Abstract
We present turbulence spectra and cospectra derived from long-term eddy-covariancemeasurements (nearly 40,000 hourly data over three to four years) and the transferfunctions of closed-path infrared gas analyzers over two mixed hardwood forests inthe mid-western U.S.A. The measurement heights ranged from 1.3 to 2.1 times themean tree height, and peak vegetation area index (VAI) was 3.5 to 4.7; the topographyat both sites deviates from ideal flat terrain. The analysis follows the approach ofKaimal et al. (Quart. J. Roy. Meteorol. Soc. 98, 563–589, 1972) whose results were based upon 15 hours of measurements atthree heights in the Kansas experiment over flatter and smoother terrain. Both thespectral and cospectral constants and stability functions for normalizing and collapsingspectra and cospectra in the inertial subrange were found to be different from those ofKaimal et al. In unstable conditions, we found that an appropriate stabilityfunction for the non-dimensional dissipation of turbulent kinetic energy is of the form Φε(ζ) = (1 - b-ζ)-1/4 - c-ζ, where ζ representsthe non-dimensional stability parameter. In stable conditions, a non-linear functionGxy(ζ) = 1 + bxyζc xy (cxy < 1) was found to benecessary to collapse cospectra in the inertial subrange. The empirical cospectralmodels of Kaimal et al. were modified to fit the somewhat more (neutraland unstable) or less (stable) sharply peaked scalar cospectra observed over forestsusing the appropriate cospectral constants and non-linear stability functions. Theempirical coefficients in the stability functions and in the cospectral models varywith measurement height and seasonal changes in VAI. The seasonal differencesare generally larger at the Morgan Monroe State Forest site (greater peak VAI) andcloser to the canopy.
The characteristics of transfer functions of the closed-path infrared gas analysersthrough long-tubes for CO2 and water vapour fluxes were studied empirically. This was done by fitting the ratio between normalized cospectra of CO2 or watervapour fluxes and those of sensible heat to the transfer function of a first-order sensor.The characteristic time constant for CO2 is much smaller than that for water vapour. The time constant for water vapour increases greatly with aging tubes. Three methods were used to estimate the flux attenuations and corrections; from June through August, the attenuations of CO2 fluxes are about 3–4% during the daytime and 6–10% at night on average. For the daytime latent heat flux (QE), the attenuations are foundto vary from less than 10% for newer tubes to over 20% for aged tubes. Correctionsto QE led to increases in the ratio (QH + QE)/(Q* - QG) by about 0.05 to0.19 (QH is sensible heat flux, Q* is net radiation and QG is soil heat flux),and thus are expected to have an important impact on the assessment of energy balanceclosure.
Similar content being viewed by others
References
Amiro, B. D.: 1990, 'Drag Coefficients and Turbulence Spectra within Three Boreal Forest Canopies', Boundary-Layer Meteorol. 52, 227-246.
Anderson, D. E., Verma, S. B., and Clement, R. J.: 1986, 'Turbulent Spectra of CO2, Water Vapour, Temperature and Velocity over a Deciduous Forest', Agric. For. Meteorol. 38, 81-99.
Baldocchi, D. D. and Meyers, T. P.: 1988, 'A Spectral and Lag-Correlation Analysis of Turbulence in a Deciduous Forest Canopy', Boundary-Layer Meteorol. 45, 31-58.
Baldocchi, D. D., Finnigan, J. J., Wilson, K. B., Paw U, K. T., and Falge, E.: 2000, 'On Measuring Net Ecosystem Carbon Exchange over Tall Vegetation on Complex Terrain', Boundary-Layer Meteorol. 96, 257-291.
Dwyer, M. J., Patton, E. G., and Shaw, R. H.: 1997, 'Turbulent Kinetic Energy Budgets from a Large-Eddy Simulation of Airflow above and within a Forest Canopy', Boundary-Layer Meteorol. 84, 23-43.
Eugster, W. and Senn, W.: 1995, 'A Cospectral CorrectionModel for Measurement of Turbulent NO2 Flux', Boundary-Layer Meteorol. 74, 321-340.
Finnigan, J. J., Clements, R., Malhi, Y., Leuning, R., and Cleugh, H. A.: 2003, 'A Re-Evaluation of Long-Term Flux Measurement Techniques Part I: Averaging and Coordinate Rotation', Boundary-Layer Meteorol. 107, 1-48.
Garratt, J. R.: 1972, 'Studies of Turbulence in the Surface Layer over Water', Quart. J. Roy. Meteorol. Soc. 98, 642-657.
Garratt, J. R.: 1992, The Atmospheric Boundary Layer, Cambridge University Press, Cambridge, U.K., 316 pp.
Högström, U.: 1990, 'Analysis of Turbulent Structure in the Surface Layer with a Modified Formulation for Near Neutral Conditions', J. Atmos. Sci. 47, 1949-1972.
Horst, T. W.: 1997, 'A Simple Formula for Attenuation of Eddy Fluxes Measured with First-Order-Response Scalar Sensors', Boundary-Layer Meteorol. 82, 219-233.
Horst, T. W.: 2000, 'On Frequency Response Corrections for Eddy Covariance Flux Measurements', Boundary-Layer Meteorol. 94, 517-520.
