The role of ice nuclei recycling in the maintenance of cloud ice in Arctic mixed-phase stratocumulus

Abstract. This study investigates the maintenance of cloud ice production in Arctic mixed phase stratocumulus in large-eddy simulations that include a prognostic ice nuclei (IN) formulation and a diurnal cycle. Balances derived from a mixed-layer model and phase analyses are used to provide insight into buffering mechanisms that maintain ice in these cloud systems. We find that for the case under investigation, IN recycling through subcloud sublimation considerably prolongs ice production over a multi-day integration. This effective source of IN to the cloud dominates over mixing sources from above or below the cloud-driven mixed layer. Competing feedbacks between dynamical mixing and recycling are found to slow the rate of ice lost from the mixed layer when a diurnal cycle is simulated. The results of this study have important implications for maintaining phase partitioning of cloud ice and liquid that determine the radiative forcing of Arctic mixed-phase clouds.

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The role of ice nuclei recycling in the maintenance of cloud ice in Arctic mixed-phase stratocumulus

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-10631-2015 ◽

2015 ◽

Vol 15 (18) ◽

pp. 10631-10643 ◽

Cited By ~ 38

Author(s):

A. Solomon ◽

G. Feingold ◽

M. D. Shupe

Keyword(s):

Mixed Layer ◽

Diurnal Cycle ◽

Radiative Forcing ◽

Mixed Phase ◽

Phase Partitioning ◽

Ice Nuclei ◽

Large Eddy ◽

Ice Production ◽

Cloud Ice ◽

Mixed Phase Clouds

Abstract. This study investigates the maintenance of cloud ice production in Arctic mixed-phase stratocumulus in large eddy simulations that include a prognostic ice nuclei (IN) formulation and a diurnal cycle. Balances derived from a mixed-layer model and phase analyses are used to provide insight into buffering mechanisms that maintain ice in these cloud systems. We find that, for the case under investigation, IN recycling through subcloud sublimation considerably prolongs ice production over a multi-day integration. This effective source of IN to the cloud dominates over mixing sources from above or below the cloud-driven mixed layer. Competing feedbacks between dynamical mixing and recycling are found to slow the rate of ice lost from the mixed layer when a diurnal cycle is simulated. The results of this study have important implications for maintaining phase partitioning of cloud ice and liquid that determine the radiative forcing of Arctic mixed-phase clouds.

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Mid-latitude mixed-phase stratocumulus clouds and their interactions with aerosols: how ice processes affect microphysical, dynamic and thermodynamic development in those clouds and interactions?

10.5194/acp-2020-1318 ◽

2021 ◽

Author(s):

Seoung Soo Lee ◽

Kyung-Ja Ha ◽

Manguttathil Gopalakrishnan Manoj ◽

Mohammad Kamruzzaman ◽

Hyungjun Kim ◽

...

Keyword(s):

Water Vapor ◽

Cloud Condensation Nuclei ◽

Mixed Phase ◽

Eddy Simulation ◽

Ice Nuclei ◽

Large Eddy ◽

Stratocumulus Clouds ◽

Evaporation Of Droplets ◽

Cloud Ice ◽

Mixed Phase Clouds

Abstract. Mid-latitude mixed-phase stratocumulus clouds and their interactions with aerosols remain poorly understood. This study examines the roles of ice processes in those clouds and interactions using a large-eddy simulation (LES) framework. Cloud mass becomes much lower in the presence of ice processes and the Wegener-Bergeron-Findeisen (WBF) mechanism in the mixed-phase clouds as compared to that in warm clouds. This is because while the WBF mechanism enhances the evaporation of droplets, the low concentration of aerosols as ice nuclei (IN) and cloud ice number concentration (CINC) prevent the efficient deposition of water vapor whose mass is contributed by the evaporation. In the mixed-phase clouds, the increasing concentration of aerosols that act as cloud condensation nuclei (CCN) decreases cloud mass by increasing the evaporation of droplets through the WBF mechanism and decreasing the intensity of updrafts. In contrast to this, in the warm clouds, the absence of the WBF mechanism makes the increase in the evaporation of droplets inefficient, eventually enabling cloud mass to increase with the increasing concentration of aerosols as CCN. Here, the results show that when there is an increasing concentration of aerosols that act as IN, the deposition of water vapor is more efficient than when there is the increasing concentration of aerosols as CCN, which in turn enables cloud mass to increase in the mixed-phase clouds.

