###### Abstract  
Polar stratospheric clouds (PSCs) form in polar regions, typically between 15 and 25 km above mean sea level, when the local temperature is sufficiently low. PSCs play an important role in the ozone chemistry and the dehydration and denitrification of the stratosphere. Lidars with a depolarization channel may be used to detect and classify different classes of PSCs. The main PSC classes are water ice, nitric acid trihydrate (NAT), and supercooled ternary solutions (STSs), the latter being liquid droplets consisting of water, nitric acid, and sulfuric acid. PSCs have been observed at the lidar observatory at Concordia Station from 2014 onward. The harsh environmental conditions at Concordia during winter render successful lidar operation difficult. To facilitate the operation of the observatory, several measures have been put in place to achieve an almost complete remote control of the system. PSC occurrence is strongly correlated with local temperatures and is affected by dynamics, as the PSC coverage during the observation season shows. PSC observations in 2021 are shown as an example of the capability and functionality of the lidar observatory. A comparison of the observations with the satellite-borne CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar has been made to demonstrate the quality of the data and their representativeness for the Antarctic Plateau. climate; ozone; stratosphere; polar stratospheric clouds; lidar +
Footnote †: journal: Remote Sensing  
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Lidars with a receiver equipped with two detectors to separate polarized and depolarized signals (see, e.g., ref. [1] for a review of polarization lidars) are thus an excellent tool that allows the classification of the different PSC types and subclasses. Ground-based lidars have been active in Antarctica since 1987 and in the Arctic polar regions since 1989. [PERSON] [2] reported lidar observations at Ny-Aalesund/Svalbard in 1989. The first lidar measurements in Antarctica were reported by [PERSON] and coworkers [3], who reported the observation of PSCs at the South Pole station using a laser emitting at 532 nm without a depolarization channel. [PERSON] [4] reported lidar observations at Dumont D'Urville from 1989 to 1993. Recent PSC observations at Dumont D'Urville have been reported in [5]. A polarization lidar was active at McMurdo from 1989 up to 2010 [6; 7], and was transferred to Concordia Station in 2014 [8]. A combination of simultaneous lidar and balloon-borne optical particle counter measurements allows the comparison of size distributions with the observed optical properties of aerosol present in PSCs [9; 10]. Very few stratospheric lidars have been operating in the Antarctic, and only two of these are primary lidar stations of the Network of Atmospheric Composition Change (NDACC). These are located at Dumont D'Urville and at Concordia Station. In a recent study [11], Concordia Station was identified as one of the best locations for observing polar stratospheric clouds. One reason is the limited cloud cover by cirrus clouds, which might partly block the lidar and reduce the useful range for PSCs. Moreover, Concordia Station is well within the polar vortex during most of the Austral winter, which implies that the conditions for PSC formation are favorable, leading to a frequent occurrence. Operating a lidar in Antarctica presents additional problems with respect to a lidar at midlatitude locations. This is mainly due to the remoteness of the station and the harsh environmental conditions, which render technical adjustments and maintenance difficult. This is mitigated by the redundancy of the most important components of the lidar, such as the laser and optical systems, as well as the data acquisition modules.