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Sample records for heterogeneous ice nucleation

  1. Heterogeneous nucleation of ice on carbon surfaces.

    PubMed

    Lupi, Laura; Hudait, Arpa; Molinero, Valeria

    2014-02-26

    Atmospheric aerosols can promote the heterogeneous nucleation of ice, impacting the radiative properties of clouds and Earth's climate. The experimental investigation of heterogeneous freezing of water droplets by carbonaceous particles reveals widespread ice freezing temperatures. It is not known which structural and chemical characteristics of soot account for the variability in ice nucleation efficiency. Here we use molecular dynamics simulations to investigate the nucleation of ice from liquid water in contact with graphitic surfaces. We find that atomically flat carbon surfaces promote heterogeneous nucleation of ice, while molecularly rough surfaces with the same hydrophobicity do not. Graphitic surfaces and other surfaces that promote ice nucleation induce layering in the interfacial water, suggesting that the order imposed by the surface on liquid water may play an important role in the heterogeneous nucleation mechanism. We investigate a large set of graphitic surfaces of various dimensions and radii of curvature and find that variations in nanostructures alone could account for the spread in the freezing temperatures of ice on soot in experiments. We conclude that a characterization of the nanostructure of soot is needed to predict its ice nucleation efficiency.

  2. Heterogeneous nucleation of ice from supercooled water

    NASA Astrophysics Data System (ADS)

    Seeley, Lane Howard

    The relaxation of a metastable phase via the formation of a critical domain of the corresponding stable phase is a phenomenon that has been studied extensively in condensed matter physics. This dissertation describes laboratory studies of this phenomenon in the context of ice nucleation from undercooled liquid water. Such a study presents unique experimental challenges because the formation of a critical embryo is a statistical event, and once it occurs the entire sample relaxes to the stable phase. In order to study this statistical process it is necessary to create a large ensemble of separate, yet identical, domains of the metastable phase. The design of an apparatus is described which creates such an ensemble, in time, by repeatedly freezing and thawing a single water drop. This apparatus allows for the collection of a large data set and therefore can identify subtle changes in nucleation statistics that are produced by external controls. This dissertation describes a series of experiments intended to probe several aspects of ice nucleation. Results are presented for homogeneous ice nucleation as well as heterogeneous ice nucleation by; silanized and unsilanized glass, aliphatic alcohol Langmuir films, ionizing radiation, electric fields and motion at the three phase contact line. These experiments are analyzed largely in the context of classical nucleation theory. The unique experimental technique described here allows for sensitive tests of the temperature dependent nucleation rates, R( T), in these systems. Analysis of the R( T) within the context of classical nucleation theory constrains thermodynamic parameters and provides insight into these nucleation processes.

  3. Glassy aerosols heterogeneously nucleate cirrus ice particles

    NASA Astrophysics Data System (ADS)

    Wilson, Theodore W.; Murray, Benjamin J.; Dobbie, Steven; Cui, Zhiqiang; Al-Jumur, Sardar M. R. K.; Möhler, Ottmar; Schnaiter, Martin; Wagner, Robert; Benz, Stefan; Niemand, Monika; Saathoff, Harald; Ebert, Volker; Wagner, Steven; Kärcher, Bernd

    2010-05-01

    Ice clouds in the tropical tropopause layer (TTL, ~12-18 km, ~180-200 K) play a key role in dehydrating air entering the stratosphere. However, in-situ measurements show that air within these clouds is unexpectedly supersaturated(1); normally the growth of ice crystals rapidly quenches any supersaturation. A number of explanations for high in-cloud humidity have been put forward, but recent research suggests high humidity may be related to the low numbers of ice crystals found within these clouds(1). Low ice number densities can be produced through selective nucleation by a small subset of aerosol particles. This is inconsistent with homogeneous nucleation of ice in liquid aerosols. However, droplets rich in organic material, ubiquitous in the TTL, are known to become glassy (amorphous, non-crystalline solid) under TTL conditions(2,3). Here we show, using a large cloud simulation chamber, that glassy solution droplets nucleate ice heterogeneously at low supersaturations. Using a one-dimensional cirrus model we also show that nucleation by glassy aerosol in the TTL may explain low TTL ice number densities and high in-cloud humidity. Recent measurements of the composition of TTL cirrus residues are consistent with our findings(4). (1) Krämer, M. et al. Ice supersaturations and cirrus cloud crystal numbers. Atm. Chem. Phys. 9, 3505-3522 (2009). (2) Murray, B. J. Inhibition of ice crystallisation in highly viscous aqueous organic acid droplets. Atm. Chem. Phys. 8, 5423-5433 (2008). (3) Zobrist, B., Marcolli, C., Pedernera, D. A. & Koop, T. Do atmospheric aerosols form glasses? Atm. Chem. Phys. 8, 5221-5244 (2008). (4) Froyd, K. D., Murphy, D. M., Lawson, P., Baumgardner, D. & Herman, R. L. Aerosols that form subvisible cirrus at the tropical tropopause. Atmos. Chem. Phys. 10, 209-218 (2010).

  4. Heterogeneous ice nucleation: bridging stochastic and singular freezing behavior

    NASA Astrophysics Data System (ADS)

    Niedermeier, D.; Shaw, R. A.; Hartmann, S.; Wex, H.; Clauss, T.; Voigtländer, J.; Stratmann, F.

    2011-01-01

    Heterogeneous ice nucleation, a primary pathway for ice formation in the atmosphere, has been described alternately as being stochastic, in direct analogy with homogeneous nucleation, or singular, with ice nuclei initiating freezing at deterministic temperatures. We present an idealized model that bridges these stochastic and singular descriptions of heterogeneous ice nucleation. This "soccer ball" model treats statistically similar particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in our research groups. We suggest that ice nucleation is fundamentally a stochastic process but that for realistic atmospheric particle populations this process can be masked by the heterogeneity of surface properties. Full evaluation of the model will require experiments with well characterized ice nucleating particles and the ability to vary both temperature and waiting time for freezing.

  5. Enhanced heterogeneous ice nucleation by special surface geometry

    PubMed Central

    Bi, Yuanfei; Cao, Boxiao; Li, Tianshu

    2017-01-01

    The freezing of water typically proceeds through impurity-mediated heterogeneous nucleation. Although non-planar geometry generically exists on the surfaces of ice nucleation centres, its role in nucleation remains poorly understood. Here we show that an atomically sharp, concave wedge can further promote ice nucleation with special wedge geometries. Our molecular analysis shows that significant enhancements of ice nucleation can emerge both when the geometry of a wedge matches the ice lattice and when such lattice match does not exist. In particular, a 45° wedge is found to greatly enhance ice nucleation by facilitating the formation of special topological defects that consequently catalyse the growth of regular ice. Our study not only highlights the active role of defects in nucleation but also suggests that the traditional concept of lattice match between a nucleation centre and crystalline lattice should be extended to include a broader match with metastable, non-crystalline structural motifs. PMID:28513603

  6. Enhanced heterogeneous ice nucleation by special surface geometry

    NASA Astrophysics Data System (ADS)

    Bi, Yuanfei; Cao, Boxiao; Li, Tianshu

    2017-05-01

    The freezing of water typically proceeds through impurity-mediated heterogeneous nucleation. Although non-planar geometry generically exists on the surfaces of ice nucleation centres, its role in nucleation remains poorly understood. Here we show that an atomically sharp, concave wedge can further promote ice nucleation with special wedge geometries. Our molecular analysis shows that significant enhancements of ice nucleation can emerge both when the geometry of a wedge matches the ice lattice and when such lattice match does not exist. In particular, a 45° wedge is found to greatly enhance ice nucleation by facilitating the formation of special topological defects that consequently catalyse the growth of regular ice. Our study not only highlights the active role of defects in nucleation but also suggests that the traditional concept of lattice match between a nucleation centre and crystalline lattice should be extended to include a broader match with metastable, non-crystalline structural motifs.

  7. Heterogeneous nucleation of ice in the atmosphere

    NASA Astrophysics Data System (ADS)

    Nicosia, A.; Piazza, M.; Santachiara, G.; Belosi, F.

    2017-05-01

    The occurrence of ice-nucleating aerosols in the atmosphere has a profound impact on the properties of clouds, and in turn, influences our understanding on weather and climate. Research on this topic has grown constantly over the last decades, driven by advances in online and offline instruments capable of measuring the characteristics of these cloud-modifying aerosol particles. This article presents different aspects to the understanding of how aerosol particles can trigger the nucleation of ice in clouds. In addition, we present some experimental results obtained with the Dynamic Filter Processing Chamber, an off-line instrument that has been applied extensively in the last years and that circumvents some of the problems related to the measurement of Ice Nucleating Particles properties.

  8. Molecular simulations of heterogeneous ice nucleation. I. Controlling ice nucleation through surface hydrophilicity

    SciTech Connect

    Cox, Stephen J.; Kathmann, Shawn M.; Slater, B.; Michaelides, Angelos

    2015-05-14

    Ice formation is one of the most common and important processes on earth and almost always occurs at the surface of a material. A basic understanding of how the physicochemical properties of a material’s surface affect its ability to form ice has remained elusive. Here, we use molecular dynamics simulations to directly probe heterogeneous ice nucleation at a hexagonal surface of a nanoparticle of varying hydrophilicity. Surprisingly, we find that structurally identical surfaces can both inhibit and promote ice formation and analogous to a chemical catalyst, it is found that an optimal interaction between the surface and the water exists for promoting ice nucleation.We use our microscopic understanding of the mechanism to design a modified surface in silico with enhanced ice nucleating ability. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

  9. Comparison of parameterizations for homogeneous and heterogeneous ice nucleation

    NASA Astrophysics Data System (ADS)

    Koop, T.; Zobrist, B.

    2009-04-01

    The formation of ice particles from liquid aqueous aerosols is of central importance for the physics and chemistry of high altitude clouds. In this paper, we present new laboratory data on ice nucleation and compare them with two different parameterizations for homogeneous as well as heterogeneous ice nucleation. In particular, we discuss and evaluate the effect of solutes and ice nuclei. One parameterization is the λ-approach which correlates the depression of the freezing temperature of aqueous droplets in comparison to pure water droplets, Tf, with the corresponding depression, Tm, of the equilibrium ice melting point: Tf = λ × Tm. Here, λ is independent of concentration and a constant that is specific for a particular solute or solute/ice nucleus combination. The other approach is water-activity-based ice nucleation theory which describes the effects of solutes on the freezing temperature Tf via their effect on water activity: aw(Tf) = awi(Tf) + aw. Here, awi is the water activity of ice and aw is a constant that depends on the ice nucleus but is independent of the type of solute. We present new data on both homogeneous and heterogeneous ice nucleation with varying types of solutes and ice nuclei. We evaluate and discuss the advantages and limitations of the two approaches for the prediction of ice nucleation in laboratory experiments and atmospheric cloud models.

  10. Heterogeneous nucleation of ice on model carbon surfaces

    NASA Astrophysics Data System (ADS)

    Molinero, V.; Lupi, L.; Hudait, A.

    2014-12-01

    Carbonaceous particles account for 10% of the particulate matter in the atmosphere. The experimental investigation of heterogeneous freezing of water droplets by carbonaceous particles reveals widespread ice freezing temperatures. The origin of the soot and its oxidation and aging modulate its ice nucleation ability, however, it is not known which structural and chemical characteristics of soot account for the variability in ice nucleation efficiency. We find that atomically flat carbon surfaces promote heterogeneous nucleation of ice, while molecularly rough surfaces with the same hydrophobicity do not. We investigate a large set of graphitic surfaces of various dimensions and radii of curvature consistent with those of soot in experiments, and find that variations in nanostructures alone could account for the spread in the freezing temperatures of ice on soot in experiments. A characterization of the nanostructure of soot is needed to predict its ice nucleation efficiency. Atmospheric oxidation and aging of soot modulates its ice nucleation ability. It has been suggested that an increase in the ice nucleation ability of aged soot results from an increase in the hydrophilicity of the surfaces upon oxidation. Oxidation, however, also impacts the nanostructure of soot, making it difficult to assess the separate effects of soot nanostructure and hydrophilicity in experiments. We investigate the effect of changes in hydrophilicity of model graphitic surfaces on the freezing temperature of ice. Our results indicate that the hydrophilicity of the surface is not in general a good predictor of ice nucleation ability. We find a correlation between the ability of a surface to promote nucleation of ice and the layering of liquid water at the surface. The results of this work suggest that ordering of liquid water in contact with the surface plays an important role in the heterogeneous ice nucleation mechanism. References: L. Lupi, A. Hudait and V. Molinero, J. Am. Chem. Soc

  11. Advances in heterogeneous ice nucleation research: Theoretical modeling and measurements

    NASA Astrophysics Data System (ADS)

    Beydoun, Hassan

    In the atmosphere, cloud droplets can remain in a supercooled liquid phase at temperatures as low as -40 °C. Above this temperature, cloud droplets freeze via heterogeneous ice nucleation whereby a rare and poorly understood subset of atmospheric particles catalyze the ice phase transition. As the phase state of clouds is critical in determining their radiative properties and lifetime, deficiencies in our understanding of heterogeneous ice nucleation poses a large uncertainty on our efforts to predict human induced global climate change. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established model and parameterizations that accurately predict heterogeneous ice nucleation. Conversely, the sparsity of reliable measurement techniques available struggle to be interpreted by a single consistent theoretical or empirical framework, which results in layers of uncertainty when attempting to extrapolate useful information regarding ice nucleation for use in atmospheric cloud models. In this dissertation a new framework for describing heterogeneous ice nucleation is developed. Starting from classical nucleation theory, the surface of an ice nucleating particle is treated as a continuum of heterogeneous ice nucleating activity and a particle specific distribution of this activity g is derived. It is hypothesized that an individual particle species exhibits a critical surface area. Above this critical area the ice nucleating activity of a particle species can be described by one g distribution, g, while below it g expresses itself expresses externally resulting in particle to particle variability in ice nucleating activity. The framework is supported by cold plate droplet freezing measurements for dust and biological particles in which the total surface area of particle material available is varied. Freezing spectra above a certain surface area

  12. Ice nucleation on carbon surface supports the classical theory for heterogeneous nucleation

    NASA Astrophysics Data System (ADS)

    Cabriolu, Raffaela; Li, Tianshu

    2015-05-01

    The prevalence of heterogeneous nucleation in nature was explained qualitatively by the classical theory for heterogeneous nucleation established over more than 60 years ago, but the quantitative validity and the key conclusions of the theory have remained unconfirmed. Employing the forward flux sampling method and the coarse-grained water model (mW), we explicitly computed the heterogeneous ice nucleation rates in the supercooled water on a graphitic surface at various temperatures. The independently calculated ice nucleation rates were found to fit well according to the classical theory for heterogeneous nucleation. The fitting procedure further yields the estimate of the potency factor, which measures the ratio of the heterogeneous nucleation barrier to the homogeneous nucleation barrier. Remarkably, the estimated potency factor agrees quantitatively with the volumetric ratio of the critical nuclei between the heterogeneous and homogeneous nucleation. Our numerical study thus provides a strong support to the quantitative power of the theory and allows understanding ice nucleation behaviors under the most relevant freezing conditions.

  13. Alteration of Heterogeneous Ice Nucleation Properties Induced by Particle Aging

    NASA Astrophysics Data System (ADS)

    Sullivan, R. C.; Polen, M.; Beydoun, H.; Lawlis, E.; Ahern, A.; Jahn, L.; Hill, T. C. J.

    2015-12-01

    Aerosol particles that can serve as ice nuclei frequently experience rapid and extensive chemical aging during atmospheric transport. This is known to significantly alter some ice nucleation modes of the few types of ice nucleation particle systems where aging effects have been simulated, such as for mineral dust. Yet much of our understanding of atmospheric particle freezing properties is derived from measurements of fresh or unaged particles. We know almost nothing regarding how atmospheric aging might alter the freezing properties of biomass burning aerosol or biological particle nucleants. We have investigated the effects of simulated aging using a chamber reactor on the heterogeneous ice nucleation properties of biomass burning aerosol (BBA) and ice-active bacteria particles. Some types of aging were found to enhance the freezing ability of BBA, exhibited as a shift in a portion of the droplet freezing curve to warmer temperatures by a few °C. Ice-active bacteria were found to consistently loose their most ice-active nucleants after repeated aging cycles. The bacterial systems always retained significantly efficient ice active sites that still allowed them to induce freezing at mild/warm temperatures, despite this decrease in freezing ability. A comprehensive series of online single-particle mass spectrometry and offline spectromicroscopic analysis of individual particles was used to determine how the aging altered the aerosol's composition, and gain mechanistic insights into how this in turn altered the freezing properties. Our new ice nucleation framework that uses a continuous distribution of ice active site ability (contact angle) was used to interpret the droplet freezing spectra and understand how aging alters the internal and external variability, and rigidity, of the ice active sites.

  14. The microscopic features of heterogeneous ice nucleation may affect the macroscopic morphology of atmospheric ice crystals.

    PubMed

    Cox, Stephen J; Raza, Zamaan; Kathmann, Shawn M; Slater, Ben; Michaelides, Angelos

    2013-01-01

    It is surprisingly difficult to freeze water. Almost all ice that forms under "mild" conditions (temperatures > -40 degrees C) requires the presence of a nucleating agent--a solid particle that facilitates the freezing process--such as clay mineral dust, soot or bacteria. In a computer simulation, the presence of such ice nucleating agents does not necessarily alleviate the difficulties associated with forming ice on accessible timescales. Nevertheless, in this work we present results from molecular dynamics simulations in which we systematically compare homogeneous and heterogeneous ice nucleation, using the atmospherically important clay mineral kaolinite as our model ice nucleating agent. From our simulations, we do indeed find that kaolinite is an excellent ice nucleating agent but that contrary to conventional thought, non-basal faces of ice can nucleate at the basal face of kaolinite. We see that in the liquid phase, the kaolinite surface has a drastic effect on the density profile of water, with water forming a dense, tightly bound first contact layer. Monitoring the time evolution of the water density reveals that changes away from the interface may play an important role in the nucleation mechanism. The findings from this work suggest that heterogeneous ice nucleating agents may not only enhance the ice nucleation rate, but also alter the macroscopic structure of the ice crystals that form.

  15. Critical humidities of homogeneous and heterogeneous ice nucleation: Inferences from extended classical nucleation theory

    NASA Astrophysics Data System (ADS)

    Khvorostyanov, Vitaly I.; Curry, Judith A.

    2009-02-01

    A generalization of classical ice nucleation theory is used to derive analytical expressions for the critical (threshold) humidities of homogeneous and heterogeneous freezing. The critical radius and energy of an ice embryo and nucleation rates were derived previously by the authors as functions of temperature, pressure, water saturation ratio, and radii of freezing particles. Here we invert the analytical expressions for the nucleation rates and solve them relative to the critical water and ice saturation ratios (or critical relative humidities). The critical humidities are expressed as analytical functions of temperature, pressure, nucleation or cooling rates, radius of freezing particles and their physico-chemical properties, misfit strain, and activation energy. Calculations of critical ice relative humidities are made using these equations over an extended temperature range down to -75°C and are compared with previous empirical parameterizations and experimental data, and differences are interpreted in the context of variation of the other parameters. It is shown that the critical humidities for heterogeneous ice nucleation are lower than those for homogeneous nucleation; however, this difference is not constant but depends substantially on the temperature and properties of freezing aerosol. Some simple parameterizations for cloud and climate models are suggested.

  16. Heterogeneous ice nucleation of mineral dust particles exposed to ozone

    NASA Astrophysics Data System (ADS)

    Kanji, Zamin A.; Welti, André; Chou, Cédric; Stetzer, Olaf; Lohmann, Ulrike

    2013-05-01

    Deposition and immersion mode ice nucleation studies of kaolinite (Ka) and Arizona Test Dust (ATD) particles exposed to ozone at 430 ppbv, 1.4 and 4.3 ppmv for approximately 2 hours in a stainless steel aerosol tank are presented. The polydisperse particles used have a mode mobility diameter of 800 nm for Ka and 400 nm for ATD. The portable ice nucleation chamber (PINC) and immersion chamber (IMCA-ZINC) were used to study deposition and immersion mode ice nucleation respectively. Both instruments sampled through a particle impactor with a diameter cut-off size of 1 μm. Preliminary results indicate that ice nucleation can be enhanced or inhibited depending on ozone concentration used for the ageing process with higher concentrations suppressing ice nucleation in both immersion and deposition modes. Additionally, Ka and ATD respond differently to the ageing process and to the different modes of ice nucleation. Ozone surface coverage and initial uptake coefficients are presented for the low exposure studies to explain the ice nucleation behavior observed. Ice Active Surface Site Densities (IASSD) are presented as a means of comparison and parameterization of the data to predict potential atmospheric ice nuclei (IN) concentrations.

  17. Heterogeneous ice nucleation of α-pinene SOA particles before and after ice cloud processing

    NASA Astrophysics Data System (ADS)

    Wagner, Robert; Höhler, Kristina; Huang, Wei; Kiselev, Alexei; Möhler, Ottmar; Mohr, Claudia; Pajunoja, Aki; Saathoff, Harald; Schiebel, Thea; Shen, Xiaoli; Virtanen, Annele

    2017-05-01

    The ice nucleation ability of α-pinene secondary organic aerosol (SOA) particles was investigated at temperatures between 253 and 205 K in the Aerosol Interaction and Dynamics in the Atmosphere cloud simulation chamber. Pristine SOA particles were nucleated and grown from pure gas precursors and then subjected to repeated expansion cooling cycles to compare their intrinsic ice nucleation ability during the first nucleation event with that observed after ice cloud processing. The unprocessed α-pinene SOA particles were found to be inefficient ice-nucleating particles at cirrus temperatures, with nucleation onsets (for an activated fraction of 0.1%) as high as for the homogeneous freezing of aqueous solution droplets. Ice cloud processing at temperatures below 235 K only marginally improved the particles' ice nucleation ability and did not significantly alter their morphology. In contrast, the particles' morphology and ice nucleation ability was substantially modified upon ice cloud processing in a simulated convective cloud system, where the α-pinene SOA particles were first activated to supercooled cloud droplets and then froze homogeneously at about 235 K. As evidenced by electron microscopy, the α-pinene SOA particles adopted a highly porous morphology during such a freeze-drying cycle. When probing the freeze-dried particles in succeeding expansion cooling runs in the mixed-phase cloud regime up to 253 K, the increase in relative humidity led to a collapse of the porous structure. Heterogeneous ice formation was observed after the droplet activation of the collapsed, freeze-dried SOA particles, presumably caused by ice remnants in the highly viscous material or the larger surface area of the particles.

  18. Ice nucleation in nature: supercooling point (SCP) measurements and the role of heterogeneous nucleation.

    PubMed

    Wilson, P W; Heneghan, A F; Haymet, A D J

    2003-02-01

    In biological systems, nucleation of ice from a supercooled aqueous solution is a stochastic process and always heterogeneous. The average time any solution may remain supercooled is determined only by the degree of supercooling and heterogeneous nucleation sites it encounters. Here we summarize the many and varied definitions of the so-called "supercooling point," also called the "temperature of crystallization" and the "nucleation temperature," and exhibit the natural, inherent width associated with this quantity. We describe a new method for accurate determination of the supercooling point, which takes into account the inherent statistical fluctuations of the value. We show further that many measurements on a single unchanging sample are required to make a statistically valid measure of the supercooling point. This raises an interesting difference in circumstances where such repeat measurements are inconvenient, or impossible, for example for live organism experiments. We also discuss the effect of solutes on this temperature of nucleation. Existing data appear to show that various solute species decrease the nucleation temperature somewhat more than the equivalent melting point depression. For non-ionic solutes the species appears not to be a significant factor whereas for ions the species does affect the level of decrease of the nucleation temperature.

  19. Heterogeneous ice nucleation: exploring the transition from stochastic to singular freezing behavior

    NASA Astrophysics Data System (ADS)

    Niedermeier, D.; Shaw, R. A.; Hartmann, S.; Wex, H.; Clauss, T.; Voigtländer, J.; Stratmann, F.

    2011-08-01

    Heterogeneous ice nucleation, a primary pathway for ice formation in the atmosphere, has been described alternately as being stochastic, in direct analogy with homogeneous nucleation, or singular, with ice nuclei initiating freezing at deterministic temperatures. We present an idealized, conceptual model to explore the transition between stochastic and singular ice nucleation. This "soccer ball" model treats particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in our research groups. Even with ice nucleation treated fundamentally as a stochastic process this process can be masked by the heterogeneity of surface properties, as might be typical for realistic atmospheric particle populations. Full evaluation of the model findings will require experiments with well characterized ice nucleating particles and the ability to vary both temperature and waiting time for freezing.

  20. The Theory of Ice Nucleation by Heterogeneous Freezing of Deliquescent Mixed CCN. Part I: Critical Radius, Energy, and Nucleation Rate.

    NASA Astrophysics Data System (ADS)

    Khvorostyanov, Vitaly I.; Curry, Judith A.

    2004-11-01

    This paper extends previous work on the theory of heterogenous ice nucleation. The goals of this analysis are to explain empirical observations of ice nucleation and to provide a suitable framework for modeling and parameterizing the ice nucleation process in cloud-scale and large-scale atmospheric models. Considered are the processes of heterogeneous freezing of deliquescent mixed cloud condensation nuclei that may serve as ice nuclei, and the properties of an ice germ critical radius, energy, and nucleation rate of ice crystals are examined as functions of temperature and supersaturation. Expressions for nucleation in a polydisperse aerosol for the deliquescence-freezing mode are developed. Equations are derived for the threshold and critical saturation ratios as functions of temperature and nucleation rate, and for the threshold and critical temperatures as functions of saturation ratio. Equivalence of the new formulation for the freezing point depression with traditional expressions is shown and the concepts of the effective temperature and supercooling are introduced. These new formulations are used in a companion paper for simulations of ice nucleation using a cloud parcel model.


  1. Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K

    SciTech Connect

    Wang, Bingbing; Laskin, Alexander; Roedel, Tobias R.; Gilles, Marry K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

    2012-09-25

    Atmospheric ice formation induced by particles with complex chemical and physical properties through heterogeneous nucleation is not well understood. Heterogeneous ice nucleation and water uptake by ambient particles collected from urban environments in Los Angeles and Mexico City are presented. Using a vapour controlled cooling system equipped with an optical microscopy, the range of onset conditions for ice nucleation and water uptake by the collected particles was determined as a function of temperature (200{273 K) and relative humidity with respect to ice (RHice) up to water saturation. Three distinctly different types of authentic atmospheric particles were investigated including soot particles associated with organics/inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn containing inorganic particles apportioned to anthropogenic emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption ne structure spectroscopy (STXM/NEXAFS). Above 230 K, signicant differences in water uptake and immersion freezing effciencies of the different particle types were observed. Below 230 K, the particles exhibited high deposition ice nucleation effciencies and formed ice at RHice values well below homogeneous ice nucleation limits. The data show that the chemical composition of these eld{collected particles plays an important role in determining water uptake and immersion freezing. Heterogeneous ice nucleation rate coeffcients, cumulative ice nuclei (IN) spectrum, and IN activated fraction for deposition ice nucleation are derived. The presented ice nucleation data demonstrate that anthropogenic and marine particles comprising of various chemical and physical properties exhibit distinctly different ice

  2. Heterogeneous formation of polar stratospheric clouds - Part 2: Nucleation of ice on synoptic scales

    NASA Astrophysics Data System (ADS)

    Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Hoyle, C. R.; Grooß, J.-U.; Dörnbrack, A.; Peter, T.

    2013-04-01

    This paper provides unprecedented evidence for the importance of heterogeneous nucleation, likely on solid particles of meteoritic origin, and of small-scale temperature fluctuations, for the formation of ice particles in the Arctic stratosphere. During January 2010, ice PSCs (Polar Stratospheric Clouds) were shown by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) to have occurred on a synoptic scale (~ 1000 km dimension). CALIPSO observations also showed widespread PSCs containing nitric acid trihydrate (NAT) particles in December 2009, prior to the occurrence of synoptic-scale regions of ice PSCs during mid-January 2010. We demonstrate by means of detailed microphysical modeling along air parcel trajectories that the formation of these PSCs is not readily reconciled with expectations from the conventional understanding of PSC nucleation mechanisms. The measurements are at odds with the previous laboratory-based understanding of PSC formation, which deemed direct heterogeneous nucleation of NAT and ice on preexisting solid particles unlikely. While a companion paper (Part 1) addresses the heterogeneous nucleation of NAT during December 2009, before the existence of ice PSCs, this paper shows that also the large-scale occurrence of stratospheric ice in January 2010 cannot be explained merely by homogeneous ice nucleation but requires the heterogeneous nucleation of ice, e.g. on meteoritic dust or preexisting NAT particles. The required efficiency of the ice nuclei is surprisingly high, namely comparable to that of known tropospheric ice nuclei such as mineral dust particles. To gain model agreement with the ice number densities inferred from observations, the presence of small-scale temperature fluctuations, with wavelengths unresolved by the numerical weather prediction models, is required. With the derived rate parameterization for heterogeneous ice nucleation we are able to explain and reproduce CALIPSO observations throughout the

  3. Heterogeneous formation of polar stratospheric clouds - Part 2: Nucleation of ice on synoptic scales

    NASA Astrophysics Data System (ADS)

    Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Hoyle, C. R.; Grooß, J.-U.; Dörnbrack, A.; Peter, T.

    2013-11-01

    This paper provides compelling evidence for the importance of heterogeneous nucleation, likely on solid particles of meteoritic origin, and of small-scale temperature fluctuations, for the formation of ice particles in the Arctic stratosphere. During January 2010, ice PSCs (polar stratospheric clouds) were shown by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) to have occurred on a synoptic scale (~1000 km dimension). CALIPSO observations also showed widespread PSCs containing NAT (nitric acid trihydrate) particles in December 2009, prior to the occurrence of synoptic-scale regions of ice PSCs during mid-January 2010. We demonstrate by means of detailed microphysical modeling along air parcel trajectories that the formation of these PSCs is not readily reconciled with expectations from the conventional understanding of PSC nucleation mechanisms. The measurements are at odds with the previous laboratory-based understanding of PSC formation, which deemed direct heterogeneous nucleation of NAT and ice on preexisting solid particles unlikely. While a companion paper (Part 1) addresses the heterogeneous nucleation of NAT during December 2009, before the existence of ice PSCs, this paper shows that also the large-scale occurrence of stratospheric ice in January 2010 cannot be explained merely by homogeneous ice nucleation but requires the heterogeneous nucleation of ice, e.g. on meteoritic dust or preexisting NAT particles. The required efficiency of the ice nuclei is surprisingly high, namely comparable to that of known tropospheric ice nuclei such as mineral dust particles. To gain model agreement with the ice number densities inferred from observations, the presence of small-scale temperature fluctuations, with wavelengths unresolved by the numerical weather prediction models, is required. With the derived rate parameterization for heterogeneous ice nucleation we are able to explain and reproduce CALIPSO observations throughout the

  4. Molecular simulations of heterogeneous ice nucleation. II. Peeling back the layers

    NASA Astrophysics Data System (ADS)

    Cox, Stephen J.; Kathmann, Shawn M.; Slater, Ben; Michaelides, Angelos

    2015-05-01

    Coarse grained molecular dynamics simulations are presented in which the sensitivity of the ice nucleation rate to the hydrophilicity of a graphene nanoflake is investigated. We find that an optimal interaction strength for promoting ice nucleation exists, which coincides with that found previously for a face centered cubic (111) surface. We further investigate the role that the layering of interfacial water plays in heterogeneous ice nucleation and demonstrate that the extent of layering is not a good indicator of ice nucleating ability for all surfaces. Our results suggest that to be an efficient ice nucleating agent, a surface should not bind water too strongly if it is able to accommodate high coverages of water.

  5. Molecular Simulations of Heterogeneous Ice Nucleation. II. Peeling back the Layers

    SciTech Connect

    Cox, Stephen J.; Kathmann, Shawn M.; Slater, B.; Michaelides, Angelos

    2015-05-14

    Coarse grained molecular dynamics simulations are presented in which the sensitivity of the ice nucleation rate to the hydrophilicity of a graphene nanoflake is investigated. We find that an optimal interaction strength for promoting ice nucleation exists, which coincides with that found previously for a face centered cubic (111) surface. We further investigate the role that the layering of interfacial water plays in heterogeneous ice nucleation and demonstrate that the extent of layering is not a good indicator of ice nucleating ability for all surfaces. Our results suggest that to be an efficient ice nucleating agent, a surface should not bind water too strongly if it is able to accommodate high coverages of water.

  6. Modelling heterogeneous ice nucleation on mineral dust and soot with parameterizations based on laboratory experiments

    NASA Astrophysics Data System (ADS)

    Hoose, C.; Hande, L. B.; Mohler, O.; Niemand, M.; Paukert, M.; Reichardt, I.; Ullrich, R.

    2016-12-01

    Between 0 and -37°C, ice formation in clouds is triggered by aerosol particles acting as heterogeneous ice nuclei. At lower temperatures, heterogeneous ice nucleation on aerosols can occur at lower supersaturations than homogeneous freezing of solutes. In laboratory experiments, the ability of different aerosol species (e.g. desert dusts, soot, biological particles) has been studied in detail and quantified via various theoretical or empirical parameterization approaches. For experiments in the AIDA cloud chamber, we have quantified the ice nucleation efficiency via a temperature- and supersaturation dependent ice nucleation active site density. Here we present a new empirical parameterization scheme for immersion and deposition ice nucleation on desert dust and soot based on these experimental data. The application of this parameterization to the simulation of cirrus clouds, deep convective clouds and orographic clouds will be shown, including the extension of the scheme to the treatment of freezing of rain drops. The results are compared to other heterogeneous ice nucleation schemes. Furthermore, an aerosol-dependent parameterization of contact ice nucleation is presented.

  7. BINARY: an optical freezing array for assessing temperature and time dependence of heterogeneous ice nucleation

    NASA Astrophysics Data System (ADS)

    Budke, C.; Koop, T.

    2015-02-01

    A new optical freezing array for the study of heterogeneous ice nucleation in microliter-sized droplets is introduced, tested and applied to the study of immersion freezing in aqueous Snomax® suspensions. In the Bielefeld Ice Nucleation ARraY (BINARY) ice nucleation can be studied simultaneously in 36 droplets at temperatures down to -40 °C (233 K) and at cooling rates between 0.1 and 10 K min-1. The droplets are separated from each other in individual compartments, thus preventing a Wegener-Bergeron-Findeisen type water vapor transfer between droplets as well as avoiding the seeding of neighboring droplets by formation and surface growth of frost halos. Analysis of freezing and melting occurs via an automated real-time image analysis of the optical brightness of each individual droplet. As an application ice nucleation in water droplets containing Snomax® at concentrations from 1 ng mL-1 to 1 mg mL-1 was investigated. Using different cooling rates, a small time dependence of ice nucleation induced by two different classes of ice nucleators (INs) contained in Snomax® was detected and the corresponding heterogeneous ice nucleation rate coefficient was quantified. The observed time dependence is smaller than those of other types of INs reported in the literature, suggesting that the BINARY setup is suitable for quantifying time dependence for most other INs of atmospheric interest, making it a useful tool for future investigations.

  8. Heterogeneous nucleation of ice on anthropogenic organic particles collected in Mexico City

    SciTech Connect

    Knopf, D.A.; Wang, B.; Laskin, A.; Moffet, R.C.; Gilles, M.K.

    2010-06-20

    This study reports on heterogeneous ice nucleation activity of predominantly organic (or coated with organic material) anthropogenic particles sampled within and around the polluted environment of Mexico City. The onset of heterogeneous ice nucleation was observed as a function of particle temperature (Tp), relative humidity (RH), nucleation mode, and particle chemical composition which is influenced by photochemical atmospheric aging. Particle analyses included computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). In contrast to most laboratory studies employing proxies of organic aerosol, we show that anthropogenic organic particles collected in Mexico City can potentially induce ice nucleation at experimental conditions relevant to cirrus formation. The results suggest a new precedent for the potential impact of organic particles on ice cloud formation and climate.

  9. Heterogeneous Nucleation of Ice on Anthropogenic Organic Particles Collected in Mexico City

    SciTech Connect

    Knopf, Daniel A.; Wang, BingBing; Laskin, Alexander; Moffet, Ryan C.; Gilles, Marry K.

    2010-06-05

    This study reports on heterogeneous ice nucleation activity of predominantly organic or coated with organic material anthropogenic particles sampled within and around the polluted environment of Mexico City. The onset of heterogeneous ice nucleation was observed as a function of particle temperature (Tp), relative humidity (RH), nucleation mode, and chemical composition of particles influenced by their photochemical atmospheric aging. Particle analyses was conducted using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). In contrast to the majority of laboratory studies employing proxies of organic aerosol, we show that anthropogenic organic particles collected in Mexico City have can potentially induce ice nucleation at experimental conditions relevant to cirrus formation. The reported results suggest a new paradigm for the potential impact of organic particles on ice cloud formation and climate.

  10. Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K

    NASA Astrophysics Data System (ADS)

    Wang, Bingbing; Laskin, Alexander; Roedel, Tobias; Gilles, Mary K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

    2011-11-01

    Ice formation induced by atmospheric particles through heterogeneous nucleation is not well understood. Onset conditions for heterogeneous ice nucleation and water uptake by particles collected in Los Angeles and Mexico City were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). Four dominant particle types were identified including soot associated with organics, soot with organic and inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn-containing particles apportioned to emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Above 230 K, significant differences in onsets of water uptake and immersion freezing of different particle types were observed. Below 230 K, particles exhibited high deposition ice nucleation efficiencies and formed ice atRHicewell below homogeneous ice nucleation limits. The data suggest that water uptake and immersion freezing are more sensitive to changes in particle chemical composition compared to deposition ice nucleation. The data demonstrate that anthropogenic and marine influenced particles, exhibiting various chemical and physical properties, possess distinctly different ice nucleation efficiencies and can serve as efficient IN at atmospheric conditions typical for cirrus and mixed-phase clouds.

  11. Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K

    NASA Astrophysics Data System (ADS)

    Wang, Bingbing; Laskin, Alexander; Roedel, Tobias; Gilles, Mary K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

    2012-09-01

    Ice formation induced by atmospheric particles through heterogeneous nucleation is not well understood. Onset conditions for heterogeneous ice nucleation and water uptake by particles collected in Los Angeles and Mexico City were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). Four dominant particle types were identified including soot associated with organics, soot with organic and inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn-containing particles apportioned to emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Above 230 K, significant differences in onsets of water uptake and immersion freezing of different particle types were observed. Below 230 K, particles exhibited high deposition ice nucleation efficiencies and formed ice atRHicewell below homogeneous ice nucleation limits. The data suggest that water uptake and immersion freezing are more sensitive to changes in particle chemical composition compared to deposition ice nucleation. The data demonstrate that anthropogenic and marine influenced particles, exhibiting various chemical and physical properties, possess distinctly different ice nucleation efficiencies and can serve as efficient IN at atmospheric conditions typical for cirrus and mixed-phase clouds.

  12. What makes a good descriptor for heterogeneous ice nucleation on OH-patterned surfaces

    NASA Astrophysics Data System (ADS)

    Pedevilla, Philipp; Fitzner, Martin; Michaelides, Angelos

    2017-09-01

    Freezing of water is arguably one of the most common phase transitions on Earth and almost always happens heterogeneously. Despite its importance, we lack a fundamental understanding of what makes substrates efficient ice nucleators. Here we address this by computing the ice nucleation (IN) ability of numerous model hydroxylated substrates with diverse surface hydroxyl (OH) group arrangements. Overall, for the substrates considered, we find that neither the symmetry of the OH patterns nor the similarity between a substrate and ice correlate well with the IN ability. Instead, we find that the OH density and the substrate-water interaction strength are useful descriptors of a material's IN ability. This insight allows the rationalization of ice nucleation ability across a wide range of materials and can aid the search and design of novel potent ice nucleators in the future.

  13. A technique for quantifying heterogeneous ice nucleation in microlitre supercooled water droplets

    NASA Astrophysics Data System (ADS)

    Whale, T. F.; Murray, B. J.; O'Sullivan, D.; Umo, N. S.; Baustian, K. J.; Atkinson, J. D.; Morris, G. J.

    2014-09-01

    The ice content of mixed phase clouds, which contain both supercooled water and ice, affects both their lifetime and radiative properties. In many clouds, the formation of ice requires the presence of particles capable of nucleating ice. One of the most important features of ice nucleating particles (INPs) is that they are rare in comparison to cloud condensation nuclei. However, the fact that only a small fraction of aerosol particles can nucleate ice means that detection and quantification of INPs is challenging. This is particularly true at temperatures above about -20 °C since the population of particles capable of serving as INPs decreases dramatically with increasing temperature. In this paper, we describe an experimental technique in which droplets of microlitre volume containing ice nucleating material are cooled down at a controlled rate and their freezing temperatures recorded. The advantage of using large droplet volumes is that the surface area per droplet is vastly larger than in experiments focused on single aerosol particles or cloud-sized droplets. This increases the probability of observing the effect of less common, but important, high temperature INPs and therefore allows the quantification of their ice nucleation efficiency. The potential artefacts which could influence data from this experiment, and other similar experiments, are mitigated and discussed. Experimentally determined heterogeneous ice nucleation efficiencies for K-feldspar (microcline), kaolinite, chlorite, Snomax®, and silver iodide are presented.

  14. Heterogeneous ice nucleation of viscous secondary organic aerosol produced from ozonolysis of α-pinene

    NASA Astrophysics Data System (ADS)

    Ignatius, Karoliina; Kristensen, Thomas B.; Järvinen, Emma; Nichman, Leonid; Fuchs, Claudia; Gordon, Hamish; Herenz, Paul; Hoyle, Christopher R.; Duplissy, Jonathan; Garimella, Sarvesh; Dias, Antonio; Frege, Carla; Höppel, Niko; Tröstl, Jasmin; Wagner, Robert; Yan, Chao; Amorim, Antonio; Baltensperger, Urs; Curtius, Joachim; Donahue, Neil M.; Gallagher, Martin W.; Kirkby, Jasper; Kulmala, Markku; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Tomé, Antonio; Virtanen, Annele; Worsnop, Douglas; Stratmann, Frank

    2016-05-01

    There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate heterogeneous ice nucleation and thus influence cloud properties. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles. The SOA particles were produced from the ozone initiated oxidation of α-pinene in an aerosol chamber at temperatures in the range from -38 to -10 °C at 5-15 % relative humidity with respect to water to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. The ice nucleation ability of SOA particles with different sizes was investigated with a new continuous flow diffusion chamber. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA for ice saturation ratios between 1.3 and 1.4 significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between -39.0 and -37.2 °C ranged from 6 to 20 % and did not depend on the particle surface area. Global modelling of monoterpene SOA particles suggests that viscous biogenic SOA particles are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nucleating particle budget.

  15. Chemical processing does not always impair heterogeneous ice nucleation of mineral dust particles

    NASA Astrophysics Data System (ADS)

    Sullivan, R. C.; Demott, P. J.; Prenni, A. J.; Minambres, L.; Kreidenweis, S. M.; Moehler, O.

    2010-12-01

    Mineral dust particles are the most abundant heterogeneous ice nuclei in the atmosphere. They also frequently become mixed with secondary material during atmospheric transport. The effect that such atmospheric processing has on the ice nucleation properties of dust particles remains under investigation. We have studied changes in the ice nucleation ability of various mineral dust sources after exposure to nitric acid in an aerosol flow tube, and after heterogeneous nucleation of α-pinene secondary organic aerosol (SOA) in the AIDA cloud expansion chamber. Both chemical treatments altered and homogenized the dust particles’ heterogeneous ice nucleation properties below water-saturation, but had no apparent impact on the immersion-freezing fraction well above water saturation. The fraction of particles capable of nucleating ice at fixed mixed-phase cloud temperatures between -35 and -15 °C was determined using a continuous flow diffusion chamber (CFDC) as the relative humidity with respect to water (RHw) was scanned from 75% to 110% RHw. Exposure to both nitric acid and SOA impaired essentially all ice nucleation in the deposition-regime below water saturation, while causing the onset of condensation-freezing to occur in a step-wise manner over a small range of RHw just below water saturation. We interpret this as the result of an increase in particle hygroscopicity following chemical treatment. This allows the mineral particles to absorb enough water to overcome solute freezing point depression effects and nucleate ice via condensation-freezing at a slightly smaller and narrower range of RHw than the less hygroscopic untreated dust can. Immersion-freezing above water saturation was not affected by either treatment. This is in stark contrast to earlier experiments where dust was exposed to sulfuric acid from a heated vapor source; ice nucleation was notably impaired in both the deposition and immersion-freezing regimes following sulfuric acid treatment.

  16. The Many Faces of Heterogeneous Ice Nucleation: Interplay Between Surface Morphology and Hydrophobicity.

    PubMed

    Fitzner, Martin; Sosso, Gabriele C; Cox, Stephen J; Michaelides, Angelos

    2015-10-28

    What makes a material a good ice nucleating agent? Despite the importance of heterogeneous ice nucleation to a variety of fields, from cloud science to microbiology, major gaps in our understanding of this ubiquitous process still prevent us from answering this question. In this work, we have examined the ability of generic crystalline substrates to promote ice nucleation as a function of the hydrophobicity and the morphology of the surface. Nucleation rates have been obtained by brute-force molecular dynamics simulations of coarse-grained water on top of different surfaces of a model fcc crystal, varying the water-surface interaction and the surface lattice parameter. It turns out that the lattice mismatch of the surface with respect to ice, customarily regarded as the most important requirement for a good ice nucleating agent, is at most desirable but not a requirement. On the other hand, the balance between the morphology of the surface and its hydrophobicity can significantly alter the ice nucleation rate and can also lead to the formation of up to three different faces of ice on the same substrate. We have pinpointed three circumstances where heterogeneous ice nucleation can be promoted by the crystalline surface: (i) the formation of a water overlayer that acts as an in-plane template; (ii) the emergence of a contact layer buckled in an ice-like manner; and (iii) nucleation on compact surfaces with very high interaction strength. We hope that this extensive systematic study will foster future experimental work aimed at testing the physiochemical understanding presented herein.

  17. A technique for quantifying heterogeneous ice nucleation in microlitre supercooled water droplets

    NASA Astrophysics Data System (ADS)

    Whale, T. F.; Murray, B. J.; O'Sullivan, D.; Wilson, T. W.; Umo, N. S.; Baustian, K. J.; Atkinson, J. D.; Workneh, D. A.; Morris, G. J.

    2015-06-01

    In many clouds, the formation of ice requires the presence of particles capable of nucleating ice. Ice-nucleating particles (INPs) are rare in comparison to cloud condensation nuclei. However, the fact that only a small fraction of aerosol particles can nucleate ice means that detection and quantification of INPs is challenging. This is particularly true at temperatures above about -20 °C since the population of particles capable of serving as INPs decreases dramatically with increasing temperature. In this paper, we describe an experimental technique in which droplets of microlitre volume containing ice-nucleating material are cooled down at a controlled rate and their freezing temperatures recorded. The advantage of using large droplet volumes is that the surface area per droplet is vastly larger than in experiments focused on single aerosol particles or cloud-sized droplets. This increases the probability of observing the effect of less common, but important, high-temperature INPs and therefore allows the quantification of their ice nucleation efficiency. The potential artefacts which could influence data from this experiment, and other similar experiments, are mitigated and discussed. Experimentally determined heterogeneous ice nucleation efficiencies for K-feldspar (microcline), kaolinite, chlorite, NX-illite, Snomax® and silver iodide are presented.

  18. A novel optical freezing array for the examination of cooling rate dependence in heterogeneous ice nucleation

    NASA Astrophysics Data System (ADS)

    Budke, Carsten; Dreischmeier, Katharina; Koop, Thomas

    2014-05-01

    Homogeneous ice nucleation is a stochastic process, implying that it is not only temperature but also time dependent. For heterogeneous ice nucleation it is still under debate whether there is a significant time dependence or not. In case of minor time dependence it is probably sufficient to use a singular or slightly modified singular approach, which mainly supposes temperature dependence and just small stochastic variations. We contribute to this discussion using a novel optical freezing array termed BINARY (Bielefeld Ice Nucleation ARraY). The setup consists of an array of microliter-sized droplets on a Peltier cooling stage. The droplets are separated from each other with a polydimethylsiloxane (PDMS) spacer to prevent a Bergeron-Findeisen process, in which the first freezing droplets grow at the expense of the remaining liquid ones due to their vapor pressure differences. An automatic detection of nucleation events is realized optically by the change in brightness during freezing. Different types of ice nucleating agents were tested with the presented setup, e. g. pollen and clay mineral dust. Exemplarily, cooling rate dependent measurements are shown for the heterogeneous ice nucleation induced by Snomax®. The authors gratefully acknowledge funding by the German Research Foundation (DFG) through the project BIOCLOUDS (KO 2944/1-1) and through the research unit INUIT (FOR 1525) under KO 2944/2-1. We particularly thank our INUIT partners for fruitful collaboration and sharing of ideas and IN samples.

  19. On the heterogeneous nucleation of mesospheric ice on meteoric smoke particles: Microphysical modeling

    NASA Astrophysics Data System (ADS)

    Asmus, Heiner; Wilms, Henrike; Strelnikov, Boris; Rapp, Markus

    2014-10-01

    Meteor smoke particles (MSP), which are thought to be the nucleation germs for mesospheric ice, are currently discussed to consist of highly absorbing materials such as magnesiowüstite, hematite or magnesium-iron-silicates and may therefore be warmer than the ambient atmosphere. In order to quantify the temperature difference between MSP and the atmosphere we developed a model to calculate the MSP equilibrium temperature in radiational and collisional balance. The temperature difference between MSP and the surrounding atmosphere strongly depends on the composition of the MSP, especially on the relative iron content, where a higher iron content leads to warmer MSP. We then derive an expression of the nucleation rate of mesospheric ice particles which explicitly accounts for this temperature difference. We find that the nucleation rate is strongly reduced by several orders of magnitude if the germ temperature is increased by only a few Kelvin. Implementing this nucleation rate depending on the germ temperature into CARMA, the Community Aerosol and Radiation Model for Atmospheres, we find that fewer but larger ice particles are formed compared to a reference scenario with no temperature difference between MSP and ambient atmosphere. This may indicate that iron-rich MSP are not ideal ice nuclei and that either other MSP-types or other nucleation pathways (e.g. wave induced heterogeneous nucleation or even homogeneous nucleation) are responsible for ice formation at the mesopause.

  20. Heterogeneous ice nucleation of viscous secondary organic aerosol produced from ozonolysis of α-pinene

    NASA Astrophysics Data System (ADS)

    Ignatius, K.; Kristensen, T. B.; Järvinen, E.; Nichman, L.; Fuchs, C.; Gordon, H.; Herenz, P.; Hoyle, C. R.; Duplissy, J.; Garimella, S.; Dias, A.; Frege, C.; Höppel, N.; Tröstl, J.; Wagner, R.; Yan, C.; Amorim, A.; Baltensperger, U.; Curtius, J.; Donahue, N. M.; Gallagher, M. W.; Kirkby, J.; Kulmala, M.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Tomé, A.; Virtanen, A.; Worsnop, D.; Stratmann, F.

    2015-12-01

    There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate deposition ice nucleation and thus influence cirrus cloud properties. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles. The SOA particles were produced from the ozone initiated oxidation of α-pinene in an aerosol chamber at temperatures in the range from -38 to -10 °C at 5-15 % relative humidity with respect to water to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. The ice nucleation ability of SOA particles with different sizes was investigated with a new continuous flow diffusion chamber. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA in the deposition mode for ice saturation ratios between 1.3 and 1.4 significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between -36.5 and -38.3 °C ranged from 6 to 20 % and did not depend on the particle surface area. Global modelling of monoterpene SOA particles suggests that viscous biogenic SOA particles are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nuclei (IN) budget.

  1. BINARY: an optical freezing array for assessing temperature and time dependence of heterogeneous ice nucleation

    NASA Astrophysics Data System (ADS)

    Budke, C.; Koop, T.

    2014-09-01

    A new optical freezing array for the study of heterogeneous ice nucleation in microliter-sized droplets is introduced, tested and applied to the study of immersion freezing in aqueous Snomax® suspensions. In the Bielefeld Ice Nucleation ARraY (BINARY) ice nucleation can be studied simultaneously in 36 droplets at temperatures down to -40 °C (233 K) and at cooling rates between 0.1 K min-1 and 10 K min-1. The droplets are separated from each other in individual compartments, thus preventing a Wegener-Bergeron-Findeisen type water vapor transfer between droplets as well as avoiding the seeding of neighboring droplets by formation and surface growth of frost halos. Analysis of freezing and melting occurs via an automated real time image analysis of the optical brightness of each individual droplet. As an application ice nucleation in water droplets containing Snomax® at concentrations from 1 ng mL-1 to 1 mg mL-1 was investigated. Using different cooling rates a minute time dependence of ice nucleation induced by Class A and Class C ice nucleators contained in Snomax® was detected. For the Class A IN a very strong increase of the heterogeneous ice nucleation rate coefficient with decreasing temperature of λ ≡ -dln(jhet)/dT = 8.7 K-1 was observed emphasizing the capability of the BINARY device. This value is larger than those of other types of IN reported in the literature, suggesting that the BINARY setup is suitable for quantifying time dependence for most other IN of atmospheric interest, making it a useful tool for future investigations.

  2. Heterogeneous ice nucleation: Exploring the transition from stochastic to singular freezing behavior

    NASA Astrophysics Data System (ADS)

    Stratmann, F.; Niedermeier, D.; Hartmann, S.; Shaw, R. A.; Clauss, T.; Wex, H.

    2011-12-01

    Heterogeneous ice nucleation directly influences cloud physical processes, precipitation formation, global radiation balances, and therefore Earth's climate (Cantrell and Heymsfield, 2005 and references therein). It is important to understand the heterogeneous freezing process at a fundamental level in order to describe this process in a physically-based way that will behave robustly in weather and climate models. There is longstanding debate as to whether heterogeneous ice nucleation is a stochastic process (e.g., Carte, 1956) or whether it exhibits singular behaviour (e.g., Langham and Mason, 1958). Fundamentally, the stochastic ice nucleation behavior implies ice nucleation being time dependent, while singular behavior is characterized by ice nucleation taking place on specific particle surface sites at a certain temperature and being time independent (Vali and Stansbury, 1966). We addressed this issue using both experimental and theoretical methods. Experiments focused on immersion freezing of Arizona Test Dust (ATD) were carried out using the Leipzig Aerosol Cloud Interaction Simulator (LACIS), a seven meter long laminar flow diffusion chamber. Both, temperature and time dependencies of ATD-particle induced immersion freezing were investigated. It was found, that ATD-particle induced immersion freezing took place over a wide temperature range and exhibited no detectable time dependence within the range investigated. The theoretical investigations were carried out using a Classical Nucleation Theory (CNT) based, i.e., purely stochastic, numerical model. This idealized model treats statistically similar particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in the past. Based on CNT alone, a population of

  3. The Theory of Ice Nucleation by Heterogeneous Freezing of Deliquescent Mixed CCN. Part II: Parcel Model Simulation.

    NASA Astrophysics Data System (ADS)

    Khvorostyanov, Vitaly I.; Curry, Judith A.

    2005-02-01

    The new theory of ice nucleation by heterogeneous freezing of deliquescent mixed cloud condensation nuclei (CCN) presented in Part I is incorporated into a parcel model with explicit water and ice bin microphysics to simulate the process of ice nucleation under transient thermodynamic conditions. Simulations are conducted over the temperature range -4° to -60°C, with vertical velocities varying from 1 to 100 cm s-1, for varying initial relative humidities and aerosol characteristics. These simulations show that the same CCN that are responsible for the drop nucleation may initiate crystal nucleation and can be identified as ice nuclei (IN) when crystals form. The simulated nucleation rates and concentrations of nucleated crystals depend on temperature and supersaturation simultaneously, showing good agreement with observations but with noticeable differences when compared with classical temperature-only and supersaturation-only parameterizations. The kinetics of heterogeneous ice nucleation exhibits a negative feedback via water supersaturation, whereby ice nucleation depends on the water supersaturation that is diminished by ice crystal diffusional growth. This feedback is stronger than the corresponding feedback for drop nucleation, and may explain discrepancies between observed ice nuclei concentrations and ice crystal concentrations, the very small fraction of CCN that may serve as IN, and the much smaller crystal concentrations as compared to drop concentrations. The relative importance of heterogeneous versus homogeneous nucleation is examined for a variety of cloud conditions. Based on these calculations, a simple parameterization for ice crystal concentration is suggested for use in cloud models and large-scale models.

  4. Investigation of heterogeneous ice nucleation in pollen suspensions and washing water

    NASA Astrophysics Data System (ADS)

    Dreischmeier, Katharina; Budke, Carsten; Koop, Thomas

    2014-05-01

    Biological particles such as pollen often show ice nucleation activity at temperatures higher than -20 °C. Immersion freezing experiments of pollen washing water demonstrate comparable ice nucleation behaviour as water containing the whole pollen bodies (Pummer et al., 2012). It was suggested that polysaccharide molecules leached from the grains are responsible for the ice nucleation. Here, heterogeneous ice nucleation in birch pollen suspensions and their washing water was investigated by two different experimental methods. The optical freezing array BINARY (Bielefeld Ice Nucleation ARraY) allows the direct observation of freezing of microliter-sized droplets. The IN spectra obtained from such experiments with birch pollen suspensions over a large concentration range indicate several different ice nucleation active species, two of which are present also in the washing water. The latter was probed also in differential scanning calorimeter (DSC) experiments of emulsified sub-picoliter droplets. Due to the small droplet size in the emulsion samples and at small concentration of IN in the washing water, such DSC experiments can exhibit the ice nucleation behaviour of a single nucleus. The two heterogeneous freezing signals observed in the DSC thermograms can be assigned to two different kinds of ice nuclei, confirming the observation from the BINARY measurements, and also previous studies on Swedish birch pollen washing water (Augustin et al., 2012). The authors gratefully acknowledge funding by the German Research Foundation (DFG) through the project BIOCLOUDS (KO 2944/1-1) and through the research unit INUIT (FOR 1525) under KO 2944/2-1. We particularly thank our INUIT partners for fruitful collaboration and sharing of ideas and IN samples. S. Augustin, H. Wex, D. Niedermeier, B. Pummer, H. Grothe, S. Hartmann, L. Tomsche, T. Clauss, J. Voigtländer, K. Ignatius, and F. Stratmann, Immersion freezing of birch pollen washing water, Atmos. Chem. Phys., 13, 10989

  5. Heterogeneous ice nucleation and phase transition of viscous α-pinene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Ignatius, Karoliina; Kristensen, Thomas B.; Järvinen, Emma; Nichman, Leonid; Fuchs, Claudia; Gordon, Hamish; Herenz, Paul; Hoyle, Christopher R.; Duplissy, Jonathan; Baltensperger, Urs; Curtius, Joachim; Donahue, Neil M.; Gallagher, Martin W.; Kirkby, Jasper; Kulmala, Markku; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Virtanen, Annele; Stratmann, Frank

    2016-04-01

    There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate deposition ice nucleation and thus influence cirrus cloud properties. Global model simulations of monoterpene SOA particles suggest that viscous biogenic SOA are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nucleating particle (INP) budget. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles at the CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN (Ignatius et al., 2015, Järvinen et al., 2015). In the CLOUD chamber, the SOA particles were produced from the ozone initiated oxidation of α-pinene at temperatures in the range from -38 to -10° C at 5-15 % relative humidity with respect to water (RHw) to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. We found that particles formed and grown in the chamber developed an asymmetric shape through coagulation. As the RHw was increased to between 35 % at -10° C and 80 % at -38° C, a transition to spherical shape was observed with a new in-situ optical method. This transition confirms previous modelling of the viscosity transition conditions. The ice nucleation ability of SOA particles was investigated with a new continuous flow diffusion chamber SPIN (Spectrometer for Ice Nuclei) for different SOA particle sizes. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA in the deposition mode for ice saturation ratios between 1.3 and 1.4, significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between -36.5 and -38.3° C ranged from 6 to 20 % and did not depend on the particle surface area. References Ignatius, K. et al., Heterogeneous ice

  6. On the ice nucleation spectrum

    NASA Astrophysics Data System (ADS)

    Barahona, D.

    2012-04-01

    This work presents a novel formulation of the ice nucleation spectrum, i.e. the function relating the ice crystal concentration to cloud formation conditions and aerosol properties. The new formulation is physically-based and explicitly accounts for the dependency of the ice crystal concentration on temperature, supersaturation, cooling rate, and particle size, surface area and composition. This is achieved by introducing the concepts of ice nucleation coefficient (the number of ice germs present in a particle) and nucleation probability dispersion function (the distribution of ice nucleation coefficients within the aerosol population). The new formulation is used to generate ice nucleation parameterizations for the homogeneous freezing of cloud droplets and the heterogeneous deposition ice nucleation on dust and soot ice nuclei. For homogeneous freezing, it was found that by increasing the dispersion in the droplet volume distribution the fraction of supercooled droplets in the population increases. For heterogeneous ice nucleation the new formulation consistently describes singular and stochastic behavior within a single framework. Using a fundamentally stochastic approach, both cooling rate independence and constancy of the ice nucleation fraction over time, features typically associated with singular behavior, were reproduced. Analysis of the temporal dependency of the ice nucleation spectrum suggested that experimental methods that measure the ice nucleation fraction over few seconds would tend to underestimate the ice nuclei concentration. It is shown that inferring the aerosol heterogeneous ice nucleation properties from measurements of the onset supersaturation and temperature may carry significant error as the variability in ice nucleation properties within the aerosol population is not accounted for. This work provides a simple and rigorous ice nucleation framework where theoretical predictions, laboratory measurements and field campaign data can be

  7. On the Ice Nucleation Spectrum

    NASA Technical Reports Server (NTRS)

    Barahona, D.