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The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase partitioning in Arctic mixed-phase stratocumulus clouds

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-17047-2018 ◽

2018 ◽

Vol 18 (23) ◽

pp. 17047-17059 ◽

Cited By ~ 12

Author(s):

Amy Solomon ◽

Gijs de Boer ◽

Jessie M. Creamean ◽

Allison McComiskey ◽

Matthew D. Shupe ◽

...

Keyword(s):

Cloud Condensation Nuclei ◽

Mixed Phase ◽

Radiative Properties ◽

Condensation Nuclei ◽

Phase Partitioning ◽

Cloud Dynamics ◽

Stratocumulus Clouds ◽

Cloud Ice ◽

Mixed Phase Clouds ◽

The Impact

Abstract. This study investigates the interactions between cloud dynamics and aerosols in idealized large-eddy simulations (LES) of Arctic mixed-phase stratocumulus clouds (AMPS) observed at Oliktok Point, Alaska, in April 2015. This case was chosen because it allows the cloud to form in response to radiative cooling starting from a cloud-free state, rather than requiring the cloud ice and liquid to adjust to an initial cloudy state. Sensitivity studies are used to identify whether there are buffering feedbacks that limit the impact of aerosol perturbations. The results of this study indicate that perturbations in ice nucleating particles (INPs) dominate over cloud condensation nuclei (CCN) perturbations; i.e., an equivalent fractional decrease in CCN and INPs results in an increase in the cloud-top longwave cooling rate, even though the droplet effective radius increases and the cloud emissivity decreases. The dominant effect of ice in the simulated mixed-phase cloud is a thinning rather than a glaciation, causing the mixed-phase clouds to radiate as a grey body and the radiative properties of the cloud to be more sensitive to aerosol perturbations. It is demonstrated that allowing prognostic CCN and INPs causes a layering of the aerosols, with increased concentrations of CCN above cloud top and increased concentrations of INPs at the base of the cloud-driven mixed layer. This layering contributes to the maintenance of the cloud liquid, which drives the dynamics of the cloud system.

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The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase-partitioning in Arctic Mixed-Phase Stratocumulus Clouds

10.5194/acp-2018-714 ◽

2018 ◽

Cited By ~ 1

Author(s):

Amy Solomon ◽

Gijs de Boer ◽

Jessie M. Creamean ◽

Allison McComiskey ◽

Matthew D. Shupe ◽

...

Keyword(s):

Cloud Condensation Nuclei ◽

Mixed Phase ◽

Radiative Properties ◽

Condensation Nuclei ◽

Phase Partitioning ◽

Cloud Dynamics ◽

Stratocumulus Clouds ◽

Cloud Ice ◽

Mixed Phase Clouds ◽

The Impact

Abstract. This study investigates the interactions between cloud dynamics and aerosols in idealized large-eddy simulations of an Arctic mixed-phase stratocumulus cloud observed at Oliktok Point, Alaska in April 2015. This case was chosen because it allows the cloud to form in response to radiative cooling starting from a cloud-free state, rather than requiring the cloud ice and liquid to adjust to an initial cloudy state. Sensitivity studies are used to identify whether there are buffering feedbacks that limit the impact of aerosol perturbations. The results of this study indicate that perturbations in ice nucleating particles (INPs) dominate over cloud condensation nuclei (CCN) perturbations, i.e., an equivalent fractional decrease in CCN and INPs results in an increase in the cloud-top longwave cooling rate, even though the droplet effective radius increases and the cloud emissivity decreases. The dominant effect of ice in the simulated mixed-phase cloud is a thinning rather than a glaciation, causing the mixed-phase clouds to radiate as a grey body and the radiative properties of the cloud to be more sensitive to aerosol perturbations. It is demonstrated that allowing prognostic CCN and INP causes a layering of the aerosols, with increased concentrations of CCN above cloud top and increased concentrations of INP at the base of the cloud-driven mixed-layer. This layering contributes to the maintenance of the cloud liquid, which drives the dynamics of the cloud system.

