In-situ cloud measurements using laser scattering at the Sonnblick Observatory

Anyone who looks up at the Hoher Sonnblick in the Austrian Alps on a cloudy evening this spring will see the summit illuminated by green laser light. This is due to the in-situ cloud measurements that have just begun as part of the ECCINT-03 campaign, organized by the team at the Sonnblick Observatory within the framework of the EU infrastructure ACTRIS (Aerosol, Clouds and Trace Gases Research Infrastructure). The IMKAAF is operating a novel cloud polarimeter here, which investigates the size distribution of cloud droplets and ice crystals via the backscattering and depolarization of a laser beam. During the campaign, the so-called HACP (Hyper-Angular Cloud Polarimeter) will be extensively tested for use at observatories and characterized in comparison with other in-situ cloud instruments.