Preprints
https://doi.org/10.5194/egusphere-2022-544
https://doi.org/10.5194/egusphere-2022-544
 
28 Jun 2022
28 Jun 2022

Ice fog observed at cirrus temperatures at Dome C, Antarctic Plateau

Étienne Vignon1, Lea Raillard1, Christophe Genthon1, Massimo Del Guasta2, Andrew J. Heymsfield3, Jean-Baptiste Madeleine1, and Alexis Berne4 Étienne Vignon et al.
  • 1Laboratoire de Météorologie Dynamique/IPSL/Sorbonne Université/CNRS, UMR 8539, Paris, France
  • 2INO-CNR, Sesto Fiorentino, Italy
  • 3National Center for Atmospheric Research, Boulder, Colorado
  • 4Environmental Remote Sensing Laboratory (LTE), École Polytechnique Fédérale de Lausanne, Switzerland

Abstract. As the near-surface atmosphere over the Antarctic Plateau is cold and pristine, its physico-chemical conditions resemble to a certain extent those of the high-troposphere where cirrus clouds form. In this paper, we carry out an observational analysis of two shallow fog clouds forming at cirrus-temperatures - that is, temperatures lower than 235 K - at Dome C, inner Antarctic Plateau. The combination of lidar profiles with temperature and humidity measurements from advanced thermo-hygrometers along a 45-m mast makes it possible to characterise the formation and development of the fog. High supersaturations with respect to ice are observed before the initiation of fog and the values attained suggest that the nucleation process at play is the homogeneous freezing of solution aerosol droplets. To our knowledge, this is the first time that in situ observations show that this nucleation pathway can be at the origin of an ice fog. Once nucleation occurs, the relative humidity gradually decreases down to subsaturated values with respect to ice in a few hours, likely owing to vapour deposition onto ice crystals and turbulent mixing. The development of fog is tightly coupled with the dynamics of the boundary-layer which, in the first study case, experiences a weak diurnal cycle while in the second case, transits from a very stable to a weakly stable dynamical regime. Overall, this paper highlights the potential of the site of Dome C for carrying out observational studies of cloud microphysical processes in natural conditions and using in-situ ground-based instruments.

Étienne Vignon et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-544', Anonymous Referee #1, 05 Jul 2022
  • RC2: 'Comment on egusphere-2022-544', Anonymous Referee #2, 26 Jul 2022

Étienne Vignon et al.

Étienne Vignon et al.

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Short summary
The near-surface atmosphere over the Antarctic Plateau is cold and pristine and resembles to a certain extent those of the high-troposphere where cirrus clouds form. In this study, we use innovative humidity measurements at Concordia station to study the formation of ice fogs at temperatures <-40 °C. We provide observational evidence that ice fogs can form through the homogeneous freezing of solution aerosols, a common nucleation pathway for cirrus clouds.