Giannakaki Elina¹, Balis Dimitris¹, Amiridis Vassilis², Kazadzis Stelios¹

¹Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki
²Institute for Space Applications and Remote Sensing, National Observatory of Athens

A climatology of cirrus clouds over Thessaloniki (40.6°, 22.9°) in Greece has been constructed from the analysis of lidar measurements performed in the period 2000 to 2006. Cirrus clouds are generally observed in a mid altitude region from 7 to 12 km, with mid temperature in the range from -65° to -25°C. A seasonality of cirrus geometrical and temperature properties is found. The cloud thickness is generally in the range from 0.85 to 5 km and most of our cases have thickness between 1.5 and 2.5 km. The retrieval of cloud’s optical depth and lidar ratio is made through three different methods. A comparison of results shows good agreement between the methods, while we present the advantages and limitations of each method. Most cirrus clouds are found to be optically thin. The temperature and thickness dependencies of cirrus properties on optical properties are also studied in detail. The cloud temperature found to be decreased with increase of cloud altitude, as expected. A maximum mid-cloud depth of ~3 km is found at temperatures around ~-45°C while there is an indication that optical depth increases with increasing thickness and mid-cloud temperature.