    2012-01-01

    This work presents a novel formulation of the ice nucleation spectrum, i.e. the function relating the ice crystal concentration to cloud formation conditions and aerosol properties. The new formulation is physically-based and explicitly accounts for the dependency of the ice crystal concentration on temperature, supersaturation, cooling rate, and particle size, surface area and composition. This is achieved by introducing the concepts of ice nucleation coefficient (the number of ice germs present in a particle) and nucleation probability dispersion function (the distribution of ice nucleation coefficients within the aerosol population). The new formulation is used to generate ice nucleation parameterizations for the homogeneous freezing of cloud droplets and the heterogeneous deposition ice nucleation on dust and soot ice nuclei. For homogeneous freezing, it was found that by increasing the dispersion in the droplet volume distribution the fraction of supercooled droplets in the population increases. For heterogeneous ice nucleation the new formulation consistently describes singular and stochastic behavior within a single framework. Using a fundamentally stochastic approach, both cooling rate independence and constancy of the ice nucleation fraction over time, features typically associated with singular behavior, were reproduced. Analysis of the temporal dependency of the ice nucleation spectrum suggested that experimental methods that measure the ice nucleation fraction over few seconds would tend to underestimate the ice nuclei concentration. It is shown that inferring the aerosol heterogeneous ice nucleation properties from measurements of the onset supersaturation and temperature may carry significant error as the variability in ice nucleation properties within the aerosol population is not accounted for. This work provides a simple and rigorous ice nucleation framework where theoretical predictions, laboratory measurements and field campaign data can be

  8. Developing a new parameterization framework for the heterogeneous ice nucleation of atmospheric aerosol particles

    NASA Astrophysics Data System (ADS)

    Ullrich, Romy; Hiranuma, Naruki; Hoose, Corinna; Möhler, Ottmar; Niemand, Monika; Steinke, Isabelle; Wagner, Robert

    2014-05-01

    Developing a new parameterization framework for the heterogeneous ice nucleation of atmospheric aerosol particles Ullrich, R., Hiranuma, N., Hoose, C., Möhler, O., Niemand, M., Steinke, I., Wagner, R. Aerosols of different nature induce microphysical processes of importance for the Earth's atmosphere. They affect not only directly the radiative budget, more importantly they essentially influence the formation and life cycles of clouds. Hence, aerosols and their ice nucleating ability are a fundamental input parameter for weather and climate models. During the previous years, the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber was used to extensively measure, under nearly realistic conditions, the ice nucleating properties of different aerosols. Numerous experiments were performed with a broad variety of aerosol types and under different freezing conditions. A reanalysis of these experiments offers the opportunity to develop a uniform parameterization framework of ice formation for many atmospherically relevant aerosols in a broad temperature and humidity range. The analysis includes both deposition nucleation and immersion freezing. The aim of this study is to develop this comprehensive parameterization for heterogeneous ice formation mainly by using the ice nucleation active site (INAS) approach. Niemand et al. (2012) already developed a temperature dependent parameterization for the INAS- density for immersion freezing on desert dust particles. In addition to a reanalysis of the ice nucleation behaviour of desert dust (Niemand et al. (2012)), volcanic ash (Steinke et al. (2010)) and organic particles (Wagner et al. (2010,2011)) this contribution will also show new results for the immersion freezing and deposition nucleation of soot aerosols. The next step will be the implementation of the parameterizations into the COSMO- ART model in order to test and demonstrate the usability of the framework. Hoose, C. and Möhler, O. (2012) Atmos

  9. Understanding Cirrus Ice Crystal Number Variability for Different Heterogeneous Ice Nucleation Spectra

    NASA Technical Reports Server (NTRS)

    Sullivan, Sylvia C.; Betancourt, Ricardo Morales; Barahona, Donifan; Nenes, Athanasios

    2016-01-01

    Along with minimizing parameter uncertainty, understanding the cause of temporal and spatial variability of the nucleated ice crystal number, Ni, is key to improving the representation of cirrus clouds in climate models. To this end, sensitivities of Ni to input variables like aerosol number and diameter provide valuable information about nucleation regime and efficiency for a given model formulation. Here we use the adjoint model of the adjoint of a cirrus formation parameterization (Barahona and Nenes, 2009b) to understand Ni variability for various ice-nucleating particle (INP) spectra. Inputs are generated with the Community Atmosphere Model version 5, and simulations are done with a theoretically derived spectrum, an empirical lab-based spectrum and two field-based empirical spectra that differ in the nucleation threshold for black carbon particles and in the active site density for dust. The magnitude and sign of Ni sensitivity to insoluble aerosol number can be directly linked to nucleation regime and efficiency of various INP. The lab-based spectrum calculates much higher INP efficiencies than field-based ones, which reveals a disparity in aerosol surface properties. Ni sensitivity to temperature tends to be low, due to the compensating effects of temperature on INP spectrum parameters; this low temperature sensitivity regime has been experimentally reported before but never deconstructed as done here.

  10. Understanding cirrus ice crystal number variability for different heterogeneous ice nucleation spectra

    DOE PAGES

    Sullivan, Sylvia C.; Morales Betancourt, Ricardo; Barahona, Donifan; ...

    2016-03-03

    Along with minimizing parameter uncertainty, understanding the cause of temporal and spatial variability of the nucleated ice crystal number, Ni, is key to improving the representation of cirrus clouds in climate models. To this end, sensitivities of Ni to input variables like aerosol number and diameter provide valuable information about nucleation regime and efficiency for a given model formulation. Here we use the adjoint model of the adjoint of a cirrus formation parameterization (Barahona and Nenes, 2009b) to understand Ni variability for various ice-nucleating particle (INP) spectra. Inputs are generated with the Community Atmosphere Model version 5, and simulations are donemore » with a theoretically derived spectrum, an empirical lab-based spectrum and two field-based empirical spectra that differ in the nucleation threshold for black carbon particles and in the active site density for dust. The magnitude and sign of Ni sensitivity to insoluble aerosol number can be directly linked to nucleation regime and efficiency of various INP. The lab-based spectrum calculates much higher INP efficiencies than field-based ones, which reveals a disparity in aerosol surface properties. Ni sensitivity to temperature tends to be low, due to the compensating effects of temperature on INP spectrum parameters; this low temperature sensitivity regime has been experimentally reported before but never deconstructed as done here.« less

  11. Can we define an asymptotic value for the ice active surface site density for heterogeneous ice nucleation?

    NASA Astrophysics Data System (ADS)

    Niedermeier, Dennis; Augustin-Bauditz, Stefanie; Hartmann, Susan; Wex, Heike; Ignatius, Karoliina; Stratmann, Frank

    2015-04-01

    The formation of ice in atmospheric clouds has a substantial influence on the radiative properties of clouds as well as on the formation of precipitation. Therefore much effort has been made to understand and quantify the major ice formation processes in clouds. Immersion freezing has been suggested to be a dominant primary ice formation process in low and mid-level clouds (mixed-phase cloud conditions). It also has been shown that mineral dust particles are the most abundant ice nucleating particles in the atmosphere and thus may play an important role for atmospheric ice nucleation (Murray et al., 2012). Additionally, biological particles like bacteria and pollen are suggested to be potentially involved in atmospheric ice formation, at least on a regional scale (Murray et al., 2012). In recent studies for biological particles (SNOMAX and birch pollen), it has been demonstrated that freezing is induced by ice nucleating macromolecules and that an asymptotic value for the mass density of these ice nucleating macromolecules can be determined (Hartmann et al., 2013; Augustin et al., 2013, Wex et al., 2014). The question arises whether such an asymptotic value can also be determined for the ice active surface site density ns, a parameter which is commonly used to describe the ice nucleation activity of e.g., mineral dust. Such an asymptotic value for ns could be an important input parameter for atmospheric modeling applications. In the presented study, we therefore investigated the immersion freezing behavior of droplets containing size-segregated, monodisperse feldspar particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). For all particle sizes considered in the experiments, we observed a leveling off of the frozen droplet fraction reaching a plateau within the heterogeneous freezing temperature regime (T > -38°C) which was proportional to the particle surface area. Based on these findings, we could determine an asymptotic value for the ice

  12. Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide - Part 1: Immersion freezing

    NASA Astrophysics Data System (ADS)

    Boose, Yvonne; Welti, André; Atkinson, James; Ramelli, Fabiola; Danielczok, Anja; Bingemer, Heinz G.; Plötze, Michael; Sierau, Berko; Kanji, Zamin A.; Lohmann, Ulrike

    2016-12-01

    Desert dust is one of the most abundant ice nucleating particle types in the atmosphere. Traditionally, clay minerals were assumed to determine the ice nucleation ability of desert dust and constituted the focus of ice nucleation studies over several decades. Recently some feldspar species were identified to be ice active at much higher temperatures than clay minerals, redirecting studies to investigate the contribution of feldspar to ice nucleation on desert dust. However, so far no study has shown the atmospheric relevance of this mineral phase.For this study four dust samples were collected after airborne transport in the troposphere from the Sahara to different locations (Crete, the Peloponnese, Canary Islands, and the Sinai Peninsula). Additionally, 11 dust samples were collected from the surface from nine of the biggest deserts worldwide. The samples were used to study the ice nucleation behavior specific to different desert dusts. Furthermore, we investigated how representative surface-collected dust is for the atmosphere by comparing to the ice nucleation activity of the airborne samples. We used the IMCA-ZINC setup to form droplets on single aerosol particles which were subsequently exposed to temperatures between 233 and 250 K. Dust particles were collected in parallel on filters for offline cold-stage ice nucleation experiments at 253-263 K. To help the interpretation of the ice nucleation experiments the mineralogical composition of the dusts was investigated. We find that a higher ice nucleation activity in a given sample at 253 K can be attributed to the K-feldspar content present in this sample, whereas at temperatures between 238 and 245 K it is attributed to the sum of feldspar and quartz content present. A high clay content, in contrast, is associated with lower ice nucleation activity. This confirms the importance of feldspar above 250 K and the role of quartz and feldspars determining the ice nucleation activities at lower temperatures as found

  13. Heterogeneous Ice Nucleation During Ozonolysis of Organic Thin Films on Aqueous Solution Droplets

    NASA Astrophysics Data System (ADS)

    Wicks, G.; Cantrell, W.

    2005-12-01

    The mechanism by which ice is created affects cloud properties and processes. Although homogeneous ice nucleation is reasonably well understood, both experimentally and theoretically, heterogeneous ice nucleation is not. Since deep convection in the tropics lofts organic materials high into the atmosphere, it is important to achieve an understanding of heterogeneous nucleation by these materials and how it affects cirrus cloud formation. Sources of atmospheric organic compounds include combustion, biomass burning, emissions from vegetation, and sea spray which contains organic material from the ocean's surface. Fatty acids such as stearic acid and oleic acid are common organic constituents. The reaction of oleic acid with atmospheric ozone has recently become a model for understanding how atmospheric oxidation processes affect organic particles. Over the past six years, more than twenty publications have described reactive uptake coefficients, primary products, secondary reactions, mechanisms, and other aspects of this oxidation. With this background information in mind, we built an ozonolysis apparatus in tandem with a solution drop freezer to study the freezing point of 10-microliter, 0.25 M sodium chloride solution droplets coated with thin layers of 18-carbon fatty acids or alcohols. We determined the freezing points before and after ozonolysis for solution droplets coated with stearic acid, oleic acid, cis-13-octadecenoic acid, oleyl alcohol, and 1-octadecanol. During the experiments, temperature cycling was controlled by a computer-driven temperature controller. Results showed little change in mean freezing temperature before and after ozonolysis for all of the organic compounds studied except oleyl alcohol. The lack of a significant temperature change for oleic acid may be good news for atmospheric modelers since the well-studied reaction of ozone with oleic acid is known to give a complex mixture of products.

  14. RAPID INDUCTION OF HETEROGENEOUS ICE NUCLEATION IN A BIOLOGICALLY COMPATIBLE COOLANT

    PubMed Central

    Lampe, Joshua; Bull, Diana; Becker, Lance

    2012-01-01

    Hypothermia is gaining recognition as an important medical treatment. To treat local cases of injury such as stroke, or certain surgical procedures, there is a need to induce local hypothermia. To treat shock or cardiac arrest survivors, there is a need to rapidly induce global hypothermia. Rapid induction of hypothermia has been achieved in animal research, but it has yet to be achieved clinically using a simple, widely practicable method. The clinical need for therapeutic hypothermia represents an engineering opportunity to develop an easy to use coolant that is sterile, biologically compatible, and maximizes coolant heat capacity. Here we present an initial characterization of a prototype platform technology designed to create a sterile, biologically compatible, high heat capacity coolant that has the potential to be used in all of these clinical applications. The coolant is a specially processed micro-particulate ice saline slurry, that can be easily pumped into a patient through surgical tubing, syringes, or minimally invasive surgical instruments. The device induces heterogeneous ice nucleation in a saline stream that has been super-cooled from room temperature to a temperature below the saline freezing point. Currently, the device begins continuous production of ice slurry that contains ~30 % ice by mass within 10 minutes. The nominal ice particle diameter is smaller than 100 μm. This work represents a significant first step toward addressing clinical needs for rapid human cooling. PMID:25954121

  15. RAPID INDUCTION OF HETEROGENEOUS ICE NUCLEATION IN A BIOLOGICALLY COMPATIBLE COOLANT.

    PubMed

    Lampe, Joshua; Bull, Diana; Becker, Lance

    Hypothermia is gaining recognition as an important medical treatment. To treat local cases of injury such as stroke, or certain surgical procedures, there is a need to induce local hypothermia. To treat shock or cardiac arrest survivors, there is a need to rapidly induce global hypothermia. Rapid induction of hypothermia has been achieved in animal research, but it has yet to be achieved clinically using a simple, widely practicable method. The clinical need for therapeutic hypothermia represents an engineering opportunity to develop an easy to use coolant that is sterile, biologically compatible, and maximizes coolant heat capacity. Here we present an initial characterization of a prototype platform technology designed to create a sterile, biologically compatible, high heat capacity coolant that has the potential to be used in all of these clinical applications. The coolant is a specially processed micro-particulate ice saline slurry, that can be easily pumped into a patient through surgical tubing, syringes, or minimally invasive surgical instruments. The device induces heterogeneous ice nucleation in a saline stream that has been super-cooled from room temperature to a temperature below the saline freezing point. Currently, the device begins continuous production of ice slurry that contains ~30 % ice by mass within 10 minutes. The nominal ice particle diameter is smaller than 100 μm. This work represents a significant first step toward addressing clinical needs for rapid human cooling.

  16. Parameterization of heterogeneous ice nucleation on mineral dust particles: An application in a regional scale model

    NASA Astrophysics Data System (ADS)

    Niemand, M.; Vogel, B.; Vogel, H.; Connolly, P.; Klein, H.; Bingemer, H.; Hoose, C.; Moehler, O.; Leisner, T.

    2010-12-01

    In climate and weather models, the quantitative description of aerosol and cloud processes relies on simplified assumptions. This contributes major uncertainties to the prediction of global and regional climate change. The parameterization of heterogeneous ice nucleation is a step towards improving our current knowledge of the importance of the cloud ice phase in weather and climate models and can aid in the theoretical understanding of such processes. This contribution presents a new parameterization derived from a large number of experiments carried out at the aerosol and cloud chamber facility AIDA [1] of Karlsruhe Institute of Technology. AIDA is especially suitable to study ice nucleation processes at tropospheric and stratospheric cloud conditions covering a wide range of temperature and pressure. During pumping expansion, cooling rates between -0.3 and -5.0 K/min, equating to vertical wind velocities of 0.5 to 8 m/s, and a relative humidity range of up to more than 200% with respect to ice can be reached. The parameterization is valid for the temperature range -35°C to -15°C. In order to derive and test the parameterization a parameter called the ice-active surface site density was calculated for a number of different experiments with mineral dust acting as ice nuclei in the immersion and/or deposition mode. An exponential function was fitted to this data of ice-active surface site density vs. temperature. The curve fit was then used within the bin microphysical model ACPIM [2] to simulate the ice formation rates from the experiments. The major dust outbreak over the Sahara in May 2008 which was followed by a dust transport over the Mediterranean and Western Europe was simulated using the regional scale online coupled model system COSMO-ART (Vogel et al., 2009). Based on the model results the exponential curve fit was used to calculate the ice nuclei number concentration at Kleiner Feldberg (Germany). The results will be compared to measurements from

  17. Ice nucleation in solutions and freeze-avoiding insects-homogeneous or heterogeneous?

    PubMed

    Zachariassen, Karl Erik; Kristiansen, Erlend; Pedersen, Sindre Andre; Hammel, Harold T

    2004-06-01

    This article challenges the common view that solutions and cold-hardy freeze-avoiding insects always freeze by heterogeneous nucleation. Data are presented to show that the nucleation temperatures of a variety of solutions and freeze-avoiding insects are a function of the water volume as described by the data previously published by Bigg in 1953. The article also points out that the relationships between melting point depression and depression of nucleation temperature are different for samples undergoing homogeneous nucleation and those undergoing heterogeneous nucleation. Aqueous solutions and freeze-avoiding insects display a relationship like that of homogeneously nucleated samples. It is also argued that the identity of the "impurities" assumed to cause heterogeneous nucleation in aqueous solutions and insects is obscure and that the "impurities" have features which make their existence rather unlikely.

  18. Importance of aerosol composition, mixing state, and morphology for heterogeneous ice nucleation: A combined field and laboratory approach

    NASA Astrophysics Data System (ADS)

    Baustian, Kelly J.; Cziczo, Daniel J.; Wise, Matthew E.; Pratt, Kerri A.; Kulkarni, Gourihar; Hallar, A. Gannet; Tolbert, Margaret A.

    2012-03-01

    In this study chemical compositions of background aerosol and ice nuclei were examined through laboratory investigations using Raman spectroscopy and field measurements by single-particle mass spectrometry. Aerosol sampling took place at Storm Peak Laboratory in Steamboat Springs, Colorado (elevation of 3210 m). A cascade impactor was used to collect coarse-mode aerosol particles for laboratory analysis by Raman spectroscopy; the composition, mixing state, and heterogeneous ice nucleation activity of individual particles were examined. For in situ analysis of fine-mode aerosol, ice nucleation on ambient particles was observed using a compact ice nucleation chamber. Ice crystals were separated from unactivated aerosol using a pumped counterflow virtual impactor, and ice nuclei were analyzed using particle analysis by laser mass spectrometry. For both fine and coarse modes, the ice nucleating particle fractions were enriched in minerals and depleted in sulfates and nitrates, compared to the background aerosol sampled. The vast majority of particles in both the ambient and ice active aerosol fractions contained a detectable amount of organic material. Raman spectroscopy showed that organic material is sometimes present in the form of a coating on the surface of inorganic particles. We find that some organic-containing particles serve as efficient ice nuclei while others do not. For coarse-mode aerosol, organic particles were only observed to initiate ice formation when oxygen signatures were also present in their spectra.

  19. Climate Impacts of Ice Nucleation

    NASA Technical Reports Server (NTRS)

    Gettelman, Andrew; Liu, Xiaohong; Barahona, Donifan; Lohmann, Ulrike; Chen, Celia

    2012-01-01

    Several different ice nucleation parameterizations in two different General Circulation Models (GCMs) are used to understand the effects of ice nucleation on the mean climate state, and the Aerosol Indirect Effects (AIE) of cirrus clouds on climate. Simulations have a range of ice microphysical states that are consistent with the spread of observations, but many simulations have higher present-day ice crystal number concentrations than in-situ observations. These different states result from different parameterizations of ice cloud nucleation processes, and feature different balances of homogeneous and heterogeneous nucleation. Black carbon aerosols have a small (0.06 Wm(exp-2) and not statistically significant AIE when included as ice nuclei, for nucleation efficiencies within the range of laboratory measurements. Indirect effects of anthropogenic aerosols on cirrus clouds occur as a consequence of increasing anthropogenic sulfur emissions with different mechanisms important in different models. In one model this is due to increases in homogeneous nucleation fraction, and in the other due to increases in heterogeneous nucleation with coated dust. The magnitude of the effect is the same however. The resulting ice AIE does not seem strongly dependent on the balance between homogeneous and heterogeneous ice nucleation. Regional effects can reach several Wm2. Indirect effects are slightly larger for those states with less homogeneous nucleation and lower ice number concentration in the base state. The total ice AIE is estimated at 0.27 +/- 0.10 Wm(exp-2) (1 sigma uncertainty). This represents a 20% offset of the simulated total shortwave AIE for ice and liquid clouds of 1.6 Wm(sup-2).

  20. Climate Impacts of Ice Nucleation

    SciTech Connect

    Gettelman, A.; Liu, Xiaohong; Barahona, Donifan; Lohmann, U.; Chen, Chih-Chieh

    2012-10-19

    [1] Several different ice nucleation parameterizations in two different General Circulation Models (GCMs) are used to understand the effects of ice nucleation on the mean climate state, and the Aerosol Indirect Effects (AIE) of cirrus clouds on climate. Simulations have a range of ice microphysical states that are consistent with the spread of observations, but many simulations have higher present-day ice crystal number concentrations than in-situ observations. These different states result from different parameterizations of ice cloud nucleation processes, and feature different balances of homogeneous and heterogeneous nucleation. Black carbon aerosols have a small (-0.06 Wm-2) and not statistically significant AIE when included as ice nuclei, for nucleation efficiencies within the range of laboratory measurements. Indirect effects of anthropogenic aerosols on cirrus clouds occur as a consequence of increasing anthropogenic sulfur emissions with different mechanisms important in different models. In one model this is due to increases in homogeneous nucleation fraction, and in the other due to increases in heterogeneous nucleation with coated dust. The magnitude of the effect is the same however. The resulting ice AIE does not seem strongly dependent on the balance between homogeneous and heterogeneous ice nucleation. Regional effects can reach several Wm-2. Indirect effects are slightly larger for those states with less homogeneous nucleation and lower ice number concentration in the base state. The total ice AIE is estimated at 0.27 ± 0.10 Wm-2 (1σ uncertainty). Finally, this represents a 20% offset of the simulated total shortwave AIE for ice and liquid clouds of -1.6 Wm-2.

  1. Laboratory Experiments on Heterogeneous CO2 Ice Nucleation and Growth Rates on Meteor Smoke Particle Analogues in the Martian Mesosphere

    NASA Astrophysics Data System (ADS)

    Nachbar, M.; Duft, D.; Mangan, T.; Gomez Martin, J. C.; Plane, J. M. C.; Leisner, T.

    2014-12-01

    CO2 ice particles with radii of about 100 nm have been detected in the Martian mesosphere region at heights between 80 km and 100 km. Gravity waves propagating upward cause a cooling of this region leading to temporary supersaturated conditions during which heterogeneous nucleation of CO2 can take place. Large uncertainties in describing the nucleation processes at the extreme conditions of the Martian mesopause region state the need of laboratory measurements. Sub-3 nanometer radius meteor smoke particle (MSP) analogues are created in a microwave plasma and stored in an electrodynamic trap for examining CO2 ice nucleation as well as growth rates at low particle temperatures between 60 K and 75 K and CO2 concentrations up to 1017 m-3 which are reasonably close to conditions present in the Martian mesosphere. Ice nucleation and growth processes of the particles are examined by analyzing the mass distribution of the particles with a time of flight spectrometer as a function of the residence time under supersaturated conditions. In this paper, first measurements of CO2 ice nucleation and growth on iron oxide and silicate particles will be presented. These results are extrapolated to realistic Martian conditions reducing the large uncertainty in dealing with CO2 ice nucleation on MSPs.

  2. Ice-Nucleating Bacteria

    NASA Astrophysics Data System (ADS)

    Obata, Hitoshi

    Since the discovery of ice-nucleating bacteria in 1974 by Maki et al., a large number of studies on the biological characteristics, ice-nucleating substance, ice nucleation gene and frost damage etc. of the bacteria have been carried out. Ice-nucleating bacteria can cause the freezing of water at relatively warm temperature (-2.3°C). Tween 20 was good substrates for ice-nucleating activity of Pseudomonas fluorescens KUIN-1. Major fatty acids of Isolate (Pseudomonas fluorescens) W-11 grown at 30°C were palmitic, cis-9-hexadecenoic and cis-11-octadecenoic which amounted to 90% of the total fatty acids. Sequence analysis shows that an ice nucleation gene from Pseudomonas fluorescens is related to the gene of Pseudomonas syringae.

  3. Influence of Surface Morphology on the Heterogeneous Ice nucleation Efficiency of Hematite Particles

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Hoffmann, N.; Steinke, I.; Kiselev, A. A.; Dreyer, A.; Zhang, K.; Kulkarni, G.; Koop, T.; Moehler, O.

    2013-12-01

    Localized morphological features, such as cracks and edges, can enhance ice nucleation through droplet-freezing and water vapor deposition at these active sites. Herein, we have conducted a comprehensive investigation examining the role of surface milling upon ice nucleation for hematite particles as a model proxy of atmospheric dust particles. The immersion and deposition mode ice nucleation efficiencies of laboratory-generated monodispersed-cubic and milled hematite particles were measured using the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber in the temperature (T) range between -28 °C and -82 °C. We observed that the immersion mode ice nucleation efficiency of milled hematite particles is almost an order of magnitude higher at -35.2 °C < T < -33.5 °C than that of the cubic hematite particles, indicating a substantial effect of morphological irregularities on the ice activation. For the deposition mode freezing below -50 °C and lower on, as previously postulated in the literature, our measurements showed that an exponential increase in supersaturations were required to achieve a constant nucleation efficiency (i.e., ns > 2.5 x 108 m-2). Deposition observations may be due to water uptake at particle surface and/or within bulk phase in subsaturated conditions. Applications of the fitted parameterization derived from AIDA measurements to modeling simulations with the single column version of the Community Atmospheric Model version 5 as well as microphysical characteristics of hematite surface are also presented.

  4. Active sites in heterogeneous ice nucleation-the example of K-rich feldspars.

    PubMed

    Kiselev, Alexei; Bachmann, Felix; Pedevilla, Philipp; Cox, Stephen J; Michaelides, Angelos; Gerthsen, Dagmar; Leisner, Thomas

    2017-01-27

    Ice formation on aerosol particles is a process of crucial importance to Earth's climate and the environmental sciences, but it is not understood at the molecular level. This is partly because the nature of active sites, local surface features where ice growth commences, is still unclear. Here we report direct electron-microscopic observations of deposition growth of aligned ice crystals on feldspar, an atmospherically important component of mineral dust. Our molecular-scale computer simulations indicate that this alignment arises from the preferential nucleation of prismatic crystal planes of ice on high-energy (100) surface planes of feldspar. The microscopic patches of (100) surface, exposed at surface defects such as steps, cracks, and cavities, are thought to be responsible for the high ice nucleation efficacy of potassium (K)-feldspar particles. Copyright © 2017, American Association for the Advancement of Science.

  5. Ice Nucleation Properties of Oxidized Carbon Nanomaterials

    PubMed Central

    2015-01-01

    Heterogeneous ice nucleation is an important process in many fields, particularly atmospheric science, but is still poorly understood. All known inorganic ice nucleating particles are relatively large in size and tend to be hydrophilic. Hence it is not obvious that carbon nanomaterials should nucleate ice. However, in this paper we show that four different readily water-dispersible carbon nanomaterials are capable of nucleating ice. The tested materials were carboxylated graphene nanoflakes, graphene oxide, oxidized single walled carbon nanotubes and oxidized multiwalled carbon nanotubes. The carboxylated graphene nanoflakes have a diameter of ∼30 nm and are among the smallest entities observed so far to nucleate ice. Overall, carbon nanotubes were found to nucleate ice more efficiently than flat graphene species, and less oxidized materials nucleated ice more efficiently than more oxidized species. These well-defined carbon nanomaterials may pave the way to bridging the gap between experimental and computational studies of ice nucleation. PMID:26267196

  6. Ice Nucleation Properties of Oxidized Carbon Nanomaterials.

    PubMed

    Whale, Thomas F; Rosillo-Lopez, Martin; Murray, Benjamin J; Salzmann, Christoph G

    2015-08-06

    Heterogeneous ice nucleation is an important process in many fields, particularly atmospheric science, but is still poorly understood. All known inorganic ice nucleating particles are relatively large in size and tend to be hydrophilic. Hence it is not obvious that carbon nanomaterials should nucleate ice. However, in this paper we show that four different readily water-dispersible carbon nanomaterials are capable of nucleating ice. The tested materials were carboxylated graphene nanoflakes, graphene oxide, oxidized single walled carbon nanotubes and oxidized multiwalled carbon nanotubes. The carboxylated graphene nanoflakes have a diameter of ∼30 nm and are among the smallest entities observed so far to nucleate ice. Overall, carbon nanotubes were found to nucleate ice more efficiently than flat graphene species, and less oxidized materials nucleated ice more efficiently than more oxidized species. These well-defined carbon nanomaterials may pave the way to bridging the gap between experimental and computational studies of ice nucleation.

  7. A first test of the hypothesis of biogenic magnetite-based heterogeneous ice-crystal nucleation in cryopreservation.

    PubMed

    Kobayashi, Atsuko; Golash, Harry N; Kirschvink, Joseph L

    2016-06-01

    An outstanding biophysical puzzle is focused on the apparent ability of weak, extremely low-frequency oscillating magnetic fields to enhance cryopreservation of many biological tissues. A recent theory holds that these weak magnetic fields could be inhibiting ice-crystal nucleation on the nanocrystals of biological magnetite (Fe3O4, an inverse cubic spinel) that are present in many plant and animal tissues by causing them to oscillate. In this theory, magnetically-induced mechanical oscillations disrupt the ability of water molecules to nucleate on the surface of the magnetite nanocrystals. However, the ability of the magnetite crystal lattice to serve as a template for heterogeneous ice crystal nucleation is as yet unknown, particularly for particles in the 10-100 nm size range. Here we report that the addition of trace-amounts of finely-dispersed magnetite into ultrapure water samples reduces strongly the incidence of supercooling, as measured in experiments conducted using a controlled freezing apparatus with multiple thermocouples. SQUID magnetometry was used to quantify nanogram levels of magnetite in the water samples. We also report a relationship between the volume change of ice, and the degree of supercooling, that may indicate lower degassing during the crystallization of supercooled water. In addition to supporting the role of ice-crystal nucleation by biogenic magnetite in many tissues, magnetite nanocrystals could provide inexpensive, non-toxic, and non-pathogenic ice nucleating agents needed in a variety of industrial processes, as well as influencing the dynamics of ice crystal nucleation in many natural environments. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  8. Ice Nucleation in Deep Convection

    NASA Technical Reports Server (NTRS)

    Jensen, Eric; Ackerman, Andrew; Stevens, David; Gore, Warren J. (Technical Monitor)

    2001-01-01

    The processes controlling production of ice crystals in deep, rapidly ascending convective columns are poorly understood due to the difficulties involved with either modeling or in situ sampling of these violent clouds. A large number of ice crystals are no doubt generated when droplets freeze at about -40 C. However, at higher levels, these crystals are likely depleted due to precipitation and detrainment. As the ice surface area decreases, the relative humidity can increase well above ice saturation, resulting in bursts of ice nucleation. We will present simulations of these processes using a large-eddy simulation model with detailed microphysics. Size bins are included for aerosols, liquid droplets, ice crystals, and mixed-phase (ice/liquid) hydrometers. Microphysical processes simulated include droplet activation, freezing, melting, homogeneous freezing of sulfate aerosols, and heterogeneous ice nucleation. We are focusing on the importance of ice nucleation events in the upper part of the cloud at temperatures below -40 C. We will show that the ultimate evolution of the cloud in this region (and the anvil produced by the convection) is sensitive to these ice nucleation events, and hence to the composition of upper tropospheric aerosols that get entrained into the convective column.

  9. Heterogeneous Ice Nucleation by Soufriere Hills Volcanic Ash Immersed in Water Droplets

    PubMed Central

    Atkinson, J. D.; Neuberg, J. W.; O’Sullivan, D.; Wilson, T. W.; Whale, T. F.; Neve, L.; Umo, N. S.; Malkin, T. L.; Murray, B. J.

    2017-01-01

    Fine particles of ash emitted during volcanic eruptions may sporadically influence cloud properties on a regional or global scale as well as influencing the dynamics of volcanic clouds and the subsequent dispersion of volcanic aerosol and gases. It has been shown that volcanic ash can trigger ice nucleation, but ash from relatively few volcanoes has been studied for its ice nucleating ability. In this study we quantify the efficiency with which ash from the Soufriere Hills volcano on Montserrat nucleates ice when immersed in supercooled water droplets. Using an ash sample from the 11th February 2010 eruption, we report ice nucleating efficiencies from 246 to 265 K. This wide range of temperatures was achieved using two separate droplet freezing instruments, one employing nanolitre droplets, the other using microlitre droplets. Soufriere Hills volcanic ash was significantly more efficient than all other ash samples that have been previously examined. At present the reasons for these differences are not understood, but may be related to mineralogy, amorphous content and surface chemistry. PMID:28056077

  10. Heterogeneous Ice Nucleation by Soufriere Hills Volcanic Ash Immersed in Water Droplets.

    PubMed

    Mangan, T P; Atkinson, J D; Neuberg, J W; O'Sullivan, D; Wilson, T W; Whale, T F; Neve, L; Umo, N S; Malkin, T L; Murray, B J

    2017-01-01

    Fine particles of ash emitted during volcanic eruptions may sporadically influence cloud properties on a regional or global scale as well as influencing the dynamics of volcanic clouds and the subsequent dispersion of volcanic aerosol and gases. It has been shown that volcanic ash can trigger ice nucleation, but ash from relatively few volcanoes has been studied for its ice nucleating ability. In this study we quantify the efficiency with which ash from the Soufriere Hills volcano on Montserrat nucleates ice when immersed in supercooled water droplets. Using an ash sample from the 11th February 2010 eruption, we report ice nucleating efficiencies from 246 to 265 K. This wide range of temperatures was achieved using two separate droplet freezing instruments, one employing nanolitre droplets, the other using microlitre droplets. Soufriere Hills volcanic ash was significantly more efficient than all other ash samples that have been previously examined. At present the reasons for these differences are not understood, but may be related to mineralogy, amorphous content and surface chemistry.

  11. Surface-charge-induced orientation of interfacial water suppresses heterogeneous ice nucleation on α-alumina (0001)

    NASA Astrophysics Data System (ADS)

    Abdelmonem, Ahmed; Backus, Ellen H. G.; Hoffmann, Nadine; Sánchez, M. Alejandra; Cyran, Jenée D.; Kiselev, Alexei; Bonn, Mischa

    2017-06-01

    Surface charge is one of the surface properties of atmospheric aerosols, which has been linked to heterogeneous ice nucleation and hence cloud formation, microphysics, and optical properties. Despite the importance of surface charge for ice nucleation, many questions remain on the molecular-level mechanisms at work. Here, we combine droplet-freezing assay studies with vibrational sum frequency generation (SFG) spectroscopy to correlate interfacial water structure to surface nucleation strength. We study immersion freezing of aqueous solutions of various pHs on the atmospherically relevant aluminum oxide α-Al2O3 (0001) surface using an isolated droplet on the surface. The high-pH solutions freeze at temperatures higher than that of the low-pH solution, while the neutral pH has the highest freezing temperature. On the molecular level, the SFG spectrum of the interfacial water changes substantially upon freezing. At all pHs, crystallization leads to a reduction of intensity of the 3400 cm-1 water resonance, while the 3200 cm-1 intensity drops for low pH but increases for neutral and high pHs. We find that charge-induced surface templating suppresses nucleation, irrespective of the sign of the surface charge. Heterogeneous nucleation is most efficient for the nominally neutral surface.

  12. A water activity based model of heterogeneous ice nucleation kinetics for freezing of water and aqueous solution droplets

    DOE PAGES

    Knopf, Daniel A.; Alpert, Peter A.

    2013-04-24

    Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, aw, which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humiditymore » (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, Jhet, to be uniquely expressed by T and aw, a result we term the aw based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, Jhet, frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log10(Jhet) values for the various IN types derived exclusively by T and aw, provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T, RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Finally, we demonstrate that ABIFM can be

  13. Laboratory studies of deposition mode heterogeneous ice nucleation: Effects of ice nuclei composition, size and surface area

    NASA Astrophysics Data System (ADS)

    Kanji, Zaminhussein Abdulali

    The indirect aerosol effect contributes to major uncertainties in determining the radiation budget of the earth. A large uncertainty is due to the formation of ice clouds onto natural or anthropogenic aerosols. Field studies have shown that mineral type particles are often associated with ice crystals in the mid-upper troposphere and given the long residence time in the atmosphere of dust particles (˜2 weeks in the absence of precipitation), their contribution to ice formation processes is not fully defined. In order to probe ice formation onto natural mineral dust in a setting where it could be suspended as aerosol, a new continuous flow diffusion chamber (CFDC) was built. This allowed investigations of the effects of total aerosol surface area and particle size. The CFDC was also used in an international inter-comparison of ice nucleation instrumentation to compare efficiencies of soot, biological aerosol (bacteria) and samples of natural desert dusts from different regions of the world. The laboratory observations were parameterized using nucleation rates (Jhet) and contact angles (theta) as described by classical nucleation theory. For both this experimental technique and a static one developed during the candidate's Masters degree, mineral dust particulate proved to be the most efficient ice nuclei (IN) activating at RH with respect to ice (RH i) as low as 105% at T=233 K. The efficiency varied with particle size and aerosol surface area (SA). Large particles or higher SA activated at lower RHi than small particles or lower SA. The static chamber was sensitive to the first ice event out of a large SA and therefore gave true onset RHi, which was lower than the onset defined by the CFDC studies, which was not sensitive to a single ice event. In addition the static chamber used a broader size range of particulate matter, including super micron particles while the CFDC particles sizes were restricted to below 0.5 microm. Soot and organic coated dust particles

  14. New cloud chamber experiments on the heterogeneous ice nucleation ability of oxalic acid in the deposition nucleation and immersion freezing modes

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Wagner, R.; Saathoff, H.; Schnaiter, M.; Leisner, T.

    2010-12-01

    crystallised from less supersaturated solution droplets and exposed to slow growth conditions in a supersaturated environment in the AIDA camber over a time period of several hours, were found to be much poorer heterogeneous ice nuclei. We speculate that under these conditions a crystal surface structure with less-active sites for the initiation of ice nucleation was generated. Such particles were found to be almost ice-inactive in both the deposition and condensation mode. At times, the heterogeneous ice nucleation ability of oxalic acid dihydrate significantly changed when the particles had been processed in preceding cloud droplet activation steps. Experimental methods, results, and atmospheric implications will be presented and discussed at the conference. [1] Kerminen et al., Atmos. Env., 33, 2089-2100, 1999. [2] Kerminen et al., J. Aerosol Sci., 31, 349-362, 2000. [3] Kawamura et al., Atmos. Env., 30, 1709-1722, 1996. [4] Marcolli et al., J. Phys. Chem. A, 108, 2216-2224, 2004. [5] Zobrist et al., Atmos. Chem. Phys., 6, 3115-3129, 2006. [6] Wagner et al., Atmos. Chem. Phys., 10, 7617-7641, 2010.

  15. Ice nucleation activity of polysaccharides

    NASA Astrophysics Data System (ADS)

    Bichler, Magdalena; Felgitsch, Laura; Haeusler, Thomas; Seidl-Seiboth, Verena; Grothe, Hinrich

    2015-04-01

    Heterogeneous ice nucleation is an important process in the atmosphere. It shows direct impact on our climate by triggering ice cloud formation and therefore it has much influence on the radiation balance of our planet (Lohmann et al. 2002; Mishchenko et al. 1996). The process itself is not completely understood so far and many questions remain open. Different substances have been found to exhibit ice nucleation activity (INA). Due to their vast differences in chemistry and morphology it is difficult to predict what substance will make good ice nuclei and which will not. Hence simple model substances must be found and be tested regarding INA. Our work aims at gaining to a deeper understanding of heterogeneous ice nucleation. We intend to find some reference standards with defined chemistry, which may explain the mechanisms of heterogeneous ice nucleation. A particular focus lies on biological carbohydrates in regards to their INA. Biological carbohydrates are widely distributed in all kingdoms of life. Mostly they are specific for certain organisms and have well defined purposes, e.g. structural polysaccharides like chitin (in fungi and insects) and pectin (in plants), which has also water-binding properties. Since they are widely distributed throughout our biosphere and mostly safe to use for nutrition purposes, they are well studied and easily accessible, rendering them ideal candidates as proxies. In our experiments we examined various carbohydrates, like the already mentioned chitin and pectin, as well as their chemical modifications. Lohmann U.; A Glaciation Indirect Aerosol Effect Caused by Soot Aerosols; J. Geoph. Res.; Vol. 24 No.4; pp 11-1 - 11-4; 2002 Mishchenko M.I., Rossow W.B., Macke A., Lacis A. A.; Sensitivity of Cirrus Cloud Albedo, Bidirectional Reflectance and Optical Thickness Retrieval Accuracy to Ice Particle Shape, J. Geoph. Res.; Vol. 101, No D12; pp. 16,973 - 16,985; 1996

  16. New cloud chamber experiments on the heterogeneous ice nucleation ability of oxalic acid in the immersion mode

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Leisner, T.

    2011-03-01

    The heterogeneous ice nucleation ability of oxalic acid in the immersion mode has been investigated by controlled expansion cooling runs with airborne, ternary solution droplets composed of, (i), sodium chloride, oxalic acid, and water (NaCl/OA/H2O) and, (ii), sulphuric acid, oxalic acid, and water (H2SO4/OA/H2O). Polydisperse aerosol populations with median diameters ranging from 0.5-0.7 μm and varying solute concentrations were prepared. The expansion experiments were conducted in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at initial temperatures of 244 and 235 K. In the ternary NaCl/OA/H2O system, solid inclusions of oxalic acid, presumably nucleated as oxalic acid dihydrate, were formed by temporarily exposing the ternary solution droplets to a relative humidity below the efflorescence point of NaCl. The matrix of the crystallised NaCl particulates triggered the precipitation of the organic crystals which later remained as solid inclusions in the solution droplets when the relative humidity was subsequently raised above the deliquescence point of NaCl. The embedded oxalic acid crystals reduced the critical ice saturation ratio required for the homogeneous freezing of pure NaCl/H2O solution droplets at a temperature of around 231 K from 1.38 to about 1.32. Aqueous solution droplets with OA inclusions larger than about 0.27 μm in diameter efficiently nucleated ice by condensation freezing when they were activated to micron-sized cloud droplets at 241 K, i.e., they froze well above the homogeneous freezing temperature of pure water droplets of about 237 K. Our results on the immersion freezing potential of oxalic acid corroborate the findings from a recent study with emulsified aqueous solutions containing crystalline oxalic acid. In those experiments, the crystallisation of oxalic acid diyhdrate was triggered by a preceding homogeneous freezing cycle with the emulsion samples. The expansion cooling cycles with ternary H2SO4/OA

  17. New cloud chamber experiments on the heterogeneous ice nucleation ability of oxalic acid in the immersion mode

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Leisner, T.

    2010-12-01

    The heterogeneous ice nucleation ability of oxalic acid in the immersion mode has been investigated by controlled expansion cooling runs with airborne, ternary solution droplets composed of, (i), sodium chloride, oxalic acid, and water (NaCl/OA/H2O) and, (ii), sulphuric acid, oxalic acid, and water (H2SO4/OA/H2O). Polydisperse aerosol populations with median diameters ranging from 0.5-0.7 μm and varying solute concentrations were prepared. The expansion experiments were conducted in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at initial temperatures of 244 and 235 K. In the ternary NaCl/OA/H2O system, solid inclusions of oxalic acid, presumably nucleated as oxalic acid dihydrate, were formed by temporarily exposing the ternary solution droplets to a relative humidity below the efflorescence point of NaCl. The matrix of the crystallised NaCl particulates triggered the precipitation of the organic crystals which later on remained as solid inclusions in the solution droplets when the relative humidity was again raised above the deliquescence point of NaCl. The embedded oxalic acid crystals reduced the critical ice saturation ratio required for the homogeneous freezing of pure NaCl/H2O solution droplets at a temperature of around 231 K from 1.38 to about 1.32. Aqueous solution droplets with OA inclusions larger than about 0.27 μm in diameter efficiently nucleated ice by condensation freezing when they were activated to micron-sized cloud droplets at 241 K, i.e., they froze well above the homogeneous freezing temperature of pure water droplets of about 237 K. Our results on the immersion freezing potential of oxalic acid corroborate the findings from a recent study with emulsified aqueous solutions containing crystalline oxalic acid. In those experiments, the crystallisation of oxalic acid diyhdrate was triggered by a preceding homogeneous freezing cycle with the emulsion samples. The expansion cooling cycles with ternary H2SO4/OA/H2O

  18. A~comprehensive parameterization of heterogeneous ice nucleation of dust surrogate: laboratory study with hematite particles and its application to atmospheric models

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Paukert, M.; Steinke, I.; Zhang, K.; Kulkarni, G.; Hoose, C.; Schnaiter, M.; Saathoff, H.; Möhler, O.

    2014-06-01

    A new heterogeneous ice nucleation parameterization that covers a~wide temperature range (-36 to -78 °C) is presented. Developing and testing such an ice nucleation parameterization, which is constrained through identical experimental conditions, is critical in order to accurately simulate the ice nucleation processes in cirrus clouds. The surface-scaled ice nucleation efficiencies of hematite particles, inferred by ns, were derived from AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber measurements under water subsaturated conditions that were realized by continuously changing temperature (T) and relative humidity with respect to ice (RHice) in the chamber. Our measurements showed several different pathways to nucleate ice depending on T and RHice conditions. For instance, almost T-independent freezing was observed at -60 °C < T < -50 °C, where RHice explicitly controlled ice nucleation efficiency, while both T and RHice played roles in other two T regimes: -78 °C < T < -60 °C and -50 °C < T < -36 °C. More specifically, observations at T colder than -60 °C revealed that higher RHice was necessary to maintain constant ns, whereas T may have played a significant role in ice nucleation at T warmer than -50 °C. We implemented new ns parameterizations into two cloud models to investigate its sensitivity and compare with the existing ice nucleation schemes towards simulating cirrus cloud properties. Our results show that the new AIDA-based parameterizations lead to an order of magnitude higher ice crystal concentrations and inhibition of homogeneous nucleation in colder temperature regions. Our cloud simulation results suggest that atmospheric dust particles that form ice nuclei at lower temperatures, below -36 °C, can potentially have stronger influence on cloud properties such as cloud longevity and initiation when compared to previous parameterizations.

  19. A water activity based model of heterogeneous ice nucleation kinetics for freezing of water and aqueous solution droplets

    SciTech Connect

    Knopf, Daniel A.; Alpert, Peter A.

    2013-04-24

    Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, aw, which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humidity (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, Jhet, to be uniquely expressed by T and aw, a result we term the aw based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, Jhet, frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log10(Jhet) values for the various IN types derived exclusively by T and aw, provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of

  20. A water activity based model of heterogeneous ice nucleation kinetics for freezing of water and aqueous solution droplets.

    PubMed

    Knopf, Daniel A; Alpert, Peter A

    2013-01-01

    Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, a(w), which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humidity (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, J(het), to be uniquely expressed by T and a(w), a result we term the a(w) based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, J(het), frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log10(J(het)) values for the various IN types derived exclusively by Tand a(w), provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T, RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Lastly, we demonstrate that ABIFM can

  1. Nucleation of Ice

    NASA Astrophysics Data System (ADS)

    Molinero, Valeria

    2009-03-01

    The freezing of water into ice is a ubiquitous transformation in nature, yet the microscopic mechanism of homogeneous nucleation of ice has not yet been elucidated. One of the reasons is that nucleation happens in time scales that are too fast for an experimental characterization and two slow for a systematic study with atomistic simulations. In this work we use coarse-grained molecular dynamics simulations with the monatomic model of water mW[1] to shed light into the mechanism of homogeneous nucleation of ice and its relationship to the thermodynamics of supercooled water. Cooling of bulk water produces either crystalline ice or low- density amorphous ice (LDA) depending on the quenching rate. We find that ice crystallization occurs faster at temperatures close to the liquid-liquid transition, defined as the point of maximum inflection of the density with respect to the temperature. At the liquid-liquid transition, the time scale of nucleation becomes comparable to the time scale of relaxation within the liquid phase, determining --effectively- the end of the metastable liquid state. Our results imply that no ultraviscous liquid water can exist at temperatures just above the much disputed glass transition of water. We discuss how the scenario is changed when water is in confinement, and the relationship of the mechanism of ice nucleation to that of other liquids that present the same phase behavior, silicon [2] and germanium [3]. [4pt] [1] Molinero, V. & Moore, E. B. Water modeled as an intermediate element between carbon and silicon. Journal of Physical Chemistry B (2008). Online at http://pubs.acs.org/cgi- bin/abstract.cgi/jpcbfk/asap/abs/jp805227c.html [0pt] [2] Molinero, V., Sastry, S. & Angell, C. A. Tuning of tetrahedrality in a silicon potential yields a series of monatomic (metal-like) glass formers of very high fragility. Physical Review Letters 97, 075701 (2006).

  2. Global model comparison of heterogeneous ice nucleation parameterizations in mixed phase clouds

    NASA Astrophysics Data System (ADS)

    Yun, Yuxing; Penner, Joyce E.

    2012-04-01

    A new aerosol-dependent mixed phase cloud parameterization for deposition/condensation/immersion (DCI) ice nucleation and one for contact freezing are compared to the original formulations in a coupled general circulation model and aerosol transport model. The present-day cloud liquid and ice water fields and cloud radiative forcing are analyzed and compared to observations. The new DCI freezing parameterization changes the spatial distribution of the cloud water field. Significant changes are found in the cloud ice water fraction and in the middle cloud fractions. The new DCI freezing parameterization predicts less ice water path (IWP) than the original formulation, especially in the Southern Hemisphere. The smaller IWP leads to a less efficient Bergeron-Findeisen process resulting in a larger liquid water path, shortwave cloud forcing, and longwave cloud forcing. It is found that contact freezing parameterizations have a greater impact on the cloud water field and radiative forcing than the two DCI freezing parameterizations that we compared. The net solar flux at top of atmosphere and net longwave flux at the top of the atmosphere change by up to 8.73 and 3.52 W m-2, respectively, due to the use of different DCI and contact freezing parameterizations in mixed phase clouds. The total climate forcing from anthropogenic black carbon/organic matter in mixed phase clouds is estimated to be 0.16-0.93 W m-2using the aerosol-dependent parameterizations. A sensitivity test with contact ice nuclei concentration in the original parameterization fit to that recommended by Young (1974) gives results that are closer to the new contact freezing parameterization.

  3. Pre-ordering of interfacial water in the pathway of heterogeneous ice nucleation does not lead to a two-step crystallization mechanism

    NASA Astrophysics Data System (ADS)

    Lupi, Laura; Peters, Baron; Molinero, Valeria

    2016-12-01

    According to Classical Nucleation Theory (CNT), the transition from liquid to crystal occurs in a single activated step with a transition state controlled by the size of the crystal embryo. This picture has been challenged in the last two decades by several reports of two-step crystallization processes in which the liquid first produces pre-ordered or dense domains, within which the crystal nucleates in a second step. Pre-ordering preceding crystal nucleation has been recently reported in simulations of ice crystallization, raising the question of whether the mechanism of ice nucleation involves two steps. In this paper, we investigate the heterogeneous nucleation of ice on carbon surfaces. We use molecular simulations with efficient coarse-grained models combined with rare event sampling methods and free energy calculations to elucidate the role of pre-ordering of liquid water at the carbon surface in the reaction coordinate for heterogeneous nucleation. We find that ice nucleation proceeds through a classical mechanism, with a single barrier between liquid and crystal. The reaction coordinate that determines the crossing of the nucleation barrier is the size of the crystal nucleus, as predicted by CNT. Wetting of the critical ice nuclei within pre-ordered domains decreases the nucleation barrier, increasing the nucleation rates. The preferential pathway for crystallization involves the early creation of pre-ordered domains that are the birthplace of the ice crystallites but do not represent a minimum in the free energy pathway from liquid to ice. We conclude that a preferential pathway through an intermediate-order precursor does not necessarily result in a two-step mechanism.

  4. Application of an online-coupled regional climate model, WRF-CAM5, over East Asia for examination of ice nucleation schemes. Part II. Sensitivity to heterogeneous ice nucleation parameterizations and dust emissions

    SciTech Connect

    Zhang, Yang; Chen, Ying; Fan, Jiwen; Leung, Lai -Yung

    2015-09-14

    Aerosol particles can affect cloud microphysical properties by serving as ice nuclei (IN). Large uncertainties exist in the ice nucleation parameterizations (INPs) used in current climate models. In this Part II paper, to examine the sensitivity of the model predictions to different heterogeneous INPs, WRF-CAM5 simulation using the INP of Niemand et al. (N12) [1] is conducted over East Asia for two full years, 2006 and 2011, and compared with simulation using the INP of Meyers et al. (M92) [2], which is the original INP used in CAM5. M92 calculates the nucleated ice particle concentration as a function of ice supersaturation, while N12 represents the nucleated ice particle concentration as a function of temperature and the number concentrations and surface areas of dust particles. Compared to M92, the WRF-CAM5 simulation with N12 produces significantly higher nucleated ice crystal number concentrations (ICNCs) in the northern domain where dust sources are located, leading to significantly higher cloud ice number and mass concentrations and ice water path, but the opposite is true in the southern domain where temperatures and moistures play a more important role in ice formation. Overall, the simulation with N12 gives lower downward shortwave radiation but higher downward longwave radiation, cloud liquid water path, cloud droplet number concentrations, and cloud optical depth. The increase in cloud optical depth and the decrease in downward solar flux result in a stronger shortwave and longwave cloud forcing, and decreases temperature at 2-m and precipitation. Changes in temperature and radiation lower surface concentrations of OH, O₃, SO₄²⁻, and PM2.5, but increase surface concentrations of CO, NO₂, and SO₂ over most of the domain. By acting as cloud condensation nuclei (CCN) and IN, dust particles have different impacts on cloud water and ice number concentrations, radiation, and temperature at 2-m and precipitation depending on

  5. Application of an Online-Coupled Regional Climate Model, WRF-CAM5, over East Asia for Examination of Ice Nucleation Schemes: Part II. Sensitivity to Heterogeneous Ice Nucleation Parameterizations and Dust Emissions

    SciTech Connect

    Zhang, Yang; Chen, Ying; Fan, Jiwen; Leung, Lai-Yung

    2015-09-01

    Aerosol particles can affect cloud microphysical properties by serving as ice nuclei (IN). Large uncertainties exist in the ice nucleation parameterizations (INPs) used in current climate models. In this Part II paper, to examine the sensitivity of the model predictions to different heterogeneous INPs, WRF-CAM5 simulation using the INP of Niemand et al. (N12) [1] is conducted over East Asia for two full years, 2006 and 2011, and compared with simulation using the INP of Meyers et al. (M92) [2], which is the original INP used in CAM5. M92 calculates the nucleated ice particle concentration as a function of ice supersaturation, while N12 represents the nucleated ice particle concentration as a function of temperature and the number concentrations and surface areas of dust particles. Compared to M92, the WRF-CAM5 simulation with N12 produces significantly higher nucleated ice crystal number concentrations (ICNCs) in the northern domain where dust sources are located, leading to significantly higher cloud ice number and mass concentrations and ice water path, but the opposite is true in the southern domain where temperatures and moistures play a more important role in ice formation. Overall, the simulation with N12 gives lower downward shortwave radiation but higher downward longwave radiation, cloud liquid water path, cloud droplet number concentrations, and cloud optical depth. The increase in cloud optical depth and the decrease in downward solar flux result in a stronger shortwave and longwave cloud forcing, and decreases temperature at 2-m and precipitation. Changes in temperature and radiation lower surface concentrations of OH, O3, SO42-, and PM2.5, but increase surface concentrations of CO, NO2, and SO2 over most of the domain. By acting as cloud condensation nuclei (CCN) and IN, dust particles have different impacts on cloud water and ice number concentrations, radiation, and temperature at 2-m and

  6. Application of an online-coupled regional climate model, WRF-CAM5, over East Asia for examination of ice nucleation schemes. Part II. Sensitivity to heterogeneous ice nucleation parameterizations and dust emissions

    DOE PAGES

    Zhang, Yang; Chen, Ying; Fan, Jiwen; ...

    2015-09-14

    Aerosol particles can affect cloud microphysical properties by serving as ice nuclei (IN). Large uncertainties exist in the ice nucleation parameterizations (INPs) used in current climate models. In this Part II paper, to examine the sensitivity of the model predictions to different heterogeneous INPs, WRF-CAM5 simulation using the INP of Niemand et al. (N12) [1] is conducted over East Asia for two full years, 2006 and 2011, and compared with simulation using the INP of Meyers et al. (M92) [2], which is the original INP used in CAM5. M92 calculates the nucleated ice particle concentration as a function of icemore » supersaturation, while N12 represents the nucleated ice particle concentration as a function of temperature and the number concentrations and surface areas of dust particles. Compared to M92, the WRF-CAM5 simulation with N12 produces significantly higher nucleated ice crystal number concentrations (ICNCs) in the northern domain where dust sources are located, leading to significantly higher cloud ice number and mass concentrations and ice water path, but the opposite is true in the southern domain where temperatures and moistures play a more important role in ice formation. Overall, the simulation with N12 gives lower downward shortwave radiation but higher downward longwave radiation, cloud liquid water path, cloud droplet number concentrations, and cloud optical depth. The increase in cloud optical depth and the decrease in downward solar flux result in a stronger shortwave and longwave cloud forcing, and decreases temperature at 2-m and precipitation. Changes in temperature and radiation lower surface concentrations of OH, O₃, SO₄²⁻, and PM2.5, but increase surface concentrations of CO, NO₂, and SO₂ over most of the domain. By acting as cloud condensation nuclei (CCN) and IN, dust particles have different impacts on cloud water and ice number concentrations, radiation, and temperature at 2-m and precipitation depending on whether the

  7. A Comprehensive Parameterization of Heterogeneous Ice Nucleation of Dust Surrogate: Laboratory Study with Hematite Particles and Its Application to Atmospheric Models

    SciTech Connect

    Hiranuma, Naruki; Paukert, Marco; Steinke, Isabelle; Zhang, Kai; Kulkarni, Gourihar R.; Hoose, Corinna; Schnaiter, Martin; Saathoff, Harald; Mohler, Ottmar

    2014-12-10

    A new heterogeneous ice nucleation parameterization that covers a wide temperature range (-36 °C to -78 °C) is presented. Developing and testing such an ice nucleation parameterization, which is constrained through identical experimental conditions, is critical in order to accurately simulate the ice nucleation processes in cirrus clouds. The surface-scaled ice nucleation efficiencies of hematite particles, inferred by ns, were derived from AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber measurements under water subsaturated conditions that were realized by continuously changing temperature (T) and relative humidity with respect to ice (RHice) in the chamber. Our measurements showed several different pathways to nucleate ice depending on T and RHice conditions. For instance, almost independent freezing was observed at -60 °C < T < -50 °C, where RHice explicitly controlled ice nucleation efficiency, while both T and RHice played roles in other two T regimes: -78 °C < T < -60 °C and -50 °C < T < -36 °C. More specifically, observations at T colder than -60 °C revealed that higher RHice was necessary to maintain constant ns, whereas T may have played a significant role in ice nucleation at T warmer than -50 °C. We implemented new ns parameterizations into two cloud models to investigate its sensitivity and compare with the existing ice nucleation schemes towards simulating cirrus cloud properties. Our results show that the new AIDA-based parameterizations lead to an order of magnitude higher ice crystal concentrations and inhibition of homogeneous nucleation in colder temperature regions. Our cloud simulation results suggest that atmospheric dust particles that form ice nuclei at lower temperatures, below -36 °C, can potentially have stronger influence on cloud properties such as cloud longevity and initiation when compared to previous parameterizations.

  8. Heterogeneous nucleation of ice catalyzed by high molecular weight organic compounds, before and after ozonolysis, using octadecene as a model

    NASA Astrophysics Data System (ADS)

    Irish, S.; Shackelford, A.; Cantrell, W.

    2007-12-01

    High altitude clouds may be affected by the products of biomass burning, which can be lofted into the upper troposphere through deep convection. To further complicate the picture, once in the atmosphere, organic compounds may be transformed through oxidation, possibly changing their characteristics as freezing catalysts. Using 1- and 9-octadecene as a model for unsaturated, non-polar high molecular weight organic compounds, we will show that exposure to ozone does not change the characteristic temperature at which a coating of octadecene catalyzes heterogeneous ice nucleation. In addition, the phase of the octadecene (liquid or crystalline) when ozonolysis takes place does not affect the characteristic freezing temperature. Results from studies of the same system using infrared spectroscopy will also be presented.

  9. A comprehensive parameterization of heterogeneous ice nucleation of dust surrogate: laboratory study with hematite particles and its application to atmospheric models

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Paukert, M.; Steinke, I.; Zhang, K.; Kulkarni, G.; Hoose, C.; Schnaiter, M.; Saathoff, H.; Möhler, O.