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The Effect of Ice Nuclei Efficiency on Arctic Mixed-Phase Clouds from Large-Eddy Simulations

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0112.1 ◽

2017 ◽

Vol 74 (12) ◽

pp. 3901-3913 ◽

Cited By ~ 8

Author(s):

Shizuo Fu ◽

Huiwen Xue

Keyword(s):

Simulation Analysis ◽

Mixed Phase ◽

Ice Formation ◽

Microphysics Scheme ◽

Large Eddy Simulation Model ◽

Eddy Simulation ◽

Ice Nuclei ◽

Large Eddy ◽

Bin Microphysics ◽

Mixed Phase Clouds

Abstract The effects of ice nuclei (IN) efficiency on the persistent ice formation in Arctic mixed-phase clouds (AMCs) are investigated using a large-eddy simulation model, coupled to a bin microphysics scheme with a prognostic IN formulation. In the three cases where the IN efficiency is high, ice formation and IN depletion are fast. When the IN concentration is 1 and 10 g−1, IN are completely depleted and the cloud becomes purely liquid phase before the end of the 24-h simulation. When the IN concentration is 100 g−1, the IN supply is sufficient but the liquid water is completely consumed so that the cloud dissipates quickly. In the three cases when the IN efficiency is low, ice formation is negligible in the first several hours but becomes significant as the temperature is decreased through longwave cooling. Before the end of the simulation, the cloud is in mixed phase when the IN concentration is 1 and 10 g−1 but dissipates when the IN concentration is 100 g−1. In the case where two types of IN are considered, ice formation persists throughout the simulation. Analysis shows that as the more efficient IN are continuously removed through ice formation, the less efficient IN gradually nucleate more ice crystals because the longwave cooling decreases the cloud temperature. This mechanism is further illustrated with a simple model. These results indicate that a spectrum of IN efficiency is necessary to maintain the persistent ice formation in AMCs.

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Midlatitude mixed-phase stratocumulus clouds and their interactions with aerosols: how ice processes affect microphysical, dynamic, and thermodynamic development in those clouds and interactions?

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-16843-2021 ◽

2021 ◽

Vol 21 (22) ◽

pp. 16843-16868

Author(s):

Seoung Soo Lee ◽

Kyung-Ja Ha ◽

Manguttathil Gopalakrishnan Manoj ◽

Mohammad Kamruzzaman ◽

Hyungjun Kim ◽

...

Keyword(s):

Water Vapor ◽

Cloud Condensation Nuclei ◽

Mixed Phase ◽

Spatiotemporal Variability ◽

Eddy Simulation ◽

Large Eddy ◽

Stratocumulus Clouds ◽

Evaporation Of Droplets ◽

Cloud Ice ◽

Mixed Phase Clouds

Abstract. Midlatitude mixed-phase stratocumulus clouds and their interactions with aerosols remain poorly understood. This study examines the roles of ice processes in those clouds and their interactions with aerosols using a large-eddy simulation (LES) framework. Cloud mass becomes much lower in the presence of ice processes and the Wegener–Bergeron–Findeisen (WBF) mechanism in the mixed-phase clouds compared to that in warm clouds. This is because while the WBF mechanism enhances the evaporation of droplets, the low concentration of aerosols acting as ice-nucleating particles (INPs) and cloud ice number concentration (CINC) prevent the efficient deposition of water vapor. Note that the INP concentration in this study is based on the observed spatiotemporal variability of aerosols. This results in the lower CINC compared to that with empirical dependence of the INP concentrations on temperature in a previous study. In the mixed-phase clouds, the increasing concentration of aerosols that act as cloud condensation nuclei (CCN) decreases cloud mass by increasing the evaporation of droplets through the WBF mechanism and decreasing the intensity of updrafts. In contrast to this, in the warm clouds, the absence of the WBF mechanism makes the increase in the evaporation of droplets inefficient, eventually enabling cloud mass to increase with the increasing concentration of aerosols acting as CCN. Here, the results show that when there is an increasing concentration of aerosols that act as INPs, the deposition of water vapor is more efficient than when there is the increasing concentration of aerosols acting as CCN, which in turn enables cloud mass to increase in the mixed-phase clouds.

