A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N-5.7° E)

This study provides an analysis of cirrus clouds properties at midlatitude in the southern part of France from ground-based and spaceborne lidars. A climatology of cirrus clouds properties and their evolution over more than 12 yr is presented and compared to other mid-latitude climatological studies. Cirrus clouds occur ~ 37% of the total observation time and remain quasi-constant across seasons with a variation within ~ 5% around the mean occurrence. Similar results are obtained from CALIOP and the ground-based lidar, with a mean difference in occurrence of ~ 5% between both instruments. From the ground-based lidar data, a slight decrease in occurrence of ~ 3% per decade is observed but found statistically insignificant. Based on a clustering analysis of cirrus cloud parameters, three distinct classes have been identified and investigations concerning their origin are discussed. Properties of these different classes are analysed, showing that thin cirrus in the upper troposphere represent ~ 50% of cloud cover detected in summer and fall, decreasing by 15-20% for other seasons