In situ characterization of mixed phase clouds using the Small Ice Detector and the Particle Phase Discriminator

[摘要] Mixed phase clouds (MPCs) represent a great source of uncertainty for bothclimate predictions and weather forecasts. In particular, there is still alack of understanding on how ice forms in these clouds. In this work wepresent a technique to analyze in situ measurements of MPCs performed withthe latest instruments from the Small Ice Detector family. These instrumentsrecord high-resolution scattering patterns of individual small cloudparticles. For the analysis of the scattering patterns we developed analgorithm that can discriminate the phase of the cloud particles. In the caseof a droplet, a Mie solution is fitted to the recorded pattern and the sizeof the corresponding particle is obtained, which allows for a sizecalibration of the instrument. In the case of an ice particle, its shape isdeduced from the scattering pattern.

We apply our data analysis method to measurements from three distinct MPCtypes. The results from laboratory measurements demonstrate that ourtechnique can discriminate between droplets and ice particles in the sameoptical size range. This ability was verified by measurements at a mountaintop station where we found an alternation of liquid- and ice-dominated cloudregions. The analysis of results from aircraft-based measurements illustratesthe ice detection threshold of the technique.

[学科分类] 几何与拓扑