    2014-12-01

    A new heterogeneous ice nucleation parameterization that covers a wide temperature range (-36 to -78 °C) is presented. Developing and testing such an ice nucleation parameterization, which is constrained through identical experimental conditions, is important to accurately simulate the ice nucleation processes in cirrus clouds. The ice nucleation active surface-site density (ns) of hematite particles, used as a proxy for atmospheric dust particles, were derived from AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber measurements under water subsaturated conditions. These conditions were achieved by continuously changing the temperature (T) and relative humidity with respect to ice (RHice) in the chamber. Our measurements showed several different pathways to nucleate ice depending on T and RHice conditions. For instance, almost T-independent freezing was observed at -60 °C < T < -50 °C, where RHice explicitly controlled ice nucleation efficiency, while both T and RHice played roles in other two T regimes: -78 °C < T < -60 °C and -50 °C < T < -36 °C. More specifically, observations at T lower than -60 °C revealed that higher RHice was necessary to maintain a constant ns, whereas T may have played a significant role in ice nucleation at T higher than -50 °C. We implemented the new hematite-derived ns parameterization, which agrees well with previous AIDA measurements of desert dust, into two conceptual cloud models to investigate their sensitivity to the new parameterization in comparison to existing ice nucleation schemes for simulating cirrus cloud properties. Our results show that the new AIDA-based parameterization leads to an order of magnitude higher ice crystal concentrations and to an inhibition of homogeneous nucleation in lower-temperature regions. Our cloud simulation results suggest that atmospheric dust particles that form ice nuclei at lower temperatures, below -36 °C, can potentially have a stronger influence on cloud

  10. Can we define an asymptotic value for the ice active surface site density for heterogeneous ice nucleation?

    NASA Astrophysics Data System (ADS)

    Niedermeier, Dennis; Augustin-Bauditz, Stefanie; Hartmann, Susan; Wex, Heike; Ignatius, Karoliina; Stratmann, Frank

    2015-05-01

    The immersion freezing behavior of droplets containing size-segregated, monodisperse feldspar particles was investigated. For all particle sizes investigated, a leveling off of the frozen droplet fraction was observed reaching a plateau within the heterogeneous freezing temperature regime (T >- 38°C). The frozen fraction in the plateau region was proportional to the particle surface area. Based on these findings, an asymptotic value for ice active surface site density ns, which we named ns⋆, could be determined for the investigated feldspar sample. The comparison of these results with those of other studies not only elucidates the general feasibility of determining such an asymptotic value but also shows that the value of ns⋆ strongly depends on the method of the particle surface area determination. However, such an asymptotic value might be an important input parameter for atmospheric modeling applications. At least it shows that care should be taken when ns is extrapolated to lower or higher temperature.

  11. Molecular Study of the Effects of Chemical Processing on Heterogeneous Ice Nucleation: Role of Active Sites and Product Formation

    NASA Astrophysics Data System (ADS)

    Sihvonen, S.; Schill, G. P.; Murphy, K. A.; Mueller, K.; Tolbert, M. A.; Freedman, M. A.

    2014-12-01

    Mineral dust aerosol is the largest global source of ice nuclei, but the identity of the active sites for nucleation is unknown. During atmospheric transport, mineral dust aerosol can encounter and react with sulfuric acid, which affects the ice nucleation activity either due to changes to reactive surface sites or product formation. In this study, we reacted two types of clays found in mineral dust, kaolinite and montmorillonite, with sulfuric acid. Variation in the mineral due to acid treatment was separated from product formation through rinsing techniques. The samples were subsequently reacted with a probe molecule, (3,3,3-trifluoropropyl)dimethylchlorosilane, that selectively binds to edge hydroxyl groups that are bonded to a silicon atom with three bridging oxygens. Hydroxyl groups are considered potential active sites, because they can hydrogen bond with water and facilitate ice nucleation. Attachment to these sites was quantified by 19F magic angle spinning nuclear magnetic resonance (MAS NMR) of the 19F atoms on the probe molecule, which provided a direct correlation of the number of hydroxyl groups. Our results indicate that the number of edge-site hydroxyl groups increases with exposure to acid. Ice nucleation measurements indicate that the sulfuric acid-treated mineral is less ice active than the untreated mineral. Surprisingly, no difference between the nucleation activity of the untreated mineral and acid-treated, rinsed mineral is observed. As a result, we hypothesize that once a critical density of active sites is reached for ice nucleation, there is no further change in nucleation activity despite a continued increase in active sites. We additionally propose that the reduced activity of the acid-treated mineral is due to product formation that blocks active sites on the mineral, rather than changes to active sites.

  12. Clustering of ice nucleation protein correlates with ice nucleation activity.

    PubMed

    Mueller, G M; Wolber, P K; Warren, G J

    1990-08-01

    Antibodies raised against a synthetic peptide specifically detect ice nucleation proteins from Pseudomonas species in Western blots. In immunofluorescent staining of whole bacteria, the antibodies reveal the protein in clusters, as indicated by patches of intense fluorescence in Escherichia coli cells heterologously expressing Pseudomonas ice nucleation genes. The abundance, size, and brightness of the clusters vary considerably from cell to cell. Their varying sizes may explain the variability in activity of bacterial ice nuclei. Growth at lower temperatures produces more ice nuclei, and gives brighter and more frequent patches, than growth at 37 degrees C. The observed clustering may thus reflect formation of functional ice nucleation sites in vivo. The presence of ice nucleation protein in clusters is also correlated with alterations in cell morphology.

  13. Molecular Ice Nucleation Activity of Birch Pollen

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Bichler, Magdalena; Häusler, Thomas; Weiss, Victor U.; Marchetti-Deschmann, Martina; Allmaier, Günter; Grothe, Hinrich

    2015-04-01

    Heterogeneous ice nucleation plays a major part in ecosystem and climate. Due to the triggering of ice cloud formation it influences the radiation balance of the earth, but also on the ground it can be found to be important in many processes of nature. So far the process of heterogeneous ice nucleation is not fully understood and many questions remain to be answered. Biological ice nucleation is hereby from great interest, because it shows the highest freezing temperatures. Several bacteria and fungi act as ice nuclei. A famous example is Pseudomonas syringae, a bacterium in commercial use (Snomax®), which increases the freezing from homogeneous freezing temperatures of approx. -40° C (for small volumes as in cloud droplets) to temperatures up to -2° C. In 2001 it was found that birch pollen can trigger ice nucleation (Diehl et al. 2001; Diehl et al. 2002). For a long time it was believed that this is due to macroscopic features of the pollen surface. Recent findings of Bernhard Pummer (2012) show a different picture. The ice nuclei are not attached on the pollen surface directly, but on surface material which can be easily washed off. This shows that not only the surface morphology, but also specific molecules or molecular structures are responsible for the ice nucleation activity of birch pollen. With various analytic methods we work on elucidating the structure of these molecules as well as the mechanism with which they trigger ice nucleation. To solve this we use various instrumental analytic techniques like Nuclear Magnetic Resonance spectroscopy (NMR), Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS), and Gas-phase Electrophoretic Mobility Molecular Analysis (GEMMA). Also standard techniques like various chromatographic separation techniques and solvent extraction are in use. We state here that this feature might be due to the aggregation of small molecules, with agglomerates showing a specific surface structure. Our results

  14. Contributions of Heterogeneous Ice Nucleation, Large-Scale Circulation, and Shallow Cumulus Detrainment to Cloud Phase Transition in Mixed-Phase Clouds with NCAR CAM5

    NASA Astrophysics Data System (ADS)

    Liu, X.; Wang, Y.; Zhang, D.; Wang, Z.

    2016-12-01

    Mixed-phase clouds consisting of both liquid and ice water occur frequently at high-latitudes and in mid-latitude storm track regions. This type of clouds has been shown to play a critical role in the surface energy balance, surface air temperature, and sea ice melting in the Arctic. Cloud phase partitioning between liquid and ice water determines the cloud optical depth of mixed-phase clouds because of distinct optical properties of liquid and ice hydrometeors. The representation and simulation of cloud phase partitioning in state-of-the-art global climate models (GCMs) are associated with large biases. In this study, the cloud phase partition in mixed-phase clouds simulated from the NCAR Community Atmosphere Model version 5 (CAM5) is evaluated against satellite observations. Observation-based supercooled liquid fraction (SLF) is calculated from CloudSat, MODIS and CPR radar detected liquid and ice water paths for clouds with cloud-top temperatures between -40 and 0°C. Sensitivity tests with CAM5 are conducted for different heterogeneous ice nucleation parameterizations with respect to aerosol influence (Wang et al., 2014), different phase transition temperatures for detrained cloud water from shallow convection (Kay et al., 2016), and different CAM5 model configurations (free-run versus nudged winds and temperature, Zhang et al., 2015). A classical nucleation theory-based ice nucleation parameterization in mixed-phase clouds increases the SLF especially at temperatures colder than -20°C, and significantly improves the model agreement with observations in the Arctic. The change of transition temperature for detrained cloud water increases the SLF at higher temperatures and improves the SLF mostly over the Southern Ocean. Even with the improved SLF from the ice nucleation and shallow cumulus detrainment, the low SLF biases in some regions can only be improved through the improved circulation with the nudging technique. Our study highlights the challenges of

  15. Probing Individual Ice Nucleation Events with Environmental Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Bingbing; China, Swarup; Knopf, Daniel; Gilles, Mary; Laskin, Alexander

    2016-04-01

    Heterogeneous ice nucleation is one of the processes of critical relevance to a range of topics in the fundamental and the applied science and technologies. Heterogeneous ice nucleation initiated by particles proceeds where microscopic properties of particle surfaces essentially control nucleation mechanisms. Ice nucleation in the atmosphere on particles governs the formation of ice and mixed phase clouds, which in turn influence the Earth's radiative budget and climate. Heterogeneous ice nucleation is still insufficiently understood and poses significant challenges in predictive understanding of climate change. We present a novel microscopy platform allowing observation of individual ice nucleation events at temperature range of 193-273 K and relative humidity relevant for ice formation in the atmospheric clouds. The approach utilizes a home built novel ice nucleation cell interfaced with Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system is applied for direct observation of individual ice formation events, determining ice nucleation mechanisms, freezing temperatures, and relative humidity onsets. Reported microanalysis of the ice nucleating particles (INP) include elemental composition detected by the energy dispersed analysis of X-rays (EDX), and advanced speciation of the organic content in particles using scanning transmission x-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The performance of the IN-ESEM system is validated through a set of experiments with kaolinite particles with known ice nucleation propensity. We demonstrate an application of the IN-ESEM system to identify and characterize individual INP within a complex mixture of ambient particles.

  16. Direct observation of ice nucleation events on individual atmospheric particles

    SciTech Connect

    Wang, Bingbing; Knopf, Daniel A.; China, Swarup; Arey, Bruce W.; Harder, Tristan H.; Gilles, Mary K.; Laskin, Alexander

    2016-01-01

    Heterogeneous ice nucleation is a physical chemistry process of critical relevance to a range of topics in the fundamental and the applied sciences and technologies. Heterogeneous ice nucleation remains insufficiently understood. This is in part due to the lack of experimental methods capable of in situ visualization of ice formation over nucleating substrates with microscopically characterized morphology and composition. We present development, validation and first applications of a novel electron microscopy platform allowing observation of individual ice nucleation events at temperature and relative humidity (RH) relevant for ice formation in a broad range of environmental and applied technology processes. The approach utilizes a custom-built ice nucleation cell, interfaced with an Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system allows dynamic observations of individual ice formation events over particles of atmospheric relevance and determination of the ice nucleation mechanisms. Additional IN-ESEM experiments allow examination of the location of ice formation on the surface of individual particles and micro-spectroscopy analysis of the ice nucleating particles (INPs). This includes elemental composition detected by the energy dispersed analysis of X-rays (EDX), speciation of the organic content in particles using scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS), and Helium ion microscopy (HeIM). The capabilities of the IN-ESEM experimental platform are demonstrated first on laboratory standards and then by chemical imaging of INPs using a complex sample of ambient particles.

  17. Freezing Rate Due to Heterogeneous Nucleation.

    NASA Astrophysics Data System (ADS)

    Vali, Gabor

    1994-07-01

    The heterogeneous nucleation of ice from supercooled water is influenced by the nature of the foreign nuclei that serve as the sites for ice embryo formation, and by the stochastic nature of the process of embryo growth to critical size. The relative roles of these two factors have been the subject of some debate, especially as they influence the way nucleation of ice is modeled in clouds. `Freezing rate' is defined as the time-dependent rate at which a population of macroscopically identical samples (e.g., drops in a volume of air) freeze due to the nuclei contained in them. Freezing rate is the combined result of nucleus content and of time dependence. The time-dependent freezing rate model (TDFR) is consistent with available empirical evidence. For droplets cooled at rates of the order of 1°C per min, the nucleus content, or nucleus spectrum, predicts the freezing rate with reasonable accuracy. For samples exposed to a fixed temperature, the time dependence of the freezing rate becomes important, but the probability of freezing is not the same for each individual of the sample population. Stochastic models are not supported by the results. Application of the TDFR model and use of measured freezing nucleus data for precipitation provide a basis for the description of ice formation via immersion-freezing nucleation in cloud models. Limitations to full development of these models arise from inadequate knowledge about the freezing nucleus content of cloud water as a function of cloud evolution.

  18. Ice nucleation properties of agricultural soil dusts

    NASA Astrophysics Data System (ADS)

    Steinke, Isabelle; Funk, Roger; Busse, Jacqueline; Iturri, Antonela; Kirchen, Silke; Leue, Martin; Möhler, Ottmar; Schwartz, Thomas; Sierau, Berko; Toprak, Emre; Ulrich, Andreas; Hoose, Corinna; Leisner, Thomas

    2015-04-01

    Soil dust particles emitted from agricultural areas contain large amounts of organic material such as fungi, bacteria and plant debris. Being carrier for potentially highly ice-active biological particles, agricultural soil dusts are candidates for being very ice-active as well. In this work, we present ice nucleation experiments conducted in the AIDA cloud chamber. We investigated the ice nucleation efficiency of four types of soil dust from different regions of the world. Results are presented for the immersion freezing and the deposition nucleation mode: all soil dusts show higher ice nucleation efficiencies than desert dusts, especially at temperatures above 254 K. For one soil dust sample, the effect of heat treatments was investigated. Heat treatments did not affect the ice nucleation efficiency which presumably excludes primary biological particles as the only source of the increased ice nucleation efficiency. Therefore, organo-mineral complexes or organic compounds may contribute substantially to the high ice nucleation activity of agricultural soil dusts.

  19. Kinetics of Ice Nucleation Confined in Nanoporous Alumina.

    PubMed

    Suzuki, Yasuhito; Steinhart, Martin; Butt, Hans-Jürgen; Floudas, George

    2015-09-03

    The nucleation mechanism of water (heterogeneous/homogeneous) can be regulated by confinement within nanoporous alumina. The kinetics of ice nucleation is studied in confinement by employing dielectric permittivity as a probe. Both heterogeneous and homogeneous nucleation, obtained at low and high undercooling, respectively, are stochastic in nature. The temperature interval of metastability extends over ∼4 and 0.4 °C for heterogeneous and homogeneous nucleation, respectively. Nucleation within a pore is spread to all pores in the template. We have examined a possible coupling of all pores through a heat wave and a sound wave, with the latter being a more realistic scenario. In addition, dielectric spectroscopy indicates that prior to crystallization undercooled water molecules relax with an activation energy of ∼50 kJ/mol, and this process acts as precursor to ice nucleation.

  20. Heterogeneous and homogeneous nucleation compared: rapid nucleation on microscopic impurities.

    PubMed

    Sear, Richard P

    2006-03-16

    We use computer simulation to calculate the rates of both homogeneous nucleation and heterogeneous nucleation on microscopic impurities. We do so in perhaps the simplest model of fluids and magnets: the two-dimensional Ising model. We expect our results to be qualitatively applicable to many simple and complex fluids. We find that heterogeneous nucleation on an impurity that is not only microscopic but also as small as possible, that is, a single fixed spin, is more than four orders of magnitude faster than homogeneous nucleation. The rate of heterogeneous nucleation then increases by a factor of approximately five for each additional fixed spin in the impurity. These results suggest that impurities as small as single molecules can result in homogeneous nucleation being irrelevant due to heterogeneous nucleation on these microscopic impurities being much faster.

  1. A detailed study of ice nucleation by feldspar minerals

    NASA Astrophysics Data System (ADS)

    Whale, T. F.; Murray, B. J.; Wilson, T. W.; Carpenter, M. A.; Harrison, A.; Holden, M. A.; Vergara Temprado, J.; Morris, J.; O'Sullivan, D.

    2015-12-01

    Immersion mode heterogeneous ice nucleation plays a crucial role in controlling the composition of mixed phase clouds, which contain both supercooled liquid water and ice particles. The amount of ice in mixed phase clouds can affect cloud particle size, lifetime and extent and so affects radiative properties and precipitation. Feldspar minerals are probably the most important minerals for ice nucleation in mixed phase clouds because they nucleate ice more efficiently than other components of atmospheric mineral dust (Atkinson et al. 2013). The feldspar class of minerals is complex, containing numerous chemical compositions, several crystal polymorphs and wide variations in microscopic structure. Here we present the results of a study into ice nucleation by a wide range of different feldspars. We found that, in general, alkali feldspars nucleate ice more efficiently than plagioclase feldspars. However, we also found that particular alkali feldspars nucleate ice relatively inefficiently, suggesting that chemical composition is not the only important factor that dictates the ice nucleation efficiency of feldspar minerals. Ice nucleation by feldspar is described well by the singular model and is probably site specific in nature. The alkali feldspars that do not nucleate ice efficiently possess relatively homogenous structure on the micrometre scale suggesting that the important sites for nucleation are related to surface topography. Ice nucleation active site densities for the majority of tested alkali feldspars are similar to those found by Atkinson et al (2013), meaning that the validity of global aerosol modelling conducted in that study is not affected. Additionally, we have found that ice nucleation by feldspars is strongly influenced, both positively and negatively, by the solute content of droplets. Most other nucleants we have tested are unaffected by solutes. This provides insight into the mechanism of ice nucleation by feldspars and could be of importance

  2. Repeatability and randomness in heterogeneous freezing nucleation

    NASA Astrophysics Data System (ADS)

    Vali, G.

    2008-08-01

    This study is aimed at clarifying the relative importance of the specific character of the nuclei and of the duration of supercooling in heterogeneous freezing nucleation by immersed impurities. Laboratory experiments were carried out in which sets of water drops underwent multiple cycles of freezing and melting. The drops contained suspended particles of mixtures of materials; the resulting freezing temperatures ranged from -6°C to -24°C. Rank correlation coefficients between observed freezing temperatures of the drops in successive runs were >0.9 with very high statistical significance, and thus provide strong support for the modified singular model of heterogeneous immersion freezing nucleation. For given drops, changes in freezing temperatures between cycles were relatively small (<1°C) for the majority of the events. These frequent small fluctuations in freezing temperatures are interpreted as reflections of the random nature of embryo growth and are associated with a nucleation rate that is a function of a temperature difference from the characteristic temperatures of nuclei. About a sixth of the changes were larger, up to ±5°C, and exhibited some systematic patterns. These are thought to arise from alterations of the nuclei, some being permanent and some transitory. The results are used to suggest ways of describing ice initiation in cloud models that account for both the temperature and the time dependence of freezing nucleation.

  3. Repeatability and randomness in heterogeneous freezing nucleation

    NASA Astrophysics Data System (ADS)

    Vali, G.

    2008-02-01

    This study is aimed at clarifying the relative importance of the specific character of the nuclei and of the duration of supercooling in heterogeneous freezing nucleation by immersed impurities. Laboratory experiments were carried out in which sets of water drops underwent multiple cycles of freezing and melting. The drops contained suspended particles of mixtures of materials; the resulting freezing temperatures ranged from -6°C to -24°C. Rank correlation coefficients between observed freezing temperatures of the drops in successive runs were >0.9 with very high statistical significance, and thus provide strong support for the modified singular model of heterogeneous immersion freezing nucleation. For given drops, changes in freezing temperatures between cycles were relatively small (<1°C) for the majority of the events. These frequent small fluctuations in freezing temperatures are interpreted as reflections of the random nature of embryo growth and are associated with a nucleation rate that is a function of a temperature difference from the characteristic temperatures of nuclei. About a sixth of the changes were larger, up to ±5°C, and exhibited some systematic patterns. These are thought to arise from alterations of the nuclei, some being permanent and some transitory. The results are used to suggest ways of describing ice initiation in cloud models that account for both the temperature and the time dependence of freezing nucleation.

  4. Laboratory Studies of Ice Nucleation on Volcanic Ash

    NASA Astrophysics Data System (ADS)

    Tolbert, M. A.; Schill, G. P.; Genareau, K. D.

    2014-12-01

    Ice nucleation on volcanic ash controls both ash aggregation and cloud glaciation, which affect human respiratory health, atmospheric transport, and global climate. We have performed laboratory studies of the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman Microscopy coupled to an environmental cell. Ash from the Fuego (Basaltic Ash, Guatemala), Soufriere Hills (Andesetic Ash, Montserrat), and Taupo (Rhyolitic Ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. We find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice at ice saturation ratios of 1.05 ± 0.1. For immersion freezing, however, only the Taupo ash exhibited efficient heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

  5. Dynamics of ice nucleation on water repellent surfaces.

    PubMed

    Alizadeh, Azar; Yamada, Masako; Li, Ri; Shang, Wen; Otta, Shourya; Zhong, Sheng; Ge, Liehui; Dhinojwala, Ali; Conway, Ken R; Bahadur, Vaibhav; Vinciquerra, A Joseph; Stephens, Brian; Blohm, Margaret L

    2012-02-14

    Prevention of ice accretion and adhesion on surfaces is relevant to many applications, leading to improved operation safety, increased energy efficiency, and cost reduction. Development of passive nonicing coatings is highly desirable, since current antiicing strategies are energy and cost intensive. Superhydrophobicity has been proposed as a lead passive nonicing strategy, yet the exact mechanism of delayed icing on these surfaces is not clearly understood. In this work, we present an in-depth analysis of ice formation dynamics upon water droplet impact on surfaces with different wettabilities. We experimentally demonstrate that ice nucleation under low-humidity conditions can be delayed through control of surface chemistry and texture. Combining infrared (IR) thermometry and high-speed photography, we observe that the reduction of water-surface contact area on superhydrophobic surfaces plays a dual role in delaying nucleation: first by reducing heat transfer and second by reducing the probability of heterogeneous nucleation at the water-substrate interface. This work also includes an analysis (based on classical nucleation theory) to estimate various homogeneous and heterogeneous nucleation rates in icing situations. The key finding is that ice nucleation delay on superhydrophobic surfaces is more prominent at moderate degrees of supercooling, while closer to the homogeneous nucleation temperature, bulk and air-water interface nucleation effects become equally important. The study presented here offers a comprehensive perspective on the efficacy of textured surfaces for nonicing applications.

  6. Effect of solute on the nucleation and propagation of ice.

    PubMed

    Charoenrein, S; Goddard, M; Reid, D S

    1991-01-01

    Using the emulsion technique, we have studied nucleation of ice in aqueous solutions containing silver iodide or Pseudomonas syringae. Using a Differential Scanning Calorimeter (DSC), we determined characteristic temperatures of nucleation, and also rates of nucleation at selected temperatures. The freezing point depression induced by added solute is linearly related to the lowering of both homogeneous and heterogeneous nucleation temperature. Nucleation kinetics depend on a fifth power function of the temperature. Solute is found to affect the parameters of this relationship in different ways, dependent upon the nature of the catalytic site for ice nucleation. We have also studied the effect of composition on the linear propagation velocity (LPV) of ice in undercooled solutions contained in a U-tube. We have determined velocities in a range of concentrations of sugar solution at the same undercooling, and also as a function of undercooling. The role of added polymer has also been investigated. It is affected by the sugar concentration.

  7. Bacterial ice nucleation: significance and molecular basis.

    PubMed

    Gurian-Sherman, D; Lindow, S E

    1993-11-01

    Several bacterial species are able to catalyze ice formation at temperatures as warm as -2 degrees C. These microorganisms efficiently catalyze ice formation at temperatures much higher than most organic or inorganic substances. Because of their ubiquity on the surfaces of frost-sensitive plants, they are responsible for initiating ice formation, which results in frost injury. The high temperature of ice catalysis conferred by bacterial ice nuclei makes them useful in ice nucleation-limited processes such as artificial snow production, the freezing of some food products, and possibly in future whether modification schemes. The rarity of other ice nuclei active at high subfreezing temperature, and the ease and sensitivity with which ice nuclei can be quantified, have made the use of a promoterless bacterial ice nucleation gene valuable as a reporter of transcription. Target genes to which this promoter is fused can be used in cells in natural habitats. Warm-temperature ice nucleation sites have also been extensively studied at a molecular level. Nucleation sites active at high temperatures (above -5 degrees C) are probably composed of bacterial ice nucleation protein molecules that form functionally aligned aggregates. Models of ice nucleation proteins predict that they form a planar array of hydrogen binding groups that closely complement that of an ice crystal face. Moreover, interdigitation of these molecules may produce a large contiguous template for ice formation.

  8. The effects of ice on methane hydrate nucleation: a microcanonical molecular dynamics study.

    PubMed

    Zhang, Zhengcai; Guo, Guang-Jun

    2017-07-26

    Although ice powders are widely used in gas hydrate formation experiments, the effects of ice on hydrate nucleation and what happens in the quasi-liquid layer of ice are still not well understood. Here, we used high-precision constant energy molecular dynamics simulations to study methane hydrate nucleation from vapor-liquid mixtures exposed to the basal, prismatic, and secondary prismatic planes of hexagonal ice (ice Ih). Although no significant difference is observed in hydrate nucleation processes for these different crystal planes, it is found, more interestingly, that methane hydrate can nucleate either on the ice surface heterogeneously or in the bulk solution phase homogeneously. Several factors are mentioned to be able to promote the heterogeneous nucleation of hydrates, including the adsorption of methane molecules at the solid-liquid interface, hydrogen bonding between hydrate cages and the ice structure, the stronger ability of ice to transfer heat than that of the aqueous solution, and the higher occurrence probability of hydrate cages in the vicinity of the ice surface than in the bulk solution. Meanwhile, however, the other factors including the hydrophilicity of ice and the ice lattice mismatch with clathrate hydrates can inhibit heterogeneous nucleation on the ice surface and virtually promote homogeneous nucleation in the bulk solution. Certainly, the efficiency of ice as a promoter and as an inhibitor for heterogeneous nucleation is different. We estimate that the former is larger than the latter under the working conditions. Additionally, utilizing the benefit of ice to absorb heat, the NVE simulation of hydrate formation with ice can mimic the phenomenon of ice shrinking during the heterogeneous nucleation of hydrates and lower the overly large temperature increase during homogeneous nucleation. These results are helpful in understanding the nucleation mechanism of methane hydrate in the presence of ice.

  9. Viscosity of interfacial water regulates ice nucleation

    SciTech Connect

    Li, Kaiyong; Chen, Jing; Zhang, Qiaolan; Zhang, Yifan; Xu, Shun; Zhou, Xin; Cui, Dapeng; Wang, Jianjun Song, Yanlin

    2014-03-10

    Ice formation on solid surfaces is an important phenomenon in many fields, such as cloud formation and atmospheric icing, and a key factor for applications in preventing freezing. Here, we report temperature-dependent nucleation rates of ice for hydrophilic and hydrophobic surfaces. The results show that hydrophilic surface presents a lower ice nucleation rate. We develop a strategy to extract the thermodynamic parameters, J{sub 0} and Γ, in the context of classical nucleation theory. From the extracted J{sub 0} and Γ, we reveal the dominant role played by interfacial water. The results provide an insight into freezing mechanism on solid surfaces.

  10. Metadynamics simulations of ice nucleation and growth.

    PubMed

    Quigley, D; Rodger, P M

    2008-04-21

    The metadynamics method for accelerating rate events in molecular simulations is applied to the problem of ice freezing. We demonstrate homogeneous nucleation and growth of ice at 180 K in the isothermal-isobaric ensemble without the presence of external fields or surfaces. This result represents the first report of continuous and dynamic ice nucleation in a system of freely evolving density. Simulations are conducted using a variety of periodic simulation domains. In all cases the cubic polymorph ice I(c) is grown. The influence of boundary effects on estimates of the nucleation free energy barrier are discussed in relation to differences between this and earlier work.

  11. Ice nucleation on hydrophilic silicon

    NASA Astrophysics Data System (ADS)

    Ochshorn, Eli; Cantrell, Will

    2008-04-01

    We have used Fourier transform infrared spectroscopy to study thin water films on a hydrophilic silicon surface in the temperature range from 20to-20°C. Throughout that range, the spectra of the water adjacent to the silicon surface are consistent with that of bulk water near 25°C. Thicker films (>1μm) freeze at -11±1°C. We reconcile the apparent paradox of a thin film of water which is quite liquidlike at a temperature where freezing of thicker films occurs by hypothesizing that the nucleation event in the thicker film is triggered by a critical ice embryo which forms at some small distance from the silicon surface, as opposed to in direct contact with it.

  12. Ice Nucleation by High Molecular Weight Organic Compounds

    NASA Astrophysics Data System (ADS)

    Cantrell, W.

    2003-12-01

    Deep convection in the tropics is frequently associated with biomass burning. Recent work has suggested that the size of ice crystals in the anvils of tropical cumulonimbus clouds may be affected by biomass burning, though the mechanism for such an effect is uncertain (Sherwood, 2002). We will present results of an investigation of the role that high molecular weight organic compounds, known to be produced in biomass burning (Elias et al., 1999), may play in tropical cirrus anvils through heterogeneous nucleation of ice. In particular, we examine the mechanisms underlying heterogeneous nucleation of ice by films of long chain alcohols by studying the interaction of the alcohols and water/ice using temperature controlled, Attenuated Total Reflection - Fourier Transform Infrared spectroscopy. The mechanisms are interpreted in the context of recent criticisms of some aspects of classical nucleation theory (Seeley and Seidler, 2001; Oxtoby, 1998). References V. Elias, B. Simoneit, A. Pereira, J. Cabral, and J. Cardoso, Detection of high molecular weight organic tracers in vegetation smoke samples by high-temperature gas chromatography-mass spectrometry. Environ. Sci. Tecnol., 33, 2369-2376, 1999. D. Oxtoby, Nucleation of first-order phase transitions. Acc. Chem. Res., 31, 91-97, 1998. L. Seeley and G. Seidler, Preactivation in the nucleation of ice by Langmuir films of aliphatic alcohols. J. Chem. Phys., 114, 10464-10470, 2001. S. Sherwood, Aerosols and ice particle size in tropical cumulonimbus. J. Climate, 15, 1051-1063, 2002.

  13. Ice Nucleation Near the Surfactant-Water Interface

    NASA Astrophysics Data System (ADS)

    Carlin, Caleb; Cantrell, Will; Taylor, Caroline

    2008-03-01

    Ice nucleation is a fundamental component of the atmospheric mechanisms driving the formation of clouds. Atmospheric nucleation occurs with a variety of compounds and conditions, but understanding the behavior of water is key in all cases. We have used multiscale molecular simulations to study heterogeneous nucleation in clouds, probing the influence of long-chain alcohols on the freezing of water droplets. Ice nucleation occurs at a finite distance from the heterogeneous surface, due to the disruption of the hydrogen bond network in response to the surfactant-water interface. The penetration depth of the disturbance is found to be dependent upon the chain length and surface organization, as well as the acidity of the terminal alcohol group.

  14. Molecular dynamics simulations of ice nucleation by electric fields.

    PubMed

    Yan, J Y; Patey, G N

    2012-07-05

    Molecular dynamics simulations are used to investigate heterogeneous ice nucleation in model systems where an electric field acts on water molecules within 10-20 Å of a surface. Two different water models (the six-site and TIP4P/Ice models) are considered, and in both cases, it is shown that a surface field can serve as a very effective ice nucleation catalyst in supercooled water. Ice with a ferroelectric cubic structure nucleates near the surface, and dipole disordered cubic ice grows outward from the surface layer. We examine the influences of temperature and two important field parameters, the field strength and distance from the surface over which it acts, on the ice nucleation process. For the six-site model, the highest temperature where we observe field-induced ice nucleation is 280 K, and for TIP4P/Ice 270 K (note that the estimated normal freezing points of the six-site and TIP4P/Ice models are ∼289 and ∼270 K, respectively). The minimum electric field strength required to nucleate ice depends a little on how far the field extends from the surface. If it extends 20 Å, then a field strength of 1.5 × 10(9) V/m is effective for both models. If the field extent is 10 Å, then stronger fields are required (2.5 × 10(9) V/m for TIP4P/Ice and 3.5 × 10(9) V/m for the six-site model). Our results demonstrate that fields of realistic strength, that act only over a narrow surface region, can effectively nucleate ice at temperatures not far below the freezing point. This further supports the possibility that local electric fields can be a significant factor influencing heterogeneous ice nucleation in physical situations. We would expect this to be especially relevant for ice nuclei with very rough surfaces where one would expect local fields of varying strength and direction.

  15. A method to study intracellular ice nucleation.

    PubMed

    Tatsutani, K; Rubinsky, B

    1998-02-01

    The thermodynamics of intracellular ice nucleation are important in low-temperature biology for understanding and controlling the process of cell destruction by freezing. We have developed a new apparatus and technique for studying the physics of intracellular ice nucleation. Employing the principle of directional solidification in conjunction with light microscopy, we can generate information on the temperature at which ice nucleates intracellularly as a function of the thermal history the cells experience. The methodology is introduced, and results with primary prostatic cancer cells are described.

  16. Activity of different proteinaceous ice nucleating particles

    NASA Astrophysics Data System (ADS)

    Hartmann, Susann; Augustin-Bauditz, Stefanie; Grawe, Sarah; Ling, Meilee; Hellner, Lisa; Zapf, Jean-Michel; Šantl-Temkiv, Tina; Pummer, Bernhard; Boesen, Thomas; Wex, Heike; Finster, Kai; Stratmann, Frank

    2017-04-01

    A variety of microorganisms (bacteria, fungi, lichen) from land produce protein structures, which act as a template for ice nucleation [1]. Also marine sources of ice nucleating particles (INPs) came in focus in the recent years. The atmospheric spatio-temporal distribution of INPs from microorganisms is still not well known. However, it is often assumed that the observed onset of atmospheric ice nucleation (T>-20°C) is due to the existence of ice-nucleation active biological particles. In this study we compare the ice nucleation activity of different proteinaceous particles produced by bacteria and fungi. For bacteria we investigate (i) cells and fragments of Pseudomonas syringae from commercially available SnomaxTM and (ii) the Pseudomonas syringae INA protein expressed in living Escherichia coli bacteria. We also analyzed freeze-dried leaves [2] where we assume that proteinaceous particles are responsible for the ice nucleation activity. For fungi the widespread soil fungus Mortierella alpina was investigated which had been extracted from natural soil [3]. Immersion freezing experiments are performed at the cold stage LINA (Leipzig Ice Nucleation Array). We attempt to describe the activity of a single proteinaceous ice nucleating particle [4] in order to achieve direct comparability. Further, the results are compared with complex natural systems e.g. soil dust. The objectives of this study are to clarify potential differences in the ice nucleation potential of proteinaceous particles and to draw conclusions concerning the need to differentiate them for modelling purposes. 1. Szyrmer, W. and I. Zawadzki, Biogenic and anthropogenic sources of ice-forming nuclei: A review, Bull. Amer. Meteorol. Soc., 1997. 2. Schnell, R.C. and G. Vali, Biogenic ice nucleai .1: Terrestrial and marine sources, doi: 10.1175/1520-0469(1976)033<1554:binpit>2.0.co;2, 1976. 3. Froehlich-Nowoisky, J. et al., Ice nucleation activity in the widespread soil fungus Mortierella alpina, doi: 10

  17. Two-Dimensional Nucleation of Ice from Supercooled Water

    NASA Astrophysics Data System (ADS)

    Seeley, L. H.; Seidler, G. T.

    2001-03-01

    Heterogeneous nucleation is the initial formation of a stable phase from a metastable phase in the presence of a catalyzing surface. This ubiquitous process has consequences ranging from metallurgy to the formation of kidney stones. Heterogeneous nucleation of ice plays a central role in cloud formation, suggesting one possible connection between anthropogenic pollutants and global climate. A key topic in the theory of nucleation is the geometry of the critical nucleus. Standard nucleation theories generally predict a compact critical nucleus with a surface of roughly constant curvature. We report measurements of the temperature dependent nucleation rate of ice from water samples supporting aliphatic alcohol Langmuir films. We use classical nucleation theory to extract thermodynamic parameters from the measured nucleation rates. From these parameters we conclude that both the effective free energy barrier and the molecular kinetics of nucleation are dominated by the physics at the interface. Our results give self-consistent evidence that the geometry of the critical nucleus in this system is essentially two-dimensional.

  18. Ice nucleation by water-soluble macromolecules

    NASA Astrophysics Data System (ADS)

    Pummer, B. G.; Budke, C.; Augustin-Bauditz, S.; Niedermeier, D.; Felgitsch, L.; Kampf, C. J.; Huber, R. G.; Liedl, K. R.; Loerting, T.; Moschen, T.; Schauperl, M.; Tollinger, M.; Morris, C. E.; Wex, H.; Grothe, H.; Pöschl, U.; Koop, T.; Fröhlich-Nowoisky, J.

    2015-04-01

    Cloud glaciation is critically important for the global radiation budget (albedo) and for initiation of precipitation. But the freezing of pure water droplets requires cooling to temperatures as low as 235 K. Freezing at higher temperatures requires the presence of an ice nucleator, which serves as a template for arranging water molecules in an ice-like manner. It is often assumed that these ice nucleators have to be insoluble particles. We point out that also free macromolecules which are dissolved in water can efficiently induce ice nucleation: the size of such ice nucleating macromolecules (INMs) is in the range of nanometers, corresponding to the size of the critical ice embryo. As the latter is temperature-dependent, we see a correlation between the size of INMs and the ice nucleation temperature as predicted by classical nucleation theory. Different types of INMs have been found in a wide range of biological species and comprise a variety of chemical structures including proteins, saccharides, and lipids. Our investigation of the fungal species Acremonium implicatum, Isaria farinosa, and Mortierella alpina shows that their ice nucleation activity is caused by proteinaceous water-soluble INMs. We combine these new results and literature data on INMs from fungi, bacteria, and pollen with theoretical calculations to develop a chemical interpretation of ice nucleation and water-soluble INMs. This has atmospheric implications since many of these INMs can be released by fragmentation of the carrier cell and subsequently may be distributed independently. Up to now, this process has not been accounted for in atmospheric models.

  19. Adjoint Techniques to Minimize the Uncertainty in Heterogeneous Nucleation Spectrum

    NASA Astrophysics Data System (ADS)

    Nenes, A.; Sullivan, S.; Sheyko, B. A.; Barahona, D.

    2014-12-01

    Although recent research has focused on more accurately representing heterogeneous ice nucleation in climate models, significant uncertainties are still associated with these nucleation spectra. Here we present adjoint techniques as a new, computationally efficient means of helping to minimize these uncertainites. Automatic differentiation tools are used to construct the adjoint model of the 2009 Barahona and Nenes ice nucleation parameterization (ABN13), run in both the Community Atmosphere Model version 5 and the Goddard Earth Observing System Model version 5 at pressure levels relevant to both cirrus and mixed-phase clouds. Ice crystal number sensitivities to dynamic and aerosol inputs are calculated using two empirical spectra (Phillips et al. 2008 and Phillips et al. 2013) and one spectrum based on classical nucleation theory (Barahona and Nenes 2009). At cirrus-relevant altitudes, the sensitivity can be used to classify freezing regime; we see large regions of homogeneous freezing in the tropics but predominantly heterogeneous freezing elsewhere. The more recent empirical spectrum indicates the importance of accumulation mode dust number; of appropriately representating vertical motions; and of accurate threshold supersaturations in determining in-cloud crystal number on a global scale. Glassy aerosol has a small, seasonally-dependent contribution at high altitudes, while the global contribution of black carbon to ice number becomes negligible. Attribution analyses also allows us to pinpoint which variables and regions generate the most variability in ice crystal number, and whether this variability comes from inherent parameterization biases or from input fluctuations.

  20. Does hydrophilicity of carbon particles improve their ice nucleation ability?

    PubMed

    Lupi, Laura; Molinero, Valeria

    2014-09-04

    Carbonaceous particles account for 10% of the particulate matter in the atmosphere. Atmospheric oxidation and aging of soot modulates its ice nucleation ability. It has been suggested that an increase in the ice nucleation ability of aged soot results from an increase in the hydrophilicity of the surfaces upon oxidation. Oxidation, however, also impacts the nanostructure of soot, making it difficult to assess the separate effects of soot nanostructure and hydrophilicity in experiments. Here we use molecular dynamics simulations to investigate the effect of changes in hydrophilicity of model graphitic surfaces on the freezing temperature of ice. Our results indicate that the hydrophilicity of the surface is not in general a good predictor of ice nucleation ability. We find a correlation between the ability of a surface to promote nucleation of ice and the layering of liquid water at the surface. The results of this work suggest that ordering of liquid water in contact with the surface plays an important role in the heterogeneous ice nucleation mechanism.

  1. Biological ice nucleation initiates hailstone formation

    NASA Astrophysics Data System (ADS)

    Michaud, Alexander B.; Dore, John E.; Leslie, Deborah; Lyons, W. Berry; Sands, David C.; Priscu, John C.

    2014-11-01

    Cloud condensation and ice nuclei in the troposphere are required precursors to cloud and precipitation formation, both of which influence the radiative balance of Earth. The initial stage of hailstone formation (i.e., the embryo) and the subsequent layered growth allow hail to be used as a model for the study of nucleation processes in precipitation. By virtue of the preserved particle and isotopic record captured by hailstones, they represent a unique form of precipitation that allows direct characterization of the particles present during atmospheric ice nucleation. Despite the ecological and economic consequences of hail storms, the dynamics of hailstone nucleation, and thus their formation, are not well understood. Our experiments show that hailstone embryos from three Rocky Mountain storms contained biological ice nuclei capable of freezing water at warm, subzero (°C) temperatures, indicating that biological particles can act as nucleation sites for hailstone formation. These results are corroborated by analysis of δD and δ18O from melted hailstone embryos, which show that the hailstones formed at similarly warm temperatures in situ. Low densities of ice nucleation active abiotic particles were also present in hailstone embryos, but their low concentration indicates they were not likely to have catalyzed ice formation at the warm temperatures determined from water stable isotope analysis. Our study provides new data on ice nucleation occurring at the bottom of clouds, an atmospheric region whose processes are critical to global climate models but which has challenged instrument-based measurements.

  2. Components of ice nucleation structures of bacteria.

    PubMed Central

    Turner, M A; Arellano, F; Kozloff, L M

    1991-01-01

    Nonprotein components attached to the known protein product of the inaZ gene of Pseudomonas syringae have been identified and shown to be necessary for the most efficient ice nucleation of supercooled H2O. Previous studies have shown that cultures of Ina+ bacteria have cells with three major classes of ice-nucleating structures with readily differentiated activities. Further, some cells in the culture have nucleating activities intermediate between those of the different classes and presumably have structures that are biosynthetic intermediates between those of the different classes. Since these structures cannot be readily isolated and analyzed, their components have been identified by the use of specific enzymes or chemical probes, by direct incorporation of labeled precursors, and by stimulation of the formation of specific classes of freezing structures by selective additions to the growth medium. From these preliminary studies it appears that the most active ice nucleation structure (class A) contains the ice nucleation protein linked to phosphatidylinositol and mannose, probably as a complex mannan, and possibly glucosamine. These nonprotein components are characteristic of those used to anchor external proteins to cell membranes of eucaryotic cells and suggest that a similar but not identical anchoring mechanism is required for efficient ice nucleation structure. The class B structure has been found to contain protein presumably linked to the mannan and glucosamine moieties but definitely not to the phosphatidylinositol. The class C structure, which has the poorest ice nucleation activity, appears to be the ice nucleation protein linked to a few mannose residues and to be partially imbedded in the outer cell membrane. Images FIG. 1 FIG. 2 FIG. 5 FIG. 9 FIG. 15 FIG. 16 PMID:1917876

  3. The Ice Nucleation Ability of Selected Atmospherically Abundant Fungal Spores

    NASA Astrophysics Data System (ADS)

    Iannone, R.; Chernoff, D. I.; Bertram, A. K.

    2010-12-01

    Ice clouds are widely recognized for their roles in the earth’s radiation budget and climate systems. However, their formation mechanisms are poorly understood thus constituting an uncertainty in the evaluation of the global radiation budget. An important mechanism of ice cloud formation is heterogeneous nucleation on aerosol particles. The surface properties of these particles, called ice nuclei (IN), directly affect the temperature at which ice nucleation occurs. There is a growing emphasis on the study of bioaerosols (e.g., bacteria, fungi, pollen) as IN since they are ubiquitous in the atmosphere. The focus of the current study is to determine the ice nucleation properties of spores obtained from a variety of fungi. Aerosolized spores were impacted onto a hydrophobic glass substrate and immersed in ultrapure water. A technique involving an optical light microscope coupled to a flow cell was used to precisely control temperature and humidity within the cell. A digital camera captured high-resolution video of the particles undergoing ice nucleation, allowing for the analyses of freezing events and particle sizes. The first experimental results using spores obtained from the fungal genera Cladosporium and Penicillium reveal an average temperature increase of ~1-5 K in the ice nucleation temperature compared to homogeneous nucleation (i.e., freezing of pure liquid water). Furthermore, there appears to be a relationship between the amount of spores present per droplet and the freezing temperature of water. These results are presented and discussed, and the potential contribution of these data to further the understanding of heterogeneous nucleation in the atmosphere is provided. Box plot summarizing freezing data for homogeneous nucleation experiments (leftmost box) and binned data from heterogeneous nucleation experiments involving spores of Cladosporium. Freezing data are distributed into 200 µm2 bins that represent the total area of all observable inclusions

  4. New Findings on Ice Nucleation in Mid-latitude Cirrus

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Mitchell, D. L.; Lawson, P.; Baker, B. A.

    2011-12-01

    Recent GCM simulations (CESM1) show a global aerosol indirect effect of -1.39 W m-2 with -2.02 W m-2 from shortwave and +0.63 W m-2 from longwave cloud forcing, the longwave being due to homogeneous nucleation of ice crystals. However, the extent of homogeneous nucleation in ice clouds is poorly understood. This study uses results from a recent field campaign, SPARTICUS (Small PARTicles In CirrUS), to evaluate the impact of homogeneous nucleation on the ice particle size distribution (PSD) shape, as well as ice particle concentration, shape, PSD effective size and fall speed. While earlier measurements were difficult to evaluate for ice nucleation effects due to the problem of ice particle shattering, recent in-situ measurements using the 2 dimensional-stereo (2D-S) probe have greatly reduced this problem resulting in provocative findings for both synoptic and anvil cirrus sampled during SPARTICUS. For mid-latitude synoptic and anvil cirrus around -40°C, these new measurements show that clear changes in the ice PSD and its properties occur regarding (1) PSD shape, (2) total number concentration-to-ice water content ratio (N/IWC), (3) PSD mean size, (4) PSD mean area ratio and (5) the mass-weighted fall velocity (Vm). These changes are consistent with a change in ice nucleation mechanism, with heterogeneous nucleation processes active at temperatures warmer than -40°C and homogeneous freezing nucleation at temperatures colder than -40°C. The change in Vm implies that cirrus colder than -40°C will have longer lifetimes and greater cloud coverage than warmer cirrus clouds, all other relevant factors remaining equal. The increase in N/IWC with colder temperatures (T < -40°C) appears consistent with homogeneous nucleation theory. Figure 1 shows normalized frequency distribution of PSD area ratios for temperatures above and below -40°C. Area ratios (ice particle projected area/area of circle defined by particle maximum dimension) are a measure of ice particle shape

  5. Homogeneous ice nucleation from supercooled water.

    PubMed

    Li, Tianshu; Donadio, Davide; Russo, Giovanna; Galli, Giulia

    2011-11-28

    Homogeneous ice nucleation from supercooled water was studied in the temperature range of 220-240 K through combining the forward flux sampling method (Allen et al., J. Chem. Phys., 2006, 124, 024102) with molecular dynamics simulations (FFS/MD), based on a recently developed coarse-grained water model (mW) (Molinero et al., J. Phys. Chem. B, 2009, 113, 4008). The calculated ice nucleation rates display a strong temperature dependence, ranging from 2.148 ± 0.635 × 10(25) m(-3) s(-1) at 220 K to 1.672 ± 0.970 × 10(-7) m(-3) s(-1) at 240 K. These rates can be fitted according to the classical nucleation theory, yielding an estimate of the effective ice-water interface energy γ(ls) of 31.01 ± 0.21 mJ m(-2) for the mW water model. Compared to experiments, our calculation underestimates the homogeneous ice nucleation rate by a few orders of magnitude. Possible reasons for the discrepancy are discussed. The nucleating ice embryo contains both cubic ice Ic and hexagonal ice Ih, with the fraction of each structure being roughly 50% when the critical size is reached. In particular, a novel defect structure containing nearly five-fold twin boundaries is identified in the ice clusters formed during nucleation. The way such defect structure is formed is found to be different from mechanisms proposed for the formation of the same defect in metallic nanoparticles and thin film. The quasi five-fold twin boundary structure found here is expected to occur in the crystallization of a wide range of materials with the diamond cubic structure, including ice.

  6. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-09-01

    The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosol particles that have re-vitrified in contact

  7. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-04-01

    The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosols that have re-vitrified in contact with the

  8. Generalized Gibbs' approach in heterogeneous nucleation.

    PubMed

    Abyzov, Alexander S; Schmelzer, Jürn W P

    2013-04-28

    Heterogeneous nucleation (condensation and boiling) on planar solid surfaces is described taking into account changes of the state parameters of the critical clusters in dependence on supersaturation. The account of the variation of the state parameters of the cluster phase on nucleation is performed in the framework of the generalized Gibbs' approach. One-component van der Waals fluids are chosen as a model for the analysis of the basic qualitative characteristics of the process. The analysis is performed for both hydrophobic and hydrophilic surfaces and similarities and differences between condensation and boiling processes are discussed for the two different cases. It is shown that, in the generalized Gibbs' approach, contact angle and catalytic factor for heterogeneous nucleation become dependent on the degree of metastability (undercooling or superheating) of the fluid. For the case of formation of a droplet in supersaturated vapor on a hydrophobic surface and bubble formation in a liquid on a hydrophilic surface the solid surface has only a minor influence on nucleation. In the alternative cases of condensation of a droplet on a hydrophilic surface and of bubble formation in a liquid on a hydrophobic surface, nucleation is significantly enhanced by the solid. Effectively, the existence of the solid surface results in a significant shift of the spinodal to lower supersaturations as compared with homogeneous nucleation. Qualitatively the same behavior is observed now near the new (solid surface induced) limits of instability of the fluid as compared with the behavior near to the spinodal curve in the case of homogeneous nucleation.

  9. Generalized Gibbs' approach in heterogeneous nucleation

    NASA Astrophysics Data System (ADS)

    Abyzov, Alexander S.; Schmelzer, Jürn W. P.

    2013-04-01

    Heterogeneous nucleation (condensation and boiling) on planar solid surfaces is described taking into account changes of the state parameters of the critical clusters in dependence on supersaturation. The account of the variation of the state parameters of the cluster phase on nucleation is performed in the framework of the generalized Gibbs' approach. One-component van der Waals fluids are chosen as a model for the analysis of the basic qualitative characteristics of the process. The analysis is performed for both hydrophobic and hydrophilic surfaces and similarities and differences between condensation and boiling processes are discussed for the two different cases. It is shown that, in the generalized Gibbs' approach, contact angle and catalytic factor for heterogeneous nucleation become dependent on the degree of metastability (undercooling or superheating) of the fluid. For the case of formation of a droplet in supersaturated vapor on a hydrophobic surface and bubble formation in a liquid on a hydrophilic surface the solid surface has only a minor influence on nucleation. In the alternative cases of condensation of a droplet on a hydrophilic surface and of bubble formation in a liquid on a hydrophobic surface, nucleation is significantly enhanced by the solid. Effectively, the existence of the solid surface results in a significant shift of the spinodal to lower supersaturations as compared with homogeneous nucleation. Qualitatively the same behavior is observed now near the new (solid surface induced) limits of instability of the fluid as compared with the behavior near to the spinodal curve in the case of homogeneous nucleation.

  10. Heterogeneous nucleation in solutions: generalized Gibbs' approach.

    PubMed

    Abyzov, Alexander S; Schmelzer, Jürn W P

    2014-06-28

    Heterogeneous nucleation in solutions on planar solid surfaces is modeled taking into account changes of the state parameters of the critical clusters in dependence on supersaturation. The account of the variation of the state parameters of the cluster phase on nucleation is performed in the framework of the generalized Gibbs' approach. A regular solution is chosen as a model for the analysis of the basic qualitative characteristics of the process. It is shown that, employing the generalized Gibbs approach, contact angle and catalytic activity factor for heterogeneous nucleation become dependent on the degree of metastability (supersaturation) of the solution. For the case of formation of a cluster in supersaturated solutions on a surface of low wettability (the macroscopic equilibrium contact angles being larger than 90°), the solid surface has only a minor influence on nucleation. In the alternative case of high wettability (for macroscopic equilibrium contact angles being less than 90°), nucleation is significantly enhanced by the solid surface. Effectively, the existence of the solid surface results in a significant shift of the spinodal to lower supersaturations as compared with homogeneous nucleation. Qualitatively, the same behavior is observed now near the new (solid surface induced) limits of instability of the solution as compared with the behavior near to the spinodal curve in the case of homogeneous nucleation.

  11. The ice nucleation activity of extremophilic algae.

    PubMed

    Kviderova, Jana; Hajek, Josef; Worland, Roger M

    2013-01-01

    Differences in the level of cold acclimation and cryoprotection estimated as ice nucleation activity in snow algae (Chlamydomonas cf. nivalis and Chloromonas nivalis), lichen symbiotic algae (Trebouxia asymmetrica, Trebouxia erici and Trebouxia glomerata), and a mesophilic strain (Chlamydomonas reinhardti) were evaluated. Ice nucleation activity was measured using the freezing droplet method. Measurements were performed using suspensions of cells of A750 (absorbance at 750 nm) ~ 1, 0.1, 0.01 and 0.001 dilutions for each strain. The algae had lower ice nucleation activity, with the exception of Chloromonas nivalis contaminated by bacteria. The supercooling points of the snow algae were higher than those of lichen photobionts. The supercooling points of both, mesophilic and snow Chlamydomonas strains were similar. The lower freezing temperatures of the lichen algae may reflect either the more extreme and more variable environmental conditions of the original localities or the different cellular structure of the strains examined.

  12. Spider silk has an ice nucleation activity.

    PubMed

    Murase, N; Ruike, M; Matsunaga, N; Hayakawa, M; Kaneko, Y; Ono, Y

    2001-03-01

    Several ice nucleating substances have been identified, which exist in vivo or can be extracted from biological materials. Spider silk, which has a strong ability for water condensation, has also been found to possess an ice nucleation activity. The freezing temperature of water droplets was higher in the presence than in the absence of spider silk. Moreover, by means of environmental scanning electron microscopy, it was observed that the activity is not due to foreign matter attached to the silk but to the silk fibroin itself.

  13. Ice nucleation and antinucleation in nature.

    PubMed

    Zachariassen, K E; Kristiansen, E

    2000-12-01

    Plants and ectothermic animals use a variety of substances and mechanisms to survive exposure to subfreezing temperatures. Proteinaceous ice nucleators trigger freezing at high subzero temperatures, either to provide cold protection from released heat of fusion or to establish a protective extracellular freezing in freeze-tolerant species. Freeze-avoiding species increase their supercooling potential by removing ice nucleators and accumulating polyols. Terrestrial invertebrates and polar marine fish stabilize their supercooled state by means of noncolligatively acting antifreeze proteins. Some organisms also depress their body fluid melting point to ambient temperature by evaporation and/or solute accumulation.

  14. Ice Nucleation and Droplet Formation by Bare and Coated Soot Particles

    SciTech Connect

    Friedman, Beth J.; Kulkarni, Gourihar R.; Beranek, Josef; Zelenyuk, Alla; Thornton, Joel A.; Cziczo, Daniel J.

    2011-09-13

    We have studied ice formation at temperatures relevant to homogeneous and heterogeneous ice nucleation, as well as droplet activation and hygroscopicity, of soot particles of variable size and composition. Coatings of adipic, malic, and oleic acid were applied to span an atmospherically relevant range of solubility, and both uncoated and oleic acid coated soot particles were exposed to ozone to simulate atmospheric oxidation. The results are interpreted in terms of onset ice nucleation, with a comparison to a mineral dust particle that acts as an efficient ice nucleus, and particle hygroscopicity. At 253K and 243K, we found no evidence of heterogeneous ice nucleation occurring above the level of detection for our experimental conditions. Above water saturation, only droplet formation was observed. At 233K, we observe the occurrence of homogeneous ice nucleation for all particles studied. Coatings also did not significantly alter the ice nucleation behavior of soot particles, but aided in the uptake of water. Hygroscopicity studies confirmed that pure soot particles were hydrophobic, and coated soot particles activated as droplets at high water supersaturations. A small amount of heterogeneous ice nucleation either below the detection limit of our instrument or concurrent with droplet formation and/or homogeneous freezing cannot be precluded, but we are able to set limits for its frequency. We conclude that both uncoated and coated soot particles representative of those generated in our studies are unlikely to significantly contribute to the global budget of heterogeneous ice nuclei at temperatures between 233K and 253K.

  15. Ice nucleation of bioaerosols - a resumee

    NASA Astrophysics Data System (ADS)

    Pummer, Bernhard G.; Atanasova, Lea; Bauer, Heidi; Bernardi, Johannes; Chazallon, Bertrand; Druzhinina, Irina S.; Grothe, Hinrich

    2013-04-01

    The role of biological particles for ice nucleation (IN) is still debated. Here, we present a summary of investigation and comparison of different ice nuclei. Apart from the bacterial ice nucleation proteins in Snomax, we further investigated a broad spectrum of pollen and fungal spores in the search for ice nucleation activity. Apart from Snomax, only few samples showed vital IN activity, like Fusarium avenaceum spores and Betula pendula pollen. Chemical characterization accentuated the differences between bacterial and pollen ice nuclei. Exposure to natural stresses, like UV and NOx, led to a significant decrease in IN activity. Furthermore, the releasable fraction of the pollen material, which includes the ice nuclei, was extracted with water and dried up. These residues were investigated with Raman spectroscopy and compared with the spectra of whole pollen grains. Measurements clearly demonstrated that the aqueous fraction contained mainly saccharides, lipids and proteins, but no sporopollenin, which is the bulk material of the outer pollen wall. Fungal spores of ecologically, economically or otherwise relevant species were also investigated. Most species showed no significant IN activity at all. A few species showed a slight increase in freezing temperature, but still significantly below the activity of the most active pollen or mineral dusts. Only Fusarium avenaceum showed strong IN activity. Cultivation of Fusarium and Trichoderma (close relatives of Fusarium) at different temperatures showed changes in total protein expression, but no impact on the IN activity.

  16. Laboratory studies of cirrus clouds: the ins and outs of ice nucleation

    NASA Astrophysics Data System (ADS)

    Tolbert, M. A.; Schill, G. P.; Baustian, K. J.

    2012-12-01

    Although cirrus clouds are ever-present in the upper troposphere, the precise mechanisms governing their formation are still uncertain. Recent field observations suggest that ice nucleation in the atmosphere is often more consistent with a heterogeneous nucleation mechanism than a homogeneous one. In the present work, we use optical microscopy coupled with Raman spectroscopy to examine ice nucleation on individual micron-sized particles. Because upper tropospheric particles as well as sub-visible cirrus residues are enhanced in both sulfates and organics, our focus is on complex particles containing these two species. Particles with well-defined structures were generated by nebulization of solutions containing ammonium sulfate and an organic. As the relative humidity was decreased, the aqueous particles underwent liquid-liquid phase separation forming an organic coating over ammonium sulfate. Lowering the relative humidity further resulted in ammonium sulfate efflorescence to a crystalline solid. Ice nucleation was then studied on the layered particles as a function of temperature and relative humidity. During particle formation and ice nucleation, Raman mapping was used to determine the particle structures. Depending on the organic composition and temperature, ice was sometimes observed to nucleate on the ammonium sulfate core within the particle and sometimes nucleated on the organic outer layer. The combination of Raman and optical microscopy allows visualization of the ice nucleation process for complex particles. These studies reveal that the mechanism of heterogeneous ice nucleation depends not just on particle size, but also on particle composition, phase and mixing state.

