Computer processing for deriving drop-size distributions and vertical air velocities from VHF Doppler radar spectra

A fully automated data processing procedure has been developed for deriving the precipitation parameters from VHF Doppler radar spectra simultaneously with the background atmospheric parameters such as the mean wind velocity. The procedure has largely enhanced our capability in analyzing the data from continuous observations, which was hardly possible with human-attained analysis. The accuracy of the derived parameters are quantitatively evaluated by means of numerical simulations. It is found that the rain parameters can be determined with an accuracy of 15% at a time and height resolution of 10 min and 600 m, respectively, for high signal-to-noise ratios, for example. Parameters for the background atmospheric turbulence are estimated with an accuracy more than twice the fitting procedure currently used to analyze clear-air data. Experimental results of the MU radar observations are compared with the rain intensity measured on the ground for the first time. It is confirmed that the radar has a capability of measuring rain parameters with a rainfall rate sensitivity of about 1 mm h−1.