Median Filter Effects on Radar Wind Profiler Spectral Noise Statistics

Timothy L. Wilfong DeTect Inc., Longmont, Colorado

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Elias M. Lau DeTect Inc., Longmont, Colorado

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Bob L. Weber DeTect Inc., Longmont, Colorado

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David A. Merritt DeTect Inc., Longmont, Colorado

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Scott A. McLaughlin DeTect Inc., Longmont, Colorado

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Abstract

Radar wind profiler (RWP) systems observe radar returns from refractive index fluctuations due to clear-air turbulence. The Doppler spectra used to compute the moments of the returned signal always include noise from various sources and may contain multiple signals. A critical first step in detecting signals is the objective determination of the noise level in each spectrum. Several spectra may be averaged to improve signal detection. In addition to or instead of a mean, a median may be applied to successive spectra in order to reject transient interference. Monte Carlo simulations were used to examine the effects of the median versus the mean on the objective noise determination. When a median is used, it was found the noise statistics calculations must be slightly modified.

Corresponding author address: Timothy L. Wilfong, DeTect Inc., 117 S. Sunset St., Ste. L, Longmont, CO 80501. E-mail: tim.wilfong@detect-inc.com

Abstract

Radar wind profiler (RWP) systems observe radar returns from refractive index fluctuations due to clear-air turbulence. The Doppler spectra used to compute the moments of the returned signal always include noise from various sources and may contain multiple signals. A critical first step in detecting signals is the objective determination of the noise level in each spectrum. Several spectra may be averaged to improve signal detection. In addition to or instead of a mean, a median may be applied to successive spectra in order to reject transient interference. Monte Carlo simulations were used to examine the effects of the median versus the mean on the objective noise determination. When a median is used, it was found the noise statistics calculations must be slightly modified.

Corresponding author address: Timothy L. Wilfong, DeTect Inc., 117 S. Sunset St., Ste. L, Longmont, CO 80501. E-mail: tim.wilfong@detect-inc.com
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