DOI: 10.1594/pangaea.984634
title: Lidar measurements taken at the ALOMAR mountain observatory at Andenes, Norway during March 2021

description: During a 2-week measurement campaign from 15-31 March 2021 (ISLAS2021), we collected a comprehensive dataset characterizing the atmospheric water vapour and precipitation stable isotope and aerosol composition at a coastal station in the European sub-Arctic. Located at the northeastern coast of the Nordic Seas, stable water isotope measurements with cavity ring-down spectrometers (CRDS) were collected at Andenes, Norway close to sea level and at the nearby ALOMAR mountain top observatory at 370 m a.s.l. Paired water vapour isotope and precipitation measurements at sub-event time resolution were collected at both station locations. These were supplemented with water vapour isotope measurements at the cities of Tromsø, Norway and Bergen, Norway. Surface precipitation samples were collected on a per-event basis along a transect towards the south to assess spatial representativeness. Measurements of ice nucleating particle concentrations were taken at sea level during precipitation events, supplemented by continuous size-resolved aerosol measurements. These detailed measurements were complemented by additional instrumentation to characterize the atmospheric conditions, including ground-based vertical-pointing rain radars, disdrometer, frequent radiosonde ascents and a ceilometer. All stable water isotope measurements have been calibrated onto the VSMOW-SLAP scale. During the campaign, weather conditions were alternating rapidly between warm mid-latitude air masses and marine cold-air outbreak conditions. The data from the ISLAS2021 measurement campaign therefore provide insight into a variety of mixed-phase precipitation processes, atmospheric long-range transport, and the dynamics of high-latitude weather system with the combined perspective of stable water isotopes and aerosol measurements. This dataset contains attenuated backscatter at 355nm, 532nm and 1064nm as well as the volume depolarization ratio at 532nm. The temporal resolution is 30s and the vertical resolution is 7.5m. The dataset consists of four observation periods. One observation period contains 1-3 measurements. In between the individual measurements, neutral density filter changes were applied to the 355nm and/or 1064nm channels, i.e. filters were removed to increase the signal or filters were added to protect the detection hardware from a too-high signal. The time periods for the individual filter configurations are included under filter_configs in this metadata. For the signals at 532nm (both polarization directions) and 355nm, there are two detection channels each, one analogue detection channel suitable for the near range (nr) and one photon-counting channel suitable for the far range (fr). They are in this dataset not glued, but the attenuated backscatter is given for each channel individually. The volume depolarization ratio at 532nm is also calculated from the analogue and photon-counting signals individually. At 1064nm, there is only one detection channel which is an analogue channel. The data processing of the data from the raw files to the published file uses the python packages atmospheric-lidar and lidar_molecular developed by Ioannis Binietoglou (https://pypi.org/project/atmospheric-lidar/, https://gitlab.com/ioannis_binietoglou/lidar_molecular). Range correction and background subtraction are applied to all channels, in addition deadtime-correction is applied to the photon-counting channels. This procedure is the same as applied by Schäfer et al., (2022). Where signals were too high in the lowest part of the atmosphere to apply deadtime-correction in the photon-counting channel, these lowest layers were removed. The number of removed layers varies between the different measurements. The calibration factors for the depolarization ratio have already been applied, but are given in the dataset together with the standard deviation of the calibration filter for uncertainty estimates using error propagation.