Simultaneous observation of raindrop size distribution by VHF and L-band Doppler radars

The determination of the vertical profile of raindrop size distribution (DSD) is a difficult, but essential task in understanding the evolution process of precipitation. Use of multiple Doppler radars is one of the promising methods. The authors made a series of simultaneous observations using the VHF MU (middle and upper atmosphere) radar and an L-band BLR (boundary-layer radar), both of which have a Doppler capability, in Japan during the Bai-u season of 1992. They developed an automated curve-fitting algorithm which derives the DSD parameters from the observed Doppler spectra, and have investigated their accuracy via numerical simulations. They critically examine the appropriateness of the gamma distribution, which is widely used in analyzing the radar data, in terms of the errors of derived parameters.