  17. Differences in ice nucleation behavior of arable and desert soil dust in deposition nucleation regime

    NASA Astrophysics Data System (ADS)

    Ullrich, Romy; Vogel, Franziska; Möhler, Ottmar; Höhler, Kristina; Schiebel, Thea

    2017-04-01

    Soil dust from arid and semi-arid regions is one of the most abundant aerosol types in the atmosphere with emission rates of about 1600 Tg per year (Andreae et al. (2009)). Therewith, soil dust plays an important role for the atmospheric radiative transfer and also for the formation of clouds. Soil dust refers to dust sampled from agricultural used areas, to dust from bare soil as well as to dust from desert regions. By mass-spectrometric measurements of the chemical composition of ice residuals, mineral dust as component of soil dust was found to be the major heterogeneous ice nucleating particle (INP) type (e.g. Cziczo et al. (2013)), in particular in the upper troposphere. Also in laboratory studies the ice nucleation efficiency of the different soil dusts was investigated. It was shown that desert dusts (Ullrich et al. (2017)) as well as soil dusts from arable regions (O'Sullivan et al. (2014), Tobo et al. (2014)) are efficient INP. However, there is still a lack of data for ice nucleation on soil dusts for temperatures below about 220 K. With the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber, we are able to characterize the ice nucleation efficiency for different aerosol types to temperatures down to 180 K and high ice supersaturations. In order to extend the already existing AIDA data base for deposition nucleation on desert dusts and agricultural soil dusts, new experiments were done in the upper tropospheric temperature regime. This contribution will show the results of the new experiments with desert dust in comparison to existing data for higher temperatures. The first data analysis confirms the temperature dependent trend of the ice nucleation activity as discussed and parameterized in a recent paper by Ullrich et al. (2017). Furthermore, the update and extension of the recently published parameterization of deposition nucleation for desert dust to lower temperatures will be discussed. The experiments with agricultural soil

  18. Ice nucleation inhibition: mechanism of antifreeze by antifreeze protein.

    PubMed

    Du, Ning; Liu, Xiang Y; Hew, Choy Leong

    2003-09-19

    The effect of antifreeze protein type III (one type of fish antifreeze protein) on ice crystallization was examined quantitatively based on a "micro-sized ice nucleation" technique. It was found for the first time that antifreeze proteins can inhibit the ice nucleation process by adsorbing onto both the surfaces of ice nuclei and dust particles. This leads to an increase of the ice nucleation barrier and the desolvation kink kinetics barrier, respectively. Based on the latest nucleation model, the increases in the ice nucleation barrier and the kink kinetics barrier were measured. This enables us to quantitatively examine the antifreeze mechanism of antifreeze proteins for the first time.

  19. Ice nucleation sensitivity studies using the detailed microphysical model MAID

    NASA Astrophysics Data System (ADS)

    Krämer, Martina; Hildebrandt, Margit

    2010-05-01

    The influence of heterogeneous freezing on the ice crystal number of cirrus clouds have been evaluated by extensive model simulations using the detailed microphysical model MAID (Bunz et al., 2008). MAID includes heterogeneous as well as homogeneous freezing and, as a new feature, freezing thresholds for different types of ice nuclei (IN), derived from ice nucleation experiments at the cloud chamber AIDA. Cirrus formation scenarios are simulated in the temperature range 180 - 240 K in 10 K steps. For each temperature, six different vertical velocities were assumed, ranging from 1 - 1000 cm/s. Thus, one scenario contains 42 model runs. A variety of scenarios are simulated by variing the IN number between 0.001 and 0.2 cm-3 and using the freezing thresholds of coated soot and mineral dust. Further, the simulations are performed for constant vertical velocities uz as well as for uz superimposed with temperature pertubations of 1 and 3 K, respectively. Earlier studies (Gierens, 2003; Kärcher and Lohmann, 2003) concluded that homogeneous nucleation dominates in regions with updrafts stronger than 20-30 cms-1. Our simulations show that heterogeneous ice formation progressively influences the ice crystal concentrations up to uz = 100 cm/s, increasing with the IN number and with the temperature. Lowering the freezing threshold decreases the ice crystal number, while temperature pertubations increases the ice concentration, but both only for uz ≤ 10 cm/s. In addition to the ice nucleation sensitivity studies, we performed an intercomparison of MAID with a detailed microphysical model (DLR Oberpfaffenhofen, B. Kärcher) and a double moment bulk microphysics scheme (ETH Zürich, P. Spichtinger), resulting in a good agreement between the models. References: Bunz, H., Benz, S., Gensch, I., and Krämer, M. (2008): MAID: a model to simulate UT/LS aerosols and ice clouds, Envir. Res. Lett., 3, doi10.1088/1748-9326/3/3/035001. Gierens, K. (2003): On the transition between

  20. Homogeneous ice nucleation at moderate supercooling from molecular simulation.

    PubMed

    Sanz, E; Vega, C; Espinosa, J R; Caballero-Bernal, R; Abascal, J L F; Valeriani, C

    2013-10-09

    Among all of the freezing transitions, that of water into ice is probably the most relevant to biology, physics, geology, or atmospheric science. In this work, we investigate homogeneous ice nucleation by means of computer simulations. We evaluate the size of the critical cluster and the nucleation rate for temperatures ranging between 15 and 35 K below melting. We use the TIP4P/2005 and the TIP4P/ice water models. Both give similar results when compared at the same temperature difference with the model's melting temperature. The size of the critical cluster varies from ∼8000 molecules (radius = 4 nm) at 15 K below melting to ∼600 molecules (radius = 1.7 nm) at 35 K below melting. We use Classical Nucleation Theory (CNT) to estimate the ice-water interfacial free energy and the nucleation free-energy barrier. We obtain an interfacial free energy of 29(3) mN/m from an extrapolation of our results to the melting temperature. This value is in good agreement both with experimental measurements and with previous estimates from computer simulations of TIP4P-like models. Moreover, we obtain estimates of the nucleation rate from simulations of the critical cluster at the barrier top. The values we get for both models agree within statistical error with experimental measurements. At temperatures higher than 20 K below melting, we get nucleation rates slower than the appearance of a critical cluster in all water of the hydrosphere during the age of the universe. Therefore, our simulations predict that water freezing above this temperature must necessarily be heterogeneous.

  1. Single Particle Laser Mass Spectrometry Applied to Differential Ice Nucleation Experiments at the AIDA Chamber

    SciTech Connect

    Gallavardin, S. J.; Froyd, Karl D.; Lohmann, U.; Moehler, Ottmar; Murphy, Daniel M.; Cziczo, Dan

    2008-08-26

    Experiments conducted at the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) chamber located in Karlsruhe, Germany permit investigation of particle properties that affect the nucleation of ice at temperature and water vapor conditions relevant to cloud microphysics and climate issues. Ice clouds were generated by heterogeneous nucleation of Arizona test dust (ATD), illite, and hematite and homogeneous nucleation of sulfuric acid. Ice crystals formed in the chamber were inertially separated from unactivated, or ‘interstitial’ aerosol particles with a pumped counterflow virtual impactor (PCVI), then evaporated. The ice residue (i.e., the aerosol which initiated ice nucleation plus any material which was scavenged from the gas- and/or particle-phase), was chemically characterized at the single particle level using a laser ionization mass spectrometer. In this manner the species that first nucleated ice could be identified out of a mixed aerosol population in the chamber. Bare mineral dust particles were more effective ice nuclei (IN) than similar particles with a coating. Metallic particles from contamination in the chamber initiated ice nucleation before other species but there were few enough that they did not compromise the experiments. Nitrate, sulfate, and organics were often detected on particles and ice residue, evidently from scavenging of trace gas-phase species in the chamber. Hematite was a more effective ice nucleus than illite. Ice residue was frequently larger than unactivated test aerosol due to the formation of aggregates due to scavenging, condensation of contaminant gases, and the predominance of larger aerosol in nucleation.

  2. Homogeneous ice nucleation and supercooled liquid water in orographic wave clouds

    NASA Technical Reports Server (NTRS)

    Heymsfield, Andrew J.; Miloshevich, Larry M.

    1993-01-01

    This study investigates ice nucleation mechanisms in cold lenticular wave clouds, a cloud type characterized by quasi-steady-state air motions and microphysical properties. It is concluded that homogeneous ice nucleation is responsible for the ice production in these clouds at temperatures below about -33 C. The lack of ice nucleation observed above -33 C indicates a dearth of ice-forming nuclei, and hence heterogeneous ice nucleation, in these clouds. Aircraft measurements in the temperature range -31 to -41 C show the following complement of simultaneous and abrupt changes in cloud properties that indicate a transition from the liquid phase to ice: disappearance of liquid water; decrease in relative humidity from near water saturation to ice saturation; increase in mean particle size; change in particle concentration; and change in temperature due to the release of latent heat. A numerical model of cloud particle growth and homogeneous ice nucleation is used to aid in interpretation of our in situ measurements. The abrupt changes in observed cloud properties compare favorably, both qualitatively and quantitatively, with results from the homogeneous ice nucleation model. It is shown that the homogeneous ice nucleation rates from the measurements are consistent with the temperature-dependent rates employed by the model (within a factor of 100, corresponding to about 1 C in temperature) in the temperature range -35 deg to -38 C. Given the theoretical basis of the modeled rates, it may be reasonable to apply them throughout the -30 to -50 C temperature range considered by the theory.

  3. Thermodynamics of ice nucleation in liquid water.

    PubMed

    Wang, Xin; Wang, Shui; Xu, Qinzhi; Mi, Jianguo

    2015-01-29

    We present a density functional theory approach to investigate the thermodynamics of ice nucleation in supercooled water. Within the theoretical framework, the free-energy functional is constructed by the direct correlation function of oxygen-oxygen of the equilibrium water, and the function is derived from the reference interaction site model in consideration of the interactions of hydrogen-hydrogen, hydrogen-oxygen, and oxygen-oxygen. The equilibrium properties, including vapor-liquid and liquid-solid phase equilibria, local structure of hexagonal ice crystal, and interfacial structure and tension of water-ice are calculated in advance to examine the basis for the theory. The predicted phase equilibria and the water-ice surface tension are in good agreement with the experimental data. In particular, the critical nucleus radius and free-energy barrier during ice nucleation are predicted. The critical radius is similar to the simulation value, suggesting that the current theoretical approach is suitable in describing the thermodynamic properties of ice crystallization.

  4. The SPectrometer for Ice Nuclei (SPIN): An instrument to investigate ice nucleation

    DOE PAGES

    Garimella, Sarvesh; Kristensen, Thomas Bjerring; Ignatius, Karolina; ...

    2016-07-06

    The SPectrometer for Ice Nuclei (SPIN) is a commercially available ice nucleating particle (INP) counter manufactured by Droplet Measurement Technologies in Boulder, CO. The SPIN is a continuous flow diffusion chamber with parallel plate geometry based on the Zurich Ice Nucleation Chamber and the Portable Ice Nucleation Chamber. This study presents a standard description for using the SPIN instrument and also highlights methods to analyze measurements in more advanced ways. It characterizes and describes the behavior of the SPIN chamber, reports data from laboratory measurements, and quantifies uncertainties associated with the measurements. Experiments with ammonium sulfate are used to investigatemore » homogeneous freezing of deliquesced haze droplets and droplet breakthrough. Experiments with kaolinite, NX illite, and silver iodide are used to investigate heterogeneous ice nucleation. SPIN nucleation results are compared to those from the literature. A machine learning approach for analyzing depolarization data from the SPIN optical particle counter is also presented (as an advanced use). Altogether, we report that the SPIN is able to reproduce previous INP counter measurements.« less

  5. The SPectrometer for Ice Nuclei (SPIN): An instrument to investigate ice nucleation

    SciTech Connect

    Garimella, Sarvesh; Kristensen, Thomas Bjerring; Ignatius, Karolina; Welti, Andre; Voigtlander, Jens; Kulkarni, Gourihar R.; Sagan, Frank; Kok, Gregory Lee; Dorsey, James; Nichman, Leonid; Rothenberg, Daniel Alexander; Rosch, Michael; Kirchgäßner, Amelie Catharina Ruth; Ladkin, Russell; Wex, Heike; Wilson, Theodore W.; Ladino, Luis Antonio; Abbatt, Jon P. D.; Stetzer, Olaf; Lohmann, Ulrike; Stratmann, Frank; Cziczo, Daniel James

    2016-07-06

    The SPectrometer for Ice Nuclei (SPIN) is a commercially available ice nucleating particle (INP) counter manufactured by Droplet Measurement Technologies in Boulder, CO. The SPIN is a continuous flow diffusion chamber with parallel plate geometry based on the Zurich Ice Nucleation Chamber and the Portable Ice Nucleation Chamber. This study presents a standard description for using the SPIN instrument and also highlights methods to analyze measurements in more advanced ways. It characterizes and describes the behavior of the SPIN chamber, reports data from laboratory measurements, and quantifies uncertainties associated with the measurements. Experiments with ammonium sulfate are used to investigate homogeneous freezing of deliquesced haze droplets and droplet breakthrough. Experiments with kaolinite, NX illite, and silver iodide are used to investigate heterogeneous ice nucleation. SPIN nucleation results are compared to those from the literature. A machine learning approach for analyzing depolarization data from the SPIN optical particle counter is also presented (as an advanced use). Altogether, we report that the SPIN is able to reproduce previous INP counter measurements.

  6. The SPectrometer for Ice Nuclei (SPIN): an instrument to investigate ice nucleation

    NASA Astrophysics Data System (ADS)

    Garimella, Sarvesh; Bjerring Kristensen, Thomas; Ignatius, Karolina; Welti, Andre; Voigtländer, Jens; Kulkarni, Gourihar R.; Sagan, Frank; Kok, Gregory Lee; Dorsey, James; Nichman, Leonid; Rothenberg, Daniel Alexander; Rösch, Michael; Kirchgäßner, Amélie Catharina Ruth; Ladkin, Russell; Wex, Heike; Wilson, Theodore W.; Ladino, Luis Antonio; Abbatt, Jon P. D.; Stetzer, Olaf; Lohmann, Ulrike; Stratmann, Frank; Cziczo, Daniel James

    2016-07-01

    The SPectrometer for Ice Nuclei (SPIN) is a commercially available ice nucleating particle (INP) counter manufactured by Droplet Measurement Technologies in Boulder, CO. The SPIN is a continuous flow diffusion chamber with parallel plate geometry based on the Zurich Ice Nucleation Chamber and the Portable Ice Nucleation Chamber. This study presents a standard description for using the SPIN instrument and also highlights methods to analyze measurements in more advanced ways. It characterizes and describes the behavior of the SPIN chamber, reports data from laboratory measurements, and quantifies uncertainties associated with the measurements. Experiments with ammonium sulfate are used to investigate homogeneous freezing of deliquesced haze droplets and droplet breakthrough. Experiments with kaolinite, NX illite, and silver iodide are used to investigate heterogeneous ice nucleation. SPIN nucleation results are compared to those from the literature. A machine learning approach for analyzing depolarization data from the SPIN optical particle counter is also presented (as an advanced use). Overall, we report that the SPIN is able to reproduce previous INP counter measurements.

  7. Heterogeneous nucleation of aspartame from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Kubota, Noriaki; Kinno, Hiroaki; Shimizu, Kenji

    1990-03-01

    Waiting times, the time from the instant of quenching needed for a first nucleus to appear, were measured at constant supercoolings for primary nucleation of aspartame (α-L-aspartyl-L-phenylalanine methylester) from aqueous solutions, which were sealed into glass ampoules (solution volume = 3.16 cm 3). Since the waiting time became shorter by filtering the solution prior to quenching, the nucleation was concluded to be heterogeneously induced. The measured waiting time consisted of two parts: time needed for the nucleus to grow to a detactable size (growth time) and stochastic time needed for nucleation (true waiting time). The distribution of the true waiting time, is well explained by a stochastic model, in which nucleation is regarded to occur heterogeneously and in a stochastic manner by two kinds of active sites. The active sites are estimated to be located on foreign particles in which such elements as Si, Al and Mg were contained. The amount of each element is very small in the order of magnitude of ppb (mass basis) of the whole solution. The growth time was correlated with the degree of supercooling.

  8. Inhibition of bacterial ice nucleators by fish antifreeze glycoproteins.

    PubMed

    Parody-Morreale, A; Murphy, K P; Di Cera, E; Fall, R; DeVries, A L; Gill, S J

    1988-06-23

    Certain bacteria promote the formation of ice in super-cooled water by means of ice nucleators which contain a unique protein associated with the cell membrane. Ice nucleators in general are believed to act by mimicking the structure of an ice crystal surface, thus imposing an ice-like arrangement on the water molecules in contact with the nucleating surface and lowering the energy necessary for the initiation of ice formation. Quantitative investigation of the bacterial ice-nucleating process has recently been made possible by the discovery of certain bacteria that shed stable membrane vesicles with ice nucleating activity. The opposite effect, inhibition of ice formation, has been described for a group of glycoproteins found in different fish and insect species. This group of substances, termed antifreeze glycoproteins (AFGPs), promotes the supercooling of water with no appreciable effect on the equilibrium freezing point or melting temperature. Substantial evidence now indicates that AFGPs act by binding to a growing ice crystal and slowing crystal growth. As the ice-nucleating protein surface is believed to have a structure similar to an embryonic ice crystal, AFGPs might be predicted to interact directly with a bacterial ice-nucleating site. We report here that AFGPs from the antarctic fish Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia herbicola. The inhibition effect shows saturation at high concentration of AFGP and conforms to a simple binding reaction between the AFGP and the nucleation centre.

  9. The ice nucleation activity of biological aerosols

    NASA Astrophysics Data System (ADS)

    Grothe, H.; Pummer, B.; Bauer, H.; Bernardi, J.

    2012-04-01

    Primary Biological Aerosol Particles (PBAPs), including bacteria, spores and pollen may be important for several atmospheric processes. Particularly, the ice nucleation caused by PBAPs is a topic of growing interest, since their impact on ice cloud formation and thus on radiative forcing, an important parameter in global climate is not yet fully understood. In laboratory model studies we investigated the ice nucleation activity of selected PBAPs. We studied the immersion mode freezing using water-oil emulsion, which we observed by optical microscopy. We particularly focused on pollen. We show that pollen of different species strongly differ in their ice nucleation behavior. The average freezing temperatures in laboratory experiments range from 240 K to 255 K. As the most efficient nuclei (silver birch, Scots pine and common juniper pollen) have a distribution area up to the Northern timberline, their ice nucleation activity might be a cryoprotective mechanism. For comparison the ice nucleation activity of Snomax, fungal spores, and mushrooms will be discussed as well. In the past, pollen have been rejected as important atmospheric IN, as they are not as abundant in the atmosphere as bacteria or mineral dust and are too heavy to reach higher altitudes. However, in our experiments (Pummer et al. 2011) it turned out that water, which had been in contact with pollen and then been separated from the bodies, nucleates as good as the pollen grains themselves. So the ice nuclei have to be easily-suspendable macromolecules (100-300 kDa) located on the pollen. Once extracted, they can be distributed further through the atmosphere than the heavy pollen grains and so augment the impact of pollen on ice cloud formation even in the upper troposphere. It is widely known, that material from the pollen, like allergens and sugars, can indeed leave the pollen body and be distributed independently. The most probable mechanism is the pollen grain bursting by rain, which releases

  10. Ice Nucleation and Droplet Formation by Bare and Coated Black Carbon Particles

    SciTech Connect

    Friedman, Beth J.; Kulkarni, Gourihar R.; Beranek, Josef; Zelenyuk, Alla; Thornton, Joel A.; Cziczo, Daniel J.

    2011-10-13

    We have studied the ice formation at heterogeneous and homogeneous temperatures, as well as droplet activation and hygroscopicity of soot particles of variable size and composition. Coatings of adipic, malic, and oleic acid were applied to span a relevant range of solubility, and both uncoated and oleic acid coated soot particles were exposed to ozone to simulate atmospheric oxidation. The results are interpreted in terms of onset ice nucleation with a comparison to a well characterized mineral dust particle that acts as an efficient ice nucleus, as well as particle hygroscopicity. At 253K and 243K, we found no evidence of heterogeneous ice nucleation occurring above the level of detection for our experimental conditions. Above water saturation, droplet formation was observed. At 233K, we observe the occurrence of homogeneous ice nucleation for all particles studied. Coatings also did not significantly alter the ice nucleation behavior of soot particles, but aided in the uptake of water. Hygroscopicity studies confirmed that pure soot particles were hydrophobic, and coated soot particles activated as droplets at high water supersaturations. A small amount of heterogeneous ice nucleation either below the detection limit of our instrument or concurrent with droplet formation and/or homogeneous freezing cannot be precluded, but we are able to set limits for its frequency. We conclude from our studies that both uncoated and coated soot particles are unlikely to contribute to the global budget of heterogeneous ice nuclei at temperatures between 233K and 253K.

  11. Ice nucleation active bacteria in precipitation are genetically diverse and nucleate ice by employing different mechanisms.

    PubMed

    Failor, K C; Schmale, D G; Vinatzer, B A; Monteil, C L

    2017-07-28

    A growing body of circumstantial evidence suggests that ice nucleation active (Ice(+)) bacteria contribute to the initiation of precipitation by heterologous freezing of super-cooled water in clouds. However, little is known about the concentration of Ice(+) bacteria in precipitation, their genetic and phenotypic diversity, and their relationship to air mass trajectories and precipitation chemistry. In this study, 23 precipitation events were collected over 15 months in Virginia, USA. Air mass trajectories and water chemistry were determined and 33 134 isolates were screened for ice nucleation activity (INA) at -8 °C. Of 1144 isolates that tested positive during initial screening, 593 had confirmed INA at -8 °C in repeated tests. Concentrations of Ice(+) strains in precipitation were found to range from 0 to 13 219 colony forming units per liter, with a mean of 384±147. Most Ice(+) bacteria were identified as members of known and unknown Ice(+) species in the Pseudomonadaceae, Enterobacteriaceae and Xanthomonadaceae families, which nucleate ice employing the well-characterized membrane-bound INA protein. Two Ice(+) strains, however, were identified as Lysinibacillus, a Gram-positive genus not previously known to include Ice(+) bacteria. INA of the Lysinibacillus strains is due to a nanometer-sized molecule that is heat resistant, lysozyme and proteinase resistant, and secreted. Ice(+) bacteria and the INA mechanisms they employ are thus more diverse than expected. We discuss to what extent the concentration of culturable Ice(+) bacteria in precipitation and the identification of a new heat-resistant biological INA mechanism support a role for Ice(+) bacteria in the initiation of precipitation.The ISME Journal advance online publication, 28 July 2017; doi:10.1038/ismej.2017.124.

  12. Identification and quantification of ice nucleation active microorganisms by digital droplet PCR (ddPCR)

    NASA Astrophysics Data System (ADS)

    Linden, Martin; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

    2015-04-01

    Several bioaerosol types, including bacteria, fungi, pollen and lichen, have been identified as sources of biological ice nucleators (IN) which induce ice formation already at temperatures as high as -10 °C or above. Accordingly, they potentially contribute widely to environmental ice nucleation in the atmosphere and are of great interest in the study of natural heterogenous ice nucleation processes. Ice nucleation active microorganisms have been found and studied among bacteria (Proteobacteria) and fungi (phyla Basidiomycota and Ascomycota). The mechanisms enabling the microorganisms to ice nucleation are subject to ongoing research. While it has been demonstrated that whole cells can act as ice nucleators in the case of bacteria due to the presence of specific membrane proteins, cell-free ice nucleation active particles seem to be responsible for this phenomenon in fungi and lichen. The identification and quantification of these ice nucleation active microorganisms and their IN in atmospheric samples is crucial to understand their contribution to the pool of atmospheric IN. This is not a trivial task since the respective microorganisms are often prevalent in lowest concentrations and a variety of states, be it viable cells, spores or cell debris from dead cells. Molecular biology provides tools to identify and quantify ice nucleation active microorganisms independent of their state by detecting genetic markers specific for the organism of interest. Those methods are not without their drawbacks in terms of sample material concentration required or reliable standardization. Digital Droplet Polymerase Chain Reaction (ddPCR) was chosen for our demands as a more elegant, quick and specific method in the investigation of ice nucleation active microorganisms in atmospheric samples. The advantages of ddPCR lie in the simultaneous detection and quantification of genetic markers and their original copy numbers in a sample. This is facilitated by the fractionation of the

  13. Investigating ice nucleation in cirrus clouds with an aerosol-enabled Multiscale Modeling Framework

    DOE PAGES

    Zhang, Chengzhu; Wang, Minghuai; Morrison, H.; ...

    2014-11-06

    In this study, an aerosol-dependent ice nucleation scheme [Liu and Penner, 2005] has been implemented in an aerosol-enabled multi-scale modeling framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10 to 100/L) at cirrus temperatures. The low ice numbermore » is attributed to the dominance of heterogeneous nucleation in ice formation. The new model simulates the observed shift of the ice supersaturation PDF towards higher values at low temperatures following homogeneous nucleation threshold. The MMF models predict a higher frequency of midlatitude supersaturation in the Southern hemisphere and winter hemisphere, which is consistent with previous satellite and in-situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to emulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation schemes and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 μm for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement to the satellite retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value.« less

  14. Investigating ice nucleation in cirrus clouds with an aerosol-enabled Multiscale Modeling Framework

    SciTech Connect

    Zhang, Chengzhu; Wang, Minghuai; Morrison, H.; Somerville, Richard C.; Zhang, Kai; Liu, Xiaohong; Li, J-L F.

    2014-11-06

    In this study, an aerosol-dependent ice nucleation scheme [Liu and Penner, 2005] has been implemented in an aerosol-enabled multi-scale modeling framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10 to 100/L) at cirrus temperatures. The low ice number is attributed to the dominance of heterogeneous nucleation in ice formation. The new model simulates the observed shift of the ice supersaturation PDF towards higher values at low temperatures following homogeneous nucleation threshold. The MMF models predict a higher frequency of midlatitude supersaturation in the Southern hemisphere and winter hemisphere, which is consistent with previous satellite and in-situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to emulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation schemes and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 μm for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement to the satellite retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value.

  15. Physiological and ecological significance of biological ice nucleators.

    PubMed

    Lundheim, Rolv

    2002-07-29

    When a pure water sample is cooled it can remain in the liquid state at temperatures well below its melting point (0 degrees C). The initiation of the transition from the liquid state to ice is called nucleation. Substances that facilitate this transition so that it takes place at a relatively high sub-zero temperature are called ice nucleators. Many living organisms produce ice nucleators. In some cases, plausible reasons for their production have been suggested. In bacteria, they could induce frost damage to their hosts, giving the bacteria access to nutrients. In freeze-tolerant animals, it has been suggested that ice nucleators help to control the ice formation so that it is tolerable to the animal. Such ice nucleators can be called adaptive ice nucleators. There are, however, also examples of ice nucleators in living organisms where the adaptive value is difficult to understand. These ice nucleators might be structures with functions other than facilitating ice formation. These structures might be called incidental ice nucleators.

  16. Identification & Characterization of Fungal Ice Nucleation Proteins

    NASA Astrophysics Data System (ADS)

    Scheel, Jan Frederik; Kunert, Anna Theresa; Kampf, Christopher Johannes; Mauri, Sergio; Weidner, Tobias; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

    2016-04-01

    Freezing of water at relatively warm subfreezing temperatures is dependent on ice nucleation catalysis facilitated by ice nuclei (IN). These IN can be of various origins and although extensive research was done and progress was achieved, the nature and mechanisms leading to an effective IN are to date still poorly understood. Some of the most important processes of our geosphere like the water cycle are highly dependent on effective ice nucleation at temperatures between -2°C - -8°C, a temperature range which is almost exclusively covered by biological IN (BioIN). BioIN are usually macromolecular structures of biological polymers. Sugars as well as proteins have been reported to serve as IN and the best characterized BioIN are ice nucleation proteins (IN-P) from gram negative bacteria. Fungal strains from Fusarium spp. were described to be effective IN at subfreezing temperatures up to -2°C already 25 years ago and more and more fungal species are described to serve as efficient IN. Fungal IN are also thought to be proteins or at least contain a proteinaceous compound, but to date the fungal IN-P primary structure as well as their coding genetic elements of all IN active fungi are unknown. The aim of this study is a.) to identify the proteins and their coding genetic elements from IN active fungi (F. acuminatum, F. avenaceum, M. alpina) and b.) to characterize the mechanisms by which fungal IN serve as effective IN. We designed an interdisciplinary approach using biological, analytical and physical methods to identify fungal IN-P and describe their biological, chemical, and physical properties.

  17. SUCCESS Evidence for Cirrus Cloud Ice Nucleation Mechanisms

    NASA Technical Reports Server (NTRS)

    Jensen, Eric; Gore, Warren J. Y. (Technical Monitor)

    1997-01-01

    During the SUCCESS mission, several measurements were made which should improve our understanding of ice nucleation processes in cirrus clouds. Temperature and water vapor concentration were made with a variety of instruments on the NASA DC-8. These observations should provide accurate upper tropospheric humidities. In particular, we will evaluate what humidities are required for ice nucleation. Preliminary results suggest that substantial supersaturations frequently exist in the upper troposphere. The leading-edge region of wave-clouds (where ice nucleation occurs) was sampled extensively at temperatures near -40 and -60C. These observations should give precise information about conditions required for ice nucleation. In addition, we will relate the observed aerosol composition and size distributions to the ice formation observed to evaluate the role of soot or mineral particles on ice nucleation. As an alternative technique for determining what particles act as ice nuclei, numerous samples of aerosols inside ice crystals were taken. In some cases, large numbers of aerosols were detected in each crystal, indicating that efficient scavenging occurred. Analysis of aerosols in ice crystals when only one particle per crystal was detected should help with the ice nucleation issue. Direct measurements of the ice nucleating activity of ambient aerosols drawn into airborne cloud chambers were also made. Finally, measurements of aerosols and ice crystals in contrails should indicate whether aircraft exhaust soot particles are effective ice nuclei.

  18. Ice Nucleation by Mineral Dust/Sulfate Particles at Cirrus Temperatures

    NASA Astrophysics Data System (ADS)

    Archuleta, C. M.; Demott, P. J.; Kreidenweis, S. M.

    2002-12-01

    This research examines the role of some types of mineral dust as heterogeneous ice nuclei at cirrus temperatures. Commercially available nanoscale powder samples of iron oxide, aluminum oxide and aluminasilicate were atomized from suspensions, dried and selected at monodisperse sizes (50 to 200 nm) for use as surrogates for atmospheric mineral dust particles. A tube furnace with a linear temperature gradient is used to condense sulfuric acid on the particles. The degree of acid coatings on the particles is determined by measuring their cloud condensation activity with a static thermal gradient diffusion chamber and applying Kohler theory for mixed particles. Measurements of ice nucleation are made using a continuous flow ice-thermal diffusion chamber (CFDC) operated to expose aerosols to temperatures between -45 and -60degC and a range of relative humidity above ice-saturated conditions. Ice nucleation results from the minerals without a sulfuric acid coating indicate that relatively pure mineral oxide aerosols nucleate ice at lower relative humidity than that required to homogeneously freeze sulfuric acid drops of the same size. Also, a clear size effect is indicated for ice formation by these particles. Larger particles nucleate ice at lower humidity than smaller particles. Currently, the freezing nucleation behavior of the same mineral oxides coated with sulfuric acid is being investigated. A sample of reference Asian dust will also be examined for ice nucleation properties in the same manner as done for the manufactured particles. Quantitative results will be presented and implications for cirrus formation will be discussed.

  19. Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash

    NASA Astrophysics Data System (ADS)

    Schill, G. P.; Genareau, K.; Tolbert, M. A.

    2015-07-01

    Ice nucleation of volcanic ash controls both ash aggregation and cloud glaciation, which affect atmospheric transport and global climate. Previously, it has been suggested that there is one characteristic ice nucleation efficiency for all volcanic ash, regardless of its composition, when accounting for surface area; however, this claim is derived from data from only two volcanic eruptions. In this work, we have studied the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman microscopy coupled to an environmental cell. Ash from the Fuego (basaltic ash, Guatemala), Soufrière Hills (andesitic ash, Montserrat), and Taupo (Oruanui eruption, rhyolitic ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. In the present study, we find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice from 225 to 235 K at ice saturation ratios of 1.05 ± 0.01, comparable to the mineral dust proxy kaolinite. Since depositional ice nucleation will be more important at colder temperatures, fine volcanic ash may represent a global source of cold-cloud ice nuclei. For immersion freezing relevant to mixed-phase clouds, however, only the Oruanui ash exhibited appreciable heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

  20. Tuning ice nucleation with counterions on polyelectrolyte brush surfaces.

    PubMed

    He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

    2016-06-01

    Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN.

  1. Tuning ice nucleation with counterions on polyelectrolyte brush surfaces

    PubMed Central

    He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

    2016-01-01

    Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN. PMID:27386581

  2. Ubiquity of biological ice nucleators in snowfall.

    PubMed

    Christner, Brent C; Morris, Cindy E; Foreman, Christine M; Cai, Rongman; Sands, David C

    2008-02-29

    Despite the integral role of ice nucleators (IN) in atmospheric processes leading to precipitation, their sources and distributions have not been well established. We examined IN in snowfall from mid- and high-latitude locations and found that the most active were biological in origin. Of the IN larger than 0.2 micrometer that were active at temperatures warmer than -7 degrees C, 69 to 100% were biological, and a substantial fraction were bacteria. Our results indicate that the biosphere is a source of highly active IN and suggest that these biological particles may affect the precipitation cycle and/or their own precipitation during atmospheric transport.

  3. Marine sources of ice nucleating particles: results from phytoplankton cultures and samples collected at sea

    NASA Astrophysics Data System (ADS)

    Wilbourn, E.; Thornton, D.; Brooks, S. D.; Graff, J.

    2016-12-01

    The role of marine aerosols as ice nucleating particles is currently poorly understood. Despite growing interest, there are remarkably few ice nucleation measurements on representative marine samples. Here we present results of heterogeneous ice nucleation from laboratory studies and in-situ air and sea water samples collected during NAAMES (North Atlantic Aerosol and Marine Ecosystems Study). Thalassiosira weissflogii (CCMP 1051) was grown under controlled conditions in batch cultures and the ice nucleating activity depended on the growth phase of the cultures. Immersion freezing temperatures of the lab-grown diatoms were determined daily using a custom ice nucleation apparatus cooled at a set rate. Our results show that the age of the culture had a significant impact on ice nucleation temperature, with samples in stationary phase causing nucleation at -19.9 °C, approximately nine degrees warmer than the freezing temperature during exponential growth phase. Field samples gathered during the NAAMES II cruise in May 2016 were also tested for ice nucleating ability. Two types of samples were gathered. Firstly, whole cells were fractionated by size from surface seawater using a BD Biosciences Influx Cell Sorter (BD BS ISD). Secondly, aerosols were generated using the SeaSweep and subsequently size-selected using a PIXE Cascade Impactor. Samples were tested for the presence of ice nucleating particles (INP) using the technique described above. There were significant differences in the freezing temperature of the different samples; of the three sample types the lab-grown cultures tested during stationary phase froze at the warmest temperatures, followed by the SeaSweep samples (-25.6 °C) and the size-fractionated cell samples (-31.3 °C). Differences in ice nucleation ability may be due to size differences between the INP, differences in chemical composition of the sample, or some combination of these two factors. Results will be presented and atmospheric implications

  4. Ice Nucleation Efficiency of Hydroxylated Organic Surfaces Is Controlled by Their Structural Fluctuations and Mismatch to Ice.

    PubMed

    Qiu, Yuqing; Odendahl, Nathan; Hudait, Arpa; Mason, Ryan; Bertram, Allan K; Paesani, Francesco; DeMott, Paul J; Molinero, Valeria

    2017-03-01

    Heterogeneous nucleation of ice induced by organic materials is of fundamental importance for climate, biology, and industry. Among organic ice-nucleating surfaces, monolayers of long chain alcohols are particularly effective, while monolayers of fatty acids are significantly less so. As these monolayers expose to water hydroxyl groups with an order that resembles the one in the basal plane of ice, it was proposed that lattice matching between ice and the surface controls their ice-nucleating efficiency. Organic monolayers are soft materials and display significant fluctuations. It has been conjectured that these fluctuations assist in the nucleation of ice. Here we use molecular dynamic simulations and laboratory experiments to investigate the relationship between the structure and fluctuations of hydroxylated organic surfaces and the temperature at which they nucleate ice. We find that these surfaces order interfacial water to form domains with ice-like order that are the birthplace of ice. Both mismatch and fluctuations decrease the size of the preordered domains and monotonously decrease the ice freezing temperature. The simulations indicate that fluctuations depress the freezing efficiency of monolayers of alcohols or acids to half the value predicted from lattice mismatch alone. The model captures the experimental trend in freezing efficiencies as a function of chain length and predicts that alcohols have higher freezing efficiency than acids of the same chain length. These trends are mostly controlled by the modulation of the structural mismatch to ice. We use classical nucleation theory to show that the freezing efficiencies of the monolayers are directly related to their free energy of binding to ice. This study provides a general framework to relate the equilibrium thermodynamics of ice binding to a surface and the nonequilibrium ice freezing temperature and suggests that these could be predicted from the structure of interfacial water.

  5. High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

    NASA Astrophysics Data System (ADS)

    Junge, K.; Swanson, B. D.

    2008-05-01

    Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for ice formation in Arctic clouds (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium - which for artificial seawater was -42.2±0.3°C. Our results suggest that immersion freezing of these marine psychro-active bacteria and viruses would not be important for heterogeneous ice nucleation processes in polar clouds or to the formation of sea ice. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

  6. Global Simulations of Ice nucleation and Ice Supersaturation with an Improved Cloud Scheme in the Community Atmosphere Model

    SciTech Connect

    Gettelman, A.; Liu, Xiaohong; Ghan, Steven J.; Morrison, H.; Park, Sungsu; Conley, Andrew; Klein, Stephen A.; Boyle, James; Mitchell, David; Li, J-L F.

    2010-09-28

    A process-based treatment of ice supersaturation and ice-nucleation is implemented in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). The new scheme is designed to allow (1) supersaturation with respect to ice, (2) ice nucleation by aerosol particles and (3) ice cloud cover consistent with ice microphysics. The scheme is implemented with a 4-class 2 moment microphysics code and is used to evaluate ice cloud nucleation mechanisms and supersaturation in CAM. The new model is able to reproduce field observations of ice mass and mixed phase cloud occurrence better than previous versions of the model. Simulations indicate heterogeneous freezing and contact nucleation on dust are both potentially important over remote areas of the Arctic. Cloud forcing and hence climate is sensitive to different formulations of the ice microphysics. Arctic radiative fluxes are sensitive to the parameterization of ice clouds. These results indicate that ice clouds are potentially an important part of understanding cloud forcing and potential cloud feedbacks, particularly in the Arctic.

  7. Laboratory studies of immersion and deposition mode ice nucleation of ozone aged mineral dust particles

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Welti, A.; Chou, C.; Stetzer, O.; Lohmann, U.

    2013-04-01

    Ice nucleation in the atmosphere is central to the understanding the microphysical properties of mixed-phase and cirrus clouds. Ambient conditions such as temperature (T) and relative humidity (RH), as well as aerosol properties such as chemical composition and mixing state play an important role in predicting ice formation in the troposphere. Previous field studies have reported the absence of sulphate and organic compounds on mineral dust ice crystal residuals sampled at mountain top stations or aircraft based measurements despite the long range transport mineral dust is subjected to. We present laboratory studies of ice nucleation for immersion and deposition mode on ozone aged mineral dust particles for 233 < T < 263 K that will represent ageing but not internal mixing with in(organic) compounds. Heterogeneous ice nucleation of untreated kaolinite (Ka) and Arizona Test Dust (ATD) particles is compared to corresponding aged particles that are subjected to ozone exposures of 0.4-4.3 ppmv in a stainless steel aerosol tank. The portable ice nucleation counter (PINC) and immersion chamber combined with the Zurich ice nucleation chamber (IMCA - ZINC) are used to conduct deposition and immersion mode measurements respectively. Ice active fractions as well as ice active surface site densities (ns) are reported and observed to increase as a function of temperature. We present first results that demonstrate enhancement of the ice nucleation ability of aged mineral dust particles in both the deposition and immersion mode due to ageing. Additionally, these are also the first results to show a suppression of heterogeneous ice nucleation without the condensation of a coating of (in)organic material. In immersion mode, low exposure Ka particles showed enhanced ice activity requiring a median freezing temperature of 1.5 K warmer than that of untreated Ka whereas high exposure ATD particles showed suppressed ice nucleation requiring a median freezing temperature of 3 K colder

  8. Observations on the nucleation of ice VII in shock compressed water

    NASA Astrophysics Data System (ADS)

    Stafford, Samuel J. P.; Chapman, David J.; Eakins, Daniel E.; Bland, Simon N.

    2015-06-01

    The ability of water to freeze into the ice VII phase under dynamic compression is a good example of a liquid to solid phase change. The ice VII is thought to nucleate and grow from the window surfaces in a relatively slow process (on the order of 100ns) that can be seen in wave profiles and a visible darkening of the sample. On silica windows the process is evident but from sapphire surfaces the heterogeneous nucleation appears to be entirely absent and the water remains metastable. To investigate the influence of silica, and under what conditions sapphire might heterogeneously nucleate ice VII, we present an experimental technique incorporating multiple liquid targets diagnosed with PDV and high speed imaging of the nucleation process from a variety of surfaces and additives. The Institute of Shock Physics acknowledges the continued support of AWE and Imperial College London.

  9. Modelling ice nucleation due to dust

    NASA Astrophysics Data System (ADS)

    Nickovic, Slobodan; Petkovic, Slavko; Pejanovic, Goran; Madonna, Fabio

    2015-04-01

    Formation of cold clouds is enhanced if ice nuclei (IN) are available. Cold clouds contribute at global scale with 60% in average in precipitation and their presence significantly affects the atmospheric radiation properties. It is expected that better description of the IN process should substantially improve cloud parameterization in climate and numerical weather prediction models. Observations show that mineral dust particles are the dominant residuals found in cloud ice. In this study we employ the regional dust DREAM model based on high horizontal and vertical grid resolution to parameterize IN caused by mineral dust. DREAM has been already deployed in a study related to IN process (Klein et al, 2010), also in model experiments using several IN parameterization schemes in support of the IN field experiment CALIMA over Canaries. The model has been also extended by adding the major dust mineral fractions as tracers in order to facilitate staying a role of dust mineralogy in ice nucleation. This study will present parameterization of IN using the simulated dust concentration, water moisture and temperature. Preliminary results of simulated IN will be shown, as well as IN validation against lidar aerosol profiles and ice cloud water profiles observed by cloud radar in the Potenza EARLINET site. This study is an initial step in improving a cloud physics parameterization using IN as an input variable in an integrated dust-atmospheric modelling system.

  10. Ice nucleation and droplet formation by bare and coated soot particles

    NASA Astrophysics Data System (ADS)

    Friedman, Beth; Kulkarni, Gourihar; BeráNek, Josef; Zelenyuk, Alla; Thornton, Joel A.; Cziczo, Daniel J.

    2011-09-01

    We have studied ice formation at temperatures relevant to homogeneous and heterogeneous ice nucleation, as well as droplet activation and hygroscopicity, of soot particles of variable size and composition. Coatings of adipic, malic, and oleic acid were applied in order to span an atmospherically relevant range of solubility, and both uncoated and oleic acid coated soot particles were exposed to ozone in order to simulate atmospheric oxidation. The results are interpreted in terms of onset ice nucleation, with a comparison to a mineral dust particle that acts as an efficient ice nucleus, and particle hygroscopicity. At 253 K and 243 K, we found no evidence of heterogeneous ice nucleation occurring above the level of detection for our experimental conditions. Above water saturation, only droplet formation was observed. At 233 K, we observe the occurrence of homogeneous ice nucleation for all particles studied. Coatings also did not significantly alter the ice nucleation behavior of soot particles but aided in the uptake of water. Hygroscopicity studies confirmed that pure soot particles were hydrophobic, and coated soot particles activated as droplets at high water supersaturations. A small amount of heterogeneous ice nucleation either below the detection limit of our instrument or concurrent with droplet formation and/or homogeneous freezing cannot be precluded, but we are able to set limits for its frequency. We conclude that both uncoated and coated soot particles comparable to those generated in our studies are unlikely to significantly contribute to the global budget of heterogeneous ice nuclei at temperatures between 233 K and 253 K.

  11. Boreal pollen contain ice-nucleating as well as ice-binding ‘antifreeze’ polysaccharides

    PubMed Central

    Dreischmeier, Katharina; Budke, Carsten; Wiehemeier, Lars; Kottke, Tilman; Koop, Thomas

    2017-01-01

    Ice nucleation and growth is an important and widespread environmental process. Accordingly, nature has developed means to either promote or inhibit ice crystal formation, for example ice-nucleating proteins in bacteria or ice-binding antifreeze proteins in polar fish. Recently, it was found that birch pollen release ice-nucleating macromolecules when suspended in water. Here we show that birch pollen washing water exhibits also ice-binding properties such as ice shaping and ice recrystallization inhibition, similar to antifreeze proteins. We present spectroscopic evidence that both the ice-nucleating as well as the ice-binding molecules are polysaccharides bearing carboxylate groups. The spectra suggest that both polysaccharides consist of very similar chemical moieties, but centrifugal filtration indicates differences in molecular size: ice nucleation occurs only in the supernatant of a 100 kDa filter, while ice shaping is strongly enhanced in the filtrate. This finding may suggest that the larger ice-nucleating polysaccharides consist of clusters of the smaller ice-binding polysaccharides, or that the latter are fragments of the ice-nucleating polysaccharides. Finally, similar polysaccharides released from pine and alder pollen also display both ice-nucleating as well as ice-binding ability, suggesting a common mechanism of interaction with ice among several boreal pollen with implications for atmospheric processes and antifreeze protection. PMID:28157236

  12. Boreal pollen contain ice-nucleating as well as ice-binding ‘antifreeze’ polysaccharides

    NASA Astrophysics Data System (ADS)

    Dreischmeier, Katharina; Budke, Carsten; Wiehemeier, Lars; Kottke, Tilman; Koop, Thomas

    2017-02-01

    Ice nucleation and growth is an important and widespread environmental process. Accordingly, nature has developed means to either promote or inhibit ice crystal formation, for example ice-nucleating proteins in bacteria or ice-binding antifreeze proteins in polar fish. Recently, it was found that birch pollen release ice-nucleating macromolecules when suspended in water. Here we show that birch pollen washing water exhibits also ice-binding properties such as ice shaping and ice recrystallization inhibition, similar to antifreeze proteins. We present spectroscopic evidence that both the ice-nucleating as well as the ice-binding molecules are polysaccharides bearing carboxylate groups. The spectra suggest that both polysaccharides consist of very similar chemical moieties, but centrifugal filtration indicates differences in molecular size: ice nucleation occurs only in the supernatant of a 100 kDa filter, while ice shaping is strongly enhanced in the filtrate. This finding may suggest that the larger ice-nucleating polysaccharides consist of clusters of the smaller ice-binding polysaccharides, or that the latter are fragments of the ice-nucleating polysaccharides. Finally, similar polysaccharides released from pine and alder pollen also display both ice-nucleating as well as ice-binding ability, suggesting a common mechanism of interaction with ice among several boreal pollen with implications for atmospheric processes and antifreeze protection.

  13. Boreal pollen contain ice-nucleating as well as ice-binding 'antifreeze' polysaccharides.

    PubMed

    Dreischmeier, Katharina; Budke, Carsten; Wiehemeier, Lars; Kottke, Tilman; Koop, Thomas

    2017-02-03

    Ice nucleation and growth is an important and widespread environmental process. Accordingly, nature has developed means to either promote or inhibit ice crystal formation, for example ice-nucleating proteins in bacteria or ice-binding antifreeze proteins in polar fish. Recently, it was found that birch pollen release ice-nucleating macromolecules when suspended in water. Here we show that birch pollen washing water exhibits also ice-binding properties such as ice shaping and ice recrystallization inhibition, similar to antifreeze proteins. We present spectroscopic evidence that both the ice-nucleating as well as the ice-binding molecules are polysaccharides bearing carboxylate groups. The spectra suggest that both polysaccharides consist of very similar chemical moieties, but centrifugal filtration indicates differences in molecular size: ice nucleation occurs only in the supernatant of a 100 kDa filter, while ice shaping is strongly enhanced in the filtrate. This finding may suggest that the larger ice-nucleating polysaccharides consist of clusters of the smaller ice-binding polysaccharides, or that the latter are fragments of the ice-nucleating polysaccharides. Finally, similar polysaccharides released from pine and alder pollen also display both ice-nucleating as well as ice-binding ability, suggesting a common mechanism of interaction with ice among several boreal pollen with implications for atmospheric processes and antifreeze protection.

  14. High-resolution ice nucleation spectra of sea-ice bacteria: implications for cloud formation and life in frozen environments

    NASA Astrophysics Data System (ADS)

    Junge, K.; Swanson, B. D.

    2007-11-01

    Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for cloud formation in the Arctic (Bigg and Leck, 2001), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium - which for artificial seawater was -42.2±0.3°C. Our results indicated that these marine psychro-active bacteria and viruses are not important for heterogeneous ice nucleation processes in sea ice or polar clouds. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater.

  15. High-Resolution ice Nucleation Spectra of Sea-Ice Bacteria: Implications for Cloud Formation and Life in Frozen Environments

    NASA Astrophysics Data System (ADS)

    Junge, K.; Swanson, B.

    2007-12-01

    Even though studies of Arctic ice forming particles suggest that a bacterial or viral source derived from open leads could be important for cloud formation in the Arctic (Bigg and Leck, 2002), the ice nucleation potential of most polar marine psychrophiles or viruses has not been examined under conditions more closely resembling those in the atmosphere. In this paper, we examined the ice nucleation activity (INA) of several representative Arctic and Antarctic sea-ice bacterial isolates and a polar Colwellia phage virus. High-resolution ice nucleation spectra were obtained for droplets containing bacterial cells or virus particles using a free-fall freezing tube technique. The fraction of frozen droplets at a particular droplet temperature was determined by measuring the depolarized light scattering intensity from solution droplets in free-fall. Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to the homogeneous nucleation temperature for the nucleation medium -- which for artificial seawater was - 42.2 degC (standdev. 0.3 degC). Our results indicated that these marine psychro-active bacteria and viruses are not important for heterogeneous ice nucleation processes in sea ice or polar clouds. These results also suggested that avoidance of ice formation in close proximity to cell surfaces might be one of the cold-adaptation and survival strategies for sea-ice bacteria. The fact that INA occurs at such low temperature could constitute one factor that explains the persistence of metabolic activities at temperatures far below the freezing point of seawater (Junge et al., 2006).

  16. Bacterial Ice Nucleation in Monodisperse D2O and H2O-in-Oil Emulsions.

    PubMed

    Weng, Lindong; Tessier, Shannon N; Smith, Kyle; Edd, Jon F; Stott, Shannon L; Toner, Mehmet

    2016-09-13

    Ice nucleation is of fundamental significance in many areas, including atmospheric science, food technology, and cryobiology. In this study, we investigated the ice-nucleation characteristics of picoliter-sized drops consisting of different D2O and H2O mixtures with and without the ice-nucleating bacteria Pseudomonas syringae. We also studied the effects of commonly used cryoprotectants such as ethylene glycol, propylene glycol, and trehalose on the nucleation characteristics of D2O and H2O mixtures. The results show that the median freezing temperature of the suspension containing 1 mg/mL of a lyophilized preparation of P. syringae is as high as -4.6 °C for 100% D2O, compared to -8.9 °C for 100% H2O. As the D2O concentration increases every 25% (v/v), the profile of the ice-nucleation kinetics of D2O + H2O mixtures containing 1 mg/mL Snomax shifts by about 1 °C, suggesting an ideal mixing behavior of D2O and H2O. Furthermore, all of the cryoprotectants investigated in this study are found to depress the freezing phenomenon. Both the homogeneous and heterogeneous freezing temperatures of these aqueous solutions depend on the water activity and are independent of the nature of the solute. These findings enrich our fundamental knowledge of D2O-related ice nucleation and suggest that the combination of D2O and ice-nucleating agents could be a potential self-ice-nucleating formulation. The implications of self-nucleation include a higher, precisely controlled ice seeding temperature for slow freezing that would significantly improve the viability of many ice-assisted cryopreservation protocols.

  17. A marine biogenic source of atmospheric ice-nucleating particles.

    PubMed

    Wilson, Theodore W; Ladino, Luis A; Alpert, Peter A; Breckels, Mark N; Brooks, Ian M; Browse, Jo; Burrows, Susannah M; Carslaw, Kenneth S; Huffman, J Alex; Judd, Christopher; Kilthau, Wendy P; Mason, Ryan H; McFiggans, Gordon; Miller, Lisa A; Nájera, Juan J; Polishchuk, Elena; Rae, Stuart; Schiller, Corinne L; Si, Meng; Temprado, Jesús Vergara; Whale, Thomas F; Wong, Jenny P S; Wurl, Oliver; Yakobi-Hancock, Jacqueline D; Abbatt, Jonathan P D; Aller, Josephine Y; Bertram, Allan K; Knopf, Daniel A; Murray, Benjamin J

    2015-09-10

    The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties. The formation of ice in clouds is facilitated by the presence of airborne ice-nucleating particles. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice. Sea-spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer. Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice-nucleating material is probably biogenic and less than approximately 0.2 micrometres in size. We find that exudates separated from cells of the marine diatom Thalassiosira pseudonana nucleate ice, and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice-nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol, in combination with our measurements, suggest that marine organic material may be an important source of ice-nucleating particles in remote marine environments such as the Southern Ocean, North Pacific Ocean and North Atlantic Ocean.

  18. A marine biogenic source of atmospheric ice-nucleating particles

    NASA Astrophysics Data System (ADS)

    Wilson, Theodore W.; Ladino, Luis A.; Alpert, Peter A.; Breckels, Mark N.; Brooks, Ian M.; Browse, Jo; Burrows, Susannah M.; Carslaw, Kenneth S.; Huffman, J. Alex; Judd, Christopher; Kilthau, Wendy P.; Mason, Ryan H.; McFiggans, Gordon; Miller, Lisa A.; Nájera, Juan J.; Polishchuk, Elena; Rae, Stuart; Schiller, Corinne L.; Si, Meng; Temprado, Jesús Vergara; Whale, Thomas F.; Wong, Jenny P. S.; Wurl, Oliver; Yakobi-Hancock, Jacqueline D.; Abbatt, Jonathan P. D.; Aller, Josephine Y.; Bertram, Allan K.; Knopf, Daniel A.; Murray, Benjamin J.

    2015-09-01

    The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties. The formation of ice in clouds is facilitated by the presence of airborne ice-nucleating particles. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice. Sea-spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer. Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice-nucleating material is probably biogenic and less than approximately 0.2 micrometres in size. We find that exudates separated from cells of the marine diatom Thalassiosira pseudonana nucleate ice, and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice-nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol, in combination with our measurements, suggest that marine organic material may be an important source of ice-nucleating particles in remote marine environments such as the Southern Ocean, North Pacific Ocean and North Atlantic Ocean.

  19. Bubble nucleation in magmas: a dominantly heterogeneous process?

    NASA Astrophysics Data System (ADS)

    Shea, T.; Hammer, J. E.; Brachfeld, S. A.

    2016-12-01

    The processes governing volatile exsolution, and particularly the timing of initial vapor phase nucleation with respect to depth in the conduit, control a magma's explosive potential. Experimental studies have shown that nucleation kinetics exert the dominant control on degassing efficiency in silicate melts. Homogeneous nucleation (i.e. without assistance from crystal substrates or other phases) often requires attainment of large supersaturation pressures (ΔPN, the change in pressure required for nucleation), while heterogeneous nucleation on pre-existing crystals can occur at significantly lower ΔPN (<50 MPa). Crystal-poor rhyolites have therefore been largely regarded as the type example of homogeneous bubble nucleation, disequilibrium degassing and heightened explosivity. while other less viscous magmas (dacite, phonolite, basalt) are thought to more often foster heterogeneous nucleation with variable departures from equilibrium. Distinguishing between the two nucleation mechanisms is vital for applications that employ classical nucleation theory and its derivatives: for instance, Toramaru's increasingly used decompression-rate meter (Toramaru 2006) links the number density of bubbles per unit volume melt (NV) of pyroclasts - a readily obtained textural characteristic - to rates of pressure change (dP/dt) during ascent. These formulations require an explicit or implicit decision as to whether magma degassing was dominated by homogeneous or heterogeneous nucleation. This study exploits the large number of textural datasets available for eruptions involving various magma compositions to examine the dominant nucleation mechanism in natural melts. Because Fe-Ti oxides are unrivaled in their capacity to favor heterogeneous nucleation, the absence of high concentrations of petrographically-observable Fe-Ti oxide crystals in erupted pyroclasts is often taken as an indicator that homogeneous nucleation dominated bubble vesiculation in rhyolites. This contribution

  20. Identification of Ice Nucleation Active Sites on Silicate Dust Particles

    NASA Astrophysics Data System (ADS)

    Zolles, Tobias; Burkart, Julia; Häusler, Thomas; Pummer, Bernhard; Hitzenberger, Regina; Grothe, Hinrich

    2015-04-01

    Mineral dusts originating from Earth's crust are known to be important atmospheric ice nuclei. In agreement with earlier studies, feldspar was found as the most active of the tested natural mineral dusts [1-3]. Nevertheless, among those structures K-feldspar showed by far the highest ice nucleation activity. In this study, the reasons for its activity and the difference in the activity of the different feldspars were investigated in closer details. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. We give a potential explanation of the increased ice nucleation activity of K-feldspar. The ice nucleating sites are very much dependent on the alkali ion present by altering the water structure and the feldspar surface. The higher activity of K-feldspar can be attributed to the presence of potassium ions on the surface and surface bilayer. The alkali-ions have different hydration shells and thus an influence on the ice nucleation activity of feldspar. Chaotropic behavior of Calcium and Sodium ions are lowering the ice nucleation potential of the other feldspars, while kosmotropic Potassium has a neutral or even positive effect. Furthermore we investigated the influence of milling onto the ice nucleation of quartz particles. The ice nucleation activity can be increased by mechanical milling, by introducing more molecular, nucleation active defects to the particle surface. This effect is larger than expected by plane surface increase. [1] Atkinson et al. The Importance of Feldspar for Ice Nucleation by Mineral Dust in Mixed-Phase Clouds. Nature 2013, 498, 355-358. [2] Yakobi-Hancock et al.. Feldspar Minerals as Efficient Deposition Ice Nuclei. Atmos. Chem. Phys. 2013, 13, 11175-11185. [3] Zolles et al. Identification of Ice Nucleation Active Sites on Feldspar Dust Particles. J. Phys. Chem. A 2015 accepted.

  1. Heterogeneous nucleation in and out of pores.

    PubMed

    Page, Amanda J; Sear, Richard P

    2006-08-11

    We study the nucleation of a new thermodynamic phase in pores and find that the nucleation often proceeds via two steps: nucleation of pore filling, and nucleation out of the pore. These two rates have opposing dependencies on pore size, resulting in a pore size at which the nucleation rate of the new phase is maximal. This finding is relevant to attempts to design and use porous media to crystallize proteins.

  2. Measurements of Ice Nuclei properties at the Jungfraujoch using the Portable Ice Nucleation Chamber (PINC)

    NASA Astrophysics Data System (ADS)

    Chou, Cédric

    2010-05-01

    Ice clouds and mixed-phase clouds have different microphysical properties. Both affect the climate in various ways. Ice phase present in these clouds have the ability to scatter the incoming solar radiation and absorb terrestrial radiation differently from water droplets. Ice is also responsible for most of the precipitation in the mid-latitudes. Ice crystals can be formed via two main processes: homogeneous and heterogeneous ice nucleation. Investigation of thermodynamic conditions at which ice nuclei (IN) trigger nucleation and their number concentrations is necessary in order to understand the formation of the ice phase in the atmosphere. In order to investigate the presence of IN in the free troposphere, the Institute for Atmospheric and Climate Sciences of the ETH Zurich has recently designed a new chamber: the Portable Ice Nucleation Chamber (PINC), which is the field version of the Zurich Ice Nucleation Chamber (Stetzer et al., 2008). Both chambers follow the principle of a "continuous flow diffusion chamber" (Rogers, 1988) and can measure the number concentration of IN at different temperatures and relative humidities. Aerosols are collected through an inlet where an impactor removes larger particles that could be counted as ice crystals. The aerosol load is layered between two dry sheath air flows as it enters the main chamber. Both walls of the chamber are covered with a thin layer of ice and maintained at two different temperatures in order to create supersaturation with respect to ice (and with respect to water in case of a larger temperature difference between the walls). At the exit of the main chamber, the sample goes throught the evaporation part that is kept saturated with respect to ice. There, water droplets evaporate and only ice crystals and smaller aerosol particles are counted by the Optical Particle Counter (OPC) at the bottom of the chamber. The high alpine research station Jungfraujoch is located at 3580 m a.s.l. It is mainly in

  3. Particle Characterization and Ice Nucleation Efficiency of Field-Collected Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Wang, B.; Gilles, M. K.; Laskin, A.; Moffet, R.; Nizkorodov, S.; Roedel, T.; Sterckx, L.; Tivanski, A.; Knopf, D. A.

