L., Olson, R., Hollinger, D., Running, S., Anthoni, P., Bernhofer, Ch., Davis, K., Evans, R., Fuentes, J., Goldstein, A., Katul, G., Law, B., Lee, X., Malhi, Y., Meyers, T., Munger, W., Oechal, W., Paw U, K. T., Pilegaard, K., Schmid, H. P., Valentini, R., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: 2001, ‘FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide,Water Vapour and Energy Flux Densities’, Bull. Amer. Meteorol. Soc. 82, 2415–2434.Google Scholar
  4. Baldocchi, D, Finnigan, J., Wilson, K., and Paw U, K. T.: 2000, ‘On Measuring Net Ecosystem Carbon Exchange over Tall Vegetation in Complex Terrain’, Boundary-Layer Meteorol. 96, 257–291.Google Scholar
  5. Baldocchi, D. D., Valentini, R., Running, S. R., Oechel, W., and Dahlman, R.: 1996, ‘Strategies for Measuring and Modelling CO2 and Water Vapor Fluxes over Terrestrial Ecosystems’, Global Change Biol. 2, 159–168.Google Scholar
  6. Baldocchi, D. D., Vogel, C. A., and Hall, B.: 1997, ‘Seasonal Variations of Energy and Water Vapor Exchange Rates above and below a Boreal Jack Pine Forest Canopy’, J. Geophys. Res. 102(D24), 28,939–28,951.Google Scholar
  7. Blanken, P. D., Black, T. A., Yang, P. C., Neumann, H. H., Nesic, Z., Staebler, R., den Hartog, G., Novak, M. D., and Lee, X.: 1997, ‘Energy Balance and Canopy Conductance of a Boreal Aspen Forest: Partitioning Overstory and Understory Components’, J. Geophys. Res. 102(D24), 28,915-28,927.Google Scholar
  8. Falk, M. B., Park, Y. S., Paw U, K. T., Pyles, R. D., Hsiao, T. C., Shaw, R. H., King, T. S., Matista, A. A., and Wabeh, H.: 2000, ‘A Comparison of the Carbon and Water Vapor Exchange Contributions of Mean Advection, Eddy Covariance and Storage in a Tall Forest’, in Proceedings of the 24th AMS Conference on Agricultural and Forest Meteorology, Davis, California, 14-18 August, 2000, American Meteorological Society, Boston, MA.Google Scholar
  9. Finnigan, J. J.: 1988, ‘Air Flow over Complex Terrain’, in W. L. Steffen and O. T. Denmead (eds.), Flow and Transport in the Natural Environment: Advances and Applications, Springer-Verlag, Heidelberg, pp. 183–229.Google Scholar
  10. Finnigan, J. J.: 1999, ‘A comment on the Paper by Lee (1998) On Micrometeorological Observations of Surface-Air Exchange over Tall Vegetation’, Agric. For. Meteorol. 97, 55–64.Google Scholar
  11. Finnigan, J. J.: 2000, ‘Turbulence in Plant Canopies’, Annu. Rev. Fluid Mech. 32, 519–571.Google Scholar
  12. Finnigan, J. J. and Leuning, R.: 2000, ‘Long Term Flux Measurements-Coordinate Systems and Averaging’, in Proceedings of the International Workshop for Advanced Flux Network and Flux Evaluation, Hakkaido, Japan, Centre for Global Environmental Research, National Institute for Environmental Studies, Japan, pp.51–56.Google Scholar
  13. Goulden, M. L., Daube, B. C., Fan, S.-M., Sutton, D. J., Bazzaz, A., Munger, J. W., and Wofsy, S. C.: 1997, ‘Physiological Responses of a Black Spruce Forest to Weather’, Geophys. Res. 102(D24), 28,987–28,996.Google Scholar
  14. Goulden, M. L., Munger, J. W., Fan, S-M., Daube, B. C., and Wofsy, S. C.: 1996, ‘Measurements of Carbon Sequestration by Long-Term Eddy Covariance Methods and a Critical Evaluation of Accuracy’, Global Change Biol. 2, 169–183.Google Scholar
  15. Hignett, P.: 1992, ‘Corrections to TemperatureMeasurements with a Sonic Anemometer’, Boundary-Layer Meteorol. 61, 175–187.Google Scholar
  16. Hodges, G. B. and Smith, E. A.: 1997, ‘Intercalibration, Objective Analysis, Intercomparison and Synthesis of BOREAS Surface Net Radiation Measurements’, J. Geophys. Res. 102(D24), 28,885-28,900.Google Scholar
