Ice nucleation by particles immersed in supercooled cloud droplets

Murray, Benjamin J.; O’Sullivan, Daniel; Atkinson, James; Webb, Michael E.

doi:10.1039/c2cs35200a

Cited by 1,082 publications

(1,526 citation statements)

References 332 publications

(700 reference statements)

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“…The glaciation of these clouds is ascribed to heterogeneous ice nucleation occurring on the foreign surfaces of ice-nucleating particles (INPs) present in the cloud droplets. Ice nucleation induced by particles located within the body of water or aqueous droplets is termed immersion freezing and is probably the most important nucleation process turning liquid droplets in relatively warm clouds into ice crystals (Murray et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…A number of field studies have demonstrated the dominant role of mineral dusts to nucleate ice in mixed phase clouds (Sassen et al, 2003;Ansmann et al, 2008;Pratt et al, 2009;Choi et al, 2010;Creamean et al, 2013) and possibly also in cirrus clouds (Cziczo et al, 2013). ATD is a commercial dust sample that has been used by many groups as a proxy of natural atmospheric mineral dust (Murray et al, 2012). It is a mixture of minerals with a considerable share of microcline, a K feldspar with a high ice nucleation ability as demonstrated in laboratory experiments (Atkinson et al, 2013;Zolles et al, 2015;Harrison et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Refreeze experiments with water droplets containing different types of ice nuclei interpreted by classical nucleation theory

et al. 2017

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Abstract. Homogeneous nucleation of ice in supercooled water droplets is a stochastic process. In its classical description, the growth of the ice phase requires the emergence of a critical embryo from random fluctuations of water molecules between the water bulk and ice-like clusters, which is associated with overcoming an energy barrier. For heterogeneous ice nucleation on ice-nucleating surfaces both stochastic and deterministic descriptions are in use. Deterministic (singular) descriptions are often favored because the temperature dependence of ice nucleation on a substrate usually dominates the stochastic time dependence, and the ease of representation facilitates the incorporation in climate models. Conversely, classical nucleation theory (CNT) describes heterogeneous ice nucleation as a stochastic process with a reduced energy barrier for the formation of a critical embryo in the presence of an ice-nucleating surface. The energy reduction is conveniently parameterized in terms of a contact angle α between the ice phase immersed in liquid water and the heterogeneous surface. This study investigates various ice-nucleating agents in immersion mode by subjecting them to repeated freezing cycles to elucidate and discriminate the time and temperature dependences of heterogeneous ice nucleation. Freezing rates determined from such refreeze experiments are presented for Hoggar Mountain dust, birch pollen washing water, Arizona test dust (ATD), and also nonadecanol coatings. For the analysis of the experimental data with CNT, we assumed the same active site to be always responsible for freezing. Three different CNT-based parameterizations were used to describe rate coefficients for heterogeneous ice nucleation as a function of temperature, all leading to very similar results: for Hoggar Mountain dust, ATD, and larger nonadecanol-coated water droplets, the experimentally determined increase in freezing rate with decreasing temperature is too shallow to be described properly by CNT using the contact angle α as the only fit parameter. Conversely, birch pollen washing water and small nonadecanol-coated water droplets show temperature dependencies of freezing rates steeper than predicted by all three CNT parameterizations. Good agreement of observations and calculations can be obtained when a pre-factor β is introduced to the rate coefficient as a second fit parameter. Thus, the following microphysical picture emerges: heterogeneous freezing occurs at ice-nucleating sites that need a minimum (critical) surface area to host embryos of critical size to grow into a crystal. Fits based on CNT suggest that the critical active site area is in the range of 10-50 nm 2 , with the exact value depending on sample, temperature, and CNT-based parameterization. Two fitting parameters are needed to characterize individual active sites. The contact angle α lowers the energy barrier that has to be overcome to form the critical embryo at the site compared to the homogeneous case where the critical embryo develops in the volume of water....