    2011-12-01

    Atmospheric ice formation by heterogeneous nucleation is one of the least understood processes resulting in cirrus and mixed-phase clouds which affect the global radiation budget, the hydrological cycle, and water vapor distribution. In particular, how organic aerosol affect ice nucleation is not well understood. Here we report on heterogeneous ice nucleation from particles collected during the CalNex campaign at the Caltech campus site, Pasadena, on May 19, 2010 at 6am-12pm (A2) and 12pm-6pm (A3) and May 23 at 6am-12pm (B2) and 6pm-12am (B4). The ice nucleation onsets and water uptake were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). The ice nucleation efficiency was related to the particle chemical composition. Single particle characterization was provided by using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The STXM/NEXAFS analysis indicates that the morning sample (A2) constitutes organic particles and organic particles with soot and inorganic inclusions. The afternoon sample (A3) is dominated by organic particles with a potentially higher degree of oxidation associated with soot. The B2 sample shows a higher number fraction of magnesium-containing particle indicative of a marine source and ~93% of the particles contained sulfur besides oxygen and carbon as derived from CCSEM/EDX analysis. The B4 sample lacks the strong marine influence and shows higher organic content. Above 230 K, we observed water uptake followed by condensation freezing at mean RH of 93-100% and 89-95% for A2 and A3, respectively. This indicates that the aged A3 particles are efficient ice nuclei (IN) for condensation freezing. Below 230 K A2 and A3 induced deposition ice nucleation between 125-155% RHice (at mean values of 134-150% RHice). The B2 and B4

  4. Understanding the ice nucleation characteristics of feldspars suspended in solution

    NASA Astrophysics Data System (ADS)

    Kumar, Anand; Marcolli, Claudia; Kaufmann, Lukas; Krieger, Ulrich; Peter, Thomas

    2017-04-01

    Freezing of liquid droplets and subsequent ice crystal growth affects optical properties of clouds and precipitation. Field measurements show that ice formation in cumulus and stratiform clouds begins at temperatures much warmer than those associated with homogeneous ice nucleation in pure water, which is ascribed to heterogeneous ice nucleation occurring on the foreign surfaces of ice nuclei (IN). Various insoluble particles such as mineral dust, soot, metallic particles, volcanic ash, or primary biological particles have been suggested as IN. Among these the suitability of mineral dusts is best established. The ice nucleation ability of mineral dust particles may be modified when secondary organic or inorganic substances are accumulating on the dust during atmospheric transport. If the coating is completely wetting the mineral dust particles, heterogeneous ice nucleation occurs in immersion mode also below 100 % RH. A previous study by Zobrist et al. (2008) Arizona test dust, silver iodide, nonadecanol and silicon dioxide suspensions in various solutes showed reduced ice nucleation efficiency (in immersion mode) of the particles. Though it is still quite unclear how surface modifications and coatings influence the ice nucleation activity of the components present in natural dust particles at a microphysical scale. To improve our understanding how solute and mineral dust particle surface interaction, we run freezing experiments using a differential scanning calorimeter (DSC) with microcline, sanidine, plagioclase, kaolinite and quartz particles suspended in pure water and solutions containing ammonia, ammonium bisulfate, ammonium sulfate, ammonium chloride, ammonium nitrate, potassium chloride, potassium sulfate, sodium sulfate and sulfuric acid. Methodology Suspensions of mineral dust samples (2 - 5 wt%) are prepared in water with varying solute concentrations (0 - 15 wt%). 20 vol% of this suspension plus 80 vol% of a mixture of 95 wt% mineral oil (Aldrich

  5. Re-evaluating the Frankfurt isothermal static diffusion chamber for ice nucleation

    NASA Astrophysics Data System (ADS)

    Schrod, Jann; Danielczok, Anja; Weber, Daniel; Ebert, Martin; Thomson, Erik S.; Bingemer, Heinz G.

    2016-03-01

    Recently significant advances have been made in the collection, detection and characterization of ice nucleating particles (INPs). Ice nuclei are particles that facilitate the heterogeneous formation of ice within the atmospheric aerosol by lowering the free energy barrier to spontaneous nucleation and growth of ice from atmospheric water and/or vapor. The Frankfurt isostatic diffusion chamber (FRankfurt Ice nucleation Deposition freezinG Experiment: FRIDGE) is an INP collection and offline detection system that has become widely deployed and shows additional potential for ambient measurements. Since its initial development FRIDGE has gone through several iterations and improvements. Here we describe improvements that have been made in the collection and analysis techniques. We detail the uncertainties inherent in the measurement method and suggest a systematic method of error analysis for FRIDGE measurements. Thus what is presented herein should serve as a foundation for the dissemination of all current and future measurements using FRIDGE instrumentation.

  6. Measurements of BC-Containing Aerosol and Ice Nucleation Active Residuals in Colorado.

    NASA Astrophysics Data System (ADS)

    Katich, J. M.

    2015-12-01

    A recent ice nucleation (IN) chamber inter-comparison study (FIN-3) provided an opportunity to deploy two single particle soot photometers (SP2s) to the Stormpeak Laboratory in the mountains of Colorado in September of 2015. Aerosol was sampled from ambient air, as well as from behind both a coarse-mode aerosol concentrator and an ice nucleation chamber providing ice residuals. The SP2s characterized the size and mixing state of refractory black carbon-containing particles. Initial analyses of laboratory and ambient data collected over 3 weeks will be presented, with an emphasis on both coarse mode BC observations and BC contributions to ice residuals. The results will help constrain the role of BC from local and regional sources on heterogeneous ice nucleation.

  7. Laboratory studies of immersion and deposition mode ice nucleation of ozone aged mineral dust particles

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Welti, A.; Chou, C.; Stetzer, O.; Lohmann, U.

    2013-09-01

    Ice nucleation in the atmosphere is central to the understanding the microphysical properties of mixed-phase and cirrus clouds. Ambient conditions such as temperature (T) and relative humidity (RH), as well as aerosol properties such as chemical composition and mixing state play an important role in predicting ice formation in the troposphere. Previous field studies have reported the absence of sulfate and organic compounds on mineral dust ice crystal residuals sampled at mountain top stations or aircraft based measurements despite the long-range transport mineral dust is subjected to. We present laboratory studies of ice nucleation for immersion and deposition mode on ozone aged mineral dust particles for 233 < T < 263 K. Heterogeneous ice nucleation of untreated kaolinite (Ka) and Arizona Test Dust (ATD) particles is compared to corresponding aged particles that are subjected to ozone concentrations of 0.4-4.3 ppmv in a stainless steel aerosol tank. The portable ice nucleation counter (PINC) and immersion chamber combined with the Zurich ice nucleation chamber (IMCA-ZINC) are used to conduct deposition and immersion mode measurements, respectively. Ice active fractions as well as ice active surface site densities (ns) are reported and observed to increase as a function of decreasing temperature. We present first results that demonstrate enhancement of the ice nucleation ability of aged mineral dust particles in both the deposition and immersion mode due to ageing. We also present the first results to show a suppression of heterogeneous ice nucleation activity without the condensation of a coating of (in)organic material. In immersion mode, low ozone exposed Ka particles showed enhanced ice activity requiring a median freezing temperature of 1.5 K warmer than that of untreated Ka, whereas high ozone exposed ATD particles showed suppressed ice nucleation requiring a median freezing temperature of 3 K colder than that of untreated ATD. In deposition mode, low

  8. International Workshop on Comparing Ice Nucleation Measuring Systems 2014

    SciTech Connect

    Cziczo, Daniel

    2016-04-30

    The relationship of ambient aerosol particles to the formation of ice-containing clouds is one of the largest uncertainties in understanding the Earth’s climate. The uncertainty is due to several poorly understood processes and measurements including, but not limited to: (1) the microphysics of how particles nucleate ice, (2) the number of ice forming particles as a function of atmospheric properties such as temperature and relative humidity, (3) the atmospheric distribution of ice forming particles and (4) the role of anthropogenic activities in producing or changing the behavior of ice forming particles. The ways in which ice forming particles can impact climate is also multi-faceted. More ice forming particles can lead to clouds with more ice crystals and different optical properties than clouds with less ice forming particles. More effective ice forming particles can lead to ice at higher temperature and/or lower saturation, resulting in clouds at lower altitude or latitude which also changes the Earth’s radiative balance. Ice nucleation also initiates most of the Earth’s precipitation, even in the mid- and low-latitudes, since cloud-top temperatures are often below freezing. The limited measurements and lack of understanding directly translates to restrictions in our ability to model atmospheric ice formation and project changes into the future. The importance of ice nucleation research is further exemplified by Figure 1 which shows the publications per decade and citations per year on the topic of ice nucleation [DeMott et al., 2011]. After a lull at the end of the last century, there has been a dramatic increase in both publications and citations related to ice nucleation; this directly corresponds to the importance of ice nucleation on the Earth’s climate and the uncertainty in this area noted by the Solomon [2007].

  9. Comparative study of ice nucleating efficiency of K-feldspar in immersion and deposition freezing modes

    NASA Astrophysics Data System (ADS)

    Hiron, T.; Hoffmann, N.; Peckhaus, A.; Kiselev, A. A.; Leisner, T.; Flossmann, A. I.

    2016-12-01

    One of the main challenges in understanding the evolution of Earth's climate resides in the understanding the role of ice nucleation on the development of tropospheric clouds as well as its initiation. K-feldspar is known to be a very active ice nucleating particle and this study focuses on the characterization of its activity in two heterogeneous nucleation modes, immersion and deposition freezing.We use a newly built humidity-controlled cold stage allowing the simultaneous observation of up to 2000 identical 0.6-nanoliter droplets containing suspension of mineral dust particles. The droplets are first cooled down to observe immersion freezing, the obtained ice crystals are then evaporated and finally, the residual particles are exposed to the water vapor supersaturated with respect to ice.The ice nucleation abilities for the individual residual particles are then compared for the different freezing modes and correlation between immersion ice nuclei and deposition ice nuclei is investigated.Based on the electron microscopy analysis of the residual particles, we discuss the possible relationship between the ice nucleation properties of feldspar and its microstructure. Finally, we discuss the atmospheric implications of our experimental results, using DESCAM, a 1.5D bin-resolved microphysics model.

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

    NASA Astrophysics Data System (ADS)

    Kaufmann, Lukas; Marcolli, Claudia; Luo, Beiping; Peter, Thomas

    2017-03-01

    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

  11. A marine biogenic source of atmospheric ice-nucleating particles

    SciTech Connect

    Wilson, T. W.; Ladino, L. A.; Alpert, Peter A.; Breckels, M. N.; Brooks, I. M.; Browse, J.; Burrows, Susannah M.; Carslaw, K. S.; Huffman, J. A.; Judd, C.; Kilthau, W. P.; Mason, R. H.; McFiggans, Gordon; Miller, L. A.; Najera, J.; Polishchuk, E. A.; Rae, S.; Schiller, C. L.; Si, M.; Vergara Temprado, J.; Whale, Thomas; Wong, J P S; Wurl, O.; Yakobi-Hancock, J. D.; Abbatt, JPD; Aller, Josephine Y.; Bertram, Allan K.; Knopf, Daniel A.; Murray, Benjamin J.

    2015-09-09

    The formation of ice in clouds is facilitated by the presence of airborne ice nucleating particles1,2. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice3–11. Here we show that material in the sea surface microlayer, which is enriched in surface active organic material representative of that found in sub-micron sea- spray aerosol12–21, nucleates ice under conditions that occur in mixed-phase clouds and high-altitude ice clouds. The ice active material is likely biogenic and is less than ~0.2 ?m in size. We also show that organic material (exudate) released by a common marine diatom nucleates ice when separated from cells and propose that organic material associated with phytoplankton cell exudates are a candidate for the observed ice nucleating ability of the microlayer samples. By combining our measurements with global model simulations of marine organic aerosol, we show that ice nucleating particles of marine origin are dominant in remote marine environments, such as the Southern Ocean, the North Pacific and the North Atlantic.

  12. Principles and biotechnological applications of bacterial ice nucleation.

    PubMed

    Margaritis, A; Bassi, A S

    1991-01-01

    Certain aerobic, Gram-negative bacteria, including the epiphytic plant pathogen, Pseudomonas syringae, possess a membrane protein that enables them to nucleate crystallization in supercooled water. Currently, these ice-nucleating (IN) bacteria are being used in snow making and have potential applications in the production and texturing of frozen foods, and as a replacement of silver iodide in cloud seeding. A negative aspect of these IN bacteria is frost damage to plant surfaces. Thus, of the various types of biological ice nucleators, bacteria have been the subject of most research and also appear relevant to the anticipated practical uses. The intent of this review is to explain the identification and ecology of the ice-nucleating bacteria, as well as to discuss aspects of molecular biology related to ice nucleation and consider existing and potential applications of this unique phenomenon.

  13. Advances in Understanding the Role of Aerosols on Ice Clouds from the Fifth International Ice Nucleation (FIN) Workshops

    NASA Astrophysics Data System (ADS)

    Cziczo, D. J.; Moehler, O.; DeMott, P. J.

    2015-12-01

    The relationship of ambient aerosol particles to the formation of ice-containing clouds is one of the largest uncertainties in understanding climate. This is due to several poorly understood processes including the microphysics of how particles nucleate ice, the number of effective heterogeneous ice nuclei and their atmospheric distribution, the role of anthropogenic activities in producing or changing the behavior of ice forming particles and the interplay between effective heterogeneous ice nuclei and homogeneous ice formation. Our team recently completed a three-part international workshop to improve our understanding of atmospheric ice formation. Termed the Fifth International Ice Nucleation (FIN) Workshops, our motivation was the limited number of measurements and a lack of understanding of how to compare data acquired by different groups. The first activity, termed FIN1, addressed the characterization of ice nucleating particle size, number and chemical composition. FIN2 addressed the determination of ice nucleating particle number density. Groups modeling ice nucleation joined FIN2 to provide insight on measurements critically needed to model atmospheric ice nucleation and to understand the performance of ice chambers. FIN1 and FIN2 took place at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) chamber at the Karlsruhe Institute of Technology. A particular emphasis of FIN1 and FIN2 was the use of 'blind' intercomparisons using a highly characterized, but unknown to the instrument operators, aerosol sample. The third activity, FIN3, took place at the Desert Research Institute's Storm Peak Laboratory (SPL). A high elevation site not subject to local emissions, SPL allowed for a comparison of ice chambers and subsequent analysis of the ice residuals under the challenging conditions of low particle loading, temperature and pressure found in the atmosphere. The presentation focuses on the improvement in understanding how mass spectra from different

  14. Controlled ice nucleation in cryopreservation--a review.

    PubMed

    Morris, G John; Acton, Elizabeth

    2013-04-01

    We review here for the first time, the literature on control of ice nucleation in cryopreservation. Water and aqueous solutions have a tendency to undercool before ice nucleation occurs. Control of ice nucleation has been recognised as a critical step in the cryopreservation of embryos and oocytes but is largely ignored for other cell types. We review the processes of ice nucleation and crystal growth in the solution around cells and tissues during cryopreservation with an emphasis on non IVF applications. The extent of undercooling that is encountered during the cooling of various cryocontainers is defined and the methods that have been employed to control the nucleation of ice are examined. The effects of controlled ice nucleation on the structure of the sample and the outcome of cryopreservation of a range of cell types and tissues are presented and the physical events which define the cellular response are discussed. Nucleation of ice is the most significant uncontrolled variable in conventional cryopreservation leading to sample to sample variation in cell recovery, viability and function and should be controlled to allow standardisation of cryopreservation protocols for cells for biobanking, cell based assays or clinical application. This intervention allows a way of increasing viability of cells and reducing variability between samples and should be included as standard operating procedures are developed.

  15. Investigating ice nucleation in cirrus clouds with an aerosol-enabled Multiscale Modeling Framework

    NASA Astrophysics Data System (ADS)

    Zhang, Chengzhu; Wang, Minghuai; Morrison, Hugh; Somerville, Richard C. J.; Zhang, Kai; Liu, Xiaohong; Li, Jui-Lin F.

    2014-12-01

    In this study, an aerosol-dependent ice nucleation scheme has been implemented in an aerosol-enabled Multiscale Modeling Framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10-100/L) at cirrus temperatures. The new model simulates the observed shift of the ice supersaturation PDF toward higher values at low temperatures following the homogeneous nucleation threshold. The MMF model predicts a higher frequency of midlatitude supersaturation in the Southern Hemisphere and winter hemisphere, which is consistent with previous satellite and in situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to simulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation scheme and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 μm for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement with the satellite-retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value.

  16. Contribution of Feldspar and Marine Organic aerosols to global ice nucleating particles concentrations

    NASA Astrophysics Data System (ADS)

    Vergara Temprado, Jesús; Murray, Benjamin J.; Wilson, Theodore W.; O'Sullivan, Daniel; Browse, Jo; Pringle, Kirsty J.; Ardon-Dryer, Karin; Bertram, Allan K.; Burrows, Susannah; Cerbunis, Darius; DeMott, Paul J.; Mason, Ryan H.; O'Dowd, Colin D.; Rinaldi, Matteo; Carslaw, Ken S.

    2017-04-01

    Ice nucleating particles (INP) are aerosol particles that can heterogeneously freeze supercooled liquid water in the mixed-phase range of temperatures where water can exist in both liquid and ice states (0 to -37 oC). They affect the amount of ice and liquid water in mixed-phase clouds changing many of their properties. Climate models tend to represent their effect by parameterizing their atmospheric concentration as function of temperature or temperature and aerosol loading. However, different aerosol species nucleate ice with different abilities affecting the concentrations in different parts of the world. Representing these differences in models can lead to a better representation of mixed-phase clouds and ice processes affecting the radiative flux and the climate sensitivity of climate models. Here, we present the simulated concentrations of K-feldspar and marine organic aerosols using a global aerosol model, and then estimate the contribution of these species to INP concentrations across the globe using laboratory developed parameterizations of their ice nucleating ability. We show that these two species combined perform better at predicting global observations of INP than typically used parameterizations. Biases appear mainly in terrestrial environments at high temperatures, which might be caused by a relevant missing source of INP in our model. This work is a step forward in our understanding of how INP are distributed and what species are needed to be included in models in order to improve the representation of heterogeneous ice nucleation.

  17. Investigation of nucleation processes during dynamic recrystallization of ice using cryo-EBSD

    NASA Astrophysics Data System (ADS)

    Chauve, T.; Montagnat, M.; Barou, F.; Hidas, K.; Tommasi, A.; Mainprice, D.

    2017-02-01

    Nucleation mechanisms occurring during dynamic recrystallization play a crucial role in the evolution of microstructures and textures during high temperature deformation. In polycrystalline ice, the strong viscoplastic anisotropy induces high strain heterogeneities between grains which control the recrystallization mechanisms. Here, we study the nucleation mechanisms occurring during creep tests performed on polycrystalline columnar ice at high temperature and stress (T=-5°C;σ=0.5 MPa) by post-mortem analyses of deformation microstructures using cryogenic electron backscatter diffraction. The columnar geometry of the samples enables discrimination of the nuclei from the initial grains. Various nucleation mechanisms are deduced from the analysis of the nuclei relations with the dislocation sub-structures within grains and at grain boundaries. Tilt sub-grain boundaries and kink bands are the main structures responsible for development of polygonization and mosaic sub-structures. Nucleation by bulging at serrated grain boundaries is also an efficient nucleation mechanism near the grain boundaries where strain incompatibilities are high. Observation of nuclei with orientations not related to the `parent' ones suggests the possibility of `spontaneous' nucleation driven by the relaxation of the dislocation-related internal stress field. The complexity of the nucleation mechanisms observed here emphasizes the impact of stress and strain heterogeneities on dynamic recrystallization mechanisms. This article is part of the themed issue 'Microdynamics of ice'.

  18. Investigation of nucleation processes during dynamic recrystallization of ice using cryo-EBSD.

    PubMed

    Chauve, T; Montagnat, M; Barou, F; Hidas, K; Tommasi, A; Mainprice, D

    2017-02-13

    Nucleation mechanisms occurring during dynamic recrystallization play a crucial role in the evolution of microstructures and textures during high temperature deformation. In polycrystalline ice, the strong viscoplastic anisotropy induces high strain heterogeneities between grains which control the recrystallization mechanisms. Here, we study the nucleation mechanisms occurring during creep tests performed on polycrystalline columnar ice at high temperature and stress (T=-5°C;σ=0.5 MPa) by post-mortem analyses of deformation microstructures using cryogenic electron backscatter diffraction. The columnar geometry of the samples enables discrimination of the nuclei from the initial grains. Various nucleation mechanisms are deduced from the analysis of the nuclei relations with the dislocation sub-structures within grains and at grain boundaries. Tilt sub-grain boundaries and kink bands are the main structures responsible for development of polygonization and mosaic sub-structures. Nucleation by bulging at serrated grain boundaries is also an efficient nucleation mechanism near the grain boundaries where strain incompatibilities are high. Observation of nuclei with orientations not related to the 'parent' ones suggests the possibility of 'spontaneous' nucleation driven by the relaxation of the dislocation-related internal stress field. The complexity of the nucleation mechanisms observed here emphasizes the impact of stress and strain heterogeneities on dynamic recrystallization mechanisms.This article is part of the themed issue 'Microdynamics of ice'. © 2016 The Author(s).

  19. Ice nucleation activity of diesel soot particles at Cirrus relevant conditions: Effects of hydration, secondary organics coating, hydration, soot morphology, and coagulation

    SciTech Connect

    Kulkarni, Gourihar R.; China, Swarup; Liu, Shang; Nandasiri, Manjula I.; Sharma, Noopur; Wilson, Jacqueline M.; Aiken, A. C.; Chand, Duli; Laskin, Alexander; Mazzoleni, Claudio; Pekour, Mikhail S.; Shilling, John E.; Shutthanandan, V.; Zelenyuk, Alla; Zaveri, Rahul A.

    2016-04-16

    The role of atmospheric relevant soot particles that are processed in the atmosphere toward ice nucleation at cirrus cloud condition is poorly understood. In this study, the ice nucleating properties of diesel soot particles subjected to various physical and chemical aging treatments were investigated at temperatures ranging from -40 to -50 °C. We show that bare soot particles nucleate ice in deposition mode, but coating with secondary organics suppresses the heterogeneous ice nucleation potential of soot particles requiring homogeneous freezing threshold conditions. However, the ice nucleation efficiency of soot particles coated with an aqueous organic layer was similar to bare soot particles. Hydration of bare soot particles slightly enhanced the ice nucleation efficiency, and the IN abilities of compact soot particles (roundness = ~ 0.6) were similar to bare lacey soot particles (roundness = ~ 0.4). These results indicate that ice nucleation properties are sensitive to the various aging treatments.

  20. Role of the electric double layer in the ice nucleation of water droplets under an electric field

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang-Xiong; Li, Xin-Hao; Chen, Min

    2016-09-01

    Figuring out the mechanism of ice nucleation on charged aerosols or in thunderstorms is of fundamental importance in atmospheric science. However, findings on whether the electric field promotes or suppresses heterogeneous ice nucleation are conflicting. In this work, we design an apparatus and test the influence of the electric field on ice nucleation by freezing a series of deionized water droplets resting on solid surfaces with an electric field perpendicular to the substrates. Results show that ice nucleation is obviously promoted under the electric field and is independent of the field direction. Theoretic analyses show that the promotion is due to the reduction of Gibbs free energy which can be partially rationalized by the electric field sustained in the electric double layer at the solid-water interface, with strength about two orders higher than that of the external electric field. Moreover, water-droplet deformation under the electric field is not expected to be the cause of the ice-nucleation promotion.

  1. Homogeneous vs. heterogeneous nucleation in water-dicarboxylic acid systems

    NASA Astrophysics Data System (ADS)

    Hienola, A. I.; Vehkamäki, H.; Riipinen, I.; Kulmala, M.

    2009-03-01

    Binary heterogeneous nucleation of water-succinic/glutaric/malonic/adipic acid on nanometer-sized particles is investigated within the frame of classical heterogeneous nucleation theory. Homogeneous nucleation is also included for comparison. It is found that the nucleation probabilities depend on the contact angle and on the size of the seed particles. New thermodynamical properties, such as saturation vapor pressure, density and surface tension for all the dicarboxylic acid aqueous solutions are included in the calculations. While the new surface tension and density formulations do not bring any significant difference in the computed nucleation rate for homogeneous nucleation for succinic and glutaric acids, the use of the newly derived equations for the vapor pressure decrease the acid concentrations in gas phase by 3 orders of magnitude. According to our calculations, the binary heterogeneous nucleation of succinic acid-water and glutaric acid-water - although it requires a 3-4 orders of magnitude lower vapor concentrations than the homogeneous nucleation - cannot take place under atmospheric conditions. On the other hand binary homogeneous nucleation of adipic acid-water systems might be possible under conditions occuring in upper boundary layer. However, a more detailed characterization of the interaction between the surface and the molecules of the nucleating vapor should be considered in the future.

  2. A nanoscale temperature-dependent heterogeneous nucleation theory

    SciTech Connect

    Cao, Y. Y.; Yang, G. W.

    2015-06-14

    Classical nucleation theory relies on the hypothetical equilibrium of the whole nucleation system, and neglects the thermal fluctuations of the surface; this is because the high entropic gains of the (thermodynamically extensive) surface would lead to multiple stable states. In fact, at the nanometer scale, the entropic gains of the surface are high enough to destroy the stability of the thermal equilibrium during nucleation, comparing with the whole system. We developed a temperature-dependent nucleation theory to elucidate the heterogeneous nucleation process, by considering the thermal fluctuations based on classical nucleation theory. It was found that the temperature not only affected the phase transformation, but also influenced the surface energy of the nuclei. With changes in the Gibbs free energy barrier, nucleation behaviors, such as the nucleation rate and the critical radius of the nuclei, showed temperature-dependent characteristics that were different from those predicted by classical nucleation theory. The temperature-dependent surface energy density of a nucleus was deduced based on our theoretical model. The agreement between the theoretical and experimental results suggested that the developed nucleation theory has the potential to contribute to the understanding and design of heterogeneous nucleation at the nanoscale.

  3. Deposition mode ice nucleation reexamined at temperatures below 200 K

    NASA Astrophysics Data System (ADS)

    Thomson, E. S.; Kong, X.; Papagiannakopoulos, P.; Pettersson, J. B. C.

    2014-09-01

    The environmental chamber of a molecular beam apparatus is used to study deposition nucleation of ice on graphite, alcohols and acetic and nitric acids at temperatures between 155 and 200 K. The critical supersaturations necessary to spontaneously nucleate water ice on six different substrate materials are observed to occur at higher supersaturations than are theoretically predicted. This contradictory result motivates more careful examination of the experimental conditions and the underlying basis of the current theories. An analysis based on classical nucleation theory supports the view that at these temperatures nucleation is primarily controlled by the rarification of the vapor and the strength of water's interaction with the substrate surface. The technique enables a careful probing of the underlying processes of ice nucleation and the substrate materials of study. The relevance of the findings to tropospheric temperatures is discussed.

  4. Ice nucleation efficiency of clay minerals in the immersion mode

    NASA Astrophysics Data System (ADS)

    Pinti, V.; Marcolli, C.; Zobrist, B.; Hoyle, C. R.; Peter, T.

    2012-07-01

    Emulsion and bulk freezing experiments were performed to investigate immersion ice nucleation on clay minerals in pure water, using various kaolinites, montmorillonites, illites as well as natural dust from the Hoggar Mountains in the Saharan region. Differential scanning calorimeter measurements were performed on three different kaolinites (KGa-1b, KGa-2 and K-SA), two illites (Illite NX and Illite SE) and four natural and acid-treated montmorillonites (SWy-2, STx-1b, KSF and K-10). The emulsion experiments provide information on the average freezing behaviour characterized by the average nucleation sites. These experiments revealed one to sometimes two distinct heterogeneous freezing peaks, which suggest the presence of a low number of qualitatively distinct average nucleation site classes. We refer to the peak at the lowest temperature as "standard peak" and to the one occurring in only some clay mineral types at higher temperatures as "special peak". Conversely, freezing in bulk samples is not initiated by the average nucleation sites, but by a very low number of "best sites". The kaolinites and montmorillonites showed quite narrow standard peaks with onset temperatures 238 Kice nucleation efficiencies of dust particles on the basis of freezing onset temperatures from bulk experiments, as has been done in some atmospheric studies, is not appropriate. Our investigations demonstrate that immersion freezing temperatures of clay minerals strongly depend on the amount of clay mineral present per droplet and on

  5. The influence of finite impurity size on heterogeneous nucleation

    NASA Technical Reports Server (NTRS)

    Weinberg, Michael C.

    1992-01-01

    The effects of the finite size of impurities upon the heterogeneous nucleation rate is examined. Simple arguments based upon probability theory are used to find the relative nucleation rate, p(j), on particles containing j nuclei. The expression for p(j) is used in turn to compute the overall nucleation rate and average number of nuclei on an impurity as a function of time.

  6. The influence of finite impurity size on heterogeneous nucleation

    NASA Technical Reports Server (NTRS)

    Weinberg, Michael C.

    1992-01-01

    The effects of the finite size of impurities upon the heterogeneous nucleation rate is examined. Simple arguments based upon probability theory are used to find the relative nucleation rate, p(j), on particles containing j nuclei. The expression for p(j) is used in turn to compute the overall nucleation rate and average number of nuclei on an impurity as a function of time.

  7. Ultrasonic emissions during ice nucleation and propagation in plant xylem.

    PubMed

    Charrier, Guillaume; Pramsohler, Manuel; Charra-Vaskou, Katline; Saudreau, Marc; Améglio, Thierry; Neuner, Gilbert; Mayr, Stefan

    2015-08-01

    Ultrasonic acoustic emission analysis enables nondestructive monitoring of damage in dehydrating or freezing plant xylem. We studied acoustic emissions (AE) in freezing stems during ice nucleation and propagation, by combining acoustic and infrared thermography techniques and controlling the ice nucleation point. Ultrasonic activity in freezing samples of Picea abies showed two distinct phases: the first on ice nucleation and propagation (up to 50 AE s(-1) ; reversely proportional to the distance to ice nucleation point), and the second (up to 2.5 AE s(-1) ) after dissipation of the exothermal heat. Identical patterns were observed in other conifer and angiosperm species. The complex AE patterns are explained by the low water potential of ice at the ice-liquid interface, which induced numerous and strong signals. Ice propagation velocities were estimated via AE (during the first phase) and infrared thermography. Acoustic activity ceased before the second phase probably because the exothermal heating and the volume expansion of ice caused decreasing tensions. Results indicate cavitation events at the ice front leading to AE. Ultrasonic emission analysis enabled new insights into the complex process of xylem freezing and might be used to monitor ice propagation in natura.

  8. The adsorption of fungal ice-nucleating proteins on mineral dusts: a terrestrial reservoir of atmospheric ice-nucleating particles

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Daniel; Murray, Benjamin J.; Ross, James; Webb, Michael E.

    2016-04-01

    The occurrence of ice-nucleating particles (INPs) in our atmosphere has a profound impact on the properties and lifetime of supercooled clouds. However, the identities, sources and abundances of airborne particles capable of efficiently nucleating ice at relatively low supercoolings (T > -15 °C) remain enigmatic. Recently, several studies have suggested that unidentified biogenic residues in soil dusts are likely to be an important source of these efficient atmospheric INPs. While it has been shown that cell-free proteins produced by common soil-borne fungi are exceptional INPs, whether these fungi are a source of ice-nucleating biogenic residues in soils has yet to be shown. In particular, it is unclear whether upon adsorption to soil mineral particles, the activity of fungal ice-nucleating proteins is retained or is reduced, as observed for other soil enzymes. Here we show that proteins from a common soil fungus (Fusarium avenaceum) do in fact preferentially bind to and impart their ice-nucleating properties to the common clay mineral kaolinite. The ice-nucleating activity of the proteinaceous INPs is found to be unaffected by adsorption to the clay, and once bound the proteins do not readily desorb, retaining much of their activity even after multiple washings with pure water. The atmospheric implications of the finding that nanoscale fungal INPs can effectively determine the nucleating abilities of lofted soil dusts are discussed.

  9. Pre-activation of ice-nucleating particles by the pore condensation and freezing mechanism

    NASA Astrophysics Data System (ADS)

    Wagner, Robert; Kiselev, Alexei; Möhler, Ottmar; Saathoff, Harald; Steinke, Isabelle

    2016-02-01

    In spite of the resurgence in ice nucleation research a comparatively small number of studies deal with the phenomenon of pre-activation in heterogeneous ice nucleation. Fifty years ago, it was shown that various mineral dust and volcanic ash particles can be pre-activated to become nuclei for ice crystal formation even at temperatures as high as 270-271 K. Pre-activation was achieved under ice-subsaturated conditions without any preceding macroscopic ice growth by just temporarily cooling the particles to temperatures below 228 K. A two-step mechanism involving capillary condensation of supercooled water and subsequent homogeneous freezing was proposed to account for the particles' enhanced ice nucleation ability at high temperatures. This work reinvestigates the efficiency of the proposed pre-activation mechanism in temperature-cycling experiments performed in a large cloud chamber with suspended particles. We find the efficiency to be highest for the clay mineral illite as well as for highly porous materials like zeolite and diatomaceous earth, whereas most aerosols generated from desert dust surface samples did not reveal a measurable pre-activation ability. The pre-activation efficiency is linked to particle pores in a certain size range. As estimated by model calculations, only pores with diameters between about 5 and 8 nm contribute to pre-activation under ice-subsaturated conditions. This range is set by a combination of requirements from the negative Kelvin effect for condensation and a critical size of ice embryos for ice nucleation and melting. In contrast to the early study, pre-activation is only observed for temperatures below 260 K. Above that threshold, the particles' improved ice nucleation ability disappears due to the melting of ice in the pores.

  10. Parameterization of homogeneous ice nucleation for cloud and climate models based on classical nucleation theory

    NASA Astrophysics Data System (ADS)

    Khvorostyanov, V. I.; Curry, J. A.

    2012-10-01

    A new analytical parameterization of homogeneous ice nucleation is developed based on extended classical nucleation theory including new equations for the critical radii of the ice germs, free energies and nucleation rates as simultaneous functions of temperature and water saturation ratio. By representing these quantities as separable products of the analytical functions of temperature and supersaturation, analytical solutions are found for the integral-differential supersaturation equation and concentration of nucleated crystals. Parcel model simulations are used to illustrate the general behavior of various nucleation properties under various conditions, for justifications of the further key analytical simplifications, and for verification of the resulting parameterization. The final parameterization is based upon the values of the supersaturation that determines the current or maximum concentrations of the nucleated ice crystals. The crystal concentration is analytically expressed as a function of time and can be used for parameterization of homogeneous ice nucleation both in the models with small time steps and for substep parameterization in the models with large time steps. The crystal concentration is expressed analytically via the error functions or elementary functions and depends only on the fundamental atmospheric parameters and parameters of classical nucleation theory. The diffusion and kinetic limits of the new parameterization agree with previous semi-empirical parameterizations.

  11. Parameterization of homogeneous ice nucleation for cloud and climate models based on classical nucleation theory

    NASA Astrophysics Data System (ADS)

    Khvorostyanov, V. I.; Curry, J. A.

    2012-03-01

    A new analytical parameterization of homogeneous ice nucleation is developed based on extended classical nucleation theory including new equations for the critical radii of the ice germs, free energies and nucleation rates as the functions of the temperature and water saturation ratio simultaneously. By representing these quantities as separable products of the analytical functions of the temperature and supersaturation, analytical solutions are found for the integral-differential supersaturation equation and concentration of nucleated crystals. Parcel model simulations are used to illustrate the general behavior of various nucleation properties under various conditions, for justifications of the further key analytical simplifications, and for verification of the resulting parameterization. The final parameterization is based upon the values of the supersaturation that determines the current or maximum concentrations of the nucleated ice crystals. The crystal concentration is analytically expressed as a function of time and can be used for parameterization of homogeneous ice nucleation both in the models with small time steps and for substep parameterization in the models with large time steps. The crystal concentration is expressed analytically via the error functions or elementary functions and depends only on the fundamental atmospheric parameters and parameters of classical nucleation theory. The diffusion and kinetic limits of the new parameterization agree with previous semi-empirical parameterizations.

  12. Temperature dependence of heterogeneous nucleation: Extension of the Fletcher model

    NASA Astrophysics Data System (ADS)

    McGraw, Robert; Winkler, Paul; Wagner, Paul

    2015-04-01

    Recently there have been several cases reported where the critical saturation ratio for onset of heterogeneous nucleation increases with nucleation temperature (positive slope dependence). This behavior contrasts with the behavior observed in homogeneous nucleation, where a decreasing critical saturation ratio with increasing nucleation temperature (negative slope dependence) seems universal. For this reason the positive slope dependence is referred to as anomalous. Negative slope dependence is found in heterogeneous nucleation as well, but because so few temperature-dependent measurements have been reported, it is not presently clear which slope condition (positive or negative) will become more frequent. Especially interesting is the case of water vapor condensation on silver nanoparticles [Kupc et al., AS&T 47: i-iv, 2013] where the critical saturation ratio for heterogeneous nucleation onset passes through a maximum, at about 278K, with higher (lower) temperatures showing the usual (anomalous) temperature dependence. In the present study we develop an extension of Fletcher's classical, capillarity-based, model of heterogeneous nucleation that explicitly resolves the roles of surface energy and surface entropy in determining temperature dependence. Application of the second nucleation theorem, which relates temperature dependence of nucleation rate to cluster energy, yields both necessary and sufficient conditions for anomalous temperature behavior in the extended Fletcher model. In particular it is found that an increasing contact angle with temperature is a necessary, but not sufficient, condition for anomalous temperature dependence to occur. Methods for inferring microscopic contact angle and its temperature dependence from heterogeneous nucleation probability measurements are discussed in light of the new theory.

  13. High-frequency gravity waves and homogeneous ice nucleation in tropical tropopause layer cirrus

    NASA Astrophysics Data System (ADS)

    Jensen, Eric J.; Ueyama, Rei; Pfister, Leonhard; Bui, Theopaul V.; Alexander, M. Joan; Podglajen, Aurélien; Hertzog, Albert; Woods, Sarah; Lawson, R. Paul; Kim, Ji-Eun; Schoeberl, Mark R.

    2016-06-01

    The impact of high-frequency gravity waves on homogeneous-freezing ice nucleation in cold cirrus clouds is examined using parcel model simulations driven by superpressure balloon measurements of temperature variability experienced by air parcels in the tropical tropopause region. We find that the primary influence of high-frequency waves is to generate rapid cooling events that drive production of numerous ice crystals. Quenching of ice nucleation events by temperature tendency reversal in the highest-frequency waves does occasionally produce low ice concentrations, but the overall impact of high-frequency waves is to increase the occurrence of high ice concentrations. The simulated ice concentrations are considerably higher than indicated by in situ measurements of cirrus in the tropical tropopause region. One-dimensional simulations suggest that although sedimentation reduces mean ice concentrations, a discrepancy of about a factor of 3 with observed ice concentrations remains. Reconciliation of numerical simulations with the observed ice concentrations will require inclusion of physical processes such as heterogeneous nucleation and entrainment.

  14. Anti-icing potential of superhydrophobic Ti6Al4V surfaces: ice nucleation and growth.

    PubMed

    Shen, Yizhou; Tao, Jie; Tao, Haijun; Chen, Shanlong; Pan, Lei; Wang, Tao

    2015-10-06

    On the basis of the icing-delay performance and ice adhesion strength, the anti-icing potential of the superhydrophobic surface has been well-investigated in the past few years. The present work mainly emphasized the investigations of ice nucleation and growth to fully explore the anti-icing potential of the superhydrophobic surface. We took the various surfaces ranging from hydrophilic to superhydrophobic as the research objects and, combining the classical nucleation theory, discussed the ice nucleation behaviors of the water droplets on these sample surfaces under the condition of supercooling. Meanwhile, the macroscopical growth processes of ice on these surfaces were analyzed on the basis of the growth mechanism of the ice nucleus. It was found that the superhydrophobic surface could greatly reduce the solid-liquid interface nucleation rate, owing to the extremely low actual solid-liquid contact area caused by the composite micro-nanoscale hierarchical structures trapping air pockets, leading to the bulk nucleation dominating the entire ice nucleation at the lower temperatures. Furthermore, ice on the superhydrophobic surface possessed a lower macroscopical growth velocity as a result of the less ice nucleation rate and the insulating action of the trapped air pockets.

  15. Suppression of heterogeneous bubble nucleation by upstream subcooled liquid flow

    NASA Astrophysics Data System (ADS)

    Li, J.; Peterson, G. P.

    2006-05-01

    The threshold levels for quasi-steady-state bubble nucleation on a smooth platinum surface located in a microchannel, both with and without liquid flow, are explored. The measured threshold for motionless liquid compares well with the theoretical value as calculated from the classical kinetics of nucleation. The measured threshold for the case of flow in the microchannel exceeds the measured value for motionless liquid and even exceeds the theoretical value. The observed phenomena suggest that in the absence of impurities, classical theory can accurately predict the heterogeneous nucleation. In addition, subcooled fluids were found to suppress bubble nucleation.

  16. How important is biological ice nucleation in clouds on a global scale? (Invited)

    NASA Astrophysics Data System (ADS)

    Hoose, C.; Kristjansson, J. E.; Burrows, S. M.; Chen, J.; Hazra, A.

    2010-12-01

    The high ice nucleating ability of some biological particles has led to speculations about living and dead organisms being involved in cloud ice and precipitation formation, exerting a possibly significant influence on weather and climate. In the present study, the role of primary biological aerosol particles (PBAPs) in competition with mineral dust and soot as heterogeneous ice nuclei is investigated with the global climate model CAM-Oslo. Emission parameterizations for bacteria, fungal spores and pollen based on recent literature are introduced, as well as heterogeneous ice nucleation parameterizations based on classical nucleation theory and laboratory measurements. The simulated PBAP number concentrations are compared to data from various locations. The agreement between measurements and observations is overall satisfactory for bacteria and fungal spore concentrations, but the model tends to underestimate total PBAP number. This likely indicates that either pollen or other (possibly submicron) PBAP that are not considered here contribute significantly to the total PBAP number at the measurement locations. The simulated contribution of PBAPs to the global average ice nucleation rate is only 10-5 %, with an uppermost estimate of 0.6% when the emission strengths and ice nucleation efficiencies are varied within the uncertainty ranges. At the same time, observed PBAP concentrations in air and biological ice nucleus concentrations in snow are reasonably well captured by the model. This implies that ‘bioprecipitation’ processes (snow and rain initiated by PBAPs) are of minor importance on the global scale. However, our results do not rule out local, regional or seasonal importance of biological ice nuclei. We will discuss the uncertainties in the underlying model assumptions, compare to results of previous modeling studies and suggest directions for future work.

  17. Type I Antifreeze Proteins Enhance Ice Nucleation above Certain Concentrations

    PubMed Central

    Wilson, Peter W.; Osterday, Katie E.; Heneghan, Aaron F.; Haymet, Anthony D. J.

    2010-01-01

    In this study, we examined the effects that antifreeze proteins have on the supercooling and ice-nucleating abilities of aqueous solutions. Very little information on such nucleation currently exists. Using an automated lag time apparatus and a new analysis, we show several dilution series of Type I antifreeze proteins. Our results indicate that, above a concentration of ∼8 mg/ml, ice nucleation is enhanced rather than hindered. We discuss this unexpected result and present a new hypothesis outlining three components of polar fish blood that we believe affect its solution properties in certain situations. PMID:20837472

  18. Thermodynamic Derivation of the Activation Energy for Ice Nucleation

    NASA Technical Reports Server (NTRS)

    Barahona, D.

    2015-01-01

    Cirrus clouds play a key role in the radiative and hydrological balance of the upper troposphere. Their correct representation in atmospheric models requires an understanding of the microscopic processes leading to ice nucleation. A key parameter in the theoretical description of ice nucleation is the activation energy, which controls the flux of water molecules from the bulk of the liquid to the solid during the early stages of ice formation. In most studies it is estimated by direct association with the bulk properties of water, typically viscosity and self-diffusivity. As the environment in the ice-liquid interface may differ from that of the bulk, this approach may introduce bias in calculated nucleation rates. In this work a theoretical model is proposed to describe the transfer of water molecules across the ice-liquid interface. Within this framework the activation energy naturally emerges from the combination of the energy required to break hydrogen bonds in the liquid, i.e., the bulk diffusion process, and the work dissipated from the molecular rearrangement of water molecules within the ice-liquid interface. The new expression is introduced into a generalized form of classical nucleation theory. Even though no nucleation rate measurements are used to fit any of the parameters of the theory the predicted nucleation rate is in good agreement with experimental results, even at temperature as low as 190 K, where it tends to be underestimated by most models. It is shown that the activation energy has a strong dependency on temperature and a weak dependency on water activity. Such dependencies are masked by thermodynamic effects at temperatures typical of homogeneous freezing of cloud droplets; however, they may affect the formation of ice in haze aerosol particles. The new model provides an independent estimation of the activation energy and the homogeneous ice nucleation rate, and it may help to improve the interpretation of experimental results and the

  19. Thermodynamic Derivation of the Activation Energy for Ice Nucleation

    NASA Technical Reports Server (NTRS)

    Barahona, D.

    2015-01-01

    Cirrus clouds play a key role in the radiative and hydrological balance of the upper troposphere. Their correct representation in atmospheric models requires an understanding of the microscopic processes leading to ice nucleation. A key parameter in the theoretical description of ice nucleation is the activation energy, which controls the flux of water molecules from the bulk of the liquid to the solid during the early stages of ice formation. In most studies it is estimated by direct association with the bulk properties of water, typically viscosity and self-diffusivity. As the environment in the ice-liquid interface may differ from that of the bulk, this approach may introduce bias in calculated nucleation rates. In this work a theoretical model is proposed to describe the transfer of water molecules across the ice-liquid interface. Within this framework the activation energy naturally emerges from the combination of the energy required to break hydrogen bonds in the liquid, i.e., the bulk diffusion process, and the work dissipated from the molecular rearrangement of water molecules within the ice-liquid interface. The new expression is introduced into a generalized form of classical nucleation theory. Even though no nucleation rate measurements are used to fit any of the parameters of the theory the predicted nucleation rate is in good agreement with experimental results, even at temperature as low as 190 K, where it tends to be underestimated by most models. It is shown that the activation energy has a strong dependency on temperature and a weak dependency on water activity. Such dependencies are masked by thermodynamic effects at temperatures typical of homogeneous freezing of cloud droplets; however, they may affect the formation of ice in haze aerosol particles. The new model provides an independent estimation of the activation energy and the homogeneous ice nucleation rate, and it may help to improve the interpretation of experimental results and the

  20. Ice nucleation by cellulose and its potential contribution to ice formation in clouds

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Möhler, O.; Yamashita, K.; Tajiri, T.; Saito, A.; Kiselev, A.; Hoffmann, N.; Hoose, C.; Jantsch, E.; Koop, T.; Murakami, M.

    2015-04-01

    Ice particles in the atmosphere influence clouds, precipitation and climate, and often form with help from aerosols that serve as ice-nucleating particles. Biological particles, including non-proteinaceous ones, contribute to the diverse spectrum of ice-nucleating particles. However, little is known about their atmospheric abundance and ice nucleation efficiency, and their role in clouds and the climate system is poorly constrained. One biological particle type, cellulose, has been shown to exist in an airborne form that is prevalent throughout the year even at remote and elevated locations. Here we report experiments in a cloud simulation chamber to demonstrate that microcrystalline cellulose particles can act as efficient ice-nucleating particles in simulated supercooled clouds. In six immersion mode freezing experiments, we measured the ice nucleation active surface-site densities of aerosolized cellulose across a range of temperatures. Using these active surface-site densities, we developed parameters describing the ice nucleation ability of these particles and applied them to observed atmospheric cellulose and plant debris concentrations in a global aerosol model. We find that ice nucleation by cellulose becomes significant (>0.1 l-1) below about -21 °C, temperatures relevant to mixed-phase clouds. We conclude that the ability of cellulose to act as ice-nucleating particles requires a revised quantification of their role in cloud formation and precipitation.

  1. The adsorption of fungal ice-nucleating proteins on mineral dusts: a terrestrial reservoir of atmospheric ice-nucleating particles

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Daniel; Murray, Benjamin J.; Ross, James F.; Webb, Michael E.

    2016-06-01

    The occurrence of ice-nucleating particles (INPs) in our atmosphere has a profound impact on the properties and lifetime of supercooled clouds. To date, the identities, sources and abundances of particles capable of nucleating ice at relatively low supercoolings (T > -15 °C) remain enigmatic. While biomolecules such as proteins and carbohydrates have been implicated as important high-temperature INPs, the lack of knowledge on the environmental fates of these species makes it difficult to assess their potential atmospheric impacts. Here we show that such nanoscale ice-nucleating proteins from a common soil-borne fungus (Fusarium avenaceum) preferentially bind to and confer their ice-nucleating properties to kaolinite. The ice-nucleating activity of the proteinaceous INPs is unaffected by adsorption to the clay, and once bound the proteins do not readily desorb, retaining much of the activity even after multiple washings with pure water. The atmospheric implications of the finding that biological residues can confer their ice-nucleating ability to dust particles are discussed.

  2. Heterogeneous critical nucleation on a completely wettable substrate

    NASA Astrophysics Data System (ADS)

    Iwamatsu, Masao

    2011-06-01

    Heterogeneous nucleation of a new bulk phase on a flat substrate can be associated with the surface phase transition called wetting transition. When this bulk heterogeneous nucleation occurs on a completely wettable flat substrate with a zero contact angle, the classical nucleation theory predicts that the free-energy barrier of nucleation vanishes. In fact, there always exists a critical nucleus and a free-energy barrier as the first-order prewetting transition will occur even when the contact angle is zero. Furthermore, the critical nucleus changes its character from the critical nucleus of surface phase transition below bulk coexistence (undersaturation) to the critical nucleus of bulk heterogeneous nucleation above the coexistence (oversaturation) when it crosses the coexistence. Recently, Sear [J. Chem. Phys. 129, 164510 (2008)], 10.1063/1.2992160 has shown, by a direct numerical calculation of nucleation rate, that the nucleus does not notice this change when it crosses the coexistence. In our work, the morphology and the work of formation of critical nucleus on a completely wettable substrate are re-examined across the coexistence using the interface-displacement model. Indeed, the morphology and the work of formation changes continuously at the coexistence. Our results support the prediction of Sear and will rekindle the interest on heterogeneous nucleation on a completely wettable substrate.

  3. Observations on the nucleation of ice VII in compressed water

    NASA Astrophysics Data System (ADS)

    Stafford, Samuel J. P.; Chapman, David J.; Bland, Simon N.; Eakins, Daniel E.

    2017-01-01

    Water can freeze upon multiple shock compression, but the window material determines the pressure of the phase transition. Several plate impact experiments were conducted with liquid targets on a single-stage gas gun, diagnosed simultaneously using photonic doppler velocimetry (PDV) and high speed imaging through the water. The experiments investigated why silica windows instigate freezing above 2.5 GPa whilst sapphire windows do not until 7 GPa. We find that the nucleation of ice occurs on the surfaces of windows and can be affected by the surface coating suggesting the surface energy of fused silica, likely due to hydroxyl groups, encourages nucleation of ice VII crystallites. Aluminium coatings prevent nucleation and sapphire surfaces do not nucleate until approximately 6.5 GPa. This is believed to be the threshold pressure for the homogeneous nucleation of water.

  4. Heterogeneous bubble nucleation on pyroxene and plagioclase in andesite magmas

    NASA Astrophysics Data System (ADS)

    Pleše, P.; Higgins, M.; Brun, F.; Casselman, J.; Fife, J.; Mancini, L.; Lanzafame, G.; Baker, D. R.

    2016-12-01

    Understanding bubble nucleation and growth has long been considered a key to improving our knowledge of magmatic evolution, and aiding our goal of predicting violent volcanic eruptions. The role crystals play as heterogeneous nucleation sites for bubbles has become an active area of research because they have the potential to reduce the supersaturation necessary for bubble growth. The nucleation sites of bubbles in magmas are elusive because they cannot be directly observed in natural volcanic systems. Studies are generally conducted on natural, post-eruption samples or quenched experimental charges, but both provide only a view of the final state and provide little information on how this state was achieved. We directly observed bubble nucleation and growth by 4D in-situ synchrotron X-ray tomography of bubble nucleation and growth at the Swiss Light Source. Experiments were conducted on previously prepared, hydrous, crystal-bearing andesitic melts to observe bubble nucleation and track bubble growth and movement. We collected 3D images every 0.5 s while heating hydrated melts at 1 atm. We observed that bubbles first nucleated heterogeneously at clinopyroxene/melt and near plagioclase/melt interfaces, rather than homogeneously within the melt. Heterogeneous nucleation on one oxide crystal and homogeneous nucleation within the melt occurred significantly after nucleation on the silicates. The measured bubble-crystal contact angle was not constant and decreased with time. Bubbles grew much larger than the crystals in the experiments, producing textures similar to those seen in some natural volcanic samples. Our results show that the presence of silicate phases in magmas must be taken into account when discussing bubble nucleation in magmatic systems.

  5. Ice Nucleating Particles and their Role in California Winter Clouds

    NASA Astrophysics Data System (ADS)

    DeMott, P. J.; Prather, K. A.; Hill, T. C. J.; McCluskey, C. S.; Levin, E. J.; Suski, K. J.; Creamean, J.; Collins, D. B.; Martin, A.; Cornwell, G.; Al-Mashat, H.; Rosenfeld, D.; Leung, L. R.; Comstock, J. M.; Tomlinson, J. M.; Kreidenweis, S. M.; Petters, M. D.

    2014-12-01

    Field studies are providing the opportunity to characterize ice nucleating particle (INP) number concentrations, their varied sources, and to examine their influence on ice formation and precipitation processes in winter clouds in California. Aerosol sources that may influence orographic cloud properties in California include pollution, marine aerosols, and transported dusts. Vertical stratification affects the role of different aerosol types. Boundary layer dust and pollution in Central Valley locations may influence cloud properties at times, but may be decoupled from cloud layers at other times or be restricted in affecting clouds by the Sierra barrier jet phenomenon. Marine layers may sometimes be lifted over topography to influence clouds. Finally, long range transported dust/biological particles may directly enter upper cloud levels to act as the trigger for ice initiation. We present analyses of INP number concentrations, INP chemical composition, and related data collected from flights on the DOE G-1 aircraft during the CalWater 1 field study in winter 2011. Sampling of mostly marine boundary layer INP during the surface-based BBACPAX (Bodega Bay Aerosol-Cloud-Precipitation in Atmospheric rivers eXperiment) study in 2014 included first sampling with an online method for measuring the mass spectral composition of INP, and new immersion freezing INP measurements extending to the warm temperature limit of heterogeneous ice formation. Studies reveal the strong influence of long range transported aerosols on INP populations and typically lower INP concentrations in marine air layers. Plans for new studies including G-1 aircraft flights during the ACAPEX (ARM Cloud Aerosol Precipitation Experiment) study, overlapping with ground-based measurements in the CalWater-2 campaign in winter 2015 will be introduced. Analyses are being applied toward numerical modeling studies of aerosol-cloud-precipitation interactions in California, presented separately in this session.

  6. Water ice cloud formation on Mars is more difficult than presumed: Laboratory studies of ice nucleation on surrogate materials

    NASA Astrophysics Data System (ADS)

    Iraci, Laura T.; Phebus, Bruce D.; Stone, Bradley M.; Colaprete, Anthony

    2010-12-01

    The role of water ice clouds in the martian water cycle and climate depends on cloud properties such as particle size and number distribution. These properties, in turn, depend on heterogeneous nucleation parameters which are poorly understood. Here we report laboratory experiments performed under martian temperature and water partial pressure conditions (158-185 K, 9 × 10 -7-1 × 10 -4 Torr H 2O) to determine the critical saturation ratio for ice onset, Scrit, as a function of temperature and dust composition. Using infrared spectroscopy to monitor ice nucleation and growth, we find a significant barrier to ice formation, with a pronounced temperature dependence. Even on clay minerals which show uptake of non-crystalline water before ice nucleation, we find a saturation ratio of 2.5 or more (RH ice > 250%) is needed to begin ice growth at temperatures near 160 K. These results could lead to changes of four orders of magnitude in the nucleation rate relative to the presumptions used currently in Mars microphysical models, which commonly set the contact parameter, m, to a single value of 0.95. Our results range from m = 0.84 to m = 0.98. For ice nucleation on Arizona Test Dust, the temperature dependence is described by m = 0.0046 * Tnucl + 0.1085, while m = 0.0055 * Tnucl + 0.0003 on a smectite-rich clay sample. Our findings suggest that cloud formation will be more difficult than previously thought, potentially leading to areas of increased near-surface humidity but generally drier conditions in the atmosphere of Mars, overall.

  7. The Leipzig Ice Nucleation chamber Comparison (LINC): An overview of ice nucleation measurements observed with four on-line ice nucleation devices

    NASA Astrophysics Data System (ADS)

    Kohn, Monika; Wex, Heike; Grawe, Sarah; Hartmann, Susan; Hellner, Lisa; Herenz, Paul; Welti, André; Stratmann, Frank; Lohmann, Ulrike; Kanji, Zamin A.

    2016-04-01

    Mixed-phase clouds (MPCs) are found to be the most relevant cloud type leading to precipitation in mid-latitudes. The formation of ice crystals in MPCs is not completely understood. To estimate the effect of aerosol particles on the radiative properties of clouds and to describe ice nucleation in models, the specific properties of aerosol particles acting as ice nucleating particles (INPs) still need to be identified. A number of devices are able to measure INPs in the lab and in the field. However, methods can be very different and need to be tested under controlled conditions with respect to aerosol generation and properties in order to standardize measurement and data analysis approaches for subsequent ambient measurements. Here, we present an overview of the LINC campaign hosted at TROPOS in September 2015. We compare four ice nucleation devices: PINC (Portable Ice Nucleation Chamber, Chou et al., 2011) and SPIN (SPectrometer for Ice Nuclei) are operated in deposition nucleation and condensation freezing mode. LACIS (Leipzig Aerosol Cloud Interaction Simulator, Hartmann et al., 2011) and PIMCA (Portable Immersion Mode Cooling chamber) measure in the immersion freezing mode. PIMCA is used as a vertical extension to PINC and allows activation and droplet growth prior to exposure to the investigated ice nucleation temperature. Size-resolved measurements of multiple aerosol types were performed including pure mineral dust (K-feldspar, kaolinite) and biological particles (Birch pollen washing waters) as well as some of them after treatment with sulfuric or nitric acid prior to experiments. LACIS and PIMCA-PINC operated in the immersion freezing mode showed very good agreement in the measured frozen fraction (FF). For the comparison between PINC and SPIN, which were scanning relative humidity from below to above water vapor saturation, an agreement was found for the obtained INP concentration. However, some differences were observed, which may result from ice

  8. Urediospores of Puccinia spp. and other rusts are warm-temperature ice nucleators and harbor ice nucleation active bacteria

    NASA Astrophysics Data System (ADS)

    Morris, C. E.; Sands, D. C.; Glaux, C.; Samsatly, J.; Asaad, S.; Moukahel, A. R.; Gonçalves, F. L. T.; Bigg, E. K.

    2012-10-01

    In light of various features of the biology of the rust fungi and of the epidemiology of the plant diseases they cause that illustrate the important role of rainfall in their life history, we have characterized the ice nucleation activity (INA) of the aerially disseminated spores (urediospores) of this group of fungi. Urediospores of this obligate plant parasite were collected from natural infections from 7 species of weeds in France, from coffee in Brazil and from field and greenhouse-grown wheat in France, the USA, Turkey and Syria. Immersion freezing was used to determine freezing onset temperatures and the abundance of ice nuclei in suspensions of washed spores. Microbiological analyses of spores and subsequent tests of the ice nucleation activity of the bacteria associated with spores were deployed to quantify the contribution of bacteria to the ice nucleation activity of the spores. All samples of spores were ice nucleation active having freezing onset temperatures as warm as -4 °C. Spores in most of the samples carried cells of ice nucleation-active strains of the bacterium Pseudomonas syringae (at rates of less than 1 bacterial cell per 100 urediospores), but bacterial INA accounted for only a small fraction of the INA observed in spore suspensions. Changes in the INA of spore suspensions after treatment with lysozyme suggest that the INA of urediospores involves a polysaccharide. Based on data from the literature, we have estimated the concentrations of urediospores in air at cloud height and in rainfall. These quantities are very similar to those reported for other biological ice nucleators in these same substrates. We suggest that air sampling techniques have ignored the spatial and temporal variability of atmospheric concentrations that occur under conditions propitious for precipitation that could increase their local abundance intermittently. Nevertheless, we propose that the relative low abundance of warm-temperature biological ice nucleators in the

  9. Surface structure, crystallographic and ice-nucleating properties of cellulose

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Kiselev, Alexei; Saathoff, Harald; Weidler, Peter; Shutthanandan, Shuttha; Kulkarni, Gourihar; Jantsch, Evelyn; Koop, Thomas

    2015-04-01

    Increasing evidence of the high diversity and efficient freezing ability of biological ice-nucleating particles is driving a reevaluation of their impact upon climate. Despite their potential importance, little is known about their atmospheric abundance and ice nucleation efficiency, especially non-proteinaceous ones, in comparison to non-biological materials (e.g., mineral dust). Recently, microcrystalline cellulose (MCC; non-proteinaceous plant structural polymer) has been identified as a potential biological ice-nucleating particle. However, it is still uncertain if the ice-nucleating activity is specific to the MCC structure or generally relevant to all cellulose materials, such that the results of MCC can be representatively scaled up to the total cellulose content in the atmosphere to address its role in clouds and the climate system. Here we use the helium ion microscopy (HIM) imaging and the X-ray diffraction (XRD) technique to characterize the nanoscale surface structure and crystalline properties of the two different types of cellulose (MCC and fibrous cellulose extracted from natural wood pulp) as model proxies for atmospheric cellulose particles and to assess their potential accessibility for water molecules. To complement these structural characterizations, we also present the results of immersion freezing experiments using the cold stage-based droplet freezing BINARY (Bielefeld Ice Nucleation ARaY) technique. The HIM results suggest that both cellulose types have a complex porous morphology with capillary spaces between the nanoscale fibrils over the microfiber surface. These surface structures may make cellulose accessible to water. The XRD results suggest that the structural properties of both cellulose materials are in agreement (i.e., P21 space group; a=7.96 Å, b=8.35 Å, c=10.28 Å) and comparable to the crystallographic properties of general monoclinic cellulose (i.e., Cellulose Iβ). The results obtained from the BINARY measurements suggest

  10. Effects of Pre-Existing Ice Crystals on Cirrus Clouds and Comparison between Different Ice Nucleation Parameterizations with the Community Atmosphere Model (CAM5)

    SciTech Connect

    Shi, Xiangjun; Liu, Xiaohong; Zhang, Kai

    2015-01-01

    In order to improve the treatment of ice nucleation in a more realistic manner in the Community Atmospheric Model version 5.3 (CAM5.3), the effects of preexisting ice crystals on ice nucleation in cirrus clouds are considered. In addition, by considering the in-cloud variability in ice saturation ratio, homogeneous nucleation takes place spatially only in a portion of cirrus cloud rather than in the whole area of cirrus cloud. With these improvements, the two unphysical limiters used in the representation of ice nucleation are removed. Compared to observations, the ice number concentrations and the probability distributions of ice number concentration are both improved with the updated treatment. The preexisting ice crystals significantly reduce ice number concentrations in cirrus clouds, especially at mid- to high latitudes in the upper troposphere (by a factor of ~10). Furthermore, the contribution of heterogeneous ice nucleation to cirrus ice crystal number increases considerably.Besides the default ice nucleation parameterization of Liu and Penner (2005, hereafter LP) in CAM5.3, two other ice nucleation parameterizations of Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006, hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice crystal number concentration, percentage contribution from heterogeneous ice nucleation to total ice crystal number, and preexisting ice effects simulated by the three ice nucleation parameterizations have similar patterns in the simulations with present-day aerosol emissions. However, the change (present-day minus pre-industrial times) in global annual mean column ice number concentration from the KL parameterization (3.24×106 m-2) is obviously less than that from the LP (8.46×106 m-2) and BN (5.62×106 m-2) parameterizations. As a result, experiment using the KL parameterization predicts a much smaller anthropogenic aerosol longwave indirect forcing (0.24 W m-2) than that using the LP (0.46 W m-2

  11. Deposition and immersion mode nucleation of ice by three distinct samples of volcanic ash using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Schill, G. P.; Genareau, K.; Tolbert, M. A.

