Climatology of Cirrus Clouds over Observatory of Haute-Provence (France) Using Multivariate Analyses on Lidar Profiles

This study aims the classification of the cirrus clouds over the Observatory of Haute-Provence (OHP) in France. Rayleigh-Mie-Raman lidar measurement altogether with ERA5 dataset, are an-alyzed in order to provide geometrical morphology and optical cirrus properties over the site. The method of the cirrus cloud climatology presented here, is based on a threefold classification scheme based on the cirrus geometrical and optical properties, and their formation history. Principal component analysis (PCA) and subsequent clustering, result on four morphological cirrus classes, three optical groups, and two origin – related categories. Cirrus clouds occur approximately 37% of the time, with most being single-layered (66.7%). The mean cloud optical depth (COD) is 0.39 ± 0.46, and the mean heights range around 10.8 ± 1.35 km. Thicker tropospheric cirrus are observed under higher temperature and humidity conditions than cirrus observed at the vicinity of the tropopause level. Monthly cirrus occurrences vary irregu-larly, while seasonal patterns peaking in spring. With respect to the mechanism of the formation, there is found that the majority of cirrus clouds, was of in situ origin. The liquid origin cirrus category consists nearly entirely of thick cirrus. Overall result, suggests that in situ origin thin cirrus, located in the upper-tropospheric and tropopause regions, have the most significant oc-currence over the site.