Monodisperse Aerosol Generator for Field Calibration of Disdrometers and Cloud Probes

A field-deployable, battery-powered monodisperse aerosol generator designed for calibration of atmospheric measurement instrumentation is presented. The principle of operation of the generator relies on Savart–Plateau–Rayleigh instability of water columns emerging from an orifice with applied periodic mechanical perturbation. The instrument can be configured in three different ways. (1) Large Drop Generator (LDG) that generates large monodisperse water drops (~100–1200 μm in diameter) and uses a simple drop size verification method involving a stroboscopic illuminator synchronized with the orifice vibration frequency. (2) Small Drop Generator (SDG) that produces water droplets ~20–100 μm in diameter. It uses an advanced optical imaging system for verification of the droplet size and droplet velocity. (3) A modification of the SDG that uses water or alcohol solutions instead of pure water (with subsequent drying) to generate monodisperse coarse mode aerosol particles (~1–10 μm) of the solute (inorganic salts, dyes, organic liquids, etc.). The three configurations can be used to calibrate precipitation measurement instruments (e.g., disdrometers), cloud probes, and coarse mode aerosol analyzers, respectively. Applications of the technology for field calibration of atmospheric measurement instruments are discussed. Results of field work on calibration of two types of optical disdrometers using the LDG and calibration of the Mesa Photonics’ cloud droplet measurement system prototypes using the SDG are presented.