Controls on surface aerosol particle number concentrations and aerosol-limited cloud regimes over the central Greenland Ice Sheet

Abstract

This study presents the first full annual cycle (2019-2020) of ambient surface aerosol particle number concentration measurements (condensation nuclei >g20gnm, N20) collected at Summit Station (Summit), in the centre of the Greenland Ice Sheet (72.58g gN, -38.45g gE; 3250gma.s.l.). The mean surface concentration in 2019 was 129gcm-3, with the 6gh mean ranging between 1 and 1441gcm-3. The highest monthly mean concentrations occurred during the late spring and summer, with the minimum concentrations occurring in February (mean: 18gcm-3). High-N20 events are linked to anomalous anticyclonic circulation over Greenland and the descent of free-tropospheric aerosol down to the surface, whereas low-N20 events are linked to anomalous cyclonic circulation over south-east Greenland that drives upslope flow and enhances precipitation en route to Summit. Fog strongly affects particle number concentrations, on average reducing N20 by 20g% during the first 3gh of fog formation. Extremely-low-N20 events (