Analysis of water vapour mixing ratio profiles in the Arctic from Raman lidar measurements during the MOSAiC-campaign

• Main Author: Seidel, Clara
• Other Authors: Universität Leipzig, Leibniz-Institut für Troposphärenforschung
• Format: Master Thesis
• Language: English
• Published: 2022
• Subjects: Vertical water vapour profiles; MOSAiC; Raman lidar; downward thermal-infrared radiation (DTIR) at the surface; Arctic Oscillation index (AO); Vertikale Wasserdampfprofile; Langwellige Einstrahlung am Boden; Atmosphärische Zirkulation in der Arktis; info:eu-repo/classification/ddc/551.5; ddc:551.5; Arctic; Boden; Arktis; Arktis*; polar night
• Online Access: https://nbn-resolving.org/urn:nbn:de:bsz:15-qucosa2-845481; https://ul.qucosa.de/id/qucosa%3A84548; https://ul.qucosa.de/api/qucosa%3A84548/attachment/ATT-0/

For the first time, vertical water vapour profiles were measured in the Central Arctic North of 85°N during the MOSAiC campaign (Multidisciplinary drifting Observatory for the Study of Arctic Climate). Continuous measurements of the Raman lidar PollyXT are used to retrieve high-resolved vertical profiles of the water vapour mixing ratio (WVMR) during the polar night. The collected data are calibrated and evaluated by use of selected clear-sky profiles between 25 October 2019 and 29 February 2020. Three different calibration methods are applied using reference data from radiosonde launches or microwave radiometer (MWR) measurements, respectively. The calibration with the least error results from a linear fit between collocated radiosonde and lidar measurements and delivers a final calibration constant of 15.96 ± 0.37 g/kg for the period from 25 Oct 2019 to 29 Feb 2020. The calibrated WVMR profiles are analysed regarding the vertical distribution of water vapour in the Arctic, its impact on the downward thermal-infrared radiation (DTIR) at the surface, and its relation to the Arctic Oscillation (AO) index as a measure for the general atmospheric circulation. The Arctic atmosphere is very dry during the winter time with WVMR values below 2 g/kg. The vertical water vapour distribution is strongly related to the temperature profile. Layers with higher WVMR values are often capped by temperature inversions. Layers with higher integrated water vapour values (IWV) are located either close to the surface (coupled) or in an elevated layer (decoupled), related to local or advective processes, respectively. The impact of the vertical distributed water vapour on the clear-sky DTIR at the surface was investigated by evaluating the evolution of the air mass at the measurement location over several hours for seven clear-sky cases. The relation between the measured DTIR at the surface and the lidar IWV shows a linear correlation for each case, but with a shift in the radiation values depending on the temperature of the vertical ...