Ice formation in Arctic mixed‐phase clouds: Insights from a 3‐D cloud‐resolving model with size‐resolved aerosol and cloud microphysics

Fan, Jiwen; Ovtchinnikov, Mikhail; Comstock, J. M.; McFarlane, Sally A.; Хаин, А.

doi:10.1029/2008jd010782

Cited by 104 publications

(137 citation statements)

References 99 publications

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“…This feedback loop is referred to from here on as "recycling". Recycling was found to be significant in large eddy simulations (LES) of a single-layer stratocumulus observed during the Department of Energy Atmospheric Radiation Measurement Program's Mixed-Phase Arctic Cloud Experiment (M-PACE; Verlinde et al, 2007;Fan et al, 2009). AMPS observed during M-PACE formed due to a cold-air outbreak, where large fluxes of heat and moisture over the open ocean forced turbulent roll clouds that were coupled to the surface layer.…”

Section: A Solomon Et Al: the Role Of Ice Nuclei Recyclingmentioning

confidence: 99%

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

Solomon¹,

Feingold²,

Shupe³

2015

Atmos. Chem. Phys.

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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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Section: A Solomon Et Al: the Role Of Ice Nuclei Recyclingmentioning

confidence: 99%

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

Solomon¹,

Feingold²,

Shupe³

2015

Atmos. Chem. Phys.

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“…Phase-dependent microphysical processes such as collision, coalescence, aggregation, riming and secondary ice formation (e.g., HallettMossop ice multiplication) determine the growth and shape of the ice particles in mixed-phase Arctic clouds (Pruppacher and Klett, 2010). Nucleation, growth, and sedimentation processes of ice crystals are still not comprehensively understood which leads to discrepancies between observed and modeled ice number concentrations (Fan et al, 2009;Morrison et al, 2008;Avramov et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Arctic low-level boundary layer clouds: in situ measurements and simulations of mono- and bimodal supercooled droplet size distributions at the top layer of liquid phase clouds

et al. 2015

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Abstract. Aircraft borne optical in situ size distribution measurements were performed within Arctic boundary layer clouds with a special emphasis on the cloud top layer during the VERtical Distribution of Ice in Arctic clouds (VERDI) campaign in April and May 2012. An instrumented Basler BT-67 research aircraft operated out of Inuvik over the Mackenzie River delta and the Beaufort Sea in the Northwest Territories of Canada. Besides the cloud particle and hydrometeor size spectrometers the aircraft was equipped with instrumentation for aerosol, radiation and other parameters. Inside the cloud, droplet size distributions with monomodal shapes were observed for predominantly liquid-phase Arctic stratocumulus. With increasing altitude inside the cloud the droplet mean diameters grew from 10 to 20 µm. In the upper transition zone (i.e., adjacent to the cloud-free air aloft) changes from monomodal to bimodal droplet size distributions (Mode 1 with 20 µm and Mode 2 with 10 µm diameter) were observed. It is shown that droplets of both modes coexist in the same (small) air volume and the bimodal shape of the measured size distributions cannot be explained as an observational artifact caused by accumulating data point populations from different air volumes. The formation of the second size mode can be explained by (a) entrainment and activation/condensation of fresh aerosol particles, or (b) by differential evaporation processes occurring with cloud droplets engulfed in different eddies. Activation of entrained particles seemed a viable possibility as a layer of dry Arctic enhanced background aerosol (which was detected directly above the stratus cloud) might form a second mode of small cloud droplets. However, theoretical considerations and model calculations (adopting direct numerical simulation, DNS) revealed that, instead, turbulent mixing and evaporation of larger droplets are the most likely reasons for the formation of the second droplet size mode in the uppermost region of the clouds.

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“…Contact freezing might eventually explain the discrepancy between the measured number of ice nuclei (IN) and observed number concentration of ice crystals in a cloud (Avramov et al, 2011;Fridlind et al, 2007). Experimental findings suggest that contact freezing efficiency (i.e., the probability of a supercooled droplet freezing on a single contact with the IN) is a function of the temperature of the supercooled droplet and the size of the contacting particle, but the comprehensive characterization of potential contact ice nuclei in the relevant temperature range is still missing (Fan et al, 2009). Currently, no theory exists that would allow for even qualitative prediction of the IN efficiency (in any freezing mode) given the chemical structure and morphology of the IN particle.…”

Section: Introductionmentioning

confidence: 99%

Experimental quantification of contact freezing in an electrodynamic balance

et al. 2013

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Heterogeneous nucleation of ice in a supercooled water droplet induced by external contact with a dry aerosol particle has long been known to be more effective than freezing induced by the same nucleus immersed in the droplet. However, the experimental quantification of contact freezing is challenging. Here we report an experimental method to determine the temperature-dependent ice nucleation probability of size-selected aerosol particles. The method is based on the suspension of supercooled charged water droplets in a laminar flow of air containing aerosol particles as contact freezing nuclei. The rate of droplet–particle collisions is calculated numerically with account for Coulomb attraction, drag force and induced dipole interaction between charged droplet and aerosol particles. The calculation is verified by direct counting of aerosol particles collected by a levitated droplet. By repeating the experiment on individual droplets for a sufficient number of times, we are able to reproduce the statistical freezing behavior of a large ensemble of supercooled droplets and measure the average rate of freezing events. The freezing rate is equal to the product of the droplet–particle collision rate and the probability of freezing on a single contact, the latter being a function of temperature, size and composition of the contact ice nuclei. Based on these observations, we show that for the types of particles investigated so far, contact freezing is the dominating freezing mechanism on the timescale of our experiment

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Ice formation in Arctic mixed‐phase clouds: Insights from a 3‐D cloud‐resolving model with size‐resolved aerosol and cloud microphysics

Cited by 104 publications

References 99 publications

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

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

Arctic low-level boundary layer clouds: in situ measurements and simulations of mono- and bimodal supercooled droplet size distributions at the top layer of liquid phase clouds

Experimental quantification of contact freezing in an electrodynamic balance

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