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

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Guy, Heather, Brooks, Ian M., Carslaw, Ken S., Murray, Benjamin J., Walden, Von P., Shupe, Matthew D., Pettersen, Claire, Turner, David D., Cox, Christopher J., Neff, William D., Bennartz, Ralf, Neely III, Ryan R.
• Format: Text
• Language: English
• Published: 2021
• Subjects: Greenland; East Greenland; Ice Sheet
• Online Access: https://doi.org/10.5194/acp-21-15351-2021; https://acp.copernicus.org/articles/21/15351/2021/

This study presents the first full annual cycle (2019–2020) of ambient surface aerosol particle number concentration measurements (condensation nuclei > 20 nm , N 20 ) collected at Summit Station (Summit), in the centre of the Greenland Ice Sheet (72.58 ∘ N, − 38.45 ∘ E; 3250 <math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">a</mi><mo>.</mo><mi mathvariant="normal">s</mi><mo>.</mo><mi mathvariant="normal">l</mi><mo>.</mo></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="36pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="275219d6474e22d64fb88665fccb126a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-15351-2021-ie00001.svg" width="36pt" height="10pt" src="acp-21-15351-2021-ie00001.png"/></svg:svg> ). The mean surface concentration in 2019 was 129 cm −3 , with the 6 h mean ranging between 1 and 1441 cm −3 . The highest monthly mean concentrations occurred during the late spring and summer, with the minimum concentrations occurring in February (mean: 18 cm −3 ). High- N 20 events are linked to anomalous anticyclonic circulation over Greenland and the descent of free-tropospheric aerosol down to the surface, whereas low- N 20 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 N 20 by 20 % during the first 3 h of fog formation. Extremely-low- N 20 events ( < 10 cm −3 ) occur in all seasons, and we suggest that fog, and potentially cloud formation, can be limited by low aerosol particle concentrations over central Greenland.