Cloud Particle Shattering during Sampling by Airborne Optical Array Probes

During sampling by airborne optical array probes, cloud particles (droplets or ice crystals) will shatter before entering into the sampling area, either by mechanical impaction with the instrument arms or by interaction with turbulence and wind shear generated by the probe housing. The shattering efficiency depends on the habit, size, and density of particles, as well as the probe inlet design, and airspeed. The phenomenon of cloud particle shattering during airborne sampling is presented in this paper. The data analyzed were from the flights of the Shanxi Y-12 research plane in the Taiyuan area from July to September 2008. It is shown that the distribution characteristics of inter-arrival times of particles can be bimodal:the long-term mode reflects the true structure of cloud particles distributed in space, and the short-term mode is the result of cloud particle shattering. An inter-arrival time threshold is proposed as a criterion for particle shattering identification. For the data analyzed in this study, the value was 2×10^-5 s and 10^-4 s for Cloud Imaging Probe (CIP) and Precipitation Imaging Probe (PIP), respectively. These values might also serve as reference thresholds for data from other Y-12 research plane flights.