Preprints
https://doi.org/10.5194/egusphere-2025-3620
https://doi.org/10.5194/egusphere-2025-3620
06 Oct 2025
 | 06 Oct 2025
Status: this preprint is open for discussion and under review for Geoscientific Model Development (GMD).

Prognostic simulations of mixed-phase clouds with model 1D-AC v1.0: The impact of freezing parameterizations on ice crystal budgets

Yijia Sun, Ann M. Fridlind, Israel Silber, Nicole Riemer, and Daniel A. Knopf

Abstract. Mixed-phase clouds at high latitudes contribute to the uncertainty in predicting cloud feedbacks and climate sensitivity, mainly due to the complexity of microphysical processes that influence the partitioning between the supercooled liquid and ice phases, and hence, cloud radiative effects on regional scales. Particularly in Arctic mixed-phase clouds, the activation of ice-nucleating particles (INPs) from various aerosol populations remains a leading source of uncertainty. Our study employs a one-dimensional aerosol-cloud model informed by large-eddy simulations to probe the impact of INP representation on predicted ice crystal number concentrations (𝑁i) and ice crystal budgets in mixed-phase Arctic stratus. We apply three immersion freezing (IMF) parameterizations, two time-independent (deterministic) and one time-dependent (classical nucleation theory), to predict the evolution of the INP reservoir and resulting ice crystal budget from polydisperse mineral dust, organic (humic-like substances), and sea spray aerosol particle size distributions. Our analysis focuses on how variations in aerosol number concentration and cloud system parameters such as cloud cooling rate, cloud-top entrainment rate, and ice crystal fall speed influence the INP reservoir and ice crystal budgets. Furthermore, this study investigates the competitive ice nucleation dynamics in mixed aerosol environments and provides a process-level quantification of the INP budget terms, which directly controls ice crystal budgets. For all studied case scenarios, the aerosol types and associated particle size distributions significantly impact INP and 𝑁i, and the choice between a time-dependent and a deterministic freezing description yields orders-of-magnitude differences in the predicted INP and 𝑁i over the 10 h simulation time, reflecting typical cloud lifetimes. Our results show that the influence of cloud cooling, INP entrainment, and sedimentation varies significantly depending on the chosen freezing parameterization. These findings underscore the critical need for robust IMF parameterizations and precise cloud system observations to enhance the accuracy of models in predicting mixed-phase cloud structure and evolution.

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Yijia Sun, Ann M. Fridlind, Israel Silber, Nicole Riemer, and Daniel A. Knopf

Status: open (until 01 Dec 2025)

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Yijia Sun, Ann M. Fridlind, Israel Silber, Nicole Riemer, and Daniel A. Knopf

Data sets

Output data from simulations supporting "Prognostic simulations of mixed-phase clouds with model 1D-AC v1.0: The impact of freezing parameterizations on ice crystal budgets" Sun, Y., Fridlind, A., Silber, I., Riemer, N., Knopf, D. A. https://doi.org/10.5281/zenodo.16413525

Model code and software

Model code and sensitivity tests supporting "Prognostic simulations of mixed-phase clouds with model 1D-AC v1.0: The impact of freezing parameterizations on ice crystal budgets" Sun, Y., Fridlind, A., Silber, I., Riemer, N., Knopf, D. A. https://doi.org/10.5281/zenodo.16414825

Analysis scripts and figure generation code supporting "Prognostic simulations of mixed-phase clouds with model 1D-AC v1.0: The impact of freezing parameterizations on ice crystal budgets" Sun, Y., Fridlind, A., Silber, I., Riemer, N., Knopf, D. A. https://doi.org/10.5281/zenodo.16414282

Yijia Sun, Ann M. Fridlind, Israel Silber, Nicole Riemer, and Daniel A. Knopf
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Latest update: 06 Oct 2025
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Short summary
The role of Arctic clouds in the regional climate remains uncertain due to insufficient understanding of the amount of liquid droplets and ice crystals present in these clouds. An aerosol-cloud model is employed to examine the role of different aerosol types and freezing parameterizations on the number of ice crystals. The choice of freezing parameterization significantly changes the number of ice crystals impacting the interpretation of the evolution and warming effect of Arctic clouds.
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