FURTHER STUDIES OF THE BACK-SCATTERING CROSS-SECTIONS OF WATER DROPS AND WET AND DRY ICE SPHERES

Abstract

By using laboratory techniques described in a previous paper, results of the measurements of the back-scattering cross-sections of falling water drops and suspended ice spheres are presented for wavelengths of 1.50 and 5.72 cm. As in the earlier study at 3.20 cm, the water-value agreement with the complete diffraction theory of Mie is excellent. Rayleigh values are a good approximation at 5.72 cm out to drop diameters of about 0.35 cm but can be used at 1.50 cm only for drops less than about 0.15 cm in diameter. In addition, recent theoretical evaluations by Herman and Battan of the Mie back-scattering from melting ice spheres are compared with earlier observations made at 3.20 cm. When a constant water film thickness of 0.01 cm is used, the observed back-scattering cross-sections versus drop diameter are in remarkable agreement with theory.