Minisodar Measurements of Rain

Abstract

Measurements of raindrop fall velocity spectra have been made with a minisodar. Amplitude calibration of the system enables the calculation of drop size parameters such as number density, water density, and surface area using methods similar to those with Doppler radar studies. The acoustic measurements are at 10 m intervals within 200 m of the surface and benefit from an almost complete separation of droplet velocity spectra from atmospheric vertical velocity spectra. Comparison of parameters with those reported in the literature shows good agreement. It is shown that the chief difficulty with the method is atmospheric attenuation; however, excess attenuation due to scattering from droplets is found to be unimportant.