The Axial Cyclone Cloud water Collector

A new aircraft-mounted probe for collecting samples of cloud water has been designed, fabricated and extensively 15 tested. Following previous designs, the probe uses inertial separation to remove cloud droplets from the airstream, which are subsequently collected and stored for offline analysis. We report details of the design, operation, and the modeled and measured probe performance. Computational Fluid Dynamics (CFD) was used to understand the flow patterns around the complex interior geometrical features that were optimized to ensure efficient capture of droplets. CFD simulations coupled with particle tracking and 20 multiphase surface transport modeling provide detailed estimates of the probe performance across the entire range of flight operating conditions and sampling scenarios. Physical operation of the probe was tested on a Lockheed C130 Hercules (fuselage mounted) and de Havilland Twin Otter (wing pylon mounted) during three field campaigns. During C130 flights on the final field campaign, the probe reflected the most developed version of the design and a median sample collection rate of 4.5 ml min-1 was achieved. This allowed 25 samples to be collected over 1-2 minutes under optimal cloud conditions. Flights on the Twin Otter featured an intercomparison of the new probe with the slotted-rod collector; an existing technique for collecting cloud water. Comparison of trace species concentrations showed a good agreement between collection techniques, with absolute concentrations of most major ions agreeing within 30%, on average, despite sampled concentrations ranging over several orders of magnitude and the samples not collected with perfect coincidence. 30