Design and Sampling Characteristics of a New Airborne Aerosol Inlet for Aerosol Measurements in Clouds

Abstract

esign of a new submicron aerosol inlet (SMAI) for airborne sampling of aerosol particles is introduced and its performance characteristics under a range of sampling conditions are presented. Analysis of inlet performance in clear-air and cloud systems shows that submicron aerosols are sampled representatively by the inlet, and in comparison with other types of inlets the SMAI has a relatively minor or nonexistent problem of droplet shatter contamination. The SMAI has a flow-through cone, with a perpendicular subsampling tube inside it. The cone acts as a virtual blunt body and decelerates the velocity directed toward a subsampling tube within the cone, resulting in reduced droplet impaction velocities and negligible artifact particle generation. The use of a perpendicular subsampling tube helps eliminate large shattered droplets from entering the sample volume, though it also results in lowering the aerosol sampling cut size. The SMAI sampling characteristics are determined from computational fluid dynamics simulations, and its cut size is calculated to be ~3 ?m. In warm clouds, the shatter artifacts in the SMAI measurements are significantly less than that in a diffuser-type inlet, and shatter artifacts are only observed to increase when concentrations of drops larger than ~100 ?m increase. In cold-cloud systems, shatter artifacts are significantly reduced with SMAI and some dependence of the inlet?s performance on the shape of the ice particles is observed.