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Archived data recorded in northern Colorado by the CSU-CHILL radar was examined to identify cases when echoes from insects and birds were observed. Dual polarization measurements at wavelengths of 11 cm (2.725 GHz) and 3 cm (9.41 GHz) from selected biological target cases are presented. The differential reflectivity (Zdr) and backscatter differential phase (δ) characteristics of these target types were examined. The insect Zdr values were significantly positive (>~3.5 dB) at both wavelengths. Backscatter differential phase at 9.41 GHz (3 cm wavelength) was larger than those at 2.725 GHz for insect targets. This relationship reversed for bird targets: the 2.725 GHz δ became larger than 9.41 GHz δ. These variations in return signal characteristics are probably due to Mie resonance effects. The CSU-CHILL radar’s capabilities to execute both RHI and PPI sector scans provided higher resolution observations vs. the full 360° volume scans conducted by most operational weather surveillance radars.

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Dual Wavelength CSU-CHILL Radar Observations of Insects and Birds

  • 章节

  • 发表日期：

    2026年

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  • Patrick C. Kennedy,
  • V. Chandrasekar

摘要

Archived data recorded in northern Colorado by the CSU-CHILL radar was examined to identify cases when echoes from insects and birds were observed. Dual polarization measurements at wavelengths of 11 cm (2.725 GHz) and 3 cm (9.41 GHz) from selected biological target cases are presented. The differential reflectivity (Zdr) and backscatter differential phase (δ) characteristics of these target types were examined. The insect Zdr values were significantly positive (>~3.5 dB) at both wavelengths. Backscatter differential phase at 9.41 GHz (3 cm wavelength) was larger than those at 2.725 GHz for insect targets. This relationship reversed for bird targets: the 2.725 GHz δ became larger than 9.41 GHz δ. These variations in return signal characteristics are probably due to Mie resonance effects. The CSU-CHILL radar’s capabilities to execute both RHI and PPI sector scans provided higher resolution observations vs. the full 360° volume scans conducted by most operational weather surveillance radars.