We present a refinement of the recursive digital filter proposed by McMillen (Boundary-Layer Meteorol 43:231–245, 1988), for separating surface-layer turbulence from low-frequency fluctuations affecting the mean flow, especially over complex terrain. In fact, a straightforward application of the filter causes both an amplitude attenuation and a forward phase shift in the filtered signal. As a consequence turbulence fluctuations, evaluated as the difference between the original series and the filtered one, as well as higher-order moments calculated from them, may be affected by serious inaccuracies. The new algorithm (i) produces a rigorous zero-phase filter, (ii) restores the amplitude of the low-frequency signal, and (iii) corrects all filter-induced signal distortions.

A Refinement of the McMillen (1988) Recursive Digital Filter for the Analysis of Atmospheric Turbulence / Falocchi, Marco; Giovannini, Lorenzo; Franceschi, Massimiliano de; Zardi, Dino. - In: BOUNDARY-LAYER METEOROLOGY. - ISSN 0006-8314. - ELETTRONICO. - 2018:168(2018), pp. 517-523. [10.1007/s10546-018-0355-5]

A Refinement of the McMillen (1988) Recursive Digital Filter for the Analysis of Atmospheric Turbulence

Falocchi, Marco;Giovannini, Lorenzo;Franceschi, Massimiliano de;Zardi, Dino
2018-01-01

Abstract

We present a refinement of the recursive digital filter proposed by McMillen (Boundary-Layer Meteorol 43:231–245, 1988), for separating surface-layer turbulence from low-frequency fluctuations affecting the mean flow, especially over complex terrain. In fact, a straightforward application of the filter causes both an amplitude attenuation and a forward phase shift in the filtered signal. As a consequence turbulence fluctuations, evaluated as the difference between the original series and the filtered one, as well as higher-order moments calculated from them, may be affected by serious inaccuracies. The new algorithm (i) produces a rigorous zero-phase filter, (ii) restores the amplitude of the low-frequency signal, and (iii) corrects all filter-induced signal distortions.
2018
168
Falocchi, Marco; Giovannini, Lorenzo; Franceschi, Massimiliano de; Zardi, Dino
A Refinement of the McMillen (1988) Recursive Digital Filter for the Analysis of Atmospheric Turbulence / Falocchi, Marco; Giovannini, Lorenzo; Franceschi, Massimiliano de; Zardi, Dino. - In: BOUNDARY-LAYER METEOROLOGY. - ISSN 0006-8314. - ELETTRONICO. - 2018:168(2018), pp. 517-523. [10.1007/s10546-018-0355-5]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/217775
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