    2015-01-01

    Ice nucleation on volcanic ash controls both ash aggregation and cloud glaciation, which affect atmospheric transport and global climate. Previously, it has been suggested that there is one characteristic ice nucleation efficiency for all volcanic ash, regardless of its composition, when accounting for surface area; however, this claim is derived from data from only two volcanic eruptions. In this work, we have studied the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman Microscopy coupled to an environmental cell. Ash from the Fuego (basaltic ash, Guatemala), Soufrière Hills (andesitic ash, Montserrat), and Taupo (Oruanui euption, rhyolitic ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. In the present study, we find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice from 225-235 K at ice saturation ratios of 1.05 ± 0.01, comparable to the mineral dust proxy kaolinite. Since depositional ice nucleation will be more important at colder temperatures, fine volcanic ash may represent a global source of cold-cloud ice nuclei. For immersion freezing relevant to mixed-phase clouds, however, only the Oruanui ash exhibited heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

  12. Thermokinetics of heterogeneous droplet nucleation on conically textured substrates

    NASA Astrophysics Data System (ADS)

    Singha, Sanat K.; Das, Prasanta K.; Maiti, Biswajit

    2015-11-01

    Within the framework of the classical theory of heterogeneous nucleation, a thermokinetic model is developed for line-tension-associated droplet nucleation on conical textures considering growth or shrinkage of the formed cluster due to both interfacial and peripheral monomer exchange and by considering different geometric configurations. Along with the principle of free energy extremization, Katz kinetic approach has been employed to study the effect of substrate conicity and wettability on the thermokinetics of heterogeneous water droplet nucleation. Not only the peripheral tension is found to have a considerable effect on the free energy barrier but also the substrate hydrophobicity and hydrophilicity are observed to switch over their roles between conical crest and trough for different growth rates of the droplet. Besides, the rate of nucleation increases and further promotes nucleation for negative peripheral tension as it diminishes the free energy barrier appreciably. Moreover, nucleation inhibition can be achievable for positive peripheral tension due to the enhancement of the free energy barrier. Analyzing all possible geometric configurations, the hydrophilic narrower conical cavity is found to be the most preferred nucleation site. These findings suggest a physical insight into the context of surface engineering for the promotion or the suppression of nucleation on real or engineered substrates.

  13. Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

    PubMed

    Hudait, Arpa; Molinero, Valeria

    2014-06-04

    Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by

  14. Re-evaluating the Frankfurt isothermal static diffusion chamber for ice nucleation

    NASA Astrophysics Data System (ADS)

    Schrod, J.; Danielczok, A.; Weber, D.; Ebert, M.; Thomson, E. S.; Bingemer, H. G.

    2015-12-01

    Recently significant advances have been made in the collection, detection, and characterization of ice nucleating particles (INP). Ice nuclei are particles that facilitate the heterogeneous formation of ice within the atmospheric aerosol by lowering the free energy barrier to spontaneous nucleation and growth of ice from atmospheric water and/or vapor. The Frankfurt isostatic diffusion chamber (FRIDGE) is an INP collection and offline detection system that has become widely deployed and shows additional potential for ambient measurements. Since its initial development FRIDGE has gone through several iterations and improvements. Here we describe improvements that have been made in the collection and analysis techniques. We detail the uncertainties inherent in the measurement method, and suggest a systematic method of error analysis for FRIDGE measurements. Thus what is presented herein should serve as a foundation for the dissemination of all current and future measurements using FRIDGE instrumentation.

  15. Effect of gravity wave temperature variations on homogeneous ice nucleation

    NASA Astrophysics Data System (ADS)

    Dinh, Tra; Podglajen, Aurélien; Hertzog, Albert; Legras, Bernard; Plougonven, Riwal

    2015-04-01

    Observations of cirrus clouds in the tropical tropopause layer (TTL) have shown various ice number concentrations (INC) (e.g., Jensen et al. 2013), which has lead to a puzzle regarding their formation. In particular, the frequently observed low numbers of ice crystals seemed hard to reconcile with homogeneous nucleation knowing the ubuquity of gravity waves with vertical velocity of the order of 0.1 m/s. Using artificial time series, Spichtinger and Krämer (2013) have illustrated that the variation of vertical velocity during a nucleation event could terminate it and limit the INC. However, their study was limited to constructed temperature time series. Here, we carry out numerical simulations of homogeneous ice nucleation forced by temperature time series data collected by isopycnic balloon flights near the tropical tropopause. The balloons collected data at high frequency (30 s), so gravity wave signals are well resolved in the temperature time series. With the observed temperature time series, the numerical simulations with homogeneous freezing show a full range of ice number concentrations (INC) as previously observed in the tropical upper troposphere. The simulations confirm that the dynamical time scale of temperature variations (as seen from observations) can be shorter than the nucleation time scale. They show the existence of two regimes for homogeneous ice nucleation : one limited by the depletion of water vapor by the nucleated ice crystals (those we name vapor events) and one limited by the reincrease of temperature after its initial decrease (temperature events). Low INC may thus be obtained for temperature events when the gravity wave perturbations produce a non-persistent cooling rate (even with large magnitude) such that the absolute change in temperature remains small during nucleation. This result for temperature events is explained analytically by a dependence of the INC on the absolute drop in temperature (and not on the cooling rate). This

  16. New Instrument INKA for Ice Nucleation and Growth Experiments

    NASA Astrophysics Data System (ADS)

    Schmitt, Thea; Levin, Ezra; Höhler, Kristina; Nadolny, Jens; Möhler, Ottmar; DeMott, Paul

    2015-04-01

    Microphysical processes in clouds, such as the formation and growth of ice crystals, significantly influence the weather and the climate. Particularly the transition from the supercooled water to the solid ice phase is of great relevance since ice formation initiates the formation of precipitation and thereby strongly affects the cloud structure and life time. However, the formulation and parameterization of these processes and further laboratory studies are needed to obtain quantitative information on the ice activity of various atmospheric aerosol species. Therefore, we have constructed and built a new continuous flow diffusion chamber (CFDC) called INKA (Ice Nucleation Instrument of the KArlsruhe Institut of Technology) to be used both in the AIDA laboratory for detailed studies of ice nucleation and growth processes and in field applications for measuring the temperature-dependent abundance of ice nucleating particles (INPs). The CFDC design was originally developed and theoretically described by Rogers et al. (1988). The main part of the new INKA instrument, the chamber, consists of two vertically-oriented, concentric tubes with a total length of 150 cm. Together with particle-free, dry sheath air, the sampled aerosol particles flow through the annular space between these two cylinders. The wall temperatures of the cylinders can be adjusted and the walls of the annular gap are coated with thin ice layers. The bottom part (about 50 cm) of the outer cylinder of INKA is separately cooled, which allows operation in two different modes: In the ice nucleation mode, the CFDC is operated with a nucleation and growth section, covering the upper 100 cm of its length, which exposes the aerosol particles to a defined temperature and supersaturation. The bottom part is the so called droplet evaporation section which allows the ice particles to grow to a detectable size on the expense of present droplets. In the ice growth mode, the full length of the cylinders is operated

  17. Anti-ice nucleation activity in xylem extracts from trees that contain deep supercooling xylem parenchyma cells.

    PubMed

    Kasuga, Jun; Mizuno, Kaoru; Arakawa, Keita; Fujikawa, Seizo

    2007-12-01

    Boreal hardwood species, including Japanese white birch (Betula platyphylla Sukat. var. japonica Hara), Japanese chestnut (Castanea crenata Sieb. et Zucc.), katsura tree (Cercidiphyllum japonicum Sieb. et Zucc.), Siebold's beech (Fagus crenata Blume), mulberry (Morus bombycis Koidz.), and Japanese rowan (Sorbus commixta Hedl.), had xylem parenchyma cells (XPCs) that adapt to subfreezing temperatures by deep supercooling. Crude extracts from xylem in all these trees were found to have anti-ice nucleation activity that promoted supercooling capability of water as measured by a droplet freezing assay. The magnitude of increase in supercooling capability of water droplets in the presence of ice-nucleation bacteria, Erwinia ananas, was higher in the ranges from 0.1 to 1.7 degrees C on addition of crude xylem extracts than freezing temperature of water droplets on addition of glucose in the same concentration (100 mosmol/kg). Crude xylem extracts from C. japonicum provided the highest supercooling capability of water droplets. Our additional examination showed that crude xylem extracts from C. japonicum exhibited anti-ice nucleation activity toward water droplets containing a variety of heterogeneous ice nucleators, including ice-nucleation bacteria, not only E. ananas but also Pseudomonas syringae (NBRC3310) or Xanthomonas campestris, silver iodide or airborne impurities. However, crude xylem extracts from C. japonicum did not affect homogeneous ice nucleation temperature as analyzed by emulsified micro-water droplets. The possible role of such anti-ice nucleation activity in crude xylem extracts in deep supercooling of XPCs is discussed.

  18. Ice nucleation in sulfuric acid/organic aerosols: implications for cirrus cloud formation

    NASA Astrophysics Data System (ADS)

    Beaver, M. R.; Elrod, M. J.; Garland, R. M.; Tolbert, M. A.

    2006-08-01

    Using an aerosol flow tube apparatus, we have studied the effects of aliphatic aldehydes (C3 to C10) and ketones (C3 and C9) on ice nucleation in sulfuric acid aerosols. Mixed aerosols were prepared by combining an organic vapor flow with a flow of sulfuric acid aerosols over a small mixing time (~60 s) at room temperature. No acid-catalyzed reactions were observed under these conditions, and physical uptake was responsible for the organic content of the sulfuric acid aerosols. In these experiments, aerosol organic content, determined by a Mie scattering analysis, was found to vary with the partial pressure of organic, the flow tube temperature, and the identity of the organic compound. The physical properties of the organic compounds (primarily the solubility and melting point) were found to play a dominant role in determining the inferred mode of nucleation (homogenous or heterogeneous) and the specific freezing temperatures observed. Overall, very soluble, low-melting organics, such as acetone and propanal, caused a decrease in aerosol ice nucleation temperatures when compared with aqueous sulfuric acid aerosol. In contrast, sulfuric acid particles exposed to organic compounds of eight carbons and greater, of much lower solubility and higher melting temperatures, nucleate ice at temperatures above aqueous sulfuric acid aerosols. Organic compounds of intermediate carbon chain length, C4-C7, (of intermediate solubility and melting temperatures) nucleated ice at the same temperature as aqueous sulfuric acid aerosols. Interpretations and implications of these results for cirrus cloud formation are discussed.

  19. Ice nucleation in sulfuric acid/organic aerosols: implications for cirrus cloud formation

    NASA Astrophysics Data System (ADS)

    Beaver, M. R.; Elrod, M. J.; Garland, R. M.; Tolbert, M. A.

    2006-03-01

    Using an aerosol flow tube apparatus, we have studied the effects of aliphatic aldehydes (C3 to C10) and ketones (C3 and C9) on ice nucleation in sulfuric acid aerosols. Mixed aerosols were prepared by combining an organic vapor flow with a flow of sulfuric acid aerosols over a small mixing time (~60 s) at room temperature. No acid-catalyzed reactions were observed under these conditions, and physical uptake was responsible for the organic content of the sulfuric acid aerosols. In these experiments, aerosol organic content, determined by a Mie scattering analysis, was found to vary with the partial pressure of organic, the flow tube temperature, and the identity of the organic compound. The physical properties of the organic compounds (primarily the solubility and melting point) were found to play a dominant role in determining the mode of nucleation (homogenous or heterogeneous) and the specific freezing temperatures observed. Overall, very soluble, low-melting organics, such as acetone and propanal, caused a decrease in aerosol ice nucleation temperatures when compared with aqueous sulfuric acid aerosol. In contrast, sulfuric acid particles exposed to organic compounds of eight carbons and greater, of much lower solubility and higher melting temperatures, nucleate ice at temperatures above aqueous sulfuric acid aerosols. Organic compounds of intermediate carbon chain length, C4-C7, (of intermediate solubility and melting temperatures) nucleated ice at the same temperature as aqueous sulfuric acid aerosols. Interpretations and implications of these results for cirrus cloud formation are discussed.

  20. Enhanced High-Temperature Ice Nucleation Ability of Crystallized Aerosol Particles after Pre-Activation at Low Temperature

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Moehler, O.; Saathoff, H.; Schnaiter, M.

    2014-12-01

    The term pre-activation in heterogeneous ice nucleation describes the observation that the ice nucleation ability of solid ice nuclei may improve after they have already been involved in ice crystal formation or have been exposed to a temperature lower than 235 K. This can be explained by the retention of small ice embryos in cavities or crevices at the particle surface or by the capillary condensation and freezing of supercooled water, respectively. In recent cloud chamber experiments with crystallized aqueous ammonium sulfate, oxalic acid, and succinic acid solution droplets, we have unraveled a further pre-activation mechanism under ice subsaturated conditions which does not require the preceding growth of ice on the seed aerosol particles (Wagner, R. et al., J. Geophys. Res. Atmos., 119, doi: 10.1002/2014JD021741). First cloud expansion experiments were performed at a high temperature (267 - 244 K) where the crystallized particles did not promote any heterogeneous ice nucleation. Ice nucleation at this temperature, however, could be triggered by temporarily cooling the crystallized particles to a lower temperature. This is because upon crystallization, residuals of the aqueous solution are trapped within the crystals. These captured liquids can freeze when cooled below their respective homogeneous or heterogeneous freezing temperature, leading to the formation of ice pockets in the crystalline particles. When warmed again to the higher temperature, ice formation by the pre-activated particles occurred via depositional and deliquescence-induced ice growth, with ice active fractions ranging from 1 to 4% and 4 to 20%, respectively. Pre-activation disappeared above the eutectic temperature, which for the organic acids are close to the melting point of ice. This mechanism could therefore contribute to the very small fraction of atmospheric aerosol particles that are still ice active well above 263 K.

  1. Effect of solutes on the heterogeneous nucleation temperature of supercooled water: an experimental determination.

    PubMed

    Wilson, P W; Haymet, A D J

    2009-04-21

    We investigate the effect of solute concentration on the heterogeneous ice nucleation temperature (T(het)) of aqueous solutions of both NaCl and d-glucose. An automatic lag time apparatus (ALTA) technique allows the dependence of T(het) on solute concentration to be determined with statistical significance. Our results point to the solute-induced lowering of T(het) being a factor of two times the equivalent melting point depression at any fixed concentration, the same factor reported for homogeneous nucleation experiments with small molecular weight solutes.

  2. Heterogeneous Nucleation of Protein Crystals on Fluorinated Layered Silicate

    PubMed Central

    Ino, Keita; Udagawa, Itsumi; Iwabata, Kazuki; Takakusagi, Yoichi; Kubota, Munehiro; Kurosaka, Keiichi; Arai, Kazuhito; Seki, Yasutaka; Nogawa, Masaya; Tsunoda, Tatsuo; Mizukami, Fujio; Taguchi, Hayao; Sakaguchi, Kengo

    2011-01-01

    Here, we describe an improved system for protein crystallization based on heterogeneous nucleation using fluorinated layered silicate. In addition, we also investigated the mechanism of nucleation on the silicate surface. Crystallization of lysozyme using silicates with different chemical compositions indicated that fluorosilicates promoted nucleation whereas the silicates without fluorine did not. The use of synthesized saponites for lysozyme crystallization confirmed that the substitution of hydroxyl groups contained in the lamellae structure for fluorine atoms is responsible for the nucleation-inducing property of the nucleant. Crystallization of twelve proteins with a wide range of pI values revealed that the nucleation promoting effect of the saponites tended to increase with increased substitution rate. Furthermore, the saponite with the highest fluorine content promoted nucleation in all the test proteins regardless of their overall net charge. Adsorption experiments of proteins on the saponites confirmed that the density of adsorbed molecules increased according to the substitution rate, thereby explaining the heterogeneous nucleation on the silicate surface. PMID:21818343

  3. Ice nucleating agents allow embryo freezing without manual seeding.

    PubMed

    Teixeira, Magda; Buff, Samuel; Desnos, Hugo; Loiseau, Céline; Bruyère, Pierre; Joly, Thierry; Commin, Loris

    2017-08-18

    Embryo slow freezing protocols include a nucleation induction step called manual seeding. This step is time consuming, manipulator dependent and hard to standardize. It requires access to samples, which is not always possible within the configuration of systems, such as differential scanning calorimeters or cryomicroscopes. Ice nucleation can be induced by other methods, e.g., by the use of ice nucleating agents. Snomax is a commercial preparation of inactivated proteins extracted from Pseudomonas syringae. The aim of our study was to investigate if Snomax can be an alternative to manual seeding in the slow freezing of mouse embryos. The influence of Snomax on the pH and osmolality of the freezing medium was evaluated. In vitro development (blastocyst formation and hatching rates) of fresh embryos exposed to Snomax and embryo cryopreserved with and without Snomax was assessed. The mitochondrial activity of frozen-thawed blastocysts was assessed by JC-1 fluorescent staining. Snomax didn't alter the physicochemical properties of the freezing medium, and did not affect embryo development of fresh embryos. After cryopreservation, the substitution of manual seeding by the ice nucleating agent (INA) Snomax did not affect embryo development or embryo mitochondrial activity. In conclusion, Snomax seems to be an effective ice nucleating agent for the slow freezing of mouse embryos. Snomax can also be a valuable alternative to manual seeding in research protocols in which manual seeding cannot be performed (i.e., differential scanning calorimetry and cryomicroscopy). Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Effects of pre-existing ice crystals on cirrus clouds and comparison between different ice nucleation parameterizations with the Community Atmosphere Model (CAM5)

    SciTech Connect

    Shi, Xiangjun; Liu, Xiaohong; Zhang, Kai

    2015-02-11

    In order to improve the treatment of ice nucleation in a more realistic manner in the Community Atmosphere Model version 5.3 (CAM5.3), the effects of pre-existing ice crystals on ice nucleation in cirrus clouds are considered. In addition, by considering the in-cloud variability in ice saturation ratio, homogeneous nucleation takes place spatially only in a portion of the cirrus cloud rather than in the whole area of the cirrus cloud. Compared to observations, the ice number concentrations and the probability distributions of ice number concentration are both improved with the updated treatment. The pre-existing ice crystals significantly reduce ice number concentrations in cirrus clouds, especially at mid- to high latitudes in the upper troposphere (by a factor of ~10). Furthermore, the contribution of heterogeneous ice nucleation to cirrus ice crystal number increases considerably.

    Besides the default ice nucleation parameterization of Liu and Penner (2005, hereafter LP) in CAM5.3, two other ice nucleation parameterizations of Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006, hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice crystal number concentration, percentage contribution from heterogeneous ice nucleation to total ice crystal number, and pre-existing ice effects simulated by the three ice nucleation parameterizations have similar patterns in the simulations with present-day aerosol emissions. However, the change (present-day minus pre-industrial times) in global annual mean column ice number concentration from the KL parameterization (3.24 × 106 m-2) is less than that from the LP (8.46 × 106 m-2) and BN (5.62 × 106 m-2) parameterizations. As a result, the experiment using the KL parameterization predicts a much smaller anthropogenic aerosol long-wave indirect forcing (0.24 W m-2) than that using the LP (0.46 W m−2

  5. Effects of pre-existing ice crystals on cirrus clouds and comparison between different ice nucleation parameterizations with the Community Atmosphere Model (CAM5)

    DOE PAGES

    Shi, Xiangjun; Liu, Xiaohong; Zhang, Kai

    2015-02-11

    In order to improve the treatment of ice nucleation in a more realistic manner in the Community Atmosphere Model version 5.3 (CAM5.3), the effects of pre-existing ice crystals on ice nucleation in cirrus clouds are considered. In addition, by considering the in-cloud variability in ice saturation ratio, homogeneous nucleation takes place spatially only in a portion of the cirrus cloud rather than in the whole area of the cirrus cloud. Compared to observations, the ice number concentrations and the probability distributions of ice number concentration are both improved with the updated treatment. The pre-existing ice crystals significantly reduce ice numbermore » concentrations in cirrus clouds, especially at mid- to high latitudes in the upper troposphere (by a factor of ~10). Furthermore, the contribution of heterogeneous ice nucleation to cirrus ice crystal number increases considerably. Besides the default ice nucleation parameterization of Liu and Penner (2005, hereafter LP) in CAM5.3, two other ice nucleation parameterizations of Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006, hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice crystal number concentration, percentage contribution from heterogeneous ice nucleation to total ice crystal number, and pre-existing ice effects simulated by the three ice nucleation parameterizations have similar patterns in the simulations with present-day aerosol emissions. However, the change (present-day minus pre-industrial times) in global annual mean column ice number concentration from the KL parameterization (3.24 × 106 m-2) is less than that from the LP (8.46 × 106 m-2) and BN (5.62 × 106 m-2) parameterizations. As a result, the experiment using the KL parameterization predicts a much smaller anthropogenic aerosol long-wave indirect forcing (0.24 W m-2) than that using the LP (0.46 W m−2) and BN (0.39 W m-2) parameterizations.« less

  6. Pre-activation of ice nucleating particles by the pore condensation and freezing mechanism

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Kiselev, A.; Möhler, O.; Saathoff, H.; Steinke, I.

    2015-10-01

    In spite of the resurgence in ice nucleation research a comparatively small number of studies deal with the phenomenon of pre-activation in heterogeneous ice nucleation. Already fifty years ago, it was shown that various mineral dust and volcanic ash particles can be pre-activated to become nuclei for ice crystal formation even at temperatures as high as 270-271 K. Pre-activation was achieved under ice subsaturated conditions without any preceding macroscopic ice growth by just temporarily cooling the particles to temperatures below 228 K. A two-step mechanism involving capillary condensation of supercooled water and subsequent homogeneous freezing was proposed to account for the particles' enhanced ice nucleation ability at high temperatures. This work reinvestigates the efficiency of the proposed pre-activation mechanism in temperature-cycling experiments performed in a large cloud chamber with suspended particles. We find the efficiency to be highest for the clay mineral illite as well as for highly porous materials like zeolite and diatomaceous earth, whereas most aerosols generated from desert dust surface samples did not reveal a measurable pre-activation ability. The pre-activation efficiency is linked to particle pores in a certain size range. As estimated by model calculations, only pores with diameters between about 5 and 8 nm contribute to pre-activation under ice subsaturated conditions. In contrast to the early study, pre-activation is only observed for temperatures below 260 K. Above that threshold, the particles' improved ice nucleation ability disappears due to the melting of ice in the pores.

  7. Ice nucleation properties of the most abundant mineral dust phases

    NASA Astrophysics Data System (ADS)

    Zimmermann, Frank; Weinbruch, Stephan; Schütz, Lothar; Hofmann, Heiko; Ebert, Martin; Kandler, Konrad; Worringen, Annette

    2008-12-01

    The ice nucleation properties of the nine most abundant minerals occurring in desert aerosols (quartz, albite, microcline, kaolinite, montmorillonite, illite, calcite, gypsum, and hematite) were investigated by environmental scanning electron microscopy (ESEM). In this instrument, the pure minerals are exposed to water vapor at variable pressures and temperatures. The crystallization of ice on the mineral particles is observed by secondary electron imaging, and the supersaturation for an activated particle fraction of 1-3% is determined as function of temperature. In all experiments, condensation of water prior to ice formation was not observed within detectable limits, even at water supersaturation. The highest temperatures for 1-3% activation vary between -10°C and -16°C for the nine minerals investigated, and the corresponding onset relative humidities relative to ice RHi between 107 and 117%. Supersaturation temperature curves for initial ice formation (1-3% activation) in the temperature range typical for mixed-phase clouds were measured for all nine minerals. The temperature dependence of the onset relative humidity is strongly dependent on mineralogy. Kaolinite, montmorillonite, and hematite show a strong increase in RHi with decreasing temperature, whereas RHi is almost constant for illite, albite, quartz, and calcite. The highly variable ice nucleation properties of the various mineral dust components should be considered for parameterization schemes. Illite and kaolinite are the most important minerals to consider, as they have high ice nucleation efficiency and are common components of desert aerosols.

  8. Three separate classes of bacterial ice nucleation structures.

    PubMed

    Turner, M A; Arellano, F; Kozloff, L M

    1990-05-01

    Studies of the properties of the ice nucleation structure exposed on the surfaces of various bacteria such as Pseudomonas syringae, Erwinia herbicola, or various strains of Ice+ recombinant Escherichia coli have shown that there are clearly three major related but chemically distinct types of structures on these cells. First, the ability of Ice+ cells to nucleate super-cooled D2O has been examined, and it has been found that this ability (relative to the ability of the same cells to nucleate super-cooled H2O) exhibited three characteristic nucleating patterns. The rarest structure, called class A, is found on only a small fraction of cells in a culture, nucleates H2O at temperatures above -4.4 degrees C, and is an effective nucleator of super-cooled D2O. A second class of structure, called class B, is found on a larger portion of the cells, nucleates H2O between -4.8 and -5.7 degrees C, and is a relatively poor nucleator of super-cooled D2O. The class C structure is found on almost all cells and nucleates at -7.6 degrees C or colder. These three classes of structures were also differentiated by their sensitivities to low concentrations of water-miscible organic solvents such as dioxane or dimethyl sulfoxide. Depending on the specific bacterial strain, the addition of these solvents to bacterial suspensions lowered the nucleation activity of the class A structure by 1,000-fold or more. The nucleation activities of class B structures in the same culture were highly resistant to these compounds and were lowered only by 20 to 40%. The class C structures were more sensitive than Class B structures were, and the nucleation activities decreased 70 to 90%. Finally, the pH sensitivity of these three classes of structures was examined. The class A structure was destroyed in buffers at pH 4.5 lower but was stable in buffers at higher pHs. The class B structure was less sensitive to acidic buffers but was destroyed at pH 5.5 or lower and was stable at higher pHs. However, the

  9. Antifreeze and ice nucleator proteins in terrestrial arthropods.

    PubMed

    Duman, J G

    2001-01-01

    Terrestrial arthropods survive subzero temperatures by becoming either freeze tolerant (survive body fluid freezing) or freeze avoiding (prevent body fluid freezing). Protein ice nucleators (PINs), which limit supercooling and induce freezing, and antifreeze proteins (AFPs), which function to prevent freezing, can have roles in both freeze tolerance and avoidance. Many freeze-tolerant insects produce hemolymph PINs, which induce freezing at high subzero temperatures thereby inhibiting lethal intracellular freezing. Some freeze-tolerant species have AFPs that function as cryoprotectants to prevent freeze damage. Although the mechanism of this cryoprotection is not known, it may involve recrystallization inhibition and perhaps stabilization of the cell membrane. Freeze-avoiding species must prevent inoculative freezing initiated by external ice across the cuticle and extend supercooling abilities. Some insects remove PINs in the winter to promote supercooling, whereas others have selected against surfaces with ice-nucleating abilities on an evolutionary time scale. However, many freeze-avoiding species do have proteins with ice-nucleating activity, and these proteins must be masked in winter. In the beetle Dendroides canadensis, AFPs in the hemolymph and gut inhibit ice nucleators. Also, hemolymph AFPs and those associated with the layer of epidermal cells under the cuticle inhibit inoculative freezing. Two different insect AFPs have been characterized. One type from the beetles D. canadensis and Tenebrio molitor consists of 12- and 13-mer repeating units with disulfide bridges occurring at least every six residues. The spruce budworm AFP lacks regular repeat units. Both have much higher activities than any known AFPs.

  10. Chemical and physical characterization of fertile soil-derived ice residuals from the Fifth International Ice Nucleation workshop in November 2014 (FIN-1)

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Kulkarni, Gourihar; Laskin, Alexander; Zelenyuk, Alla

    2017-04-01

    The climate impact of ice-nucleating particles (INPs) derived from fertile soils on global scale has been recently accented by their diversity and efficient freezing ability. However, their representation in atmospheric models is limited in part due to our incomplete knowledge of fertile soil composition, abundance and associated sensitivity to heterogeneous ice nucleation. To fill given knowledge gap, we have investigated a unique/rich set of ice crystal residual samples derived from a variety of fertile soil samples obtained through our participation in the Fifth International Ice Nucleation workshop (FIN-1). FIN-1 was held at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) facility at Karlsruhe Institute of Technology (KIT), which is the world's foremost facility for studying ice clouds in a controlled setting, in November 2014 to comprehensively study the heterogeneous ice formation in the atmosphere with collaboration among 10 international groups that were funded through European consortium, NSF and USDOE agencies. Here, we will present the nanoscale surface morphology and elemental/molecular composition of ice crystal residuals as well as that of total aerosol samples from the FIN-1 activity to identify and classify any specific mineral and organic inclusions that may have promoted nucleation of ice. Comparing total aerosols to residuals will shed light on the composition and abundance of certain particle types in INPs. Acknowledgements: The valuable contributions of the INUIT (Ice Nuclei Research Unit) collaborators, the FIN organizers, their institutions and the FIN-1 Workshop science team are gratefully acknowledged.

  11. Change of supercooling capability in solutions containing different kinds of ice nucleators by flavonol glycosides from deep supercooling xylem parenchyma cells in trees.

    PubMed

    Kuwabara, Chikako; Kasuga, Jun; Wang, Donghui; Fukushi, Yukiharu; Arakawa, Keita; Koyama, Toshie; Inada, Takaaki; Fujikawa, Seizo

    2011-12-01

    Deep supercooling xylem parenchyma cells (XPCs) in Katsura tree contain flavonol glycosides with high supercooling-facilitating capability in solutions containing the ice nucleation bacterium (INB) Erwinia ananas, which is thought to have an important role in deep supercooling of XPCs. The present study, in order to further clarify the roles of these flavonol glycosides in deep supercooling of XPCs, the effects of these supercooling-facilitating (anti-ice nucleating) flavonol glycosides, kaempferol 3-O-β-D-glucopyranoside (K3Glc), kaempferol 7-O-β-D-glucopyranoside (K7Glc) and quercetin 3-O-β-D-glucopyranoside (Q3Glc), in buffered Milli-Q water (BMQW) containing different kinds of ice nucleators, including INB Xanthomonas campestris, silver iodide and phloroglucinol, were examined by a droplet freezing assay. The results showed that all of the flavonol glycosides promoted supercooling in all solutions containing different kinds of ice nucleators, although the magnitudes of supercooling capability of each flavonol glycoside changed in solutions containing different kinds of ice nucleators. On the other hand, these flavonol glycosides exhibited complicated nucleating reactions in BMQW, which did not contain identified ice nucleators but contained only unidentified airborne impurities. Q3Glc exhibited both supercooling-facilitating and ice nucleating capabilities depending on the concentrations in such water. Both K3Glc and K7Glc exhibited only ice nucleation capability in such water. It was also shown by an emulsion freezing assay in BMQW that K3Glc and Q3Glc had no effect on homogeneous ice nucleation temperature, whereas K7Glc increased ice nucleation temperature. The results indicated that each flavonol glycoside affected ice nucleation by very complicated and varied reactions. More studies are necessary to determine the exact roles of these flavonol glycosides in deep supercooling of XPCs in which unidentified heterogeneous ice nucleators may exist.

  12. Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation?

    NASA Astrophysics Data System (ADS)

    Lienhard, D. M.; Huisman, A. J.; Krieger, U. K.; Rudich, Y.; Marcolli, C.; Luo, B. P.; Bones, D. L.; Reid, J. P.; Lambe, A. T.; Canagaratna, M. R.; Davidovits, P.; Onasch, T. B.; Worsnop, D. R.; Steimer, S. S.; Koop, T.; Peter, T.

    2015-09-01

    New measurements of water diffusion in aerosol particles produced from secondary organic aerosol (SOA) material and from a number of organic/inorganic model mixtures (3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), levoglucosan, levoglucosan/NH4HSO4, raffinose) indicate that water diffusion coefficients are determined by several properties of the aerosol substance and cannot be inferred from the glass transition temperature or bouncing properties. Our results suggest that water diffusion in SOA particles is faster than often assumed and imposes no significant kinetic limitation on water uptake and release at temperatures above 220 K. The fast diffusion of water suggests that heterogeneous ice nucleation on a glassy core is very unlikely in these systems. At temperatures below 220 K, model simulations of SOA droplets suggest that heterogeneous ice nucleation may occur in the immersion mode on glassy cores which remain embedded in a liquid shell when experiencing fast updraft velocities. The particles absorb significant quantities of water during these updrafts which plasticize their outer layers such that these layers equilibrate readily with the gas phase humidity before the homogeneous ice nucleation threshold is reached. Glass formation is thus unlikely to restrict homogeneous ice nucleation. Only under most extreme conditions near the very high tropical tropopause may the homogeneous ice nucleation rate coefficient be reduced as a consequence of slow condensed-phase water diffusion. Since the differences between the behavior limited or non limited by diffusion are small even at the very high tropical tropopause, condensed-phase water diffusivity is unlikely to have significant consequences on the direct climatic effects of SOA particles under tropospheric conditions.

  13. Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation?

    NASA Astrophysics Data System (ADS)

    Lienhard, D. M.; Huisman, A. J.; Krieger, U. K.; Rudich, Y.; Marcolli, C.; Luo, B. P.; Bones, D. L.; Reid, J. P.; Lambe, A. T.; Canagaratna, M. R.; Davidovits, P.; Onasch, T. B.; Worsnop, D. R.; Steimer, S. S.; Koop, T.; Peter, T.

    2015-12-01

    New measurements of water diffusion in secondary organic aerosol (SOA) material produced by oxidation of α-pinene and in a number of organic/inorganic model mixtures (3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), levoglucosan, levoglucosan/NH4HSO4, raffinose) are presented. These indicate that water diffusion coefficients are determined by several properties of the aerosol substance and cannot be inferred from the glass transition temperature or bouncing properties. Our results suggest that water diffusion in SOA particles is faster than often assumed and imposes no significant kinetic limitation on water uptake and release at temperatures above 220 K. The fast diffusion of water suggests that heterogeneous ice nucleation on a glassy core is very unlikely in these systems. At temperatures below 220 K, model simulations of SOA particles suggest that heterogeneous ice nucleation may occur in the immersion mode on glassy cores which remain embedded in a liquid shell when experiencing fast updraft velocities. The particles absorb significant quantities of water during these updrafts which plasticize their outer layers such that these layers equilibrate readily with the gas phase humidity before the homogeneous ice nucleation threshold is reached. Glass formation is thus unlikely to restrict homogeneous ice nucleation. Only under most extreme conditions near the very high tropical tropopause may the homogeneous ice nucleation rate coefficient be reduced as a consequence of slow condensed-phase water diffusion. Since the differences between the behavior limited or non limited by diffusion are small even at the very high tropical tropopause, condensed-phase water diffusivity is unlikely to have significant consequences on the direct climatic effects of SOA particles under tropospheric conditions.

  14. Ice Formation via Deposition Mode Nucleation Onto Dust Particulates: The University of Toronto Continuous Flow Diffusion Chamber

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Abbatt, J. P.; Cotton, R.; Demott, P.; Jones, H.; Möhler, O.; Stetzer, O.

    2008-12-01

    Laboratory studies are described whereby the heterogeneous ice nucleating ability of various dust samples were studied, for particles suspended in a newly built thermal gradient continuous flow diffusion chamber (TG-CFDC). Ice formation is observed using an optical particle counter (OPC) and the relative humidity (RH) and temperature conditions of the flow system are validated by observing homogenous freezing of H2SO4 aerosols. At the Fourth International Ice Nucleation Workshop (ICIS 07) in Karslruhe, Germany this system was used to investigate ice nucleation primarily in the vapor deposition mode, for Arizona Test Dust (ATD), Israeli Desert Dust (ID), Canary Island Dust (CID), Saharan Dust (SD), Graphite Spark Soot, Snomax® (dead bacteria) and live bacteria. The aerosol size was in the submicron range with an approximate cut off of 700 nm and a mode of 350 nm. Temperatures for nucleation were varied from 265 - 230 K. The dust aerosols were generally found to be more efficient than soot. At warmer temperatures (263 K) the bacteria were found to be active in the deposition mode which was not the case for dusts. Among the various dust types at 248 K, the CID was more efficient than ATD at nucleating ice when efficiency is based on lowest onset RH conditions for ice formation in our chamber. We also present preliminary results for the effect of total surface area versus size of aerosols on ice nucleation using ATD as a surrogate for naturally occurring mineral dust.

  15. Contact ice nucleation by submicron atmospheric aerosols

    NASA Technical Reports Server (NTRS)

    Deshler, T.

    1982-01-01

    An apparatus designed to measure the concentrations of submicron contact ice nuclei is described. Here, natural forces transfer nuclei to supercooled sample drops suspended in an aerosol stream. Experimental measurements of the scavenging rate of the sample drops for several humidities and aerosol sizes are found to be in agreement with theory to within a factor of two. This fact, together with the statistical tests showing a difference between the data and control samples, is seen as indicating that a reliable measurement of the concentrations of submicron contact ice nuclei has been effected. A figure is included showing the ice nucleus concentrations as a function of temperature and assumed aerosol radius. For a 0.01 micron radius, the average is 1/liter at -15 C and 3/liter at -18 C. It is noted that the measurements are in fair agreement with ice crystal concentrations in stable winter clouds measured over Elk Mountain, WY (Vali et al., 1982).

  16. Biological residues define the ice nucleation properties of soil dust

    NASA Astrophysics Data System (ADS)

    Conen, F.; Morris, C. E.; Leifeld, J.; Yakutin, M. V.; Alewell, C.

    2011-06-01

    Soil dust is a major driver of ice nucleation in clouds leading to precipitation. It consists largely of mineral particles with a small fraction of organic matter constituted mainly of remains of micro-organisms that participated in degrading plant debris before their own decay. Some micro-organisms have been shown to be much better ice nuclei than the most efficient soil mineral. Yet, current aerosol schemes in global climate models do not consider a difference between soil dust and mineral dust in terms of ice nucleation activity. Here, we show that particles from the clay and silt size fraction of four different soils naturally associated with 0.7 to 11.8 % organic carbon (w/w) can have up to four orders of magnitude more ice nuclei per unit mass active in the immersion freezing mode at -12 °C than montmorillonite, the most efficient pure clay mineral. Most of this activity was lost after heat treatment. Removal of biological residues reduced ice nucleation activity to, or below that of montmorillonite. Desert soils, inherently low in organic content, are a large natural source of dust in the atmosphere. In contrast, agricultural land use is concentrated on fertile soils with much larger organic matter contents than found in deserts. It is currently estimated that the contribution of agricultural soils to the global dust burden is less than 20 %. Yet, these disturbed soils can contribute ice nuclei to the atmosphere of a very different and much more potent kind than mineral dusts.

  17. Ice Nucleation Properties of Amospherically Aged Biomass Burning Aerosol

    NASA Astrophysics Data System (ADS)

    Polen, M.; Lawlis, E.; Sullivan, R. C.

    2015-12-01

    Biomass burning can sometimes emit surprisingly active ice nucleating particles, though these emissions are not at all consistent between biomass fuel sources and burns. Soot from biomass combustion has been attributed to some but not all of the ice nucleating potential of biomass burning aerosol (BBA), while fossil fuel combustion soot emits very weak ice nucleants. The causes of the sometimes significant but variable ice nucleating ability of BBA are still largely unknown. BBA experiences significant atmospheric aging as the plume evolves and mixes with background air, yet almost no reports exploring the effects of atmospheric aging on the freezing properties of BBA have been made. We have performed some of the first experiments to determine the effects of simulated atmospheric aging on these ice nucleation properties, using a chamber reactor. The fresh and aged BBA was collected for subsequent droplet freezing array analysis using an impinger sampler to collect aerosol in water, and by deposition onto substrates in a MOUDI sampler. Droplets containing the chamber particles were then suspended in oil on a cold plate for freezing temperature spectrum measurement. Aging of Sawgrass flaming-phase combustion BBA by exposure to hydroxyl radicals (from H2O2 photolysis) enhanced the ice nucleation ability, observed by a shift to warmer droplet freezing temperatures by ~2-3°C. The changes in the aerosol's chemical composition during aging were observed using a laser ablation single-particle mass spectrometer and a soot-particle aerosol mass spectrometer. We will report our observations of the effects of other types of simulated aging (including photochemistry under high and low NOx conditions, dark ozonolysis, and nitric acid exposure) on Sawgrass and BBA from other grass and palm fuels.

  18. Impact of heterogeneous ice nuclei on homogeneous freezing events in cirrus clouds

    SciTech Connect

    Spichtinger, Peter; Cziczo, Daniel J.

    2010-07-29

    The influence of initial heterogeneous nucleation on subsequent homogeneous nucleation events in cirrus clouds is investigated using a box model which includes the explicit impact of aerosols on the nucleation of ice crystals and sedimentation. Different effects are discussed, namely the impact of external mixtures of heterogeneous ice nuclei and the influence of size-dependent freezing thresholds. Several idealized experiments are carried out, which show that the treatment of external mixtures of ice nuclei can strongly change later homogeneous nucleation events (i.e., the ice crystal number densities) in different matters. The use of size-dependent freezing thresholds can also change the cloud prop erties when compared to more simple parameterizations. This size effect is most important for large IN concentrations. Based upon these findings, recommendations for future modeling and measurement efforts are presented.

  19. Heterogeneous nucleation and growth of nanoparticles at environmental interfaces

    DOE PAGES

    Jun, Young -Shin; Kim, Doyoon; Neil, Chelsea W.

    2016-08-11

    Here, mineral nucleation is a phase transformation of aqueous components to solids with an accompanying creation of new surfaces. In this evolutional, yet elusive, process, nuclei often form at environmental interfaces, which provide remarkably reactive sites for heterogeneous nucleation and growth. Naturally occurring nucleation processes significantly contribute to the biogeochemical cycles of important components in the Earth’s crust, such as iron and manganese oxide minerals and calcium carbonate. However, in recent decades, these cycles have been significantly altered by anthropogenic activities, which affect the aqueous chemistry and equilibrium of both surface and subsurface systems. These alterations can trigger the dissolutionmore » of existing minerals and formation of new nanoparticles (i.e., nucleation and growth) and consequently change the porosity and permeability of geomedia in subsurface environments. Newly formed nanoparticles can also actively interact with components in natural and engineered aquatic systems, including those posing a significant hazard such as arsenic. These interactions can bilaterally influence the fate and transport of both newly formed nanoparticles and aqueous components. Due to their importance in natural and engineered processes, heterogeneous nucleation at environmental interfaces has started to receive more attention. However, a lack of time-resolved in situ analyses makes the evaluation of heterogeneous nucleation challenging because the physicochemical properties of both the nuclei and surfaces significantly and dynamically change with time and aqueous chemistry. This Account reviews our in situ kinetic studies of the heterogeneous nucleation and growth behaviors of iron(III) (hydr)oxide, calcium carbonate, and manganese (hydr)oxide minerals in aqueous systems. In particular, we utilized simultaneous small-angle and grazing incidence small-angle X-ray scattering (SAXS/GISAXS) to investigate in situ and in real

  20. Ice Nucleation Activity of Various Agricultural Soil Dust Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Schiebel, Thea; Höhler, Kristina; Funk, Roger; Hill, Thomas C. J.; Levin, Ezra J. T.; Nadolny, Jens; Steinke, Isabelle; Suski, Kaitlyn J.; Ullrich, Romy; Wagner, Robert; Weber, Ines; DeMott, Paul J.; Möhler, Ottmar

    2016-04-01

    Recent investigations at the cloud simulation chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) suggest that agricultural soil dust has an ice nucleation ability that is enhanced up to a factor of 10 compared to desert dust, especially at temperatures above -26 °C (Steinke et al., in preparation for submission). This enhancement might be caused by the contribution of very ice-active biological particles. In addition, soil dust aerosol particles often contain a considerably higher amount of organic matter compared to desert dust particles. To test agricultural soil dust as a source of ice nucleating particles, especially for ice formation in warm clouds, we conducted a series of laboratory measurements with different soil dust samples to extend the existing AIDA dataset. The AIDA has a volume of 84 m3 and operates under atmospherically relevant conditions over wide ranges of temperature, pressure and humidity. By controlled adiabatic expansions, the ascent of an air parcel in the troposphere can be simulated. As a supplement to the AIDA facility, we use the INKA (Ice Nucleation Instrument of the KArlsruhe Institute of Technology) continuous flow diffusion chamber based on the design by Rogers (1988) to expose the sampled aerosol particles to a continuously increasing saturation ratio by keeping the aerosol temperature constant. For our experiments, soil dust was dry dispersed into the AIDA vessel. First, fast saturation ratio scans at different temperatures were performed with INKA, sampling soil dust aerosol particles directly from the AIDA vessel. Then, we conducted the AIDA expansion experiment starting at a preset temperature. The combination of these two different methods provides a robust data set on the temperature-dependent ice activity of various agriculture soil dust aerosol particles with a special focus on relatively high temperatures. In addition, to extend the data set, we investigated the role of biological and organic matter in more

  1. The nucleation rate of crystalline ice in amorphous solid water.

    PubMed

    Safarik, D J; Mullins, C B

    2004-09-22

    The kinetics of crystalline ice nucleation and growth in nonporous, molecular beam deposited amorphous solid water (ASW) films are investigated at temperatures near 140 K. We implement an experimental methodology and corresponding model of crystallization kinetics to decouple growth from nucleation and quantify the temperature dependence and absolute rates of both processes. Nucleation rates are found to increase from approximately 3x10(13) m(-3) s(-1) at 134 K to approximately 2x10(17) m(-3) s(-1) at 142 K, corresponding to an Arrhenius activation energy of 168 kJ/mol. Over the same temperature range, the growth velocity increases from approximately 0.4 to approximately 4 A s(-1), also exhibiting Arrhenius behavior with an activation energy of 47 kJ/mol. These nucleation rates are up to ten orders of magnitude larger than in liquid water near 235 K, while growth velocities are approximately 10(9) times smaller. Crystalline ice nucleation kinetics determined in this study differ significantly from those reported previously for porous, background vapor deposited ASW, suggesting the nucleation mechanism is dependent upon film morphology.

  2. Scaling properties of induction times in heterogeneous nucleation

    NASA Technical Reports Server (NTRS)

    Shneidman, Vitaly A.; Weinberg, Michael C.

    1991-01-01

    The heterogeneous-to-homogeneous induction time ratio is obtained as a function of the contact angle in the asymptotic limit of a high nucleation barrier. Model-dependent corrections to t(ind) are investigated, particularly in cases of the Turnbull-Fisher model used in numerical simulations by Greer et al. (1990).

  3. Heterogeneous Formation of Polar Stratospheric Clouds- Part 1: Nucleation of Nitric Acid Trihydrate (NAT)

    NASA Technical Reports Server (NTRS)

    Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooss, J.-U.; Peter, T.

    2013-01-01

    Satellite-based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid-December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled a thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed polar stratospheric clouds (PSCs) very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

  4. Heterogeneous formation of polar stratospheric clouds - Part 1: Nucleation of nitric acid trihydrate (NAT)

    NASA Astrophysics Data System (ADS)

    Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooß, J.-U.; Peter, T.

    2013-03-01

    Satellite based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarisation (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled the thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed PSCs very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

  5. Heterogeneous formation of polar stratospheric clouds - Part 1: Nucleation of nitric acid trihydrate (NAT)

    NASA Astrophysics Data System (ADS)

    Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooß, J.-U.; Peter, T.

    2013-09-01

    Satellite-based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid-December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled a thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed polar stratospheric clouds (PSCs) very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

  6. Urediospores of rust fungi are ice nucleation active at > -10 °C and harbor ice nucleation active bacteria

    NASA Astrophysics Data System (ADS)

    Morris, C. E.; Sands, D. C.; Glaux, C.; Samsatly, J.; Asaad, S.; Moukahel, A. R.; Gonçalves, F. L. T.; Bigg, E. K.

    2013-04-01

    Various features of the biology of the rust fungi and of the epidemiology of the plant diseases they cause illustrate the important role of rainfall in their life history. Based on this insight we have characterized the ice nucleation activity (INA) of the aerially disseminated spores (urediospores) of this group of fungi. Urediospores of this obligate plant parasite were collected from natural infections of 7 species of weeds in France, from coffee in Brazil and from field and greenhouse-grown wheat in France, the USA, Turkey and Syria. Immersion freezing was used to determine freezing onset temperatures and the abundance of ice nuclei in suspensions of washed spores. Microbiological analyses of spores from France, the USA and Brazil, and subsequent tests of the ice nucleation activity of the bacteria associated with spores were deployed to quantify the contribution of bacteria to the ice nucleation activity of the spores. All samples of spores were ice nucleation active, having freezing onset temperatures as high as -4 °C. Spores in most of the samples carried cells of ice nucleation-active strains of the bacterium Pseudomonas syringae (at rates of less than 1 bacterial cell per 100 urediospores), but bacterial INA accounted for only a small fraction of the INA observed in spore suspensions. Changes in the INA of spore suspensions after treatment with lysozyme suggest that the INA of urediospores involves a polysaccharide. Based on data from the literature, we have estimated the concentrations of urediospores in air at cloud height and in rainfall. These quantities are very similar to those reported for other biological ice nucleators in these same substrates. However, at cloud level convective activity leads to widely varying concentrations of particles of surface origin, so that mean concentrations can underestimate their possible effects on clouds. We propose that spatial and temporal concentrations of biological ice nucleators active at temperatures > -10

  7. Understanding ice nucleation characteristics of selective mineral dusts suspended in solution

    NASA Astrophysics Data System (ADS)

    Kumar, Anand; Marcolli, Claudia; Kaufmann, Lukas; Krieger, Ulrich; Peter, Thomas

    2016-04-01

    Introduction & Objectives Freezing of liquid droplets and subsequent ice crystal growth affects optical properties of clouds and precipitation. Field measurements show that ice formation in cumulus and stratiform clouds begins at temperatures much warmer than those associated with homogeneous ice nucleation in pure water, which is ascribed to heterogeneous ice nucleation occurring on the foreign surfaces of ice nuclei (IN). Various insoluble particles such as mineral dust, soot, metallic particles, volcanic ash, or primary biological particles have been suggested as IN. Among these the suitability of mineral dusts is best established. The ice nucleation ability of mineral dust particles may be modified when secondary organic or inorganic substances are accumulating on the dust during atmospheric transport. If the coating is completely wetting the mineral dust particles, heterogeneous ice nucleation occurs in immersion mode also below 100 % RH. A previous study by Kaufmann (PhD Thesis 2015, ETHZ) with Hoggar Mountain dust suspensions in various solutes (ammonium sulfate, PEG, malonic acid and glucose) showed reduced ice nucleation efficiency (in immersion mode) of the particles. Though it is still quite unclear of how surface modifications and coatings influence the ice nucleation activity of the components present in natural dust samples. In view of these results we run freezing experiments using a differential scanning calorimeter (DSC) with the following mineral dust particles suspended in pure water and ammonium sulfate solutions: Arizona Test Dust (ATD), microcline, and kaolinite (KGa-2, Clay Mineral Society). Methodology Suspensions of mineral dust samples (ATD: 2 weight%, microcline: 5% weight, KGa-2: 5% weight) are prepared in pure water with varying solute concentrations (ammonium sulfate: 0 - 10% weight). 20 vol% of this suspension plus 80 vol% of a mixture of 95 wt% mineral oil (Aldrich Chemical) and 5 wt% lanolin (Fluka Chemical) is emulsified with a

  8. First Principles Simulations of Ice Nucleation at Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Michaelides, Angelos

    2005-03-01

    Ice nucleation at solid surfaces is of relevance to countless scientific and technological processes. In particular the nucleation of ice nano-crystals on metal surfaces is often a key first step in cloud formation and corrosion [1]. Yet unfortunately this remains one of the most poorly understood natural phenomena; severely lacking in atomic level understanding. Here, we discuss detailed density functional theory studies aimed at putting our understanding of ice nucleation at metals on a much firmer footing. Specifically the properties of H2O hexamers - the smallest `building blocks' of ice - adsorbed on a number of close-packed transition metal surfaces have been examined. We find that the competing influences of substrate reactivity and hexamer-substrate epitaxial mismatch conspire to yield a rich variety of (novel) hexameric ice structures, some of which have been observed by recent scanning tunnelling microscopy experiments [2]. [1] H.R. Pruppacher and J.D. Klett, Microphysics of Clouds and Precipitation, (Kluwer, Dordrecht, 2003). [2] K. Morgenstern, et al., (To be published).

  9. Identification of Ice Nucleation Active Sites on Feldspar Dust Particles

    PubMed Central

    2015-01-01

    Mineral dusts originating from Earth’s crust are known to be important atmospheric ice nuclei. In agreement with earlier studies, feldspar was found as the most active of the tested natural mineral dusts. Here we investigated in closer detail the reasons for its activity and the difference in the activity of the different feldspars. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. K-feldspar showed by far the highest ice nucleation activity. Finally, we give a potential explanation of this effect, finding alkali-metal ions having different hydration shells and thus an influence on the ice nucleation activity of feldspar surfaces. PMID:25584435

  10. Influence of surface morphology on the immersion mode ice nucleation efficiency of hematite particles

    SciTech Connect

    Hiranuma, N.; Hoffmann, N.; Kiselev, A.; Dreyer, A.; Zhang, K.; Kulkarni, G.; Koop, T.; Möhler, O.

    2014-01-01

    In this paper, the effect of the morphological modification of aerosol particles with respect to heterogeneous ice nucleation is comprehensively investigated for laboratory-generated hematite particles as a model substrate for atmospheric dust particles. The surface-area-scaled ice nucleation efficiencies of monodisperse cubic hematite particles and milled hematite particles were measured with a series of expansion cooling experiments using the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud simulation chamber. Complementary offline characterization of physico-chemical properties of both hematite subsets were also carried out with scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, dynamic light scattering (DLS), and an electro-kinetic particle charge detector to further constrain droplet-freezing measurements of hematite particles. Additionally, an empirical parameterization derived from our laboratory measurements was implemented in the single-column version of the Community Atmospheric Model version 5 (CAM5) to investigate the model sensitivity in simulated ice crystal number concentration on different ice nucleation efficiencies. From an experimental perspective, our results show that the immersion mode ice nucleation efficiency of milled hematite particles is almost an order of magnitude higher at -35.2 °C < T < -33.5 °C than that of the cubic hematite particles, indicating a substantial effect of morphological irregularities on immersion mode freezing. Our modeling results similarly show that the increased droplet-freezing rates of milled hematite particles lead to about one order magnitude higher ice crystal number in the upper troposphere than cubic hematite particles. Finally and overall, our results suggest that the surface irregularities and associated active sites lead to greater ice activation through droplet freezing.

  11. Cellulose and Their Characteristic Ice Nucleation Activity- Freezing on a Chip

    NASA Astrophysics Data System (ADS)

    Häusler, Thomas; Felgitsch, Laura; Grothe, Hinrich

    2016-04-01

    The influence of clouds on the Earth's climate system is well known (IPCC, 2013). Cloud microphysics determines for example cloud lifetime and precipitation properties. Clouds are cooling the climate system by reflecting incoming solar radiation and warm its surface by trapping outgoing infrared radiation (Baker and Peter, 2008). In all these processes, aerosol particles play a crucial role by acting as cloud condensation nuclei (CCN) for liquid droplets and as an ice nucleation particle (INP) for the formation of ice particles. Freezing processes at higher temperatures than -38°C occur heterogeneously (Pruppacher and Klett 1997). Therefore aerosol particles act like a catalyst, which reduces the energy barrier for nucleation. The nucleation mechanisms, especially the theory of functional sites are not entirely understood. It remains unclear which class of compound nucleates ice. Here we present a unique technique to perform drop- freezing experiments in a more efficient way. A self-made freezing- chip will be presented. Measurements done to proof the efficiency of our setup as well as advantages compared with other setups will be discussed. Furthermore we present a proxy for biological INPs, microcrystalline cellulose. Cellulose is the main component of herbal cell walls (about 50 wt%). It is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose can contribute to the diverse spectrum of ice nucleation particles. We present results of the nucleation activity measurements of MCCs as well as the influence of concentration, preparation or chemical modification.

  12. On the role of cubic structure in ice nucleation

    NASA Astrophysics Data System (ADS)

    Takahashi, Tōru

    1982-10-01

    To clarify the formation mechanism of snow polycrystals the possibility of formation of a cubic ice embryo is discussed on the basis of the homogeneous nucleation theory for supercooled water formed from ambient water molecules in the phase of supersaturated vapour. In this connection, attention is paid to a finding from a model of broken hydrogen bonds that the plane {111} of a cubic ice crystal has a smaller specific interfacial energy than each of the {0001} or {10ovbar|10} planes of a hexagonal ice crystal. Hence, it follows that a critical cubic embryo has a smaller activation energy than a critical hexagonal embryo below a critical temperature; namely, Ostwald's step rule (Stufenregel) holds for a change from cubic ice to hexagonal ice below a critical temperature. This discussion is reinforced by examining, from the viewpoint of this step rule, the observed misorientation of the c-axis of natural snow polycrystals and the results of experiments using frozen water droplets.

  13. Reduced pressure ice fog technique for controlled ice nucleation during freeze-drying.

    PubMed

    Patel, Sajal M; Bhugra, Chandan; Pikal, Michael J

    2009-01-01

    A method to achieve controlled ice nucleation during the freeze-drying process using an ice fog technique was demonstrated in an earlier report. However, the time required for nucleation was about 5 min, even though only one shelf was used, which resulted in Ostwald ripening (annealing) in some of the vials that nucleated earlier than the others. As a result, the ice structure was not optimally uniform in all the vials. The objective of the present study is to introduce a simple variation of the ice fog method whereby a reduced pressure in the chamber is utilized to allow more rapid and uniform freezing which is also potentially easier to scale up. Experiments were conducted on a lab scale freeze dryer with sucrose as model compound at different concentration, product load, and fill volume. Product resistance during primary drying was measured using manometric temperature measurement. Specific surface area of the freeze-dried cake was also determined. No difference was observed either in average product resistance or specific surface area for the different experimental conditions studied, indicating that with use of the reduced pressure ice fog technique, the solutions nucleated at very nearly the same temperature (-10 degrees C). The striking feature of the "Reduced Pressure Ice Fog Technique" is the rapid ice nucleation (less than a minute) under conditions where the earlier procedure required about 5 min; hence, effects of variable Ostwald ripening were not an issue.

  14. Nucleation of ice and its management in ecosystems.

    PubMed

    Franks, Felix

    2003-03-15

    In addition to the gas and liquid phases, water can exist in many different solid states. Some of these are the well-studied crystalline ice polymorphs and the clathrate hydrates, but at least two distinguishable amorphous solid forms have also been shown to exist. This diversity of possible condensed states implies a multiplicity of transitions, each of them presumably associated with a nucleation step. Disagreement still exists as to whether the amorphous states can be regarded as metastable phases, and whether the phenomenon of polyamorphism can be treated in terms of phase transitions. In the Earth's hydrosphere, several of the crystalline and amorphous water phases can be formed from vapour, under given conditions of temperature, pressure and supersaturation, and classical nucleation theory is believed to account reasonably well for the observed growth of condensed forms of water in the upper atmosphere. Many terrestrial organisms are able to activate mechanisms to control the nucleation and growth of ice when exposed to sub-zero temperatures, thus enabling them to minimize the lethal effects of extreme freeze desiccation. The substances involved in these mechanisms include carbohydrates, amino acids and so-called cold-shock proteins, but the actual mechanisms of interfering with ice nucleation, although quite well documented, are as yet imperfectly understood. This is particularly true for the genetic control associated with biochemical processes that produce freeze resistance and freeze tolerance. The molecular biology of cold stress is currently a subject of intensive study.

  15. Homogeneous ice freezing temperatures and ice nucleation rates of aqueous ammonium sulfate and aqueous levoglucosan particles for relevant atmospheric conditions.