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Refreeze experiments with water droplets containing different types of ice nuclei interpreted by classical nucleation theory

et al. 2017

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“…Consequently, nucleation of water droplets and ice crystals in the atmosphere is a focus of a large body of research (Kärcher 2012;Murray et al 2012;Yakobi-Hancock et al 2013). Pure water droplets that contain no particulate matter do not form ice crystals at temperatures above −38°C.…”

Section: Introductionmentioning

confidence: 99%

Novel aerosol analysis approach for characterization of nanoparticulate matter in snow

Nazarenko

Rangel-Alvarado

Kos

et al. 2016

Environ Sci Pollut Res

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Tropospheric aerosols are involved in several key atmospheric processes: from ice nucleation, cloud formation, and precipitation to weather and climate. The impact of aerosols on these atmospheric processes depends on the chemical and physical characteristics of aerosol particles, and these characteristics are still largely uncertain. In this study, we developed a system for processing and aerosolization of melted snow in particle-free air, coupled with a real-time measurement of aerosol size distributions. The newly developed technique involves bringing snow-borne particles into an airborne state, which enables application of high-resolution aerosol analysis and sampling techniques. This novel analytical approach was compared to a variety of complementary existing analytical methods as applied for characterization of snow samples from remote sites in Alert (Canada) and Barrow (USA), as well as urban Montreal (Canada). The dry aerosol measurements indicated a higher abundance of particles of all sizes, and the 30 nm size dominated in aerosol size distributions for the Montreal samples, closely followed by Barrow, with about 30% fewer 30 nm particles, and about four times lower 30 nm particle abundance in Alert samples, where 15 nm particles were most abundant instead. The aerosolization technique, used together with nanoparticle tracking analysis and electron microscopy, allowed measurement of a wide size range of snow-borne particles in various environmental snow samples. Here, we discuss the application of the new technique to achieve better physicochemical understanding of atmospheric and snow processes. The results showed high sensitivity and reduction of particle aggregation, as well as the ability to measure a high-resolution snow-borne particle size distribution, including nanoparticulate matter in the range of 10 to 100 nm.

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“…3). Nominally, only one in a million particles can act as an INP at -20°C (39)(40)(41)(42)(43)(44)(45). If the temperature is reduced sufficiently, then all CCN can potentially act as sites for ice to form on by homogeneous freezing.…”

Section: Ice and Mixed-phase Cloudsmentioning

confidence: 99%

Improving our fundamental understanding of the role of aerosol−cloud interactions in the climate system

Seinfeld

Bretherton

Carslaw

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

591

474

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The effect of an increase in atmospheric aerosol concentrations on the distribution and radiative properties of Earth's clouds is the most uncertain component of the overall global radiative forcing from preindustrial time. General circulation models (GCMs) are the tool for predicting future climate, but the treatment of aerosols, clouds, and aerosol−cloud radiative effects carries large uncertainties that directly affect GCM predictions, such as climate sensitivity. Predictions are hampered by the large range of scales of interaction between various components that need to be captured. Observation systems (remote sensing, in situ) are increasingly being used to constrain predictions, but significant challenges exist, to some extent because of the large range of scales and the fact that the various measuring systems tend to address different scales. Fine-scale models represent clouds, aerosols, and aerosol−cloud interactions with high fidelity but do not include interactions with the larger scale and are therefore limited from a climatic point of view. We suggest strategies for improving estimates of aerosol−cloud relationships in climate models, for new remote sensing and in situ measurements, and for quantifying and reducing model uncertainty.climate | aerosol−cloud effects | general circulation models | radiative forcing | satellite observations Clouds play a key role in Earth's radiation budget, and aerosols serve as the seeds upon which cloud droplets form. Anthropogenic activity has led to an increase in aerosol particle concentrations globally and an increase in those particles that act as cloud condensation nuclei (CCN) and ice nucleating particles (INP). The effect of an increase in aerosols on cloud optical properties, and associated radiative forcing, is the most uncertain component of historical radiative forcing of Earth's climate caused by greenhouse gases (GHGs) and aerosols. The Intergovernmental Panel on Climate Change (IPCC) AR5 assessment of climate forcing factors (Fig. S1) ascribes "high" confidence to the estimate of direct aerosol radiative forcing (mean

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Ice nucleation by particles immersed in supercooled cloud droplets

Cited by 1,082 publications

References 332 publications

Refreeze experiments with water droplets containing different types of ice nuclei interpreted by classical nucleation theory

Refreeze experiments with water droplets containing different types of ice nuclei interpreted by classical nucleation theory

Novel aerosol analysis approach for characterization of nanoparticulate matter in snow

Improving our fundamental understanding of the role of aerosol−cloud interactions in the climate system

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