  17. Jarvis, P. G., Massheder, J. M., Hale, S. E., Moncrieff, J. B., Rayment, M., and Scott, S. L.: 1997, ‘Seasonal Variation of Carbon Dioxide, Water Vapor, and Energy Exchanges of a Boreal Black Spruce Forest’, J. Geophys. Res. 102(D24), 28953-28,966.Google Scholar
  18. Kaimal, J. C. and Finnigan J. J.: 1994, Atmospheric Boundary Layer Flows: Their Structure and Management, Oxford University Press, New York, 289 pp.Google Scholar
  19. Kaimal, J. C. and Gaynor, J. E.: 1983, ‘The Boulder Atmospheric Observatory’, J. Clim. Appl. Meteorol. 22, 863–880.Google Scholar
  20. Kaimal, J. C., Eversole, R. A., Lenschow, D. H., Stankov, B. B., Kahn, P. H., and Businger, J. H.: 1982, ‘Spectral Characteristics of the Convective Boundary Layer over Uneven Terrain’, J. Atmos. Sci. 39, 1098–1114.Google Scholar
  21. Kaimal, J. C., Wyngaard, Izumi, Y., and Cote, O. R.: 1972, ‘Spectral Characteristics of Surface Layer Turbulence’, Quart. J. Roy. Meteorol. Soc. 98, 563–589.Google Scholar
  22. Lee, X.: 1998, ‘On Micrometeorological Observations of Surface-Air Exchange over Tall Vegetation’, Agric. For. Meteorol. 91, 39–49.Google Scholar
  23. Lee, X. and Barr, A. G.: 1998, ‘Climatology of Gravity Waves in a Forest’, Quart. J. Roy. Meteorol. Soc. 124, 1403–1419.Google Scholar
  24. Lee, X. H., Black, T. A., den Hartog, G., Neumann, H., Nesic, Z., and Olejnik, J.: 1996, ‘Carbon Dioxide Exchange and Nocturnal Processes over a Mixed Deciduous Forest’, Agric. For. Meteorol. 81, 13–29.Google Scholar
  25. Leuning, R. and Judd, M.: 1996, ‘The Relative Merits of Open-and Closed-Path Analysers for the Measurement of Eddy Fluxes’, Global Change Biol. 2, 241–254.Google Scholar
  26. Malhi, Y., Nobre, A. D., Grace, J., Kruijt, B., Pereira, M. G. P., Culf, A. D., and Scott, S.: 1998, ‘Carbon Dioxide Transfer over a Central Amazonian Rain Forest’, J. Geophys. Res. 103(D24), 31593-31,612.Google Scholar
  27. Malhi, Y., Pegoraro, E., Nobre, A. D., Pereira, M. G. P., Grace, J., Culf, A. D., and Clement, R.: 2001, ‘The Energy and Water Dynamics of a Central Amazonian Rain Forest’, J. Geophys. Res., in press.Google Scholar
  28. Mason, P. J.: 1988, ‘The Formation of Areally-Averaged Roughness Lengths’, Quart. J. Roy. Meteorol. Soc. 114, 399–420.Google Scholar
  29. Massman, W. J. and Lee, X.: 2002, ‘Eddy Covariance Flux Corrections and Uncertainties in Long-Term Studies of Carbon and Energy Exchanges’, Agric. For. Meteorol. 113, 121–144.Google Scholar
  30. McMillen, R. T.: 1988, ‘An Eddy Correlation Technique with Extended Applicability to Non-Simple Terrain’, Boundary-Layer Meteorol. 43, 231–245.Google Scholar
  31. McNaughton, K. G. and Laubach, J.: 1999, ‘Power Spectra and Cospectra forWinds and Scalars in a Disturbed Surface Layer at the Base of an Advective Inversion’, Boundary-Layer Meteorol. 96, 143–185.Google Scholar
  32. Moncrieff, J. B., Malhi, Y., and Leuning, R.: 1996: ‘The Propagation of Errors in Long Term Measurements of Land-Atmosphere Fluxes of Energy and Water’, Global Change Biol. 2, 231–240.Google Scholar
  33. Moncrieff, J. B., Massheder, J. M., De Bruin, H., Elbers, J., Friborg, T., Huesunkveld, B., Kabat, P., Scott, S., Soedaard, H., and Verhoef, A.: 1997, ‘A System to Measure Surface Fluxes of Momentum, Sensible Heat, Water Vapour and Carbon Dioxide’, J. Hydrol. 188/189, 589–611.Google Scholar
  34. Moore, C. J.: 1986, ‘Frequency Response Corrections for Eddy Correlation Systems’, Boundary-Layer Meteorol. 37, 17–35.Google Scholar
  35. Panin, G. N., Tetzlaff, G., and Raabe, A.: 1998, ‘Inhomogeneity of the Land Surface and Problems in the Parameterization of Surface Fluxes in Natural Conditions’, Theor. Appl. Climatol. 60, 163–178.Google Scholar
