Annual cycle of aerosol properties over the central Arctic during MOSAiC 2019–2020 — light-extinction, CCN, and INP levels from the boundary layer to the tropopause

• Main Authors: Ansmann, Albert, Ohneiser, Kevin, Engelmann, Ronny, Radenz, Martin, Griesche, Hannes, Hofer, Julian, Althausen, Dietrich, Creamean, Jessie M., Boyer, Matthew C., Knopf, Daniel A., Dahlke, Sandro, Maturilli, Marion, Gebauer, Henriette, Bühl, Johannes, Jimenez, Cristofer, Seifert, Patric, Wandinger, Ulla
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Arctic
• Online Access: https://doi.org/10.5194/egusphere-2023-444; https://noa.gwlb.de/receive/cop_mods_00065463; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00063984/egusphere-2023-444.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-444/egusphere-2023-444.pdf

Continuous height-resolved observations of aerosol profiles over the central Arctic throughout a full year were performed for the first time. Such measurements covering aerosol layering features are required for an adequate modeling of Arctic climate conditions, especially with respect to a realistic consideration of cloud formation and here, in particular, of ice nucleation processes. MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) offered this favorable opportunity to monitor aerosol and clouds over the central Arctic over all four seasons, from October 2019 to September 2020. In this article, a summary of MOSAiC lidar observations aboard the icebreaker Polarstern of tropospheric aerosol products is presented. Particle optical properties, i.e., light-extinction profiles and aerosol optical thickness (AOT), and estimates of cloud-relevant aerosol properties (cloud condensation nucleus, CCN, and ice-nucleating particle concentrations, INPs) are discussed, separately for the lowest part of the troposphere (near the surface at 250 m height), within the lower free troposphere (2000 m height), and regarding INPs also near the tropopause (cirrus level, 8–10 km height). In situ observations of the particle number concentration and INPs aboard Polarstern are included in the study. Strong differences between summer and winter aerosol conditions were found. During the winter months (Arctic haze period) a strong decrease of the aerosol light extinction coefficient (532 nm) with height up to about 4–5 km height was found with values of 20–100 Mm-1 close to the surface and an order of magnitude less at 1500–2000 m height. Lofted aged wildfire smoke layers caused a re-increase of the aerosol concentration from the middle troposphere up to stratospheric heights and were continuously observable from October 2019 to May 2020. In summer (June to August 2020), much lower particle extinction coefficients, frequently as low as 1–5 Mm-1, were observed. Aerosol removal, controlled by cloud scavenging ...