The cloud-radiation interaction plays an important role in global climate system and has been investigated by many researchers. However, the understanding of mixed-phase boundary layer cloud in Arctic has remained one of the unknown factor. During the period of May to June, 2011, in situ measurements of mixed phase boundary layer clouds were carried out at Zeppelin Station of Norwegian Polar Institute (NPI) in Ny-Alesund (78.9N, 11.9E), Svalbard.

The instruments consist of Cloud, Aerosol and Precipitation Spectrometer (CAPS), PVM-100(Gerber Particulate Volume Monitor) and Cloud Particle Microscope imager (CPM). CAPS is composed of Cloud and Aerosol Spectrometer (CAS)and Cloud Imaging Probe (CIP). CAPS-CAS and CAPS-CIP have same measurement capabilities of Forward Scattering Spectrometer Probe (FSSP) models 100 and 300 and tow dimensional optical imaging probe (2D-OAP), respectively. PVM-100 measures liquid water content and effective radius of water droplet clouds. CPM, which was newly developed by one of authors, consists of CCD camera and microscope and takes an image of cloud particles. These instruments were installed on the roof of Zeppelin Station of NPI, which is near the top of Mt. Zeppelin and is at the altitude of 474 m.

During the observation period, the clouds associated with cyclonic disturbance and the clouds associated with outbreak of westerly cold air mass from the sea were observed. The atmospheric temperature during all the measurements is from 0 to -5 C. In every case, the large part of cloud particles that were measured by CAPS-CIP were consist of column type. We show the cloud microphysical properties in these case studies; cloud particle size spectrum, liquid water content, ice water content and so on.