  36. Paw U, K. T., Baldocchi, D., Meyers, T. P., and Wilson, K. B.: 2000, Correction of Eddy-Covariance Measurements Incorporating Both Advective Effects and Density Fluxes’, Boundary-Layer Meteorol. 97, 487–511.Google Scholar
  37. Philip, J. R.: 1996, ‘One-Dimensional Checkerboards and Blending Heights’, Boundary-Layer Meteorol. 77, 135–151.Google Scholar
  38. Raupach, M. R.: 2001, ‘Inferring Biogeochemical Sources and Sinks from Atmospheric Concentrations: General Considerations and Applications in Vegetation Canopies’, in E.-D. Shulze, M. Heimann, S. Harrison, E. Holland, J. Lloyd, I. C. Prentice, and D. Schimel, D.(eds.), Global Biogeochemical Cycles in the Climate System, Academic Press, pp. 350: 41-59.Google Scholar
  39. Raupach, M. R., Finnigan, J. J., and Brunet, Y.: 1996, ‘Coherent Eddies and Turbulence in Vegetation Canopies: The Mixing Layer Analogy’, Boundary-Layer Meteorol. 78, 351–382.Google Scholar
  40. Raupach, M. R., Weng, W. S., Carruthers, D. J., and Hunt, J. C. R.: 1992, ‘Temperature and Humidity Fields and Fluxes over Low Hills’, Quart. J. Roy. Meteorol. Soc. 118, 191–225.Google Scholar
  41. Sakai, R. K., Fitzjarrald, D. R., and Moore, K. E.: 2001, ‘Importance of Low-Frequency Contributions to Eddy Fluxes Observed over Rough Surfaces’, J. Appl. Meteorol. 40, 2178–2192.Google Scholar
  42. Schmid, H. P.: 2002, ‘Footprint Modeling for Vegetation Atmosphere Exchange Studies: A Review and Perspective’, Agric. For. Meteorol. 113, 159–183.Google Scholar
  43. Schotanus, P, Niewstadt, F. T. M., and De Bruin H. A. R.: 1983, ‘Temperature Measurements with a Sonic Anemometer and its Application to Heat and Moisture Fluxes’, Boundary-Layer Meteorol. 26, 81–93.Google Scholar
  44. Sellers, P. J., Hall, F. G., Kelly, R. D., Black, A., Baldocchi, D., Berry, J., Ryan, M., Ranson, K. J., Crill, P. M., Lettenmaier, D. P., Margolis, H., Cihlar, J., Newcomer, J., Fitzjarrald, D., Jarvis, P.G., Gower, S.T., Halliwell, D., Williams, D., Goodison, B., Wickland, D. E., and Guertin, F. E.: 1997, ‘BOREAS in 1997: Experiment Overview, Scientific Results, and Future Directions’, J. Geophys. Res. 102D24), 28,731-28,769.Google Scholar
  45. Tanner, C. B. and Thurtell, G. W.: 1969, Anemoclinometer Measurements of Reynolds Stress and Heat Transport in the Atmospheric Surface Layer, Department of Soil Science, University of Wisconsin, Madison, WI, Research and Development Technical Report ECOM 66-G22-F to the US Army Electronics Command.Google Scholar
  46. Van Loon, W. K. P., Bastings, H. M. H., and Moors, E. J.: 1998, ‘Calibration of Soil Heat Flux Sensors’, Agric. For. Meteorol. 92, 1–8.Google Scholar
  47. Van Ulden, A. P. and Wieringa, J.: 1996, ‘Atmospheric Boundary-Layer Research at Cabauw’, Boundary-Layer Meteorol. 78, 39–69.Google Scholar
  48. Webb, E. K., Pearman, G. I., and Leuning, R.: 1980, ‘Correction of Flux Measurements for Density Effects Due to Heat and Water Vapour Transfer’, Quart. J. Roy. Meteorol. Soc. 196, 85–100.Google Scholar
  49. Zeman, O. and Jensen, N. O.: 1987, ‘Modification of Turbulence Characteristics in Flow over Hills’, Quart. J. Roy. Meteorol. Soc. 113, 55–80.Google Scholar

Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • J. J. Finnigan
    • 1
  • R. Clement
    • 2
  • Y. Malhi
    • 2
  • R. Leuning
    • 1
  • H.A. Cleugh
    • 1
  1. 1.CSIRO Atmospheric ResearchCanberraAustralia
  2. 2.Institute of Ecology and Resource ManagementUniversity of EdinburghScotland

Personalised recommendations