Another Simple Method of Spectral Correction to Obtain Robust Eddy-Covariance Results |
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Authors: | Uwe Spank Christian Bernhofer |
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Institution: | 1. Department of Meteorology, Institute of Hydrology and Meteorology, Technische Universit?t Dresden, Piennerstra?e 23, 01737, Tharandt, Germany
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Abstract: | The eddy-covariance method is the state-of-the-art tool to measure mass and energy fluxes, though many measuring systems (particularly
closed-path systems) show strong spectral attenuation that causes significant underestimates of actual mass fluxes. The standard
way to correct these underestimates is to use theoretically derived transfer functions. Practical implementation has shown
that the attenuation, especially of closed-path systems, is underestimated by this method, even when the additional tube damping
is considered. This paper introduces and tests three alternative site-specific and hardware specific correction methods based
on spectral analysis, which typically enhance—additionally to the classical correction—the calculated mass fluxes based on
closed-path analysers, as their inevitable tubing and the filters used cause additional flow attenuation. Two of the three
methods are based on a site-specific and hardware specific transfer functions, the third uses direct comparison of cospectra.
Primarily the methods based on transfer functions proved to be easy-to-handle once established for the specific set-up and
measurement site. They represent practical and robust methods to correct for spectral attenuation. |
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Keywords: | Closed-path system Damping correction Eddy covariance Mass fluxes Spectral attenuation |
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