Kaimal, J. C. and Finnigan, J. J.: 1994, Atmospheric Boundary Layer Flows: Their Structure and Measurement, Oxford University Press, Oxford, U.K., 289 pp.
Kaimal, J. C., Wyngaard, J. C., and Coté, O. R.: 1972, 'Spectral Characteristics of Surface-Layer Turbulence', Quart. J. Roy. Meteorol. Soc. 98, 563-589.
Lee, X.-H.: 1998, 'On Micrometeorological Observations of Surface-Air Exchange over Tall Vegetation', Agric. For. Meteorol. 91, 39-49.
Lenschow, D. H. and Raupach, M. R.: 1991, 'The Attenuation of Fluctuations in Scalar Concentrations through Sampling Tubes', J. Geophys. Res. 96(D8), 15259-15268.
Leuning, R. and Judd, M. J.: 1996, 'The Relative Merits of Open-and Closed-Path Analyzers for Measurement of Eddy Fluxes', Global Change Biol. 2, 241-253.
Massman, W. J.: 1991, 'The Attenuation of Concentration Fluctuations in Turbulent Flow through a Tube', J. Geogphys. Res. 96(D8), 15269-15273.
Massman, W. J.: 2000, 'A Simple Method for Estimating Frequency Response Corrections for Eddy Covariance Systems', Agric. For. Meteorol. 104, 185-198.
McMillen, R. T.: 1988, 'An Eddy Correlation Technique with Extended Applicability to Non-Simple Terrain', Boundary-Layer Meteorol. 43, 231-245.
Moore, C. J.: 1986, 'Frequency Response Corrections for Eddy Correlation Systems', Boundary-Layer Meteorol. 37, 17-35.
Paw U, K. T., Baldocchi, D. 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.
Raupach, M. R., Coppin, P. A., and Legg, B. J.: 1986, 'Experiments on Scalar Dispersion within a Model Plant Canopy Part I: The Turbulence Structure', Boundary-Layer Meteorol. 35, 21-52.
Rißmann, J. and Tetzlaff, G.: 1994, 'Application of a Spectral Correction Method for Measurements of Covariances with Fast-Response Sensors in the Atmospheric Boundary Layer up to a Height of 120 m and Testing of the Corrections', Boundary-Layer Meteorol. 70, 293-305.
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.
Schmid, H. P., Grimmond, C. S. B., Offerle, B., Cropley, F. D., and Su, H.-B.: 2000, 'Measurements of CO2 and Energy Fluxes over a Mixed Hardwood Forest in the Midwestern United States', Agric. For. Meteorol. 103, 355-373.
Schmid, H. P., Su, H.-B., Vogel, C. S., and Curtis, P. S.: 2003, 'Ecosystem-Atmosphere Exchange of Carbon Dioxide over a Mixed Hardwood Forest in Northern Lower Michigan', J. Geophys. Res. 108(D14), 4417, doi:10.1029/2002JD003011.
Shaw, R. H., Silversides, R. H., and Thurtell, G. W.: 1974, 'Some Observations of Turbulence and Turbulent Transport within and above Plant Canopies', Boundary-Layer Meteorol. 5, 429-449.
Sorbjan, Z.: 1989, Structure of the Atmospheric Boundary Layer Meteorology, Prentice Hall Inc., Englewood Cliffs, NJ, 317 pp.
Stull, R. B.: 1988, An Introduction to Boundary Layer Meteorology, Kluwer Academic Publishers, Dordrecht, 666 pp.
Su, H.-B., Shaw, R. H., Paw U, K. T., Moeng, C.-H., and Sullivan, P. P.: 1998, 'Turbulent Statistics of Neutrally Stratified Flow within and above a Sparse Forest from Large-Eddy Simulation and Field Observations', Boundary-Layer Meteorol. 88, 363-397.
Vickers, D. and Mahrt, L.: 1997, 'Quality Control and Flux Sampling Problems for Tower and Aircraft Data', J. Atmos. Oceanic Tech. 14, 512-526.
Wilczak, J. M., Oncley, S. P., and Stage, S. A.: 2001, 'Sonic Anemometer Tilt Correction Algorithms', Boundary-Layer Meteorol. 99, 127-150.
Wyngaard, J. C.: 1975, 'Modeling the Planetary Boundary-Extension to the Stable Case', Boundary-Layer Meteorol. 9, 441-460.
Wyngaard, J. C. and Coté, O. R.: 1971, 'The Budgets of Turbulent Kinetic Energy and Temperature Variance in the Atmospheric Surface Layer', J. Atmos. Sci. 28, 190-201.
Wyngaard, J. C. and Coté, O. R.: 1972, 'Cospectral Similarity in the Atmospheric Surface Layer', Quart. J. Roy. Meteorol. Soc. 98, 590-603.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Su, HB., Schmid, H.P., Grimmond, C.S.B. et al. Spectral Characteristics and Correction of Long-Term Eddy-Covariance Measurements Over Two Mixed Hardwood Forests in Non-Flat Terrain. Boundary-Layer Meteorology 110, 213–253 (2004). https://doi.org/10.1023/A:1026099523505
Issue Date:
DOI: https://doi.org/10.1023/A:1026099523505