Understanding Aerosol-Cloud Interactions in Ice Saturated Environments using AHSRL, CALIOP and Trajectory Cluster Analysis

Ice clouds do not necessarily form when saturation with respect to ice is reached. This can be readily observed by using lidar measurements in conjunction with temperature profiles. It is also observed that attempts to model ice clouds using saturation with respect to ice as a sufficient condition produce far too many ice clouds. For this reason investigations into specific cases of ice nucleation or the failure of ice nucleation are very important in the understanding of the interactions between aerosols and arctic clouds. This study analyzes measurements obtained from the Arctic High Spectral Resolution Lidar and CALIOP on board CALIPSO and classifies them with respect to relative humidity obtained from radiosonde. These two instruments provide a unique opportunity to study aerosol-cloud events simultaneously from both the ground and space. An analysis of airmass history is also conducted by back-tracking air-parcels. The influence of this history is assessed through the classification of trajectories with a clustering algorithm and determining the effect of cluster grouping on the distribution of specific lidar observables such as particle backscatter and particle effective diameter.