Design and evaluation of BOOGIE: a collector for the analysis of cloud composition and processes: Biological, Organics, Oxidants, soluble Gases, inorganic Ions and metal Elements

Abstract. Cloud/fog droplets comprise a myriad of chemical compounds and are living environments in which microorganisms are present and active. These chemical and biological elements can evolve in various ways within the cloud system, and the aqueous transformation of chemicals contributes to atmospheric chemistry. In situ cloud studies are fundamental in this sense, because they enable us to study the variability in cloud chemical composition as a function of environmental conditions and assess their potential for transforming chemical compounds. To achieve this objective, cloud water collectors have been developed in recent decades to recover water from clouds and fogs using different designs and collection methods. In this study, a new active ground-based cloud collector was developed and tested for sampling cloud water to assess the cloud microbiology and chemistry. This new instrument, BOOGIE, is an easy mobile sampler for cloud water collection with the objective of being cleanable and sterilisable, respecting chemical and microbial cloud integrity, and presenting an efficient collection rate of cloud water. Computational fluid dynamics simulations were performed to theoretically assess the capture of cloud droplets by this new sampler. Few turbulences have been observed inside the collector and a 50 % collection efficiency cutoff of 10 µm has been estimated. The collector was deployed at Puy de Dôme station under cloudy conditions for evaluation. The water collection rates were measured at 156 ± 52 mL h^-1 for a collection of 17 cloud events; considering the measured liquid water content, the sampling efficiency of this new collector has been estimated at 87.2 ± 8.6 % over the same set of cloud events. BOOGIE was compared with other active cloud collectors commonly used by the scientific community (Cloud Water Sampler and Caltech Active Strand Cloud Collector version 2). Four cloud events were collected; the three samplers presented similar collection efficiencies (between 79 % and 88 % on average). The measured ionic composition was comparable even if differences were highlighted between collectors, the consequence of different designs, and the intrinsic homogeneity in the chemical composition within the cloud system.