Reflection and scattering of VHF radar signals from atmospheric refractivity structures

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Abstract
Very high frequency (VHF) radar echoes received with a quasi‐vertical antenna beam from the troposphere and stratosphere are caused by reflection and scattering. The essential difference between these mechanisms is described by different atmospheric refractivity structures, viz., stable laminae and turbulent irregularities. Several methods for discriminating between reflection and scattering are described and tested experimentally. These involve comparing estimates of the reflection coefficient and the turbulence refractive index structure constant using acceptable models. They also involve the wavelength and volume dependence, as well as the angular distribution of the radar echoes. Doppler spectra, phase and amplitude distributions, temporal and spatial correlation functions, and the dependence between radar echo power and coherence are examined. Diffuse reflection from refractivity laminae, corrugated by turbulence, appears to be an appropriate model for many observations. Finally, the implications of this process for VHF radar investigations of the atmosphere are outlined.