Preprints
https://doi.org/10.5194/acp-2020-1326
https://doi.org/10.5194/acp-2020-1326

  22 Feb 2021

22 Feb 2021

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

Sensitivity of precipitation formation to secondary ice production in winter orographic mixed-phase clouds

Zane Dedekind, Annika Lauber, Sylvaine Ferrachat, and Ulrike Lohmann Zane Dedekind et al.
  • Institute of Atmospheric and Climate Science, ETH Zurich, Switzerland

Abstract. The discrepancy between the observed concentration of ice nucleating particles (INPs) and the ice crystal number concentration (ICNC) remains unresolved and limits our understanding of ice formation and hence precipitation amount, location and intensity. Enhanced ice formation through secondary ice production (SIP) could be accounting for this discrepancy. Here, we present the results from a sensitivity model study in the Eastern Swiss Alps with additional simulated in-cloud SIP on precipitation formation and consequently on surface precipitation. The SIP processes considered include rime splintering, droplet shattering during freezing and breakup through ice-ice collisions. We simulated the passage of a cold front at Gotschnagrat, a peak at 2281 m above sea level (a.s.l.), on 7 March 2019 with COSMO, at a 1 km horizontal resolution, as part of the RACLETS field campaign in the Davos region in Switzerland. The largest simulated difference in the ICNC at the surface originated from the breakup simulations. Indeed, breakup caused a 1 to 3 order of magnitude increase in the ICNC compared to SIP from rime splintering or without SIP processes in the control simulations. The ICNCs from the collisional breakup simulations at Gotschnagrat were in better agreement with the ICNCs measured on a gondola near the surface. However, these simulations were not able to reproduce the ice crystal habits near the surface. Enhanced ICNCs from collisional breakup reduced localized regions of higher precipitation and thereby improving the model performance in terms of surface precipitation over the domain.

Zane Dedekind et al.

Status: open (until 19 Apr 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Zane Dedekind et al.

Data sets

Sensitivity of precipitation formation to secondary ice production in winter orographic mixed-phase clouds Zane Dedekind; Lauber Annika; Ferrachat Sylvaine; Lohmann Ulrike https://doi.org/10.5281/zenodo.4311566

Supplement for Sensitivity of precipitation formation to secondary ice production in winter orographic mixed-phase clouds Zane Dedekind; Lauber Annika; Ferrachat Sylvaine; Lohmann Ulrike https://doi.org/10.5281/zenodo.4316876

Model code and software

Software for Sensitivity of precipitation formation to secondary ice production in winter orographic mixed-phase clouds Zane Dedekind; Lauber Annika; Ferrachat Sylvaine; Lohmann Ulrike https://doi.org/10.5281/zenodo.4316922

Zane Dedekind et al.

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Short summary
The RACLETS campaign combined cloud and snow research to improve the understanding of precipitation formation in clouds. A numerical weather prediction model, COSMO, was used to assess the importance of ice crystal enhancement by ice-ice collisions on cloud properties. We found that the number of ice crystals increased 1 to 3 orders of magnitude when ice-ice collisions were permitted to occur reducing localized regions of high precipitation and thereby improving the model performance.
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