Investigations of mesoscopic complexity of small ice crystals in midlatitude cirrus

During the Mid-Latitude CIRRUS campaign small (<50 mu m) ice crystals were characterized for their mesoscopic complexity using the Small Ice Detector Mk. 3. It was found that the majority (76%) of all measured small ice crystals were complex. Although some differences were found between the distributions of the complexity parameters between different cloud systems, no real correlation between the mesoscopic complexity and cloud formation mechanisms (liquid origin or in situ) was found. Some decrease in mesoscopic complexity was detected during those missions affected by Saharan dust outbreaks. The link between the crystal growth conditions and the observed mesoscopic complexity was investigated in a case study of an in situ cirrus with the help of trajectory analysis. A relatively weak correlation of r = 0.33 was found between the mesoscopic complexity and the maximum supersaturation with respect to ice along the ice particle trajectory.