The Small-Particle Response of an Optical Array Precipitation Probe

Abstract

The response characteristics of an optical array precipitation spectrometer probe (PMS-OAP-200Y) have been studied in the laboratory using precision glass beads ejected from a specially constructed air gun. The low-end behavior of the probe is described in terms of a high-pass filter characteristic, which can be used to explain the response of the instrument to a particle population having a wide distribution of sizes. It is shown that the particle concentrations measured in channel 1 of the OAP-200Y require correction by a factor which is a function of particle size distribution. For typical experimental situations in rain, the correction factor is approximately 1.8. The remaining size channels do not require correction, provided that the probe sample area and channel width have been properly determined.