    PubMed

    Knopf, Daniel Alexander; Lopez, Miguel David

    2009-09-28

    Homogeneous ice nucleation from micrometre-sized aqueous (NH4)2SO4 and aqueous levoglucosan particles is studied employing the optical microscope technique. A new experimental method is introduced that allows us to control the initial water activity of the aqueous droplets. Homogeneous ice freezing temperatures and ice melting temperatures of these aqueous solution droplets, 10 to 80 microm in diameter, are determined. Homogeneous ice nucleation from aqueous (NH4)2SO4 particles 5-39 wt% in concentration and aqueous levoglucosan particles with initial water activities of 0.85-0.99 yield upper limits of the homogeneous ice nucleation rate coefficients of up to 1x10(10) cm(-3) s(-1). The experimentally derived homogeneous ice freezing temperatures and upper limits of the homogeneous ice nucleation rate coefficients are compared with corresponding predictions of the water-activity-based ice nucleation theory [T. Koop, B. P. Luo, A. Tsias and T. Peter, Nature, 2000, 406, 611]. It is found that the water-activity-based ice nucleation theory can capture the experimentally derived ice freezing temperatures and homogeneous ice nucleation rate coefficients of the aqueous (NH4)2SO4 and aqueous levoglucosan particles. However, the level of agreement between experimentally derived and predicted values, in particular for homogeneous ice nucleation rate coefficients, crucially depends on the extrapolation method to obtain water activities at corresponding freezing temperatures. It is suggested that the combination of experimentally derived ice freezing temperatures and homogeneous ice nucleation rate coefficients can serve as a better validation of the water-activity-based ice nucleation theory than when compared to the observation of homogeneous ice freezing temperatures alone. The atmospheric implications with regard to the application of the water-activity-based ice nucleation theory and derivation of maximum ice particle production rates are briefly discussed.

  16. Ice nucleation efficiency of soot from biomass combustion

    NASA Astrophysics Data System (ADS)

    Umo, N. S.; Murray, B. J.; O'Sullivan, D.; Baeza-Romero, M. T.; Plane, J. C.

    2013-05-01

    Do Soot aerosols in the atmosphere indirectly influence the radiative budget of the Earth by modifying cloud properties, either by acting as cloud condensation nuclei (CCN) or as ice nuclei (IN). The ice nucleation activity of soot remains poorly quantified and there is a need to parameterise its impact for use in cloud-aerosol models. Here, we investigate the ice nucleation activity of eugenol soot in the immersion mode at conditions relevant to mixed-phase clouds. Eugenol is used as a proxy for a biomass combustion source. The efficiency of soot as an IN was quantified using droplet freezing techniques with droplet volumes ranging from nanolitre (˜100 μm diameter) to microliter (˜1 mm diameter). We show that soot nucleates ice in our experiments at temperatures up to -14°C, although the efficiency with which it does so is less than for mineral dust on a per surface area basis. An estimation of the IN number concentration that could result from our eugenol soot showed that, on a global average basis, IN from soot is secondary in importance to mineral dust below about -20°C. However, it may be important as IN in some locations which are deficient in dust, but rich in soot particles. We conclude that its overall impact can be significant considering its relative regional and global abundance.

  17. Ice Nucleation Activity in the Widespread Soil Fungus Mortierella alpina

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, J.; Hill, T. C. J.; Pummer, B. G.; Franc, G. D.; Pöschl, U.

    2014-08-01

    Biological residues in soil dust are a potentially strong source of atmospheric ice nuclei (IN). So far, however, the abundance, diversity, sources, seasonality, and role of biological - in particular, fungal - IN in soil dust have not been characterized. By analysis of the culturable fungi in topsoils, from a range of different land use and ecosystem types in south-east Wyoming, we found ice nucleation active (INA) fungi to be both widespread and abundant, particularly in soils with recent inputs of decomposable organic matter. Across all investigated soils, 8% of fungal isolates were INA. All INA isolates initiated freezing at -5 to -6 °C, and belonged to a single zygomycotic species, Mortierella alpina (Mortierellales, Mortierellomycotina). By contrast, the handful of fungal species so far reported as INA all belong within the Ascomycota or Basidiomycota phyla. M. alpina is known to be saprobic, widespread in soil and present in air and rain. Sequencing of the ITS region and the gene for γ-linolenic-elongase revealed four distinct clades, affiliated to different soil types. The IN produced by M. alpina seem to be proteinaceous, <300 kDa in size, and can be easily washed off the mycelium. Ice nucleating fungal mycelium will ramify topsoils and probably also release cell-free IN into it. If these IN survive decomposition or are adsorbed onto mineral surfaces, their contribution might accumulate over time, perhaps to be transported with soil dust and influencing its ice nucleating properties.

  18. Ice nucleation properties of mineral dust particles: Determination of onset RHi, IN active fraction, nucleation time-lag, and the effect of active sites on contact angles

    NASA Astrophysics Data System (ADS)

    Kulkarni, G.; Dobbie, S.

    2009-05-01

    A newly developed ice nucleation experimental set up was used to investigate the heterogeneous ice nucleation properties of three Saharan and one Spanish dust particle samples. It was observed that the spread in the onset relative humidities with respect to ice (RHi) for Saharan dust particles varied from 104% to 110%, whereas for the Spanish dust from 106% to 110%. The elemental composition analysis shows a prominent Ca feature in the Spanish dust sample which could potentially explain the differences in nucleation threshold. Although the spread in the onset RHi) for the Saharan dust samples were in agreement, the active fractions and nucleation time-lags calculated at various temperature and RHi) conditions were found to differ. This could be due to the subtle variation in the elemental composition of the dust samples, and surface irregularities like steps, cracks, cavities etc. A combination of classical nucleation theory and active site theory is used to understand the importance of these surface irregularities on the nucleability parameter contact angle that is widely used in the ice cloud modeling. These calculations show that the surface irregularities can reduce the contact angle by approximately 10°.

  19. Ice nucleation properties of mineral dust particles: determination of onset RHi, IN active fraction, nucleation time-lag, and the effect of active sites on contact angles

    NASA Astrophysics Data System (ADS)

    Kulkarni, G.; Dobbie, S.

    2010-01-01

    A newly developed ice nucleation experimental set up was used to investigate the heterogeneous ice nucleation properties of three Saharan and one Spanish dust particle samples. It was observed that the spread in the onset relative humidities with respect to ice (RHi) for Saharan dust particles varied from 104% to 110%, whereas for the Spanish dust from 106% to 110%. The elemental composition analysis shows a prominent Ca feature in the Spanish dust sample which could potentially explain the differences in nucleation threshold. Although the spread in the onset RHi for the three Saharan dust samples were in agreement, the active fractions and nucleation time-lags calculated at various temperature and RHi conditions were found to differ. This could be due to the subtle variation in the elemental composition of the dust samples, and surface irregularities like steps, cracks, cavities etc. A combination of classical nucleation theory and active site theory is used to understand the importance of these surface irregularities on the nucleability parameter, contact angle that is widely used in ice cloud modeling. These calculations show that the surface irregularities can reduce the contact angle by approximately 10 degrees.

  20. Ice nucleation properties of mineral dust particles: Determination of onset RHi, IN active fraction, nucleation time-lag, and the effect of active sites on contact angles

    SciTech Connect

    Kulkarni, Gourihar R.; Dobbie, Steven

    2010-01-08

    A newly developed ice nucleation experimental set up was used to investigate the heterogeneous ice nucleation properties of three Saharan and one Spanish dust particle samples. It is observed that the spread in the onset relative humidities with respect to ice (RHi) for Saharan dust particles varies from 104% to 110%, whereas for the Spanish dust from 106% to 110%. The elemental composition analysis shows a prominent Ca feature in the Spanish dust sample which could potentially explain the differences in nucleation threshold. Although spread in the onset RHi for Saharan dust samples were in agreement, their active fractions and nucleation time-lags calculated at various temperature and RHi conditions, for two Saharan dust samples, were not found to be in complete agreement. This could be because of the subtle variation in the elemental composition of the dust samples, and the surface irregularities like steps, cracks, cavities etc. A combination of classical nucleation theory and active site theory is used to understand the importance of these surface irregularities, expressed in terms of active sites, on the nucleability parameter (contact angle) that is widely used in the ice cloud modeling studies. These calculations show that the surface irregularities reduce the contact angle by approximately 10 degrees.

  1. A marine biogenic source of atmospherically relevant ice nucleating particles

    NASA Astrophysics Data System (ADS)

    Wilson, Theodore W.; Ladino, Luis A.; Alpert, Peter A.; Chance, Rosie; Whale, Thomas F.; Vergara Temprado, Jesús; Burrows, Susannah M.; Breckels, Mark N.; Kilthau, Wendy P.; Browse, Jo; Bertram, Allan K.; Miller, Lisa A.; Carpenter, Lucy J.; Hamilton, Jacqui F.; Carslaw, Kenneth S.; Brooks, Ian M.; Abbatt, Jonathan P. D.; Aller, Josephine Y.; Knopf, Daniel A.; Murray, Benjamin J.

    2016-04-01

    There are limited observations describing marine sources of ice nucleating particles (INPs), despite sea spray aerosol being one of the dominant sources of atmospheric particles globally. Evidence indicates that some marine aerosol particles act as INPs, but the source of these particles is unclear. The sea surface microlayer is enriched in surface active organic material representative of that found in sub-micron sea-spray aerosol. We show that the sea surface microlayer is enriched in INPs that nucleate ice under conditions pertinent to both high-altitude ice clouds and low to mid-altitude mixed-phase clouds. The INPs pass through 0.2 μm pore filters, are heat sensitive and spectroscopic analysis indicates the presence of material consistent with phytoplankton exudates. Mass spectrometric analysis of solid phase extracted dissolved organic material from microlayer and sub-surface water samples showed that the relative abundance of certain ions correlated with microlayer ice nucleation activity. However, these ions were not themselves directly responsible for ice nucleation. We propose that material associated with phytoplankton exudates is a candidate for the observed activity of the microlayer samples. We show that laboratory produced exudate from a ubiquitous marine diatom contains INPs despite its separation from diatom cells. Finally we use a parameterisation of our field data to estimate the atmospheric INP contribution from primary marine organic emissions using a global model and test the model against existing INP measurements in the remote oceans. We find that biogenic marine INPs can be dominant in remote marine environments, such as the Southern Ocean.

  2. Ice Nucleation properties of Air-Plane Soot Surrogates Using Vibrational Micro-spectroscopy: a preliminary study

    NASA Astrophysics Data System (ADS)

    Pirim, Claire; Ikhenazene, Raouf; Ortega, Ismael; Carpentier, Yvain; Focsa, Cristian; Chazallon, Bertrand

    2015-04-01

    Aircraft emissions have been studied extensively since the late 1960s and the interest was mainly driven by their direct and indirect effects on climate and the generation of contrails [1-4]. Emissions of solid-state particles (soots) from engine exhausts due to incomplete fuel combustion are considered to influence ice and liquid water cloud droplet activation [4]. The activity of these aerosols would originate from their ability to be important centers of ice-particle nucleation by promoting ice formation above water homogeneous freezing point. While some experiments focused on ice nucleation on soot particles did not yet reach definitive conclusions, soot are reported to be generally worse ice nuclei than mineral dust, nucleating at higher ice-supersaturations for deposition nucleation and at lower temperatures for immersion freezing. However, there are still numerous opened questions on the ice nucleation properties of soot particles [5], most likely due to the lack of information on the abundance, on the physico-chemical properties (structure and chemical compositions) of these aerosols, competition between different ice nucleation modes and dynamical factors that affect ice nucleation. Furthermore, the soot emitted from aircraft may be associated with soluble components like sulphate that can act as heterogeneous ice nuclei and initiate freezing at supersaturation of only 120-130% [6]. Therefore, more detailed studies of aerosol nucleation activity combined with throughout structural and compositional analyzes are needed in order to establish any association between the particles' hygroscopicity and their physico-chemical properties. In the present preliminary work, nucleation activity of air-plane soot particle surrogates is monitored using a temperature-controlled reactor in which the sample's relative humidity is precisely measured with a cryo-hygrometer. Formation of water/ice onto the particles is followed both optically and spectroscopically, using a

  3. Homogeneous ice nucleation from aqueous inorganic/organic particles representative of biomass burning: water activity, freezing temperatures, nucleation rates.

    PubMed

    Knopf, Daniel A; Rigg, Yannick J

    2011-02-10

    Homogeneous ice nucleation plays an important role in the formation of cirrus clouds with subsequent effects on the global radiative budget. Here we report on homogeneous ice nucleation temperatures and corresponding nucleation rate coefficients of aqueous droplets serving as surrogates of biomass burning aerosol. Micrometer-sized (NH(4))(2)SO(4)/levoglucosan droplets with mass ratios of 10:1, 1:1, 1:5, and 1:10 and aqueous multicomponent organic droplets with and without (NH(4))(2)SO(4) under typical tropospheric temperatures and relative humidities are investigated experimentally using a droplet conditioning and ice nucleation apparatus coupled to an optical microscope with image analysis. Homogeneous freezing was determined as a function of temperature and water activity, a(w), which was set at droplet preparation conditions. The ice nucleation data indicate that minor addition of (NH(4))(2)SO(4) to the aqueous organic droplets renders the temperature dependency of water activity negligible in contrast to the case of aqueous organic solution droplets. The mean homogeneous ice nucleation rate coefficient derived from 8 different aqueous droplet compositions with average diameters of ∼60 μm for temperatures as low as 195 K and a(w) of 0.82-1 is 2.18 × 10(6) cm(-3) s(-1). The experimentally derived freezing temperatures and homogeneous ice nucleation rate coefficients are in agreement with predictions of the water activity-based homogeneous ice nucleation theory when taking predictive uncertainties into account. However, the presented ice nucleation data indicate that the water activity-based homogeneous ice nucleation theory overpredicts the freezing temperatures by up to 3 K and corresponding ice nucleation rate coefficients by up to ∼2 orders of magnitude. A shift of 0.01 in a(w), which is well within the uncertainty of typical field and laboratory relative humidity measurements, brings experimental and predicted freezing temperatures and homogeneous ice

  4. Ice nucleation efficiency of clay minerals in the immersion mode

    NASA Astrophysics Data System (ADS)

    Pinti, V.; Marcolli, C.; Zobrist, B.; Hoyle, C. R.; Peter, T.

    2012-01-01

    Emulsion and bulk freezing experiments were performed to investigate immersion ice nucleation on clay minerals in pure water, using various kaolinites, montmorillonites, illites as well as natural dust from the Hoggar Mountains in the Saharan region. DSC (differential scanning calorimeter) measurements were performed on the kaolinites KGa-1b and KGa-2 from the Clay Mineral Society and kaolinite from Sigma-Aldrich; the montmorillonites SWy-2 and STx-1b from the Clay Mineral Society and the acid treated montmorillonites KSF and K-10 from Sigma Aldrich; the illites NX and SE from Arginotec. The emulsion experiments provide information on the average freezing behaviour characterized by the average nucleation sites. These experiments revealed one to two distinct heterogeneous freezing peaks, which suggest the presence of a low number of qualitatively distinct average nucleation site classes. We refer to the peak at the lowest temperature as "standard peak" and to the one at higher temperatures as "special peak". Conversely, freezing in bulk samples is not initiated by the average nucleation sites, but by a very low number of "best sites". The kaolinites showed quite narrow standard peaks with onset temperatures 239 K < Tonstd < 242 K and best sites with averaged median freezing temperature Tmedbest = 257 K. Only the kaolinite from Sigma Aldrich featured a special peak with freezing onset at 248 K. The illites showed broad standard peaks with freezing onsets at 244 K < Tonstd < 246 K and best sites with averaged median freezing temperature Tmedbest = 262 K. Montmorillonites had standard peaks with onsets 238 K < Tonstd < 240 K and best sites with Tmedbest=257 K. SWy-2, M K10, and KSF featured special peaks with onsets at Tonspcl=247, 240, and 242 K, respectively. M K10 and KSF both from Sigma Aldrich had less intense standard peaks compared to the ones from the Clay Mineral Society suggesting that a fraction of the standard sites are lost by the acid treatment. The acid

  5. Characterization of ice nucleation on different natural dust samples

    NASA Astrophysics Data System (ADS)

    Kaufmann, Lukas; Hofer, Julian; Marcolli, Claudia; Pinti, Valeria; Hoyle, Christopher; Peter, Thomas

    2014-05-01

    The impact of aerosols on Earth's climate is still uncertain. Therefore a better understanding of direct and indirect effects of aerosols is essential to improve models and the ability to predict future climate change. A natural source of aerosols is desert dust. Laboratory measurements investigating the influence of dust on heterogeneous freezing of water droplets are presented. We performed measurements with seven dust samples collected in the Etosha pan in Namibia, in the Makgadikgadi pan in Botswana (from three different locations), on the Altiplano in Bolivia, in Qatar and in the Hoggar mountains in Algeria. After sieving, the particle diameters of these dusts were < 32 μm. The mineralogical composition of the dusts was determined by X-ray diffraction. For the investigation of the ice nucleation ability of these dusts, emulsion as well as bulk freezing measurements were performed with a differential scanning calorimeter (DSC). For the emulsion measurements a suspension of a dust was mixed with water. Mixed with a mineral oil/lanolin mixture, the water droplets in the emulsion had mean diameters of around 2 μm. Heterogeneous freezing of dusts was characterized by three temperatures for frozen fractions of 0.1, 0.25, and 0.5, respectively. Heterogeneous freezing temperatures for all 7 samples were quite similar, namely 245 - 246.5 K (for frozen fractions of 0.1), 243 - 244.5 K (for 0.25) and 240 - 241.5 K (for 0.5). Emulsions consisting of pure water suspensions froze with onset temperatures of around 237 K. Emulsion measurements with Hoggar mountain dust were also performed with an additional solute such as ammonium sulfate, malonic acid, glucose or PEG 300. Immersion freezing was found to be suppressed in the presence of solutes. For the bulk measurements dusts were suspended in pure water and droplets with radii of about 1 mm were subjected to repeated freezing cycles. Freezing temperatures in the range of 253 - 265 K were found for cooling rates of 10 K

  6. Ice nucleation in the upper troposphere: Sensitivity to aerosol number density, temperature, and cooling rate

    SciTech Connect

    Jensen, E.J.; Toon, O.B.

    1994-09-01

    We have investigated the processes that control ice crystal nucleation in the upper troposphere using a numerical model. Nucleation of ice resulting from cooling was simulated for a range of aerosol number densities, initial temperatures, and cooling rates. In contrast to observations of stratus clouds, we find that the number of ice crystals that nucleate in cirrus is relatively insensitive to the number of aerosols present. The ice crystal size distribution at the end of the nucleation process is unaffected by the assumed initial aerosol number density. Essentially, nucleation continues until enough ice crystals are present such that their deposition growth rapidly depletes the vapor and shuts off any further nucleation. However, the number of ice crystals nucleated increases rapidly with decreasing initial temperature and increasing cooling rate. This temperature dependence alone could explain the large ice crystal number density observed in very cold tropical cirrus.

  7. Heterogeneous Nucleation of Dicalcium Phosphate Dihydrate on Modified Silica Surfaces.

    PubMed

    Miller, Carrie; Komunjer, Ljepša; Hlady, Vladimir

    2010-01-01

    Heterogeneous nucleation of dicalcium phosphate dihydrate, CaHPO4•2H2O (DCPD) was studied on untreated planar fused silica and on three modified silica surfaces: octadecylsilyl (OTS) modified silica, human serum albumin treated OTS silica, and UV-oxidized 3-mercaptopropyltriethoxysilyl (MTS) modified silica. The supersaturation ratio of calcium and phosphate solution with respect to DCPD was kept below ~10. The nucleated crystals were observed 24 hours and one week after initial contact between supersaturated solutions and substrate surfaces using bright field and reflectance interference contrast microscopy. No DCPD crystals nucleated on albumin-treated OTS-silica. Majority of the DCDP crystals formed on the other modified silica surfaces appeared to be morphologically similar irrespective of the nature of nucleating substrate. Reflectance interference contrast microscopy provided a proof that the majority of the crystals on these substrates do not develop an extended contact with the substrate surface. The images showed that the most extended contact planes were between the DCPD crystals and MTS modified silica surface. The crystals nucleated on OTS-treated and untreated silica surfaces showed only few or none well-developed contact planes.

  8. Ice nucleation efficiency of natural dust samples in the immersion mode

    NASA Astrophysics Data System (ADS)

    Kaufmann, Lukas; Marcolli, Claudia; Hofer, Julian; Pinti, Valeria; Hoyle, Christopher R.; Peter, Thomas

    2016-09-01

    A total of 12 natural surface dust samples, which were surface-collected on four continents, most of them in dust source regions, were investigated with respect to their ice nucleation activity. Dust collection sites were distributed across Africa, South America, the Middle East, and Antarctica. Mineralogical composition has been determined by means of X-ray diffraction. All samples proved to be mixtures of minerals, with major contributions from quartz, calcite, clay minerals, K-feldspars, and (Na, Ca)-feldspars. Reference samples of these minerals were investigated with the same methods as the natural dust samples. Furthermore, Arizona test dust (ATD) was re-evaluated as a benchmark. Immersion freezing of emulsion and bulk samples was investigated by differential scanning calorimetry. For emulsion measurements, water droplets with a size distribution peaking at about 2 µm, containing different amounts of dust between 0.5 and 50 wt % were cooled until all droplets were frozen. These measurements characterize the average freezing behaviour of particles, as they are sensitive to the average active sites present in a dust sample. In addition, bulk measurements were conducted with one single 2 mg droplet consisting of a 5 wt % aqueous suspension of the dusts/minerals. These measurements allow the investigation of the best ice-nucleating particles/sites available in a dust sample. All natural dusts, except for the Antarctica and ATD samples, froze in a remarkably narrow temperature range with the heterogeneously frozen fraction reaching 10 % between 244 and 250 K, 25 % between 242 and 246 K, and 50 % between 239 and 244 K. Bulk freezing occurred between 255 and 265 K. In contrast to the natural dusts, the reference minerals revealed ice nucleation temperatures with 2-3 times larger scatter. Calcite, dolomite, dolostone, and muscovite can be considered ice nucleation inactive. For microcline samples, a 50 % heterogeneously frozen fraction occurred above 245 K for all

  9. Ice nucleating activity of Pseudomonas syringae and Erwinia herbicola.

    PubMed Central

    Kozloff, L M; Schofield, M A; Lute, M

    1983-01-01

    Chemical and biological properties of the ice nucleating sites of Pseudomonas syringae, strain C-9, and Erwinia herbicola have been characterized. The ice nucleating activity (INA) for both bacteria was unchanged in buffers ranging from pH 5.0 to 9.2, suggesting that there were no essential groups for which a change in charge in this range was critical. The INA of both bacteria was also unaffected by the addition of metal chelating compounds. Borate compounds and certain lectins markedly inhibited the INA of both types of bacterial cells. Butyl borate was not an inhibitor, but borate, phenyl borate, and m-nitrophenyl borate were, in order, increasingly potent inhibitors. These compounds have a similar order of affinity for cis hydroxyls, particularly for those found on sugars. Lentil lectin and fava bean lectin, which have binding sites for mannose or glucose, inhibited the INA of both bacteria. All other lectins examined had no effect. The inhibition of INA by these two types of reagents indicate that sugar-like groups are at or near the ice nucleating site. Sulfhydryl reagents were potent inhibitors of the INA of both bacteria. When treated with N-ethylmaleimide, p-hydroxymercuribenzoate, or iodoacetamide, the INA was irreversibly inhibited by 99%. The kinetics of inactivation with N-ethylmaleimide suggested that E. herbicola cells have at least two separate ice nucleating sites, whereas P. syringae cells have possibly four or more separate sites. The effect of infection with a virulent phage (Erh 1) on the INA of E. herbicola was examined. After multiple infection of a bacterial culture the INA was unchanged until 40 to 45 min, which was midway through the 95-min latent period. At that time, the INA activity began falling and 99% of the INA was lost by 55 min after infection, well before any cells had lysed. This decrease in INA before lysis is attributed to phage-induced changes in the cell wall. PMID:6848483

  10. Ice nucleation by soil dust compared to desert dust aerosols

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Steinke, I.; Ullrich, R.; Höhler, K.; Schiebel, T.; Hoose, C.; Funk, R.

    2015-12-01

    A minor fraction of atmospheric aerosol particles, so-called ice-nucleating particles (INPs), initiates the formation of the ice phase in tropospheric clouds and thereby markedly influences the Earth's weather and climate systems. Whether an aerosol particle acts as an INP depends on its size, morphology and chemical compositions. The INP fraction of certain aerosol types also strongly depends on the temperature and the relative humidity. Because both desert dust and soil dust aerosols typically comprise a variety of different particles, it is difficult to assess and predict their contribution to the atmospheric INP abundance. This requires both accurate modelling of the sources and atmospheric distribution of atmospheric dust components and detailed investigations of their ice nucleation activities. The latter can be achieved in laboratory experiments and parameterized for use in weather and climate models as a function of temperature and particle surface area, a parameter called ice-nucleation active site (INAS) density. Concerning ice nucleation activity studies, the soil dust is of particular interest because it contains a significant fraction of organics and biological components, both with the potential for contributing to the atmospheric INP abundance at relatively high temperatures compared to mineral components. First laboratory ice nucleation experiments with a few soil dust samples indicated their INP fraction to be comparable or slightly enhanced to that of desert dust. We have used the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud simulation chamber to study the immersion freezing ability of four different arable soil dusts, sampled in Germany, China and Argentina. For temperatures higher than about -20°C, we found the INP fraction of aerosols generated from these samples by a dry dispersion technique to be significantly higher compared to various desert dust aerosols also investigated in AIDA experiments. In this contribution, we

  11. Cirrus cloud formation and the role of heterogeneous ice nuclei

    NASA Astrophysics Data System (ADS)

    Froyd, Karl D.; Cziczo, Daniel J.; Hoose, Corinna; Jensen, Eric J.; Diao, Minghui; Zondlo, Mark A.; Smith, Jessica B.; Twohy, Cynthia H.; Murphy, Daniel M.

    2013-05-01

    Composition, size, and phase are key properties that define the ability of an aerosol particle to initiate ice in cirrus clouds. Properties of cirrus ice nuclei (IN) have not been well constrained due to a lack of systematic measurements in the upper troposphere. We have analyzed the size and composition of sublimated cirrus particles sampled from a high altitude research aircraft using both in situ and offline techniques. Mineral dust and metallic particles are the most enhanced residue types relative to background aerosol. Using a combination of cirrus residue composition, relative humidity, and cirrus particle concentration measurements, we infer that heterogeneous nucleation is a dominant cirrus formation mechanism for the mid-latitude, subtropical, and tropical regions under study. Other proposed heterogeneous IN including biomass burning particles, elemental carbon, and biological material were not abundant in cirrus residuals.

  12. Ice nucleating particles in the Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Boose, Yvonne; Sierau, Berko; García, M. Isabel; Rodríguez, Sergio; Alastuey, Andrés; Linke, Claudia; Schnaiter, Martin; Kupiszewski, Piotr; Kanji, Zamin A.; Lohmann, Ulrike

    2016-07-01

    This study aims at quantifying the ice nucleation properties of desert dust in the Saharan Air Layer (SAL), the warm, dry and dust-laden layer that expands from North Africa to the Americas. By measuring close to the dust's emission source, before aging processes during the transatlantic advection potentially modify the dust properties, the study fills a gap between in situ measurements of dust ice nucleating particles (INPs) far away from the Sahara and laboratory studies of ground-collected soil. Two months of online INP concentration measurements are presented, which were part of the two CALIMA campaigns at the Izaña observatory in Tenerife, Spain (2373 m a.s.l.), in the summers of 2013 and 2014. INP concentrations were measured in the deposition and condensation mode at temperatures between 233 and 253 K with the Portable Ice Nucleation Chamber (PINC). Additional aerosol information such as bulk chemical composition, concentration of fluorescent biological particles as well as the particle size distribution was used to investigate observed variations in the INP concentration. The concentration of INPs was found to range between 0.2 std L-1 in the deposition mode and up to 2500 std L-1 in the condensation mode at 240 K. It correlates well with the abundance of aluminum, iron, magnesium and manganese (R: 0.43-0.67) and less with that of calcium, sodium or carbonate. These observations are consistent with earlier results from laboratory studies which showed a higher ice nucleation efficiency of certain feldspar and clay minerals compared to other types of mineral dust. We find that an increase of ammonium sulfate, linked to anthropogenic emissions in upwind distant anthropogenic sources, mixed with the desert dust has a small positive effect on the condensation mode INP per dust mass ratio but no effect on the deposition mode INP. Furthermore, the relative abundance of biological particles was found to be significantly higher in INPs compared to the ambient

  13. Soot Aerosol Particles as Cloud Condensation Nuclei: from Ice Nucleation Activity to Ice Crystal Morphology

    NASA Astrophysics Data System (ADS)

    Pirim, Claire; Ikhenazene, Raouf; Ortega, Isamel Kenneth; Carpentier, Yvain; Focsa, Cristian; Chazallon, Bertrand; Ouf, François-Xavier

    2016-04-01

    Emissions of solid-state particles (soot) from engine exhausts due to incomplete fuel combustion is considered to influence ice and liquid water cloud droplet activation [1]. The activity of these aerosols would originate from their ability to be important centers of ice-particle nucleation, as they would promote ice formation above water homogeneous freezing point. Soot particles are reported to be generally worse ice nuclei than mineral dust because they activate nucleation at higher ice-supersaturations for deposition nucleation and at lower temperatures for immersion freezing than ratios usually expected for homogeneous nucleation [2]. In fact, there are still numerous opened questions as to whether and how soot's physico-chemical properties (structure, morphology and chemical composition) can influence their nucleation ability. Therefore, systematic investigations of soot aerosol nucleation activity via one specific nucleation mode, here deposition nucleation, combined with thorough structural and compositional analyzes are needed in order to establish any association between the particles' activity and their physico-chemical properties. In addition, since the morphology of the ice crystals can influence their radiative properties [3], we investigated their morphology as they grow over both soot and pristine substrates at different temperatures and humidity ratios. In the present work, Combustion Aerosol STandart soot samples were produced from propane using various experimental conditions. Their nucleation activity was studied in deposition mode (from water vapor), and monitored using a temperature-controlled reactor in which the sample's relative humidity is precisely measured with a cryo-hygrometer. Formation of water/ice onto the particles is followed both optically and spectroscopically, using a microscope coupled to a Raman spectrometer. Vibrational signatures of hydroxyls (O-H) emerge when the particle becomes hydrated and are used to characterize ice

  14. Giant Dipole Moments of Submicron Ice Crystallites Nucleated on Dust Particles Cause Polarization Catastrophe, Sprites

    NASA Astrophysics Data System (ADS)

    Handel, P. H.

    2007-05-01

    Supersaturation of water vapor in the atmosphere is known to be low, limited to just a few percent, because the nucleation processes of water aggregates and ice crystallites are heterogeneous. Nucleation is on dust particles, known as aerosol particles. Ice nuclei are often sub-micron SiO2 particles. The ice crystallite formed on such a nucleus is different from bulk ice, which has a hindered ferroelectric transition at 78 K, according to Hentschel's calculation and to other, Japanese studies. At this transition temperature the free energy difference between the ordered and disordered states is zero, DF=0. However, the thin ice layer deposited on the nucleus has a preferential direction, the radial direction, roughly perpendicular to the surface. This spoils in the crystallite the isotropy characterizing bulk ice. Therefore, in the free energy difference DF=DU- TDS, between the entropy difference DS that tries to lower the transition temperature, and the internal energy difference DU, the entropy term looses much of its importance. Therefore, the ferroelectric transition temperature of a sub-micron, heterogeneously nucleated, ice crystallite will be much higher, close to the melting temperature of bulk ice. For temperatures below 253 K this could remain valid even for slightly larger crystallites, almost up to 10 microns. The present paper is focused on this collective ordering effect. The ferroelectric transition is never observed in bulk ice, because the activation energy needed to achieve ferroelectric ordering is prohibitive, and causes the transition time to be infinite. On the other hand, at the much higher temperature estimated for the small, defect ridden, ice crystallites, the transition time is finite and the crystallites grow from the beginning with a ferroelectric saturation polarization. This causes each crystallite to have a giant dipole moment, and causes the whole cloud of crystallites to lapse into a Clausius-Mossotti type polarization catastrophe

  15. Small particles big effect? - Investigating ice nucleation abilities of soot particles

    NASA Astrophysics Data System (ADS)

    Mahrt, Fabian; David, Robert O.; Lohmann, Ulrike; Stopford, Chris; Wu, Zhijun; Kanji, Zamin A.

    2017-04-01

    Atmospheric soot particles are primary particles produced by incomplete combustion of biomass and/or fossil fuels. Thus soot mainly originates from anthropogenic emissions, stemming from combustion related processes in transport vehicles, industrial and residential uses. Such soot particles are generally complex mixtures of black carbon (BC) and organic matter (OM) (Bond et al., 2013; Petzold et al., 2013), depending on the sources and the interaction of the primary particles with other atmospheric matter and/or gases BC absorbs solar radiation having a warming effect on global climate. It can also act as a heterogeneous ice nucleating particle (INP) and thus impact cloud-radiation interactions, potentially cooling the climate (Lohmann, 2002). Previous studies, however, have shown conflicting results concerning the ice nucleation ability of soot, limiting the ability to predict its effects on Earth's radiation budget. Here we present a laboratory study where we systematically investigate the ice nucleation behavior of different soot particles. Commercial soot samples are used, including an amorphous, industrial carbon frequently used in coatings and coloring (FW 200, Orion Engineered Carbons) and a fullerene soot (572497 ALDRICH), e.g. used as catalyst. In addition, we use soot generated from a propane flame Combustion Aerosol Standard Generator (miniCAST, JING AG), as a proxy for atmospheric soot particles. The ice nucleation ability of these soot types is tested on size-selected particles for a wide temperature range from 253 K to 218 K, using the Horizontal Ice Nucleation Chamber (HINC), a Continuous Flow Diffusion Chamber (CFDC) (Kanji and Abbatt, 2009). Ice nucleation results from these soot surrogates will be compared to chemically more complex real world samples, collected on filters. Filters will be collected during the 2016/2017 winter haze periods in Beijing, China and represent atmospheric soot particles with sources from both industrial and residential

  16. Thermodynamics of homogeneous nucleation of mesospheric ice particles

    NASA Astrophysics Data System (ADS)

    Zasetsky, A. Y.; Petelina, S. V.

    2009-05-01

    Although our knowledge of the upper mesospheric region is continuously improving, many aspects of mesospheric dynamics and thermodynamics are still unclear. We address some of these open questions related to the thermodynamics of water at the conditions intrinsic for the polar summer mesosphere. For this we use recently published theoretical and laboratory results on the properties of water at very low temperatures. We present the hypothesis of homogeneous nucleation of ice nano-particles in the polar summer mesosphere. The nucleation of condensed phase is traced back to the first step on the formation pathway, which is assumed to be the transition of water vapor to amorphous cluster. Amorphous clusters then freeze into water ice, likely metastable cubic ice, when they reach the critical size. The estimates based on the equilibrium thermodynamics give the critical size (radius) of amorphous water clusters as about 1.0 nm. The same estimates for the final transition step, that is the transformation of cubic to hexagonal ice, give the critical size of about 15 nm at typical upper mesospheric conditions during the polar summer (about 150K temperature and about 109cm-3 water vapor density).

  17. Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina, and Germany

    NASA Astrophysics Data System (ADS)

    Steinke, I.; Funk, R.; Busse, J.; Iturri, A.; Kirchen, S.; Leue, M.; Möhler, O.; Schwartz, T.; Schnaiter, M.; Sierau, B.; Toprak, E.; Ullrich, R.; Ulrich, A.; Hoose, C.; Leisner, T.

    2016-11-01

    Soil dust particles emitted from agricultural areas contain considerable mass fractions of organic material. Also, soil dust particles may act as carriers for potentially ice-active biological particles. In this work, we present ice nucleation experiments conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber. We investigated the ice nucleation efficiency of four types of soil dust from different regions of the world. The results are expressed as ice nucleation active surface site (INAS) densities and presented for the immersion freezing and the deposition nucleation mode. For immersion freezing occurring at 254 K, samples from Argentina, China, and Germany show ice nucleation efficiencies which are by a factor of 10 higher than desert dusts. On average, the difference in ice nucleation efficiencies between agricultural and desert dusts becomes significantly smaller at temperatures below 247 K. In the deposition mode the soil dusts showed higher ice nucleation activity than Arizona Test Dust over a temperature range between 232 and 248 K and humidities RHice up to 125%. INAS densities varied between 109 and 1011 m-2 for these thermodynamic conditions. For one soil dust sample (Argentinian Soil), the effect of treatments with heat was investigated. Heat treatments (383 K) did not affect the ice nucleation efficiency observed at 249 K. This finding presumably excludes proteinaceous ice-nucleating entities as the only source of the increased ice nucleation efficiency.

  18. Freezing activities of flavonoids in solutions containing different ice nucleators.

    PubMed

    Kuwabara, Chikako; Wang, Donghui; Kasuga, Jun; Fukushi, Yukiharu; Arakawa, Keita; Koyama, Toshie; Inada, Takaaki; Fujikawa, Seizo

    2012-06-01

    In this study, we examined the effects on freezing of 26 kinds of flavonoid compounds, which were randomly selected as compounds with structures similar to those of flavonoid compounds existing in deep supercooling xylem parenchyma cells (XPCs) in trees, in solutions containing different kinds of ice nucleators, including the ice nucleation bacterium (INB) Erwinia ananas, INB Xanthomonas campestris, silver iodide, phloroglucinol and unidentified airborne impurities in buffered Milli-Q water (BMQW). Cumulative freezing spectra were obtained in each solution by cooling 2 μL droplets at 0.2 °C/min by a droplet freezing assay. Freezing temperature of 50% droplets (FT(50)) was obtained from each spectra in a separate analysis with more than 20 droplets and mean FT(50) were obtained from more than five separate analyses using more than 100 droplets in total in each flavonoid. Supercooling-promoting activities (SCA) or ice nucleation-enhancing activities (INA) of these flavonoids were determined by the difference in FT(50) between control solutions without flavonoids and experimental solutions with flavonoids. In mean values, most of the compounds examined exhibited SCA in solutions containing the INB E. ananas, INB X. campestris, silver iodide, and phloroglucinol although the magnitudes of their activities were different depending on the ice nucleator. In solutions containing the INB E. ananas, 10 compounds exhibited SCAs with significant differences (p<0.05) in the range of 1.4-4.2 °C. In solutions containing silver iodide, 23 compounds exhibited SCAs with significant differences in the range of 2.0-7.1 °C. In solutions containing phloroglucinol, six compounds exhibited SCAs with significant differences in the range of 2.4-3.5 °C. In solutions containing the INB X. campestris, only three compounds exhibited SCAs with significant differences in the range of 0.9-2.3 °C. In solutions containing unidentified airborne impurities (BMQW alone), on the other hand, many

  19. Rocket effluent: Its ice nucleation activity and related properties

    NASA Technical Reports Server (NTRS)

    Parungo, F. P.; Allee, P. A.

    1978-01-01

    To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.

  20. Analysis of isothermal and cooling rate dependent immersion freezing by a unifying stochastic ice nucleation model

    NASA Astrophysics Data System (ADS)

    Alpert, P. A.; Knopf, D. A.

    2015-05-01

    Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature (T) and relative humidity (RH) at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling rate dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nuclei (IN) all have the same IN surface area (ISA), however the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses physically observable parameters including the total number of droplets (Ntot) and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time dependent isothermal frozen fractions exhibiting non-exponential behavior with time can be readily explained by this model considering varying ISA. An

  1. Depression of the ice-nucleation temperature of rapidly cooled mouse embryos by glycerol and dimethyl sulfoxide.

    PubMed Central

    Rall, W F; Mazur, P; McGrath, J J

    1983-01-01

    The temperature at which ice formation occurs in supercooled cytoplasm is an important element in predicting the likelihood of intracellular freezing of cells cooled by various procedures to subzero temperatures. We have confirmed and extended prior indications that permeating cryoprotective additives decrease the ice nucleation temperature of cells, and have determined some possible mechanisms for the decrease. Our experiments were carried out on eight-cell mouse embryos equilibrated with various concentrations (0-2.0 M) of dimethyl sulfoxide or glycerol and then cooled rapidly. Two methods were used to assess the nucleation temperature. The first, indirect, method was to determine the in vitro survival of the rapidly cooled embryos as a function of temperature. The temperatures over which an abrupt drop in survival occurs are generally diagnostic of the temperature range for intracellular freezing. The second, direct, method was to observe the microscopic appearance during rapid cooling and note the temperature at which nucleation occurred. Both methods showed that the nucleation temperature decreased from - 10 to - 15 degrees C in saline alone to between - 38 degrees and - 44 degrees C in 1.0-2.0 M glycerol and dimethyl sulfoxide. The latter two temperatures are close to the homogeneous nucleation temperatures of the solutions in the embryo cytoplasm, and suggest that embryos equilibrated in these solutions do not contain heterogeneous nucleating agents and are not accessible to any extracellular nucleating agents, such as extracellular ice. The much higher freezing temperatures of cells in saline or in low concentrations of additive indicate that they are being nucleated by heterogeneous agents or, more likely, by extracellular ice. Images FIGURE 5 FIGURE 6 PMID:6824748

  2. Ice nucleation activity in the widespread soil fungus Mortierella alpina

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, Janine; Hill, Thomas C. J.; Pummer, Bernhard G.; Yordanova, Petya; Franc, Gary D.; Pöschl, Ulrich

    2015-04-01

    Biological residues in soil dust are a potentially strong source of atmospheric ice nucleators (IN). However, the sources and characteristics of biological - in particular, fungal - IN in soil dust have not been characterized. By analysis of the culturable fungi in topsoils, from a range of different land use and ecosystem types in south-east Wyoming, we found ice nucleation active (INA, i.e., inducing ice formation in the probed range of temperature and concentration) fungi to be both widespread and abundant, particularly in soils with recent inputs of decomposable organic matter. For example, in harvested and ploughed sugar beet and potato fields, and in the organic horizon beneath Lodgepole pine forest, their relative abundances and concentrations among the cultivable fungi were 25% (8 x 103 CFU g-1), 17% (4.8 x 103 CFU g-1) and 17% (4 x 103 CFU g-1), respectively. Across all investigated soils, 8% (2.9 x 103 CFU g-1) of fungal isolates were INA. All INA isolates initiated freezing at -5° C to -6° C and all belonged to a single zygomycotic species, Mortierella alpina (Mortierellales, Mortierellomycotina). By contrast, the handful of fungal species so far reported as INA all belong within the Ascomycota or Basidiomycota phyla. Mortierella alpina is known to be saprobic (utilizing non-living organic matter), widespread in soil and present in air and rain. Sequencing of the ITS region and the gene for γ-linolenic elongase revealed four distinct clades, affiliated to different soil types. The IN produced by M. alpina seem to be extracellular proteins of 100-300 kDa in size which are not anchored in the fungal cell wall. Ice nucleating fungal mycelium will ramify topsoils and probably also release cell-free IN into it. If these IN survive decomposition or are adsorbed onto mineral surfaces, these small cell-free IN might contribute to the as yet uncharacterized pool of atmospheric IN released by soils as dusts.

  3. Heterogeneous nucleation from a supercooled ionic liquid on a carbon surface

    NASA Astrophysics Data System (ADS)

    He, Xiaoxia; Shen, Yan; Hung, Francisco R.; Santiso, Erik E.

    2016-12-01

    Classical molecular dynamics simulations were used to study the nucleation of the crystal phase of the ionic liquid [dmim+][Cl-] from its supercooled liquid phase, both in the bulk and in contact with a graphitic surface of D = 3 nm. By combining the string method in collective variables [Maragliano et al., J. Chem. Phys. 125, 024106 (2006)], with Markovian milestoning with Voronoi tessellations [Maragliano et al., J. Chem. Theory Comput. 5, 2589-2594 (2009)] and order parameters for molecular crystals [Santiso and Trout, J. Chem. Phys. 134, 064109 (2011)], we computed minimum free energy paths, the approximate size of the critical nucleus, the free energy barrier, and the rates involved in these nucleation processes. For homogeneous nucleation, the subcooled liquid phase has to overcome a free energy barrier of ˜85 kcal/mol to form a critical nucleus of size ˜3.6 nm, which then grows into the monoclinic crystal phase. This free energy barrier becomes about 42% smaller (˜49 kcal/mol) when the subcooled liquid phase is in contact with a graphitic disk, and the critical nucleus formed is about 17% smaller (˜3.0 nm) than the one observed for homogeneous nucleation. The crystal formed in the heterogeneous nucleation scenario has a structure that is similar to that of the bulk crystal, with the exception of the layers of ions next to the graphene surface, which have larger local density and the cations lie with their imidazolium rings parallel to the graphitic surface. The critical nucleus forms near the graphene surface separated only by these layers of ions. The heterogeneous nucleation rate (˜4.8 × 1011 cm-3 s-1) is about one order of magnitude faster than the homogeneous rate (˜6.6 × 1010 cm-3 s-1). The computed free energy barriers and nucleation rates are in reasonable agreement with experimental and simulation values obtained for the homogeneous and heterogeneous nucleation of other systems (ice, urea, Lennard-Jones spheres, and oxide glasses).

  4. The Ice Nucleation Activity of Surface Modified Soot

    NASA Astrophysics Data System (ADS)

    Häusler, Thomas; Witek, Lorenz; Felgitsch, Laura; Hitzenberger, Regina; Grothe, Hinrich

    2017-04-01

    The ice nucleation efficiency of many important atmospheric particles remains poorly understood. Since soot is ubiquitous in the Earth's troposphere, they might have the potential to significantly impact the Earth's climate (Finlayson-Pitts and Pitts, 2000; Seinfeld and Pandis, 1998). Here we present the ice nucleation activity (INA) in immersion freezing mode of different types of soot. Therefor a CAST (combustion aerosol standard) generator was used to produce different kinds of soot samples. The CAST generator combusts a propane-air-mixture and deposits thereby produced soot on a polyvinyl fluoride filter. By varying the propane to air ratio, the amount of organic portion of the soot can be varied from black carbon (BC) with no organic content to brown carbon (BrC) with high organic content. To investigate the impact of functional sites of ice nuclei (IN), the soot samples were exposed to NO2 gas for a certain amount of time (30 to 360 minutes) to chemically modify the surface. Immersion freezing experiments were carried out in a unique reaction gadget. In this device a water-in-oil suspension (with the soot suspended in the aqueous phase) was cooled till the freezing point and was observed through a microscope (Pummer et al., 2012; Zolles et al., 2015) It was found that neither modified nor unmodified BC shows INA. On the contrary, unmodified BrC shows an INA at -32˚ C, which can be increased up to -20˚ C. The INA of BrC depends on the duration of NO2- exposure. To clarify the characteristics of the surface modifications, surface sensitive analysis like infrared spectroscopy and X-ray photoelectron spectroscopy were carried out. Finlayson-Pitts, B. J. and Pitts, J. N. J.: Chemistry of the Upper and Lower Atmosphere, Elsevier, New York, 2000. Pummer, B. G., Bauer, H., Bernardi, J., Bleicher, S., and Grothe, H.: Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen, Atmos Chem Phys, 12, 2541-2550, 2012. Seinfeld, J

  5. Ice nucleation of Snomax® particles below water vapor saturation: immersion freezing in concentrated solution droplets

    NASA Astrophysics Data System (ADS)

    Wex, Heike; Kanji, Zamin A.; Boose, Yvonne; Beyer, Alexander; Henning, Silvia; Augustin-Bauditz, Stefanie

    2015-04-01

    Heterogeneous ice nucleation has received an increasing amount of interest in the past years, as it initiates the ice phase in mixed phase clouds (MPCs) and, to some extent, also in cirrus clouds. The presence of ice influences cloud radiative properties and, for mixed phase clouds, also the formation of precipitation. Immersion freezing is thought to be the most important mechanism through which ice formation could take place in MPCs. Here, we examine the ice nucleation activity of biological ice nucleating particles (INP) derived from bacteria, namely, particles generated from Snomax® suspensions, both above and below water vapor saturation. During a measurement campaign in Leipzig, ice nucleation measurements were conducted with PINC (Portable Ice Nucleus Counter, Chou et al., 2011) and LACIS (Leipzig Aerosol Cloud Interaction Simulator, see e.g. Wex et al., 2014a). Immersion freezing measurements from PINC and LACIS were in agreement in the temperature regime for which both instruments operate reliably. Here, we will show that measurements done below water vapour saturation and above the deliquescence relative humidity of the Snomax® particles follow what would be expected for immersion freezing in concentrated solutions, similar to what was suggested for coated kaolinite particles in Wex et al. (2014b). Additionally, some measurements reported in the literature that were done in the water vapour sub-saturated regime will be evaluated based on the assumption made above, showing that at least some of the ice nucleation which previously was ascribed to deposition ice nucleation rather follows the behavior of immersion freezing in concentrated solutions. Literature: Chou, C., O. Stetzer, E. Weingartner, Z. Juranyi, Z. A. Kanji, and U. Lohmann (2011), Ice nuclei properties within a Saharan dust event at the Jungfraujoch in the Swiss Alps, Atmos. Chem. Phys., 11(10), 4725-4738, doi:10.5194/acp-11-4725-2011. Wex, H. et al. (2014a) Intercomparing different devices

  6. Agar plate freezing assay for the in situ selection of transformed ice nucleating bacteria.

    PubMed

    Anastassopoulos, Elias

    2006-10-01

    An agar plate freezing assay is described based on the incorporation of fluorescein dye in agar medium. Upon addition of fluorescein the medium becomes transparent. This facilitates the monitoring of the ice nucleation event in vivo and the subsequent in situ selection of transformed ice nucleating bacteria. In comparison with known assays for the screening of transformants, the proposed assay is very accurate and reproducible. It may be applied in environmental samples screening for ice nucleating organisms, or in cDNA or genomic libraries for identifying novel ice nucleation genes. It may also prove useful in comparative studies of the ice nucleation activity, e.g. in directed evolution experiments involving ice nucleation genes.

  7. Determining the necessary conditions for Martian cloud formation: Ice nucleation in an electrodynamic balance (EDB)

    NASA Astrophysics Data System (ADS)

    Berlin, S.; Bauer, A. J.; Cziczo, D. J.

    2013-12-01

    The Martian atmosphere contains water ice clouds similar to Earth's cirrus clouds. These clouds influence the atmospheric temperature profile, alter the balance of incoming and outgoing radiation, and vertically redistribute water and mineral dust. Extrapolations of classical heterogeneous nucleation theory from Earth-like conditions to colder temperature and lower pressure regimes present in extraterrestrial atmospheres may be inaccurate, and thus hydrological models describing these regimes could lack physical meaning. In this project, we use an electrodynamic balance (EDB) to levitate individual aerosol particles and study their freezing properties. We test previously characterized aerosols such as Arizona Test Dust (ATD) and sodium chloride (NaCl). Then, we examine the less well-studied Mojave Mars Simulant (MMS) dust, which mimics the composition and size of dust particles found in the Martian atmosphere. A relative humidity, temperature, and inert atmosphere are utilized to emulate conditions found in the Martian atmosphere. We will discuss the supersaturations under which heterogeneous ice nucleation occurs on surrogate Martian ice nuclei at various temperatures.

  8. Manchester Ice Nucleus Counter (MINC) measurements from the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007)

    NASA Astrophysics Data System (ADS)

    Jones, H. M.; Flynn, M. J.; Demott, P. J.; Möhler, O.

    2010-08-01

    An ice nucleus counter was developed and constructed to enable investigation of potential ice nucleating materials. The Manchester Ice Nucleus Chamber (MINC) is a concentric-cylinder continuous flow diffusion chamber (CFDC). A full explanation of the MINC instrument is given here, along with first results and a comparison to an established instrument of similar design (Colorado State University CFDC) during sampling of common ice nucleating aerosols at the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007). Both instruments detected the onset of ice nucleation under similar conditions of temperature and supersaturation for several different types of ice nuclei. Comparisons of the ratio of ice nuclei to total aerosol concentrations as a function of relative humidity (RH) showed agreement within one order of magnitude. Possible reasons for differences between the two instruments relating to differences in their design are discussed, along with suggestions to future improvements to the current design.

  9. Manchester Ice Nucleus Counter (MINC) measurements from the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007)

    NASA Astrophysics Data System (ADS)

    Jones, H. M.; Flynn, M. J.; Demott, P. J.; Möhler, O.

    2011-01-01

    An ice nucleus counter was developed and constructed to enable investigation of potential ice nucleating materials. The Manchester Ice Nucleus Chamber (MINC) is a concentric-cylinder continuous flow diffusion chamber (CFDC). A full explanation of the MINC instrument is given here, along with first results and a comparison to an established instrument of similar design (Colorado State University CFDC) during sampling of common ice nucleating aerosols at the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007). MINC and CSU-CFDC detected the onset of ice nucleation under similar conditions of temperature and supersaturation for several different types of ice nuclei. Comparisons of the ratio of ice nuclei to total aerosol concentrations as a function of supersaturation with respect to water (SSw) showed agreement within one order of magnitude. Possible reasons for differences between the two instruments relating to differences in their design are discussed, along with suggestions to future improvements to the current design.

  10. Heterogeneous Nucleation of Naphthalene Vapor on Water Surface

    PubMed

    Smolík; Schwarz

    1997-01-15

    The evaporation of a water drop into a ternary gaseous mixture of air, steam, and naphthalene vapor was investigated. The experimental results were compared with a theoretical prediction based on a numerical solution of coupled boundary layer equations for heat and mass transfer from a drop moving in ternary gas. In the experiments the naphthalene vapor condensed on the water drop as a supercooled liquid even at temperatures far below the melting point of naphthalene. The condensation on drop surface is discussed in terms of classical theory of heterogeneous nucleation on smooth surfaces.

  11. Biological particles capable of triggering ice nucleation in the atmosphere

    NASA Astrophysics Data System (ADS)

    Felgitsch, Laura; Bichler, Magdalena; Vogel, André; Häusler, Thomas; Grothe, Hinrich

    2016-04-01

    Ice-nucleating particles (INPs) have a huge impact on atmospheric processes, since they can trigger ice cloud formation. In general, ice clouds interfere with the radiation balance of planet Earth effectively at high altitudes. Since ambient matter of biological origin tends to have rather large aerodynamic diameters, it exhibits a fast sinking velocity and can only reach limited altitudes. Therefore, research focused on materials found in higher quantities in the upper atmosphere. However, recent findings indicate that the role of biological INPs has been underestimated in the past. In 2012 Pummer and colleagues found that the INPs from birch pollen can be washed off and constitute of macromolecules in the size-range of a few nanometres. With such a small diameter, they show a much longer life span in the upper atmosphere than expected. Further, Huffman and colleagues showed in 2013 a burst of biological INPs over woodlands triggered by rain events, which matches the finding of Pummer et al. well. Plants originating from the northern timberline experience harsh conditions with night frost even during the warm seasons. To prevent frost damages, those plants developed coping mechanisms. Many plant species, which are domestic in cold weather zones, exhibit ice nucleation activity. Therefore, it is important to examine those plants to understand the scale at which biological INPs can be emitted. For the presented results we focus on two types of samples: Berries and tree pollen. Both belong to plants domestic at the northern timberline. With our results we are able to show that INPs are spread vastly throughout different species. Furthermore, all those INPs show certain similarities to each other, most importantly, all of the found INPs seem to be associated to macromolecules in the nano-particulate size range. We examined the INPs from birch pollen more closely. Results indicate that proteins play a major role. Pummer, B., Bauer, H., Bernardi, J., Bleicher, S

  12. Contribution of feldspar and marine organic aerosols to global ice nucleating particle concentrations

    SciTech Connect

    Vergara-Temprado, Jesús; Murray, Benjamin J.; Wilson, Theodore W.; O'Sullivan, Daniel; Browse, Jo; Pringle, Kirsty J.; Ardon-Dryer, Karin; Bertram, Allan K.; Burrows, Susannah M.; Ceburnis, Darius; DeMott, Paul J.; Mason, Ryan H.; O'Dowd, Colin D.; Rinaldi, Matteo; Carslaw, Ken S.

    2017-01-01

    Ice-nucleating particles (INPs) are known to affect the amount of ice in mixed-phase clouds, thereby influencing many of their properties. The atmospheric INP concentration changes by orders of magnitude from terrestrial to marine environments, which typically contain much lower concentrations. Many modelling studies use parameterizations for heterogeneous ice nucleation and cloud ice processes that do not account for this difference because they were developed based on INP measurements made predominantly in terrestrial environments without considering the aerosol composition. Errors in the assumed INP concentration will influence the simulated amount of ice in mixed-phase clouds, leading to errors in top-of-atmosphere radiative flux and ultimately the climate sensitivity of the model. Here we develop a global model of INP concentrations relevant for mixed-phase clouds based on laboratory and field measurements of ice nucleation by K-feldspar (an ice-active component of desert dust) and marine organic aerosols (from sea spray). The simulated global distribution of INP concentrations based on these two species agrees much better with currently available ambient measurements than when INP concentrations are assumed to depend only on temperature or particle size. Underestimation of INP concentrations in some terrestrial locations may be due to the neglect of INPs from other terrestrial sources. Our model indicates that, on a monthly average basis, desert dusts dominate the contribution to the INP population over much of the world, but marine organics become increasingly important over remote oceans and they dominate over the Southern Ocean. However, day-to-day variability is important. Because desert dust aerosol tends to be sporadic, marine organic aerosols dominate the INP population on many days per month over much of the mid- and high-latitude Northern Hemisphere. This study advances our understanding of which aerosol species need to be included in order to

  13. Contribution of feldspar and marine organic aerosols to global ice nucleating particle concentrations

    NASA Astrophysics Data System (ADS)

    Vergara-Temprado, Jesús; Murray, Benjamin J.; Wilson, Theodore W.; O'Sullivan, Daniel; Browse, Jo; Pringle, Kirsty J.; Ardon-Dryer, Karin; Bertram, Allan K.; Burrows, Susannah M.; Ceburnis, Darius; DeMott, Paul J.; Mason, Ryan H.; O'Dowd, Colin D.; Rinaldi, Matteo; Carslaw, Ken S.

    2017-03-01

    Ice-nucleating particles (INPs) are known to affect the amount of ice in mixed-phase clouds, thereby influencing many of their properties. The atmospheric INP concentration changes by orders of magnitude from terrestrial to marine environments, which typically contain much lower concentrations. Many modelling studies use parameterizations for heterogeneous ice nucleation and cloud ice processes that do not account for this difference because they were developed based on INP measurements made predominantly in terrestrial environments without considering the aerosol composition. Errors in the assumed INP concentration will influence the simulated amount of ice in mixed-phase clouds, leading to errors in top-of-atmosphere radiative flux and ultimately the climate sensitivity of the model. Here we develop a global model of INP concentrations relevant for mixed-phase clouds based on laboratory and field measurements of ice nucleation by K-feldspar (an ice-active component of desert dust) and marine organic aerosols (from sea spray). The simulated global distribution of INP concentrations based on these two species agrees much better with currently available ambient measurements than when INP concentrations are assumed to depend only on temperature or particle size. Underestimation of INP concentrations in some terrestrial locations may be due to the neglect of INPs from other terrestrial sources. Our model indicates that, on a monthly average basis, desert dusts dominate the contribution to the INP population over much of the world, but marine organics become increasingly important over remote oceans and they dominate over the Southern Ocean. However, day-to-day variability is important. Because desert dust aerosol tends to be sporadic, marine organic aerosols dominate the INP population on many days per month over much of the mid- and high-latitude Northern Hemisphere. This study advances our understanding of which aerosol species need to be included in order to

  14. Characterization of Ice Nucleating Particles at the Western US Coast

    NASA Astrophysics Data System (ADS)

    Rocci, K.; McCluskey, C. S.; Hill, T. C. J.; DeMott, P. J.; Kreidenweis, S. M.

    2015-12-01

    In temperate climates, ice nucleating particles (INPs) are vital for precipitation initiation. Because INPs may affect precipitation efficiency, and thereby the supply of water resources, it is paramount to have a clear understanding of both natural and anthropogenic sources of INPs. This is especially important to understand in California where drought continues to be a major problem. The CalWater 2015 field campaign, which took place in California from January 15 - March 9, 2015, included comprehensive characterizations of aerosols and their ice nucleating ability via ground-, air-, and ship-based measurements. As part of this campaign, we characterized and analyzed the intra-air mass differences of INPs at a coastal site (Bodega Bay) using immersion freezing measurements of particles collected on filters. Aerosol filters collected throughout the campaign were characterized by their loading and dominant type using meteorology, aerosol size distributions, aerosol composition, and trace gas concentration data. Samples contained a variety of aerosol influences, including biomass burning, nitrogen pollution, sulfur pollution, and sea spray. This study had a particular focus on the INP activity spectra of sea spray aerosol (SSA). We used the online aerosol data to infer variations in SSA types and heat-treated specific samples to look for the presence of heat-labile biological INPs. Furthermore, we ran the NOAA HYSPLIT model to obtain back trajectories for samples dominated by SSA. We found that air masses dominated by distinct terrestrial source types are not well distinguished by their INP number concentrations. However, we did see significantly higher (up to 5000-fold) INP number concentrations in SSA samples taken at the coast compared with number concentrations in samples obtained over open ocean. This difference could be attributable to differences in overall aerosol abundance, which will be evaluated in future studies. Overall, our findings suggest that an

  15. Sources of organic ice nucleating particles in soils

    NASA Astrophysics Data System (ADS)

    Hill, Tom C. J.; DeMott, Paul J.; Tobo, Yutaka; Fröhlich-Nowoisky, Janine; Moffett, Bruce F.; Franc, Gary D.; Kreidenweis, Sonia M.

