Aerosol-layer structure and wind profile in the high Arctic

We present an investigation of the structure of the aerosol layer at the Villum Research Station located at Station Nord in the high Arctic. Knowledge of the aerosol layering is of interest for the interpretation of measurements of atmospheric chemistry and particles that control air pollution in the pristine atmosphere and for climate change (Arctic amplification). Based on one year of remote sensing measurements by a ceilometer and a wind lidar, we discovered that the structure of the atmosphere was very different from what is usually found at mid-latitudes. Combining the ceilometer and wind lidar observations indicated that the aerosol layer has depths of about 100 m and 230 m and few cases of depth between 100 and 230 m. Studies of profiles with no aerosol-layer depth, based on high frequency ceilometer observations, reveal cases of entraining air. We found that the annual wind roses indicate generally westerly wind veering by more than 30 degrees between 40 and 200 m and a wind speed slowly increasing with height of about 5 m/s. It was found that the individual wind speed profiles between 40 and 200 m can roughly be categorized into 4 groups: 1. The wind speed increases from the ground up to 100m and thereafter decreasing (likely drainage); 2. The wind profile decreases from the ground up to a minimum at about 100 m; above this minimum the wind speed increases (no explanation for this type of wind profile is offered); 3. Wind speed increases with altitude; 4. Wind speed decreases from the ground throughout the whole layer. The two-layer structure of the aerosols and the different categories of wind profiles complicates the interpretation of surface observations. We discuss the implication in terms of local versus remote sources of aerosols and the uncertainty in backward trajectory modelling. These data can be used further for meteorological and aerosol model validation in the lower atmosphere of the High Arctic.

Funding information: Danish Environmental Agency ‘Monitoring of short-lived climate components in Arctic’; European Cooperation in Science and Technology, Grant/Award Number: COST Action CA18235 PROBE; National Science Fund of Bulgaria, Grant/Award Number: KП-06-Н34/1; Nationalt Udvalg for Forskningsinfrastruktur (NUFI)