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Aerosol Influence on Mixed-Phase Clouds in CAM-Oslo

Journal of the Atmospheric Sciences ◽

10.1175/2008jas2430.1 ◽

2008 ◽

Vol 65 (10) ◽

pp. 3214-3230 ◽

Cited By ~ 86

Author(s):

Trude Storelvmo ◽

Jón Egill Kristjánsson ◽

Ulrike Lohmann

Keyword(s):

General Circulation ◽

Cloud Microphysics ◽

Number Concentration ◽

Mixed Phase ◽

Ice Crystal ◽

Anthropogenic Aerosols ◽

Ice Nuclei ◽

New Treatment ◽

Cloud Ice ◽

Mixed Phase Clouds

A new treatment of mixed-phase cloud microphysics has been implemented in the general circulation model, Community Atmosphere Model (CAM)-Oslo, which combines the NCAR CAM2.0.1 and a detailed aerosol module. The new treatment takes into account the aerosol influence on ice phase initiation in stratiform clouds with temperatures between 0° and −40°C. Both supersaturation and cloud ice fraction, that is, the fraction of cloud ice compared to the total cloud water in a given grid box, are now determined based on a physical reasoning in which not only temperature but also the ambient aerosol concentration play a role. Included in the improved microphysics treatment is also a continuity equation for ice crystal number concentration. Ice crystal sources are heterogeneous and homogeneous freezing processes and ice multiplication. Sink terms are collection processes and precipitation formation, that is, melting and sublimation. Instead of using an idealized ice nuclei concentration for the heterogeneous freezing processes, a common approach in global models, the freezing processes are here dependent on the ability of the ambient aerosols to act as ice nuclei. Additionally, the processes are dependent on the cloud droplet number concentration and hence the aerosols’ ability to act as cloud condensation nuclei. Sensitivity simulations based on the new microphysical treatment of mixed-phase clouds are presented for both preindustrial and present-day aerosol emissions. Freezing efficiency is found to be highly sensitive to the amount of sulphuric acid available for ice nuclei coating. In the simulations, the interaction of anthropogenic aerosols and freezing mechanisms causes a warming of the earth–atmosphere system, counteracting the cooling effect of aerosols influencing warm clouds. The authors find that this reduction of the total aerosol indirect effect amounts to 50%–90% for the specific assumptions on aerosol properties used in this study. However, many microphysical processes in mixed-phase clouds are still poorly understood and the results must be interpreted with that in mind.

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Characterizing secondary ice production events in mixed-phase clouds using ground-based polarimetric radar

10.5194/egusphere-egu2020-12599 ◽

2020 ◽

Author(s):

Nicholas Kedzuf ◽

J. Christine Chiu ◽

Venkatachalam Chandrasekar ◽

Christopher Westbrook

Keyword(s):

Doppler Radar ◽

Radar Data ◽

Number Concentration ◽

Mixed Phase ◽

Polarimetric Radar ◽

Triple Frequency ◽

Ice Production ◽

The Uk ◽

Cloud Ice ◽

Mixed Phase Clouds

Secondary ice production processes are widely proposed as the pathway by which observed cloud ice number concentration can markedly exceed what is expected from primary ice nucleation alone. These processes play a critical, yet poorly constrained, role in the lifecycle of mixed-phase clouds. Presently, main constraints on secondary ice production come from airborne observations, but the transiency of such observations makes it difficult to paint a complete picture of these processes. Here, we develop a novel method for retrieving ice number concentration in a Lagrangian reference frame, allowing us to unearth information not accessible from existing aircraft observations. Our retrieval method employs an iterative ensemble approach, advanced ice crystal models, and the traditional suite of polarimetric radar observables. We will present examples from the Atmospheric Radiation Measurement (ARM) program Mobile Facility deployment in Finland and evaluations against in-situ observations from the UK Parameterizing Ice Clouds using Airborne obServationS and triple-frequency dOppler radar data (PICASSO) field campaign. We will also present a climatology of cloud ice number concentration from the Finland campaign, shedding light on the spatiotemporal evolution, process rates, and trigger requirements of secondary ice production events.

