Preprints
https://doi.org/10.5194/acp-2021-491
https://doi.org/10.5194/acp-2021-491

  29 Jun 2021

29 Jun 2021

Review status: this preprint is currently under review for the journal ACP.

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

Heather Guy1,2, Ian M. Brooks2, Ken S. Carslaw2, Benjamin J. Murray2, Von P. Walden3, Matthew D. Shupe4,5, Claire Pettersen6, David D. Turner8, Christopher J. Cox5, William D. Neff4,5, Ralf Bennartz6,7, and Ryan R. Neely III1,2 Heather Guy et al.
  • 1National Centre for Atmospheric Science, Leeds, U.K.
  • 2School of Earth and Environment, University of Leeds, Leeds, U.K.
  • 3Department of Civil and Environmental Engineering, Laboratory for Atmospheric Research, Washington State University, Pullman, WA, USA
  • 4Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
  • 5Physical Science Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
  • 6Space Science and Engineering Center, UW-Madison, Madison, WI, USA
  • 7Earth and Environmental Sciences, Vanderbilt University, Nashville, TN, USA
  • 8Global Systems Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA

Abstract. This study presents the first full annual cycle (2019–2020) of ambient surface aerosol number concentration (condensation nuclei > 20 nm, N20) measurements collected at Summit Station, in the centre of the Greenland Ice Sheet (72.58° N, −38.45° E, 3250 m asl). The mean surface N20 concentration in 2019 was 129 cm−3, with the 6 h mean ranging between 1 cm−3 and 1441 cm−3. The highest monthly mean concentrations occurred during the late spring and summer, with the 5 minimum concentrations occurring in February (mean: 18 cm−3), demonstrating an opposite seasonal cycle in aerosol concentrations compared to low altitude Arctic stations (with latitudes > 66° N). High aerosol concentration events are linked to anomalous anticyclonic circulation over Greenland and the descent of free tropospheric aerosol down to the surface, whereas low aerosol concentration events are linked to cyclonic circulation over south-east Greenland that drives upslope flow and enhances precipitation en-route to Summit. Fog strongly effects N20 concentrations, on average reducing N20 by 20 % during the first three hours of fog formation. Extremely low N20 concentrations (< 10 cm−3) occur in all seasons, and we suggest that fog, and potentially cloud formation, can be limited by low aerosol concentrations over central Greenland.

Heather Guy et al.

Status: open (until 10 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-491', Anonymous Referee #1, 14 Jul 2021 reply

Heather Guy et al.

Data sets

Radiosonde temperature and humidity profiles taken at Summit Station, Greenland Von P. Walden and Matthew Shupe https://doi.org/10.18739/A20P0WR53

ERA5 hourly data on pressure levels from 1979 to present Hersbach, H., Bell, B., Berrisford, P., Biavati, G., Horányi, A., Muñoz Sabater, J., Nicolas, J., Peubey, C., Radu, R., Rozum, I., Schepers, D., Simmons, A., Soci, C., Dee, D., Thépaut, J.-N. https://doi.org/10.24381/cds.bd0915c6

Microwave Radiometer measurements of sky brightness temperature taken at Summit Station, Greenland, 2019. David Turner and Ralf Bennartz https://doi.org/10.18739/A2TX3568P

ICECAPS-ACE: surface aerosol concentration measurements (condensation nuclei > 5nm diameter) taken at Summit Station Greenland Guy, H.; Neely III, R. R.; Brooks, I. https://catalogue.ceda.ac.uk/uuid/f56980457ce240ccab5ac6d403c81e7a

Millimeter Cloud Radar measurements taken at Summit Station, Greenland, 2019. Matthew Shupe https://doi.org/10.18739/A2Q52FD4V

Micropulse lidar (MPL) measurements taken at Summit Station, Greenland, 2019. Matthew Shupe https://doi.org/10.18739/A2862BC30

Precipitation Occurrence Sensor System measurements taken at Summit Station, Greenland, 2019. Matthew Shupe https://doi.org/10.18739/A2GQ6R30G

Heather Guy et al.

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Short summary
We present the first full year of surface aerosol number concentration measurements from the central Greenland Ice Sheet. Aerosol concentrations here have an opposite seasonal cycle to those at lower altitude Arctic sites, which is driven by large-scale atmospheric circulation. Our results can be used to help understand the role aerosols might play in Greenland surface melt through the modification of cloud properties. This is crucial in a rapidly changing region where observations are sparse.
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