Preprints
https://doi.org/10.5194/acp-2022-69
https://doi.org/10.5194/acp-2022-69
11 Feb 2022
 | 11 Feb 2022
Status: this preprint was under review for the journal ACP. A final paper is not foreseen.

Measurements of ice crystal fluxes from the surface at a mountain top site

Waldemar Schledewitch, Gary Lloyd, Keith Bower, Thomas Choularton, Michael Flynn, and Martin Gallagher

Abstract. New observations of anomalously high cloud ice crystal concentrations at the Jungfraujoch research station (Switzerland, 3.5 km a.s.l.) are presented. High-resolution measurements of these ice crystals using a high-speed 2D imaging cloud particle spectrometer confirm that the concentrations far exceed those expected from any known primary ice production mechanisms and are at temperatures well below those for known secondary ice production processes to contribute. A detailed analysis of the cloud ice crystal sizes and habits with respect to wind speed and growth regimes confirms, as hypothesised in previous studies, that their origin is not due to blowing snow or related wind speed influences. As first hypothesised by Vali et al. (Vali et al., 2012) using remote sensing and by Lloyd et al., (2015) with in situ measurements, the most likely explanation is due to a strong surface source generated by the interaction of turbulent deposition of supercooled droplets to fragile ice-covered snow surfaces. This process enhances the detachment of crystal fragments wherein the smaller size mode is turbulently re-suspended even at low wind speeds below expected blowing snow thresholds. These then continue to grow, adding significantly to the ice crystal number concentrations whose size and habit is determined by the transport time between the ice crystal source and measurement location and liquid water profile within the cloud. We confirm, using eddy covariance measurements of ice particle number fluxes, that the likely source is significantly far upwind to preclude flow distortion effects such that the source plume has homogenised by the time they are measured at the mountain top summit.

This preprint has been withdrawn.

Waldemar Schledewitch, Gary Lloyd, Keith Bower, Thomas Choularton, Michael Flynn, and Martin Gallagher

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-69', Anonymous Referee #1, 15 Feb 2022
  • RC2: 'Comment on acp-2022-69', Anonymous Referee #2, 11 Mar 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-69', Anonymous Referee #1, 15 Feb 2022
  • RC2: 'Comment on acp-2022-69', Anonymous Referee #2, 11 Mar 2022
Waldemar Schledewitch, Gary Lloyd, Keith Bower, Thomas Choularton, Michael Flynn, and Martin Gallagher
Waldemar Schledewitch, Gary Lloyd, Keith Bower, Thomas Choularton, Michael Flynn, and Martin Gallagher

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This preprint has been withdrawn.

Short summary
Ice crystals on the surface of ice and snow covered terrain are thought to be transported into clouds that cover the surface. This has important implications for the properties of clouds in these regions. This research measured the potential transport of surface based ice crystals into the surrounding clouds at a mountain top site.
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