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Secondary ice production processes in wintertime alpine mixed-phase clouds

10.5194/acp-2021-760 ◽

2021 ◽

Author(s):

Paraskevi Georgakaki ◽

Georgia Sotiropoulou ◽

Étienne Vignon ◽

Anne-Claire Billault-Roux ◽

Alexis Berne ◽

...

Keyword(s):

Mixed Phase ◽

Ice Crystals ◽

Swiss Alps ◽

Blowing Snow ◽

Production Processes ◽

Break Up ◽

Ice Production ◽

Cloud Ice ◽

Droplet Shattering ◽

Mixed Phase Clouds

Abstract. Observations of orographic mixed-phase clouds (MPCs) have long shown that measured ice crystal number concentrations (ICNCs) can exceed the concentration of ice nucleating particles by orders of magnitude. Additionally, model simulations of alpine clouds are frequently found to underestimate the amount of ice compared with observations. Surface-based blowing snow, hoar frost and secondary ice production processes have been suggested as potential causes, but their relative importance and persistence remains highly uncertain. Here we study ice production mechanisms in wintertime orographic MPCs observed during the Cloud and Aerosol Characterization Experiment (CLACE) 2014 campaign at the Jungfraujoch site in the Swiss Alps with the Weather Research and Forecasting model (WRF). Simulations suggest that droplet shattering is not a significant source of ice crystals at this specific location – but break-up upon collisions between ice particles is quite active, elevating the predicted ICNCs by up to 3 orders of magnitude, which is consistent with observations. The initiation of the ice-ice collisional break-up mechanism is primarily associated with the occurrence of seeder-feeder events from higher precipitating cloud layers. The enhanced aggregation of snowflakes is found to drive secondary ice formation in the simulated clouds, the role of which is strengthened when the large hydrometeors interact with the primary ice crystals formed in the feeder cloud. Including a constant source of cloud ice crystals from blowing snow, through the action of the break-up mechanism, can episodically enhance ICNCs. Increases in secondary ice fragment generation can be counterbalanced by enhanced orographic precipitation, which seems to prevent explosive multiplication and cloud dissipation. These findings highlight the importance of secondary ice and "seeding" mechanisms – primarily falling ice from above and to a lesser degree blowing ice from the surface – which frequently enhance primary ice and determine the phase state and properties of MPCs.

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Modelling mixed-phase clouds with large-eddy model UCLALES-SALSA

10.5194/egusphere-egu2020-13448 ◽

2020 ◽

Cited By ~ 1

Author(s):

Jaakko Ahola ◽

Hannele Korhonen ◽

Juha Tonttila ◽

Sami Romakkaniemi ◽

Harri Kokkola ◽

...

Keyword(s):

Liquid Layer ◽

Cloud Model ◽

Ice Nucleation ◽

Mixed Phase ◽

Ice Nuclei ◽

Active Particles ◽

Large Eddy ◽

Ice Microphysics ◽

Intercomparison Study ◽

Mixed Phase Clouds

We have extended the large-eddy model UCLALES-SALSA (Tonttila et al., 2017) to include formation of ice and mixed-phase clouds. The model has exceptionally detailed aerosol description for both aerosol number and chemical composition. We confirmed the accuracy of newly implemented ice microphysics with a comparison to a previous mixed-phase cloud model intercomparison study.In a further simulation the model captured the typical layered structure of Arctic mixed-phase clouds: a liquid layer near cloud top and ice within and below the liquid layer. The simulation also demonstrated how larger droplets froze first. Moreover, the simulation showed realistic freezing rates of droplets within the vertical cloud structure. These characteristics were possible to capture with a heterogeneous ice nucleation scheme, where also ice nucleating particles (INP) are prognosed. Here, dust containing particles acted as INPs.The prognostic simulation showed the importance of the self-adjustment of ice nucleation active particles. This is in good agreement with an observational study where resilient mixed-phase clouds are seen together with relatively high ice nuclei concentrations.The implemented detailed sectional ice microphysics with prognostic aerosols is essentially important in reproducing the characteristics of mixed-phase clouds. The manuscript of this study is submitted for publication.

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