Radially Classified Aerosol Detector for Aircraft-Based Submicron Aerosol Measurements

A radially classified aerosol detector (RCAD) for fast characterization of fine particle size distributions aboard aircraft has been designed and implemented. The measurement system includes a radial differential mobility analyzer and a high-flow, high-efficiency condensation nuclei counter based on modifications to a commercial model (TST, model 3010). Variations in pressure encountered during changes in altitude in flight are compensated by feedback control of volumetric flow rates with a damped proportional control algorithm. Sampling resolution is optimized with the use of an automated dual-bag sampling system. This new system has been tested aboard the University of Washington Cl31a research aircraft to demonstrate its in-flight performance capabilities. The system was used to make measurements of aerosol, providing observations of the spatial variability within the cloud-topped boundary layer off the coast of Monterey, California.