Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 5.509 IF 5.509
  • IF 5-year value: 5.689 IF 5-year 5.689
  • CiteScore value: 5.44 CiteScore 5.44
  • SNIP value: 1.519 SNIP 1.519
  • SJR value: 3.032 SJR 3.032
  • IPP value: 5.37 IPP 5.37
  • h5-index value: 86 h5-index 86
  • Scimago H index value: 161 Scimago H index 161
Discussion papers
https://doi.org/10.5194/acp-2018-829
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2018-829
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 22 Aug 2018

Research article | 22 Aug 2018

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Chemistry and Physics (ACP).

Direct evidence for secondary ice formation at around −15 °C in mixed-phase clouds

Claudia Mignani1, Jessie M. Creamean2,3, Lukas Zimmermann1, Christine Alewell1, and Franz Conen1 Claudia Mignani et al.
  • 1Institute of Environmental Geosciences, University of Basel, Basel, 4056, Switzerland
  • 2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
  • 3Physical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO 80305, USA

Abstract. Ice crystal numbers can exceed the numbers of ice-nucleating particles (INP) observed in mixed-phase clouds by several orders of magnitude also at temperatures that are colder than required for the Hallett-Mossop process (−3°C to −8°C). These observations provide circumstantial evidence of secondary ice formation. Attempting a more direct observational approach we made use of the fact that planar, branched snow crystals (e.g. dendrites) grow within a relatively narrow temperature range (about −12°C to −17°C) and can be analysed individually for INP using a field-suitable drop freezing assay technique. During February and March 2018, we analysed 190 dendritic crystals (an average of ∼3mm in size and between 1.3 to 7.6mm) deposited within mixed-phase clouds at the High Altitude Research Station Jungfraujoch (3580ma.s.l.), Switzerland. Overall, one in eight of these crystals contained an INP active at −17°C or warmer, while the remaining seven of eight most likely resulted from secondary ice formation within the clouds. The ice multiplication factor we observed was small (8), but relatively stable throughout the course of the experiment. These measurements show that secondary ice can be observed at temperatures around −15 °C in the atmosphere and thus advance our understanding of the extent of secondary ice formation in mixed-phase clouds, even where the multiplication factor is smaller than 10.

Claudia Mignani et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Login for Authors/Co-Editors] [Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
Claudia Mignani et al.
Claudia Mignani et al.
Viewed  
Total article views: 408 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
291 114 3 408 15 3 5
  • HTML: 291
  • PDF: 114
  • XML: 3
  • Total: 408
  • Supplement: 15
  • BibTeX: 3
  • EndNote: 5
Views and downloads (calculated since 22 Aug 2018)
Cumulative views and downloads (calculated since 22 Aug 2018)
Viewed (geographical distribution)  
Total article views: 408 (including HTML, PDF, and XML) Thereof 406 with geography defined and 2 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Cited  
Saved  
No saved metrics found.
Discussed  
No discussed metrics found.
Latest update: 19 Nov 2018
Publications Copernicus
Download
Short summary
Observed discrepancies in number concentrations of ice crystals and ice-nucleating particles (INP) provide indirect evidence of secondary ice formation. In this study we made use of the fact that dendritic crystals grow within a narrow temperature range (−12 to −17 °C) and can be analysed individually for INP. Overall, we found that one in eight of the analysed crystals contained an INP. These measurements show directly that secondary ice formation can occur at temperatures around −15 °C.
Observed discrepancies in number concentrations of ice crystals and ice-nucleating particles...
Citation
Share