Design and validation of a digital recursive filter for the analysis of surface-layer turbulence data in complex terrain.
Falocchi M., de Franceschi M., Giovannini L., Tomasi E., Zardi D.
The unsteadiness of the mean flow in complex terrain determines low-frequency fluctuations that, even if characterised by small time scales, cannot be regarded as surface-layer turbulence. As the block average and the linear detrending are not enough to separate the turbulence signal from the mean motion components, more sophisticated algorithms are required, $e.g.$ digital recursive filters (DRF). In this contribution, a procedure based on a first-order DRF is disclosed. The filter, designed to manage the signal distortions, was tuned with cut-off frequencies obtained from the spectral analysis of wind data collected on the valley-floor of the Adige Valley (Italy).