Preprints
https://doi.org/10.5194/egusphere-2024-2988
https://doi.org/10.5194/egusphere-2024-2988
27 Sep 2024
 | 27 Sep 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Arctic Multilayer Clouds Require Accurate Thermodynamic Profiles and Efficient Primary and Secondary Ice Processes for a Realistic Structure and Composition

Gabriella Wallentin, Annika Oertel, Luisa Ickes, Peggy Achtert, Matthias Tesche, and Corinna Hoose

Abstract. Multilayered clouds are frequent in the Arctic but their detailed analysis is underrepresented. Here, we simulate two cases observed during the 2019/2020 MOSAiC expedition using the ICosahedral Non-hydrostatic (ICON) model to explore the most accurate representation of these multilayer clouds. With a limited area setup, we investigate how cloud layers respond to perturbations in cloud droplet activation, primary ice, and secondary ice production (SIP). Using the measured aerosol concentration, we constrain our model through a new immersion freezing parameterisation. We find that multilayered clouds are challenging to simulate in remote areas without locally assimilated thermodynamics and that large-scale biases in the global forcing carry over to high-resolution simulations. Regarding cloud microphysics, warm-temperature ice nucleating particles (INP) are crucial to model mixed-phase clouds. However, constraining the model to the observed INPs is insufficient; a factor of 106 is required to reach observed ice mass concentrations, which is also achieved by including SIP. Breakup upon ice-ice collisions is explosive and can increase the integrated cloud ice number concentration by a factor of 105. Furthermore, the seeder-feeder mechanism significantly boosts snowfall by a factor of 103. An accurate representation of these microphysical processes is crucial to simulate multilayer clouds.

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Gabriella Wallentin, Annika Oertel, Luisa Ickes, Peggy Achtert, Matthias Tesche, and Corinna Hoose

Status: open (until 08 Nov 2024)

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Gabriella Wallentin, Annika Oertel, Luisa Ickes, Peggy Achtert, Matthias Tesche, and Corinna Hoose
Gabriella Wallentin, Annika Oertel, Luisa Ickes, Peggy Achtert, Matthias Tesche, and Corinna Hoose

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Short summary
Multilayer clouds are common in the Arctic but remain understudied. We use an atmospheric model to simulate multilayer cloud cases from the Arctic expedition MOSAiC 2019/2020. We find that it is complex to accurately model these cloud layers due to the lack of correct temperature and humidity profiles. The model also struggles to capture the observed cloud phase, the relative concentration of cloud droplets and cloud ice. We constrain our model to measured aerosols to mitigate this issue.