COMPARISON OF RAINDROP SIZE DISTRIBUTION MEASUREMENTS BY A JOSS WALDVOGEL DISDROMETER, A PMS 2DG SPECTROMETER, AND A POSS DOPPLER RADAR

Three techniques for the measurement of raindrop size distributions are compared using data from a Joss-Waldvogel disdrometer (JWD), a Particle Measuring Systems 2DG spectrometer (PMS), and an Atmospheric Environment Service (AES) Precipitation Occurrence Sensor System (POSS). The techniques used are impact measurement by the JWD, optical imaging by the PMS, and Doppler velocity spectrum by the POSS. The sampling size errors are compared. The effects of both vertical and horizontal winds on the measurements are evaluated. Accumulated rainfall amounts derived from the drop size distributions (DSDs) are compared to measurements by conventional gauges at the radar facility of AES at King City, Ontario, Canada. In general, DSDs and rain rates averaged for 1 min were in agreement between the three sensors. While 1-min-averaged DSDs were multimodal, long-time-period averages followed the Marshall-Palmer distribution.