11 Feb 2022
11 Feb 2022
Status: this preprint is currently under review for the journal ACP.

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

Waldemar Schledewitch1,a, Gary Lloyd1,2, Keith Bower1, Thomas Choularton1, Michael Flynn1, and Martin Gallagher1 Waldemar Schledewitch et al.
  • 1Department of Earth and Environmental Sciences, School of Natural Sciences University of Manchester, M13 9PL
  • 2National Centre for Atmospheric Science, University of Manchester
  • anow at: Max Planck Institute for Chemistry, Particle Chemistry Department, Mainz, Germany

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.

Waldemar Schledewitch 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 acp-2022-69', Anonymous Referee #1, 15 Feb 2022
  • RC2: 'Comment on acp-2022-69', Anonymous Referee #2, 11 Mar 2022

Waldemar Schledewitch et al.

Waldemar Schledewitch et al.


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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.