EXPERIMENTAL DETERMINATIONS OF THE BACK-SCATTERING CROSS-SECTIONS OF WATER DROPS AND OF WET AND DRY ICE SPHERES AT 3.2 CENTIMETERS

Abstract

Measurements are presented of the back-scattering cross-sections of individual water drops and ice pellets at a wavelength of 3.2 cm which cover a diameter range of about 2 to 7 mm for water and 3 to 35 mm for ice. The cross-sections were measured under laboratory conditions using a C.W. radar with an aluminum sphere calibration. The water returns were in excess of both the Mie and Rayleigh values for diameters up to about 3.5 mm but agreed closely with Mie theory for larger values. The ice measurements were in excellent agreement with the theoretical values of Mie with the exception of an increasing scatter at the large diameters. A series of semi-quantitative observations on water-covered ice pellets gave detinite evidence of a change in cross-section toward water values at low particle diameters but showed no conclusive tendency at medium and large diameters.