Experimental Determination of the Radar Cross Sections of Artificial Hailstones Containing Water

Abstract

The radar cross sections of particles grown in a hail tunnel (ice spheres with a spongy ice shell) and snow spheres dipped in water (spongy ice throughout) were measured at wavelengths of 3.21 cm, 4.67 cm, and 10 cm. The results were comparable and did not show obvious systematic differences either for the three wavelengths or for the two kinds of particles. The average normalized cross section versus α(α = πd/?, where d is the particle diameter and ? the wave-length) is given in the range of 0.4 < α < for liquid water contents of 0 per cent (frozen particles), 5, 10, 20, and 30 per cent. For α > 1, a water content of more than 10 per cent was sufficient to produce a mean cross section equivalent to that of an all-water sphere.