    2016-06-01

    Soil organic matter (SOM) may be a significant source of atmospheric ice nucleating particles (INPs), especially of those active > -15 °C. However, due to both a lack of investigations and the complexity of the SOM itself, the identities of these INPs remain unknown. To more comprehensively characterize organic INPs we tested locally representative soils in Wyoming and Colorado for total organic INPs, INPs in the heat-labile fraction, ice nucleating (IN) bacteria, IN fungi, IN fulvic and humic acids, IN plant tissue, and ice nucleation by monolayers of aliphatic alcohols. All soils contained ≈ 106 to ≈ 5 × 107 INPs g-1 dry soil active at -10 °C. Removal of SOM with H2O2 removed ≥ 99 % of INPs active > -18 °C (the limit of testing), while heating of soil suspensions to 105 °C showed that labile INPs increasingly predominated > -12 °C and comprised ≥ 90 % of INPs active > -9 °C. Papain protease, which inactivates IN proteins produced by the fungus Mortierella alpina, common in the region's soils, lowered INPs active at ≥ -11 °C by ≥ 75 % in two arable soils and in sagebrush shrubland soil. By contrast, lysozyme, which digests bacterial cell walls, only reduced INPs active at ≥ -7.5 or ≥ -6 °C, depending on the soil. The known IN bacteria were not detected in any soil, using PCR for the ina gene that codes for the active protein. We directly isolated and photographed two INPs from soil, using repeated cycles of freeze testing and subdivision of droplets of dilute soil suspensions; they were complex and apparently organic entities. Ice nucleation activity was not affected by digestion of Proteinase K-susceptible proteins or the removal of entities composed of fulvic and humic acids, sterols, or aliphatic alcohol monolayers. Organic INPs active colder than -10 to -12 °C were resistant to all investigations other than heat, oxidation with H2O2, and, for some, digestion with papain. They may originate from decomposing plant material, microbial

  16. Controlled ice nucleation using freeze-dried Pseudomonas syringae encapsulated in alginate beads.

    PubMed

    Weng, Lindong; Tessier, Shannon N; Swei, Anisa; Stott, Shannon L; Toner, Mehmet

    2017-03-14

    The control of ice nucleation is of fundamental significance in many process technologies related to food and pharmaceutical science and cryobiology. Mechanical perturbation, electromagnetic fields and ice-nucleating agents (INAs) have been known to induce ice nucleation in a controlled manner. But these ice-nucleating methods may suffer from cumbersome manual operations, safety concerns of external fields, and biocompatibility and recovery issues of INA particles, especially when used in living systems. Given the automatic ice-seeding nature of INAs, a promising solution to overcome some of the above limitations is to engineer a biocomposite that accommodates the INA particles but minimizes their interactions with biologics, as well as enabling the recovery of used particles. In this study, freeze-dried Pseudomonas syringae, a model ice-nucleating agent, was encapsulated into microliter-sized alginate beads. We evaluated the performance of the bacterial hydrogel beads to initiate ice nucleation in water and aqueous glycerol solution by investigating factors including the size and number of the beads and the local concentration of INA particles. In the aqueous sample of a fixed volume, the total mass of the INA particles (m) was found to be the governing parameter that is solely responsible for determining the ice nucleation performance of the bacterial hydrogel beads. The freezing temperature has a strong positive linear correlation with log10m. The findings in this study provide an effective, predictable approach to control ice nucleation, which can improve the outcome and standardization of many ice-assisted process technologies.

  17. Biological Ice Nucleation Activity in Cloud Water (Invited)

    NASA Astrophysics Data System (ADS)

    Delort, A.

    2013-12-01

    Ice nucleation active (INA) biological particles, in particular microorganisms, were studied in cloud water. Twelve cloud samples were collected over a period of 16 months from the puy de Dôme summit (1465 m, France) using sterile cloud droplet impactors. The samples were characterized through biological (cultures, cell counts) and physico-chemical measurements (pH, ion concentrations, carbon content...), and biological ice nuclei were investigated by droplet-freezing assays from -3°C to -13°C. The concentration of total INA particles within this temperature range typically varied from ~1 to ~100 per mL of cloud water; the concentrations of biological IN were several orders of magnitude higher than the values previously reported for precipitations. At -12°C, at least 76% of the IN were biological in origin, i.e. they were inactivated by heating at 95°C, and at temperatures above -8°C only biological material could induce ice. By culture, 44 Pseudomonas-like strains of bacteria were isolated from cloud water samples; 16% of them were found INA at the temperature of -8°C and they were identified as Pseudomonas syringae, Xanthomonas sp. and Pseudoxanthomonas sp.. Two strains induced freezing at as warm as -2°C, positioning them among the most active ice nucleators described so far. We estimated that, in average, 0.18% and more than 1%.of the bacterial cells present in clouds (~104 mL-1) are INA at the temperatures of -8°C and -12°C, respectively.

  18. Studies of Ice Nucleating Aerosol Particles in Arctic Cloud Systems

    NASA Technical Reports Server (NTRS)

    Rogers, David C.; DeMott, Paul J.; Kreidenweis, Sonia M.

    2001-01-01

    The focus of this research is to improve the understanding of ice nucleating aerosol particles (IN) and the role they play in ice formation in Arctic clouds. IN are important for global climate issues in a variety of ways. The primary effect is their role in determining the phase (liquid or solid) of cloud particles. The microscale impact is on cloud particle size, growth rate, shape, fall speed, concentration, radiative properties, and scavenging of gases and aerosols. On a larger scale, ice formation affects the development of precipitation (rate, amount, type, and distribution), latent heat release (rate and altitude), ambient humidity, the persistence of clouds, and cloud albedo. The overall goals of our FIRE 3 research are to characterize the concentrations and variability of Arctic IN during the winter-spring transition, to compare IN measurements with ice concentrations in Arctic clouds, and to examine selected IN samples for particle morphology and chemical there are distinguishable chemical signatures. The results can be combined with other measurements of aerosols, gaseous species, and cloud characteristics in order to understand the processes that determine the phase and concentration of cloud particles.

  19. Ice nucleation active particles are efficiently removed by precipitating clouds

    PubMed Central

    Stopelli, Emiliano; Conen, Franz; Morris, Cindy E.; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine

    2015-01-01

    Ice nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of ice nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ18O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs active at temperatures ≥ −10 °C (INPs−10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs active at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space. PMID:26553559

  20. Ice nucleation active particles are efficiently removed by precipitating clouds.

    PubMed

    Stopelli, Emiliano; Conen, Franz; Morris, Cindy E; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine

    2015-11-10

    Ice nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of ice nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ(18)O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs active at temperatures ≥ -10 °C (INPs-10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs active at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space.

  1. Potential Sites for Ice Nucleation on Aluminosilicate Clay Minerals and Related Materials.

    PubMed

    Freedman, Miriam Arak

    2015-10-01

    Few aerosol particles in clouds nucleate the formation of ice. The surface sites available for nucleus formation, which can include surface defects and functional groups, determine in part the activity of an aerosol particle toward ice formation. Although ice nucleation on particles has been widely studied, exploration of the specific sites at which the initial germ forms has been limited, but is important for predicting the microphysical properties of clouds, which impact climate. This Perspective focuses on what is currently known about surface sites for ice nucleation on aluminosilicate clay minerals, which are commonly found in ice residuals, as well as related materials.

  2. Surface design for controlled crystallization: the role of surface chemistry and nanoscale pores in heterogeneous nucleation.

    PubMed

    Diao, Ying; Myerson, Allan S; Hatton, T Alan; Trout, Bernhardt L

    2011-05-03

    Current industrial practice for control of primary nucleation (nucleation from a system without pre-existing crystalline matter) during crystallization from solution involves control of supersaturation generation, impurity levels, and solvent composition. Nucleation behavior remains largely unpredictable, however, due to the presence of container surfaces, dust, dirt, and other impurities that can provide heterogeneous nucleation sites, thus making the control and scale-up of processes that depend on primary nucleation difficult. To develop a basis for the rational design of surfaces to control nucleation during crystallization from solution, we studied the role of surface chemistry and morphology of various polymeric substrates on heterogeneous nucleation using aspirin as a model compound. Nucleation induction time statistics were utilized to investigate and quantify systematically the effectiveness of polymer substrates in inducing nucleation. The nucleation induction time study revealed that poly(4-acryloylmorpholine) and poly(2-carboxyethyl acrylate), each cross-linked by divinylbenzene, significantly lowered the nucleation induction time of aspirin while the other polymers were essentially inactive. In addition, we found the presence of nanoscopic pores on certain polymer surfaces led to order-of-magnitude faster aspirin nucleation rates when compared with surfaces without pores. We studied the preferred orientation of aspirin crystals on polymer films and found the nucleation-active polymer surfaces preferentially nucleated the polar facets of aspirin, guided by hydrogen bonds. A model based on interfacial free energies was also developed which predicted the same trend of polymer surface nucleation activities as indicated by the nucleation induction times.

  3. Cloud condensation nuclei and ice nucleation activity of hydrophobic and hydrophilic soot particles.

    PubMed

    Koehler, Kirsten A; DeMott, Paul J; Kreidenweis, Sonia M; Popovicheva, Olga B; Petters, Markus D; Carrico, Christian M; Kireeva, Elena D; Khokhlova, Tatiana D; Shonija, Natalia K

    2009-09-28

    Cloud condensation nuclei (CCN) activity and ice nucleation behavior (for temperaturesheterogeneity in our experiments, which showed evidence of two or more particle sub-types even within a narrow size cut. The heterogeneity could have resulted from both chemical and sizing differences, the latter attributable in part to particle non-sphericity. Neither GTS nor TS, hydrophobic particles distinguished only by the lower porosity and polarity of the GTS surface, showed CCN activity at or below water supersaturations required for wettable, insoluble particles (the Kelvin limit). TC1 soot particles, despite classification as hydrophilic, did not show CCN activity at or below the Kelvin limit. We attribute this result to the microporosity of this soot. In contrast, oxidized, non-porous, and hydrophilic TOS particles exhibited CCN activation at very near the Kelvin limit, with a small percentage of these particles CCN-active even at lower supersaturations. Due to containing a range of surface coverage of organic and inorganic hydrophilic and hygroscopic compounds, up to approximately 35% of hygroscopic AEC particles were active as CCN, with a small percentage of these particles CCN-active at lower supersaturations. In ice nucleation experiments below -40 degrees C, AEC particles nucleated ice near the expected condition for homogeneous freezing of water from aqueous solutions. In

  4. Unprecedented Evidence for Large Scale Heterogeneous Nucleation of Polar Stratospheric Clouds, Likely by Nanometer-Sized Meteoritic Particles

    NASA Astrophysics Data System (ADS)

    Engel, I.; Pitts, M. C.; Luo, B.; Hoyle, C. R.; Zobrist, B.; Jacot, L.; Poole, L. R.; Grooss, J.; Weigel, R.; Borrmann, S.; Ebert, M.; Duprat, J.; Peter, T.

    2012-12-01

    Recent observations cast serious doubts on our understanding of the processes responsible for polar stratospheric cloud (PSC) formation. PSCs play crucial roles in polar ozone chemistry by hosting heterogeneous reactions and by removal of reactive nitrogen through sedimenting nitric acid trihydrate (NAT) particles. An extensive field campaign took place in the Arctic during the winter 2009/2010 within the European Union project RECONCILE, complemented by measurements from the spaceborne CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) instrument. Through trajectory and microphysical box model calculations, we analyzed CALIOP data from the RECONCILE winter to investigate the nucleation of PSC particles in detail. One significant finding was that liquid/NAT mixture PSCs were prevalent in late December 2009, a period during which no ice PSCs were observed, and temperatures were higher by 6 K than required for homogeneous ice freezing at the onset of PSC formation. These NAT particles must have formed through some non-ice nucleation mechanism, which runs counter to the widely held view that the only efficient NAT nuclei were ice crystals formed by homogeneous freezing of STS droplets. Furthermore, in mid-January 2010, a large region of the Arctic vortex cooled below the frost point, leading to widespread synoptic-scale ice PSCs, unusual for the Arctic. Our modeling studies indicate that a match with the CALIOP data calls for new heterogeneous nucleation mechanisms for both NAT and ice particles, namely freezing on nanometer-sized, solid nuclei immersed in the liquid stratospheric aerosols. Number concentrations of non-volatile particles were measured in situ during RECONCILE by means of the heated channel of the condensation nuclei (CN) counter COPAS on board of the high-flying aircraft Geophysica. 60-80 % of all CN survived heating to 250 °C. Offline Environmental Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis of RECONCILE impactor samples

  5. New species of ice nucleating fungi in soil and air

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, Janine; Hill, Thomas C. J.; Pummer, Bernhard G.; Franc, Gray D.; Pöschl, Ulrich

    2014-05-01

    Primary biological aerosol particles (PBAP) are ubiquitous in the atmosphere (1,2). Several types of PBAP have been identified as ice nuclei (IN) that can initiate the formation of ice at relatively high temperatures (3, 4). The best-known biological IN are common plant-associated bacteria. The IN activity of these bacteria is due to a surface protein on the outer cell membrane that catalyses ice formation, for which the corresponding gene has been identified and detected by DNA analysis (3). Fungal spores or hyphae can also act as IN, but the biological structures responsible for their IN activity have not yet been elucidated. Furthermore, the abundance, diversity, sources, seasonality, properties, and effects of fungal IN in the atmosphere have neither been characterized nor quantified. Recent studies have shown that airborne fungi are highly diverse (1), and that atmospheric transport leads to efficient exchange of species among different ecosystems (5, 6). The results presented in Fröhlich-Nowoisky et al. 2012 (7) clearly demonstrate the presence of geographic boundaries in the global distribution of microbial taxa in air, and indicate that regional differences may be important for the effects of microorganisms on climate and public health. DNA analyses of aerosol samples collected during rain events showed higher diversity and frequency of occurrence for fungi belonging to the Sordariomycetes, than samples that were collected under dry conditions (8). Sordariomycetes is the class that comprises known ice nucleation active species (Fusarium spp.). By determination of freezing ability of fungal colonies isolated from air samples two species of ice nucleation active fungi that were not previously known as biological ice nucleators were found. By DNA-analysis they were identified as Isaria farinosa and Acremonium implicatum. Both fungi belong to the phylum Ascomycota, produce fluorescent spores in the range of 1-4 µm in diameter, and induced freezing at -4 and

  6. Dynamic Recrystallization in Ice : In-Situ Observation of the Strain Field during Grain Nucleation.

    NASA Astrophysics Data System (ADS)

    Chauve, T.; Montagnat, M.; Tommasi, A.; Vacher, P.

    2014-12-01

    Dynamic recrystallization (DRX) occurs in minerals, metals, ice and impact on large scale mechanisms as seismic anisotropy, mechanical properties inside the Earth mantle, material forming and anisotropic flow in polar ice sheet, for instance. In this frame, ice can be considered as a model material due to a strong viscoplastic anisotropy and deformation heterogeneities, which are precursors of the recrystallization. During creep deformation at high temperature, DRX occurs from 1% strain and involves grain nucleation and grain boundary migration. As DRX induces an evolution of microstructure and texture, it strongly affects the mechanical behavior, and it is expected to modify the strain field at the grain and/or the sample scale. Creep test (σ=0.5-0.8 MPa) were performed at high temperature (T/Tf 0,98) on granular polycrystalline ice (grains size 1mm) and columnar polycrystalline ice (microstructure 2D 1/2 in plane grain size 10mm) up to 18 % strain. Columnar ice provides interesting feature as it contains only one grain through the thickness and the columns are parallel. Post-deformation texture analysis with an Automatic Ice Texture Analyzer (AITA) and with EBSD (Geoscience Montpellier) were used to investigate DRX impact on texture and microstructure, at different scales. With increasing strain texture evolves to a strong concentrated girdle with a preferential orientation of c-axis close to 35° from the compression axis. During the experiment, local strain field is measured on the surface of the sample by Digital Image Correlation (DIC) with a spatial resolution between 0.2 and 0.5 mm, and a strain resolution between 0.2% to 1%. Grain size being large, we obtain a relatively good intra-granular resolution of the strain field. Thanks to the 2D configuration of the columnar ice samples, we can superimpose the strain field measured by DIC. We will present an overview of the impact of DRX on the texture and microstructure, from the 3D configuration down to a

  7. Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model

    DOE PAGES

    Alpert, Peter A.; Knopf, Daniel A.

    2016-02-24

    Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature, T, and relative humidity, RH, at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling-rate-dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nucleating particles (INPs) all have the same INP surface area (ISA); however, the validity of this assumption or the impact it may have on analysis and interpretation of the experimentalmore » data is rarely questioned. Descriptions of ice active sites and variability of contact angles have been successfully formulated to describe ice nucleation experimental data in previous research; however, we consider the ability of a stochastic freezing model founded on classical nucleation theory to reproduce previous results and to explain experimental uncertainties and data scatter. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses parameters including the total number of droplets, Ntot, and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA-dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically

  8. Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model

    NASA Astrophysics Data System (ADS)

    Alpert, Peter A.; Knopf, Daniel A.

    2016-02-01

    Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature, T, and relative humidity, RH, at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling-rate-dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nucleating particles (INPs) all have the same INP surface area (ISA); however, the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. Descriptions of ice active sites and variability of contact angles have been successfully formulated to describe ice nucleation experimental data in previous research; however, we consider the ability of a stochastic freezing model founded on classical nucleation theory to reproduce previous results and to explain experimental uncertainties and data scatter. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses parameters including the total number of droplets, Ntot, and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA-dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets

  9. Dynamic Nucleation of Ice Induced by a Single Stable Cavitation Bubble

    NASA Technical Reports Server (NTRS)

    Ohsaka, Kenichi; Trinh, Eugene H.

    1997-01-01

    Dynamic nucleation of ice induced by caviation bubble in undercooled water is observed using an acoustic levitation technique. The observation indicates that a high pressure pulse associated with a collapsing bubble is indeed responsible for the nucleation of a high pressure phase of ice.

  10. Observations of Ice Nucleation and Propagation in Plants Using Infrared Video Thermography.

    PubMed Central

    Wisniewski, M.; Lindow, S. E.; Ashworth, E. N.

    1997-01-01

    We evaluated the use of infrared (IR) video thermography to observe directly ice nucleation and propagation in plants. An imaging radiometer with an HgCdTe long-wave (8-12 [mu]m) detector was utilized to image the thermal response of plants during freezing. IR images were analyzed in real time and recorded on videotape. Information on the videotape was subsequently accessed and analyzed utilizing IR image analysis software. Freezing of water droplets as small as 0.5 [mu]L was clearly detectable with the radiometer. Additionally, a comparison of temperature tracking data collected by the radiometer with data collected with thermocouples showed close correspondence. Monitoring of an array of plant species under different freezing conditions revealed that ice nucleation and propagation are readily observable by thermal imaging. In many instances, the ice nucleation-active bacterium Pseudomonas syringae placed on test plants could be seen to initiate freezing of the whole plant. Apparent ice nucleation by intrinsic nucleators, despite the presence of ice nucleation-active bacteria, was also evident in some species. Floral bud tissues of peach (Prunus persica) could be seen to supercool below the temperature of stem tissues, and ice nucleation at the site of insertion of the thermocouple was frequently observed. Rates of propagation of ice in different tissues were also easily measured by thermal imaging. This study demonstrates that IR thermography is an excellent method for studying ice nucleation and propagation in plants. PMID:12223611

  11. Dynamic Nucleation of Ice Induced by a Single Stable Cavitation Bubble

    NASA Technical Reports Server (NTRS)

    Ohsaka, Kenichi; Trinh, Eugene H.

    1997-01-01

    Dynamic nucleation of ice induced by caviation bubble in undercooled water is observed using an acoustic levitation technique. The observation indicates that a high pressure pulse associated with a collapsing bubble is indeed responsible for the nucleation of a high pressure phase of ice.

  12. Note: Homogeneous TIP4P/2005 ice nucleation at low supercooling.

    PubMed

    Reinhardt, Aleks; Doye, Jonathan P K

    2013-09-07

    We present a partial free energy profile for the homogeneous nucleation of ice using an all-atom model of water at low supercooling, at which ice growth dynamics are reasonably accessible to simulation. We demonstrate that the free energy profile is well described by classical nucleation theory, and that the nucleation barrier is entropic in origin. We also estimate to first order the temperature dependence of the interfacial free energy.

  13. Note: Homogeneous TIP4P/2005 ice nucleation at low supercooling

    NASA Astrophysics Data System (ADS)

    Reinhardt, Aleks; Doye, Jonathan P. K.

    2013-09-01

    We present a partial free energy profile for the homogeneous nucleation of ice using an all-atom model of water at low supercooling, at which ice growth dynamics are reasonably accessible to simulation. We demonstrate that the free energy profile is well described by classical nucleation theory, and that the nucleation barrier is entropic in origin. We also estimate to first order the temperature dependence of the interfacial free energy.

  14. Interfacial Free Energy as the Key to the Pressure-Induced Deceleration of Ice Nucleation

    NASA Astrophysics Data System (ADS)

    Espinosa, Jorge R.; Zaragoza, Alberto; Rosales-Pelaez, Pablo; Navarro, Caridad; Valeriani, Chantal; Vega, Carlos; Sanz, Eduardo

    2016-09-01

    The avoidance of water freezing is the holy grail in the cryopreservation of biological samples, food, and organs. Fast cooling rates are used to beat ice nucleation and avoid cell damage. This strategy can be enhanced by applying high pressures to decrease the nucleation rate, but the physics behind this procedure has not been fully understood yet. We perform computer experiments to investigate ice nucleation at high pressures consisting in embedding ice seeds in supercooled water. We find that the slowing down of the nucleation rate is mainly due to an increase of the ice I -water interfacial free energy with pressure. Our work also clarifies the molecular mechanism of ice nucleation for a wide pressure range. This study is not only relevant to cryopreservation, but also to water amorphization and climate change modeling.

  15. Properties of a novel extracellular cell-free ice nuclei from ice-nucleating Pseudomonas antarctica IN-74.

    PubMed

    Muryoi, Naomi; Kawahara, Hidehisa; Obata, Hitoshi

    2003-09-01

    Some ice-nucleating bacterial strains, including Pantoea ananatis (Erwinia uredovora), Pseudomonas fluorescens, and Pseudomonas syringae isolates, were examined for the ability to shed ice nuclei into the growth medium. A novel ice-nucleating bacterium, Pseudomonas antarctica IN-74, was isolated from Ross Island, Antarctica. Cell-free ice nuclei from P. antarctica IN-74 were different from the conventional cell-free ice nuclei and showed a unique characterization. Cell-free ice nuclei were purified by centrifugation, filtration (0.45 microm), ultrafiltration, and gel filtration. In an ice-nucleating medium in 1 liter of cell culture, maximum growth was obtained with the production of 1.9 mg of cell-free ice nuclei. Ice nucleation activity in these cell-free ice nuclei preparations was extremely sensitive to pH. It was demonstrated that the components of cell-free ice nuclei were protein (33%), saccharide (12%), and lipid (55%), indicating that cell-free ice nuclei were lipoglycoproteins. Also, carbohydrate and lipid stains showed that cell-free ice nuclei contained both carbohydrate and lipid moieties.

  16. Ice nucleation activity of diesel soot particles at cirrus relevant temperature conditions: Effects of hydration, secondary organics coating, soot morphology, and coagulation

    NASA Astrophysics Data System (ADS)

    Kulkarni, Gourihar; China, Swarup; Liu, Shang; Nandasiri, Manjula; Sharma, Noopur; Wilson, Jacqueline; Aiken, Allison C.; Chand, Duli; Laskin, Alexander; Mazzoleni, Claudio; Pekour, Mikhail; Shilling, John; Shutthanandan, Vaithiyalingam; Zelenyuk, Alla; Zaveri, Rahul A.

    2016-04-01

    Ice formation by diesel soot particles was investigated at temperatures ranging from -40 to -50°C. Size-selected soot particles were physically and chemically aged in an environmental chamber, and their ice nucleating properties were determined using a continuous flow diffusion type ice nucleation chamber. Bare (freshly formed), hydrated, and compacted soot particles, as well as α-pinene secondary organic aerosol (SOA)-coated soot particles at high relative humidity conditions, showed ice formation activity at subsaturation conditions with respect to water but below the homogeneous freezing threshold conditions. However, SOA-coated soot particles at dry conditions were observed to freeze at homogeneous freezing threshold conditions. Overall, our results suggest that heterogeneous ice nucleation activity of freshly emitted diesel soot particles are sensitive to some of the aging processes that soot can undergo in the atmosphere.

  17. Aerosol Effects on Cirrus through Ice Nucleation in the Community Atmosphere Model CAM5 with a Statistical Cirrus Scheme

    SciTech Connect

    Wang, Minghuai; Liu, Xiaohong; Zhang, Kai; Comstock, Jennifer M.

    2014-09-01

    A statistical cirrus cloud scheme that tracks ice saturation ratio in the clear-sky and cloudy portion of a grid box separately has been implemented into NCAR CAM5 to provide a consistent treatment of ice nucleation and cloud formation. Simulated ice supersaturation and ice crystal number concentrations strongly depend on the number concentrations of heterogeneous ice nuclei (IN), subgrid temperature formulas and the number concentration of sulfate particles participating in homogeneous freezing, while simulated ice water content is insensitive to these perturbations. 1% to 10% dust particles serving as heterogeneous IN is 20 found to produce ice supersaturaiton in better agreement with observations. Introducing a subgrid temperature perturbation based on long-term aircraft observations of meso-scale motion produces a better hemispheric contrast in ice supersaturation compared to observations. Heterogeneous IN from dust particles significantly alter the net radiative fluxes at the top of atmosphere (TOA) (-0.24 to -1.59 W m-2) with a significant clear-sky longwave component (0.01 to -0.55 W m-2). Different cirrus treatments significantly perturb the net TOA anthropogenic aerosol forcing from -1.21 W m-2 to -1.54 W m-2, with a standard deviation of 0.10 W m-2. Aerosol effects on cirrus clouds exert an even larger impact on the atmospheric component of the radiative fluxes (two or three times the changes in the TOA radiative fluxes) and therefore on the hydrology cycle through the fast atmosphere response. This points to the urgent need to quantify aerosol effects on cirrus clouds through ice nucleation and how these further affect the hydrological cycle.

  18. Anti-ice nucleating activity of polyphenol compounds against silver iodide.

    PubMed

    Koyama, Toshie; Inada, Takaaki; Kuwabara, Chikako; Arakawa, Keita; Fujikawa, Seizo

    2014-10-01

    Freeze-avoiding organisms survive sub-zero temperatures without freezing in several ways, such as removal of ice nucleating agents (INAs), production of polyols, and dehydration. Another way is production of anti-ice nucleating agents (anti-INAs), such as has been reported for several antifreeze proteins (AFPs) and polyphenols, that inhibit ice nucleation by inactivating INAs. In this study, the anti-ice nucleating activity of five polyphenol compounds, including flavonoid and tannin compounds of both biological and synthetic origin, against silver iodide (AgI) was examined by measuring the ice nucleation temperature in emulsified polyphenol solutions containing AgI particles. The emulsified solutions eliminated the influence of contamination by unidentified INAs, thus enabling examination of the anti-ice nucleating activity of the polyphenols against AgI alone. Results showed that all five polyphenol compounds used here have anti-ice nucleating activities that are unique compared with other known anti-INAs, such as fish AFPs (type I and III) and synthetic polymers (poly(vinyl alcohol), poly(vinylpyrrolidone) and poly(ethylene glycol)). All five polyphenols completely inactivated the ice nucleating activity of AgI even at relatively low temperatures, and the first ice nucleation event was observed at temperatures between -14.1 and -19.4°C, compared with between -8.6 and -11.8°C for the fish AFPs and three synthetic polymers. These anti-ice nucleating activities of the polyphenols at such low temperatures are promising properties for practical applications where freezing should be prevented. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Microbial ice nucleators scavenged from the atmosphere during simulated rain events

    NASA Astrophysics Data System (ADS)

    Hanlon, Regina; Powers, Craig; Failor, Kevin; Monteil, Caroline L.; Vinatzer, Boris A.; Schmale, David G.

    2017-08-01

    Rain and snow collected at ground level have been found to contain biological ice nucleators. These ice nucleators have been proposed to have originated in clouds, where they may have participated in the formation of precipitation via ice phase nucleation. We conducted a series of field experiments to test the hypothesis that at least some of the microbial ice nucleators (prokaryotes and eukaryotes) present in rain may not originate in clouds but instead be scavenged from the lower atmosphere by rainfall. Thirty-three simulated rain events were conducted over four months off the side of the Smart Road Bridge in Blacksburg, VA, USA. In each event, sterile water was dispensed over the side of the bridge and recovered in sterile containers in an open fallow agricultural field below (a distance of ∼55 m). Microbes scavenged from the simulated rain events were cultured and their ice nucleation activity was examined. Putative microbial ice nucleators were cultured from 94% (31/33) of the simulated rain events, and represented 1.5% (121/8331) of the total colonies assayed. Putative ice nucleators were subjected to additional droplet freezing assays, and those confirmed through these repeated assays represented 0.4% (34/8331) of the total. Mean CFUs scavenged by simulated rain ranged from 2 to 267 CFUs/mL. Scavenged ice nucleators belong to a number of taxa including the bacterial genera Pseudomonas, Pantoea, and Xanthomonas, and the fungal genera Fusarium, Humicola, and Mortierella. An ice-nucleating strain of the fungal genus Penicillium was also recovered from a volumetric air sampler at the study site. This work expands our knowledge of the scavenging properties of rainfall, and suggests that at least some ice nucleators in natural precipitation events may have been scrubbed from the atmosphere during rainfall, and thus are not likely to be involved in precipitation.

  20. Technical Note: A proposal for ice nucleation terminology

    NASA Astrophysics Data System (ADS)

    Vali, G.; DeMott, P. J.; Möhler, O.; Whale, T. F.

    2015-09-01

    Terminology dealing with ice nucleation in the atmosphere, in biological systems, and in other areas has not kept pace with the growth of empirical evidence and the development of new ideas over recent decades. Ambiguities and misinterpretations could be seen in the literature. This paper offers a set of definitions for various terms in common use, adds some qualifications, and introduces some new ones. Input has been received on the interpretation of various terms from a fair number of researchers; diverse views have been accommodated with some success. It is anticipated that the terminology proposed here will be helpful both to those who adopt it and to those who wish to explain a different perspective.

  1. Application of Ice Nucleation - Active Bacteria to Food

    NASA Astrophysics Data System (ADS)

    Arai, Soichi; Watanabe, Michiko

    Ice nucleation-active bacteria act as nuclei and are able to freeze water without supercooling to a great degree. They are known as a major cause of the frost damage to crops. We have been trying with success to positively apply these bacteria to freeze texturing of food materials, freeze concentration of fresh liquid foods, formation of new physical properties of foods by freezing, and so forth. The most useful species for these applications is Xanthomonas campestris which has recently been designated as a food additive by the Japan Ministry of Health and Welfare and produced on an industrial scale. This paper reviews these topics, with some practical examples quoted primarily from our studies.

  2. Significant alterations in anisotropic ice growth rate induced by the ice nucleation-active bacteria Xanthomonas campestris

    NASA Astrophysics Data System (ADS)

    Nada, Hiroki; Zepeda, Salvador; Miura, Hitoshi; Furukawa, Yoshinori

    2010-09-01

    In the present study, we found that the ice nucleation-active bacteria Xanthomonas campestris significantly altered anisotropic ice growth rate. Results of ice growth experiments in the presence of X. campestris showed that this bacterium decreased the ice crystal growth rate in the c-axis, whereas it increased growth rates in directions normal to the c-axis. These results indicate that these alterations in anisotropic growth rate are the result of selective binding of bacterial ice-nucleating proteins along the {0 0 0 1} basal plane.

  3. Laboratory investigations of mixed organic/inorganic particles: Ice nucleation and optical hygroscopic growth

    NASA Astrophysics Data System (ADS)

    Beaver, Melinda R.

    The interactions of ambient aerosol particles with the atmosphere influence global climate and local visibility. Many of these atmospheric interactions are determined by the chemical composition of the aerosol particles. Ice nucleation in the upper troposphere is influenced and modified by the presence of anthropogenic aerosol particles. Also, interactions between particles and solar radiation are influenced by hygroscopic growth upon humidification. This thesis contains laboratory investigations into the role organic compounds play in ice nucleation and optical hygroscopic growth. Using an aerosol flow tube apparatus, we have studied the effects of aliphatic aldehydes (C3 to C10) and ketones (C 3 and C9) on ice nucleation in sulfuric acid aerosols. No acid-catalyzed reactions were observed under these conditions, and physical uptake was responsible for the organic content of the sulfuric acid aerosols. The physical properties of the organic compounds (primarily the solubility and melting point) were found to play a dominant role in determining the inferred mode of nucleation (homogenous or heterogeneous) and the specific freezing temperatures observed. Overall, very soluble, low-melting organics, such as acetone and propanal, caused a decrease in aerosol ice nucleation temperatures when compared with aqueous sulfuric acid aerosol. In contrast, sulfuric acid particles exposed to organic compounds of eight carbons and greater, of much lower solubility and higher melting temperatures, nucleate ice at temperatures above aqueous sulfuric acid aerosols. Organic compounds of intermediate carbon chain length, C4-C7, (of intermediate solubility and melting temperatures) nucleated ice at the same temperature as aqueous sulfuric acid aerosols. Light extinction by atmospheric particles is strongly dependent on the size, chemical composition, and water content of the aerosol. Since light extinction by particles directly impacts climate and visibility, measurements of

  4. Microphysical Consequences of the Spatial Distribution of Ice Nucleation in Mixed-Phase Stratiform Clouds

    SciTech Connect

    Yang, Fan; Ovchinnikov, Mikhail; Shaw, Raymond A.

    2014-07-28

    Mixed-phase stratiform clouds can persist even with steady ice precipitation fluxes, and the origin and microphysical properties of the ice crystals are of interest. Vapor deposition growth and sedimentation of ice particles along with a uniform volume source of ice nucleation, leads to a power law relation between ice water content wi and ice number concentration ni with exponent 2.5. The result is independent of assumptions about the vertical velocity structure of the cloud and is therefore more general than the related expression of Yang et al. [2013]. The sensitivity of the wi-ni relationship to the spatial distribution of ice nucleation is confirmed by Lagrangian tracking and ice growth with cloud-volume, cloud-top, and cloud-base sources of ice particles through a time-dependent cloud field. Based on observed wi and ni from ISDAC, a lower bound of 0.006 m^3/s is obtained for the ice crystal formation rate.

  5. The influence of organic-containing soil dust on ice nucleation and cloud properties

    NASA Astrophysics Data System (ADS)

    Hummel, Matthias; Grini, Alf; Berntsen, Terje K.; Ekman, Annica

    2017-04-01

    Natural mineral dust from desert regions is known to be the most important contributor to atmospheric ice-nucleating particles (INP) which induce heterogeneous ice nucleation in mixed-phase clouds. Its ability to nucleate ice effectively is shown by various laboratory (Hoose and Möhler 2012) and field results (DeMott et al. 2015) and its abundance in ice crystal residuals has also been shown (Cziczo et al. 2013). Thus it is an important player when representing mixed-phase clouds in climate models. MODIS satellite data indicate that 1 /4 of the global dust emission originates from semi-arid areas rather than from arid deserts (Ginoux et al. 2012). Here, organic components can mix with minerals within the soil and get into the atmosphere. These so-called 'soil dust' particles are ice-nucleating active at high sub-zero temperatures, i.e. at higher temperatures than pure desert dust (Steinke et al. 2016). In this study, soil dust is incorporated into the Norwegian Earth System Model (NorESM, Bentsen et al. 2013) and applied to a modified ice nucleation parameterization (Steinke et al. 2016). Its influence on the cloud ice phase is evaluated by comparing a control run, where only pure desert dust is considered, and a sensitivity experiment, where a fraction of the dust emissions are classified as soil dust. Both simulations are nudged to ERA-interim meteorology and they have the same loading of dust emissions. NorESM gives a lower annual soil dust emission flux compared to Ginoux et al. (2012), but the desert dust flux is similar to the MODIS-retrieved data. Although soil dust concentrations are much lower than desert dust, the NorESM simulations indicate that the annual INP concentrations from soil dust are on average lower by a just a factor of 4 than INP concentrations from pure desert dust. The highest soil dust INP concentrations occur at a lower height than for desert dust, i.e at warmer temperatures inside mixed-phase clouds. Furthermore, soil dust INP

  6. Ice nucleation efficiency of AgI: review and new insights

    NASA Astrophysics Data System (ADS)

    Marcolli, Claudia; Nagare, Baban; Welti, André; Lohmann, Ulrike

    2016-07-01

    AgI is one of the best-investigated ice-nucleating substances. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Theoretical and experimental studies over the last 60 years provide a complex picture of silver iodide as an ice-nucleating agent with conflicting and inconsistent results. This review compares experimental ice nucleation studies in order to analyze the factors that influence the ice nucleation ability of AgI. The following picture emerges from this analysis: the ice nucleation ability of AgI seems to be enhanced when the AgI particle is on the surface of a droplet, which is indeed the position that a particle takes when it can freely move in a droplet. The ice nucleation by particles with surfaces exposed to air depends on water adsorption. AgI surfaces seem to be most efficient at nucleating ice when they are exposed to relative humidity at or even above water saturation. For AgI particles that are completely immersed in water, the freezing temperature increases with increasing AgI surface area. Higher threshold freezing temperatures seem to correlate with improved lattice matches as can be seen for AgI-AgCl solid solutions and 3AgI·NH4I·6H2O, which have slightly better lattice matches with ice than AgI and also higher threshold freezing temperatures. However, the effect of a good lattice match is annihilated when the surfaces have charges. Also, the ice nucleation ability seems to decrease during dissolution of AgI particles. This introduces an additional history and time dependence for ice nucleation in cloud chambers with short residence times.

  7. Ice Nucleating Particles around the world - a global review

    NASA Astrophysics Data System (ADS)

    Kanji, Zamin A.; Atkinson, James; Sierau, Berko; Lohmann, Ulrike

    2017-04-01

    In the atmosphere the formation of new ice particles at temperatures above -36 °C is due to a subset of aerosol called Ice Nucleating Particles (INP). However, the spatial and temporal evolution of such particles is poorly understood. Current modelling of INP is attempting to estimate the sources and transport of INP, but is hampered by the availability and convenience of INP observations. As part of the EU FP7 project impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding (BACCHUS), historical and contemporary observations of INP have been collated into a database (http://www.bacchus-env.eu/in/) and are reviewed here. Outside of Europe and North America the coverage of measurements is sparse, especially for modern day climate - in many areas the only measurements available are from the mid-20th century. As well as an overview of all the data in the database, correlations with several accompanying variables are presented. For example, immersion freezing INP seem to be negatively correlated with altitude, whereas CFDC based condensation freezing INP show no height correlation. An initial global parameterisation of INP concentrations taking into account freezing temperature and relative humidity for use in modelling is provided.

  8. Ice nucleating particle concentration during a combustion aerosol event

    NASA Astrophysics Data System (ADS)

    Adams, Mike; O'Sullivan, Daniel; Porter, Grace; Sanchez-Marroquin, Alberto; Tarn, Mark; Harrison, Alex; McQuaid, Jim; Murray, Benjamin

    2017-04-01

    The formation of ice in supercooled clouds is important for cloud radiative properties, their lifetime and the formation of precipitation. Cloud water droplets can supercool to below -33oC, but in the presence of Ice Nucleating Particles (INPs) freezing can be initiated at much higher temperatures. The concentration of atmospheric aerosols that are active as INPs depends on a number of factors, such as temperature and aerosol composition and concentration. However, our knowledge of which aerosol types serve as INPs is limited. For example, there has been much discussion over whether aerosol from combustion processes are important as INP. This is significant because combustion aerosol have increased in concentration dramatically since pre-industrial times and therefore have the potential to exert a significant anthropogenic impact on clouds and climate. In this study we made measurements of INP concentrations in Leeds over a specific combustion aerosol event in order to test if there was a correlation between INP concentrations and combustion aerosol. The combustion aerosol event was on the 5th November which is a major bonfire and firework event celebrated throughout the UK. During the event we observed a factor of five increase in aerosol and a factor of 10 increase in black carbon, but observed no significant increase in INP concentration. This implies that black carbon and combustion aerosol did not compete with the background INP during this event.

  9. Deposition-mode ice nucleation reexamined at temperatures below 200 K

    NASA Astrophysics Data System (ADS)

    Thomson, E. S.; Kong, X.; Papagiannakopoulos, P.; Pettersson, J. B. C.

    2015-02-01

    The environmental chamber of a molecular beam apparatus is used to study deposition nucleation of ice on graphite, alcohols and acetic and nitric acids at temperatures between 155 and 200 K. The critical supersaturations necessary to spontaneously nucleate water ice on six different substrate materials are observed to occur at higher supersaturations than are theoretically predicted. This contradictory result motivates more careful examination of the experimental conditions and the underlying basis of the current theories. An analysis based on classical nucleation theory supports the view that at these temperatures nucleation is primarily controlled by the rarification of the vapor and the strength of water's interaction with the substrate surface. The technique enables a careful probing of the underlying processes of ice nucleation and the substrate materials of study. The findings are relevant to atmospheric nucleation processes that are intrinsically linked to cold cloud formation and lifetime.

  10. Ice Nucleation of Snomax® Particles below Water Vapor Saturation: Immersion Freezing in Concentrated Solution Droplets

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Boose, Y.; Augustin, S.; Wex, H.

    2014-12-01

    Heterogeneous ice nucleation in the atmosphere is important and has received an increasing amount of interest in the past years, as it initiates the ice phase in mixed phase clouds and, to some extent, also in cirrus clouds. The presence of ice influences cloud radiative properties and, for mixed phase clouds, also the formation of precipitation and cloud lifetime. Immersion freezing has been in the focus of ice nucleation research in recent years. Here, we examine ice nucleation activity of biological ice nuclei (IN) derived from bacteria, namely of particles generated from a suspensions of Snomax®, both above and below water vapor saturation. Measurements were done with PINC (Portable Ice Nucleus Counter, Chou et al., 2011) during a measurement campaign at LACIS (Leipzig Aerosol Cloud Interaction Simulator, see e.g. Wex et al., 2014) in Leipzig. Immersion freezing measurements from PINC and LACIS were in agreement in the temperature regime for which both instruments operate reliably. Here, we will show that measurements done below water vapor saturation follow what would be expected for immersion freezing in concentrated solutions, similar to what was suggested for coated kaolinite particles in Wex et al. (2014). Chou, C., O. Stetzer, E. Weingartner, Z. Juranyi, Z. A. Kanji, and U. Lohmann (2011), Ice nuclei properties within a Saharan dust event at the Jungfraujoch in the Swiss Alps, Atmos. Chem. Phys., 11(10), 4725-4738, doi:10.5194/acp-11-4725-2011. Wex, H., P. J. DeMott, Y. Tobo, S. Hartmann, M. Rösch, T. Clauss, L. Tomsche, D. Niedermeier, and F. Stratmann (2014), Kaolinite particles as ice nuclei: learning from the use of different kaolinite samples and different coatings, Atmos. Chem. Phys., 14, doi:10.5194/acp-14-5529-2014.

  11. A case of type I polar stratospheric cloud formation by heterogeneous nucleation

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Ferry, G. V.; Snetsinger, K. G.; Goodman, J.; Dye, J. E.; Baumgardner, D.; Gandrud, B. W.

    1992-01-01

    The NASA ER-2 aircraft flew on January 24, 1989, from Stavanger to Spitsbergen, Norway, at the 430-440 K potential temperature surface (19.2-19.8 km pressure altitude). Aerosols were sampled continuously by an optical particle counter (PMS-FSSP300) for concentration and size analyses, and during five 10-min intervals by four wire and one replicator impactor for concentration, size, composition, and phase analysis. During sampling, the air saturation of H2O with respect to ice changed from 20 to 100 percent, and of HNO3 with respect to nitric acid trihydrate (NAT) from subsaturation to supersaturation. Data from both instruments indicate a condensation of hydrochloric acid and, later, nitric acid on the background aerosol particles as the ambient temperature decreases along the flight track. This heterogeneous nucleation mechanism generates type I polar stratospheric cloud particles of 10-fold enhanced optical depth, which could play a role in stratospheric ozone depletion.

  12. Ice Nucleation in the Tropical Tropopause Layer: Implications for Cirrus Occurrence, Cirrus Microphysical Properties, and Dehydration of Air Entering the Stratosphere

    NASA Technical Reports Server (NTRS)

    Jensen, Eric; Kaercher, Bernd; Ueyama, Rei; Pfister, Leonhard

    2017-01-01

    Recent laboratory experiments have advanced our understanding of the physical properties and ice nucleating abilities of aerosol particles atlow temperatures. In particular, aerosols containing organics will transition to a glassy state at low temperatures, and these glassy aerosols are moderately effective as ice nuclei. These results have implications for ice nucleation in the cold Tropical Tropopause Layer (TTL; 13-19 km). We have developed a detailed cloud microphysical model that includes heterogeneous nucleation on a variety of aerosol types and homogeneous freezing of aqueous aerosols. This model has been incorporated into one-dimensional simulations of cirrus and water vapor driven by meteorological analysis temperature and wind fields. The model includes scavenging of ice nuclei by sedimenting ice crystals. The model is evaluated by comparing the simulated cloud properties and water vapor concentrations with aircraft and satellite measurements. In this presentation, I will discuss the relative importance of homogeneous and heterogeneous ice nucleation, the impact of ice nuclei scavenging as air slowly ascends through the TTL, and the implications for the final dehydration of air parcels crossing the tropical cold-point tropopause and entering the tropical stratosphere.

  13. The decisive role of free water in determining homogenous ice nucleation behavior of aqueous solutions

    PubMed Central

    Wang, Qiang; Zhao, Lishan; Li, Chenxi; Cao, Zexian

    2016-01-01

    It is a challenging issue to quantitatively characterize how the solute and pressure affect the homogeneous ice nucleation in a supercooled solution. By measuring the glass transition behavior of solutions, a universal feature of water-content dependence of glass transition temperature is recognized, which can be used to quantify hydration water in solutions. The amount of free water can then be determined for water-rich solutions, whose mass fraction, Xf, is found to serve as a universal relevant parameter for characterizing the homogeneous ice nucleation temperature, the meting temperature of primary ice, and even the water activity of solutions of electrolytes and smaller organic molecules. Moreover, the effects of hydrated solute and pressure on ice nucleation is comparable, and the pressure, when properly scaled, can be incorporated into the universal parameter Xf. These results help establish the decisive role of free water in determining ice nucleation and other relevant properties of aqueous solutions. PMID:27225427

  14. Effect of photochemical aging on the ice nucleation properties of diesel and wood burning particles

    NASA Astrophysics Data System (ADS)

    Chou, C.; Stetzer, O.; Tritscher, T.; Chirico, R.; Heringa, M. F.; Kanji, Z. A.; Weingartner, E.; Prévôt, A. S. H.; Baltensperger, U.; Lohmann, U.

    2012-06-01

    A measurement campaign (IMBALANCE) was conducted in 2009 and aimed at characterizing the physical and chemical properties of freshly emitted and photochemically aged combustion particles emitted from a log wood burner and diesel vehicles: a EURO3 Opel Astra with a diesel oxidation catalyst (DOC) but no particle filter and a EURO2 Volkswagen Transporter TDI Syncro with no emission after-treatment. Ice nucleation experiments in the deposition and condensation freezing modes were conducted with the Portable Ice Nucleation Chamber (PINC) at three nominal temperatures, -30 °C, -35 °C and -40 °C. Freshly emitted diesel particles showed ice formation only at -40 °C in the deposition mode at 137% relative humidity with respect to ice (RHi) and 92% relative humidity with respect to water (RHw), and photochemical aging did not play a role in modifying their ice nucleation behavior. Only one diesel experiment where α-pinene was added, showed an ice nucleation enhancement after the aging at -35 °C. Wood burning particles also act as ice nuclei (IN) at -40 °C in the deposition mode at the same conditions as for diesel particles and photochemical aging did also not alter the ice formation properties of the wood burning particles. Unlike diesel particles, wood burning particles form ice via condensation freezing at -35 °C with no ice nucleation observed at -30 °C for wood burning particles. Photochemical aging did not affect the ice nucleation ability of the diesel and wood burning particles at the three different temperatures investigated but a broader range of temperatures below -30 °C need to be investigated in order to draw an overall conclusion on the effect of photochemical aging on deposition/condensation ice nucleation across the entire temperature range relevant to cold clouds.

  15. Effect of photochemical ageing on the ice nucleation properties of diesel and wood burning particles

    NASA Astrophysics Data System (ADS)

    Chou, C.; Kanji, Z. A.; Stetzer, O.; Tritscher, T.; Chirico, R.; Heringa, M. F.; Weingartner, E.; Prévôt, A. S. H.; Baltensperger, U.; Lohmann, U.

    2013-01-01

    A measurement campaign (IMBALANCE) conducted in 2009 was aimed at characterizing the physical and chemical properties of freshly emitted and photochemically aged combustion particles emitted from a log wood burner and diesel vehicles: a EURO3 Opel Astra with a diesel oxidation catalyst (DOC) but no particle filter and a EURO2 Volkswagen Transporter TDI Syncro without emission aftertreatment. Ice nucleation experiments in the deposition and condensation freezing modes were conducted with the Portable Ice Nucleation Chamber (PINC) at three nominal temperatures, -30 °C, -35 °C and -40 °C. Freshly emitted diesel particles showed ice formation only at -40 °C in the deposition mode at 137% relative humidity with respect to ice (RHi) and 92% relative humidity with respect to water (RHw), and photochemical ageing did not play a role in modifying their ice nucleation behaviour. Only one diesel experiment where α-pinene was added for the ageing process, showed an ice nucleation enhancement at -35 °C. Wood burning particles also act as ice nuclei (IN) at -40 °C in the deposition mode at the same conditions as for diesel particles and photochemical ageing also did not alter the ice formation properties of the wood burning particles. Unlike diesel particles, wood burning particles form ice via condensation freezing at -35 °C whereas no ice nucleation was observed at -30 °C. Photochemical ageing did not affect the ice nucleation ability of the diesel and wood burning particles at the three different temperatures investigated but a broader range of temperatures below -40 °C need to be investigated in order to draw an overall conclusion on the effect of photochemical ageing on deposition/condensation ice nucleation across the entire temperature range relevant to cold clouds.

  16. Ice nucleation by combustion ash particles at conditions relevant to mixed-phase clouds

    NASA Astrophysics Data System (ADS)

    Umo, N. S.; Murray, B. J.; Baeza-Romero, M. T.; Jones, J. M.; Lea-Langton, A. R.; Malkin, T. L.; O'Sullivan, D.; Neve, L.; Plane, J. M. C.; Williams, A.

    2015-05-01

    Ice-nucleating particles can modify cloud properties with implications for climate and the hydrological cycle; hence, it is important to understand which aerosol particle types nucleate ice and how efficiently they do so. It has been shown that aerosol particles such as natural dusts, volcanic ash, bacteria and pollen can act as ice-nucleating particles, but the ice-nucleating ability of combustion ashes has not been studied. Combustion ashes are major by-products released during the combustion of solid fuels and a significant amount of these ashes are emitted into the atmosphere either during combustion or via aerosolization of bottom ashes. Here, we show that combustion ashes (coal fly ash, wood bottom ash, domestic bottom ash, and coal bottom ash) nucleate ice in the immersion mode at conditions relevant to mixed-phase clouds. Hence, combustion ashes could play an important role in primary ice formation in mixed-phase clouds, especially in clouds that are formed near the emission source of these aerosol particles. In order to quantitatively assess the impact of combustion ashes on mixed-phase clouds, we propose that the atmospheric abundance of combustion ashes should be quantified since up to now they have mostly been classified together with mineral dust particles. Also, in reporting ice residue compositions, a distinction should be made between natural mineral dusts and combustion ashes in order to quantify the contribution of combustion ashes to atmospheric ice nucleation.

  17. Heterogeneous nucleation of catalyst-free InAs nanowires on silicon

    NASA Astrophysics Data System (ADS)

    Gomes, U. P.; Ercolani, D.; Zannier, V.; Battiato, S.; Ubyivovk, E.; Mikhailovskii, V.; Murata, Y.; Heun, S.; Beltram, F.; Sorba, L.

    2017-02-01

    We report on the heterogeneous nucleation of catalyst-free InAs nanowires on Si(111) substrates by chemical beam epitaxy. We show that nanowire nucleation is enhanced by sputtering the silicon substrate with energetic particles. We argue that particle bombardment introduces lattice defects on the silicon surface that serve as preferential nucleation sites. The formation of these nucleation sites can be controlled by the sputtering parameters, allowing the control of nanowire density in a wide range. Nanowire nucleation is accompanied by unwanted parasitic islands, but careful choice of annealing and growth temperature allows us to strongly reduce the relative density of these islands and to realize samples with high nanowire yield.

  18. Effects of sulfuric acid and ammonium sulfate coatings on the ice nucleation properties of kaolinite particles

    NASA Astrophysics Data System (ADS)

    Eastwood, Michael L.; Cremel, Sebastien; Wheeler, Michael; Murray, Benjamin J.; Girard, Eric; Bertram, Allan K.

    2009-01-01

    The onset conditions for ice nucleation on H2SO4 coated, (NH4)2SO4 coated, and uncoated kaolinite particles at temperatures ranging from 233 to 246 K were studied. We define the onset conditions as the relative humidity and temperature at which the first ice nucleation event was observed. Uncoated particles were excellent ice nuclei; the onset relative humidity with respect to ice (RHi) was below 110% at all temperatures studied, consistent with previous measurements. H2SO4 coatings, however, drastically altered the ice nucleating ability of kaolinite particles, increasing the RHi required for ice nucleation by approximately 30%, similar to the recent measurements by Möhler et al. [2008b]. (NH4)2SO4 coated particles were poor ice nuclei at 245 K, but effective ice nuclei at 236 K. The differences between H2SO4 and (NH4)2SO4 coatings may be explained by the deliquescence and efflorescence properties of (NH4)2SO4. These results support the idea that emissions of SO2 and NH3 may influence the ice nucleating properties of mineral dust particles.

  19. The role of heterogeneity in long-range interacting systems: From nucleation to earthquake fault systems

    NASA Astrophysics Data System (ADS)

    Silva, James Brian

    The role of heterogeneity in two long-range systems is explored with a focus on the interplay of this heterogeneity with the component system interactions. The first will be the heterogeneous Ising model with long-range interactions. Earthquake fault systems under long-range stress transfer with varying types of heterogeneity will be the second system of interest. First I will review the use of the intervention method to determine the time and place of nucleation and extend its use as an indicator for spinodal nucleation. The heterogeneous Ising model with fixed magnetic sites will then be reformulated as a dilute random field Ising model. This reformulation will allow for the application of spinodal nucleation theory to the heterogeneous Ising model by correcting the spinodal field and the critical exponent sigma describing the critical behavior of clusters in spinodal nucleation theory. The applicability of this correction is shown by simulations that determine the cluster scaling of the nucleating droplets near the spinodal. Having obtained a reasonable definition of the saddle point object describing the nucleation droplet, the density profile of the nucleating droplet is measured and deviations from homogeneous spinodal nucleation are found due to the excess amount of sparseness in the nucleating droplet due to the heterogeneity. Earthquake fault systems are then introduced and a connection is shown of two earthquake models. Heterogeneity is introduced in the form of asperities with the intent of modeling the effect of hard rocks on earthquake statistics. The asperities are observed to be a crucial element in explaining the behavior of aftershocks resulting in Omori's law. A second form of heterogeneity is introduced by coupling the Olami-Feder-Christensen model to an invasion percolation model for the purpose of modeling an earthquake fault system undergoing hydraulic fracturing. The ergodicty and event size statistics are explored in this extended model. The

  20. Microbial ice nucleators are scavenged from the atmosphere during artificial rain events

    NASA Astrophysics Data System (ADS)

    Hanlon, Regina; Powers, Craig; Failor, Kevin; Vinatzer, Boris; Schmale, David

    2016-04-01

    Some microorganisms associated with rain may catalyze the nucleation of ice crystals at significantly warmer temperatures than would normally be required for ice formation, suggesting that they may play an important role in the onset of precipitation. Rain samples collected near the surface of the earth contain an array of microbial ice nucleators, but the little is known about their source(s) and life history. We conducted a series of field experiments to test the hypothesis that microbial ice nucleators are scavenged from the atmosphere by rainfall. Thirty three artificial rain events were conducted over four months (Nov 2014, Dec 2014, April 2015, and June 2015) off the side of the Smart Road Bridge in Blacksburg, VA, USA. In each event, sterile water was dispensed over the side of the bridge and recovered in sterile containers following gravitational settling from the bridge to an open fallow agricultural field below (a distance of ~55m). Microbes scavenged from the artificial rain events were cultured on six different types of agar media (R2A, TSA, CA; +/-cycloheximide), and the ice nucleation activity was examined for colonies cultured from the different media types. Mean CFUs scavenged by artificial rain ranged from 2 to 267 CFUs/mL. Microbial ice nucleators were cultured from 94% (31/33) of the simulated rain events, and represented 1.4% (121/8871) of the total number of colonies assayed. This percentage is similar to the percentage of culturable microbial ice nucleators occurring in about half of the natural rain events studied in Blacksburg, VA. Sequence-assisted identification of the repeatable microbial ice nucleators that were scavenged from the atmosphere showed a number of unique prokaryotic and eukaryotic taxa. This work expands our knowledge of the scavenging properties of rainfall, and suggests that at least some ice nucleators in natural precipitation events may have been scrubbed from the atmosphere during rainfall, and thus are not likely to be

  1. Nucleation and growth of ice crystals inside cultured hepatocytes during freezing in the presence of dimethyl sulfoxide.

    PubMed Central

    Karlsson, J O; Cravalho, E G; Borel Rinkes, I H; Tompkins, R G; Yarmush, M L; Toner, M

    1993-01-01

    A three-part, coupled model of cell dehydration, nucleation, and crystal growth was used to study intracellular ice formation (IIF) in cultured hepatocytes frozen in the presence of dimethyl sulfoxide (DMSO). Heterogeneous nucleation temperatures were predicted as a function of DMSO concentration and were in good agreement with experimental data. Simulated freezing protocols correctly predicted and explained experimentally observed effects of cooling rate, warming rate, and storage temperature on hepatocyte function. For cells cooled to -40 degrees C, no IIF occurred for cooling rates less than 10 degrees C/min. IIF did occur at faster cooling rates, and the predicted volume of intracellular ice increased with increasing cooling rate. Cells cooled at 5 degrees C/min to -80 degrees C were shown to undergo nucleation at -46.8 degrees C, with the consequence that storage temperatures above this value resulted in high viability independent of warming rate, whereas colder storage temperatures resulted in cell injury for slow warming rates. Cell damage correlated positively with predicted intracellular ice volume, and an upper limit for the critical ice content was estimated to be 3.7% of the isotonic water content. The power of the model was limited by difficulties in estimating the cytosol viscosity and membrane permeability as functions of DMSO concentration at low temperatures. Images FIGURE 1 PMID:8312489

  2. On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

    NASA Technical Reports Server (NTRS)

    Jensen, Eric J.

    2016-01-01

    Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

  3. Immersion freezing of supermicron mineral dust particles: freezing results, testing different schemes for describing ice nucleation, and ice nucleation active site densities.

    PubMed

    Wheeler, M J; Mason, R H; Steunenberg, K; Wagstaff, M; Chou, C; Bertram, A K

    2015-05-14

    Ice nucleation on mineral dust particles is known to be an important process in the atmosphere. To accurately implement ice nucleation on mineral dust particles in atmospheric simulations, a suitable theory or scheme is desirable to describe laboratory freezing data in atmospheric models. In the following, we investigated ice nucleation by supermicron mineral dust particles [kaolinite and Arizona Test Dust (ATD)] in the immersion mode. The median freezing temperature for ATD was measured to be approximately -30 °C compared with approximately -36 °C for kaolinite. The freezing results were then used to test four different schemes previously used to describe ice nucleation in atmospheric models. In terms of ability to fit the data (quantified by calculating the reduced chi-squared values), the following order was found for ATD (from best to worst): active site, pdf-α, deterministic, single-α. For kaolinite, the following order was found (from best to worst): active site, deterministic, pdf-α, single-α. The variation in the predicted median freezing temperature per decade change in the cooling rate for each of the schemes was also compared with experimental results from other studies. The deterministic model predicts the median freezing temperature to be independent of cooling rate, while experimental results show a weak dependence on cooling rate. The single-α, pdf-α, and active site schemes all agree with the experimental results within roughly a factor of 2. On the basis of our results and previous results where different schemes were tested, the active site scheme is recommended for describing the freezing of ATD and kaolinite particles. We also used our ice nucleation results to determine the ice nucleation active site (INAS) density for the supermicron dust particles tested. Using the data, we show that the INAS densities of supermicron kaolinite and ATD particles studied here are smaller than the INAS densities of submicron kaolinite and ATD particles

  4. Free energy landscapes for homogeneous nucleation of ice for a monatomic water model

    NASA Astrophysics Data System (ADS)

    Reinhardt, Aleks; Doye, Jonathan P. K.

    2012-02-01

    We simulate the homogeneous nucleation of ice from supercooled liquid water at 220 K in the isobaric-isothermal ensemble using the MW monatomic water potential. Monte Carlo simulations using umbrella sampling are performed in order to determine the nucleation free energy barrier. We find the Gibbs energy profile to be relatively consistent with that predicted by classical nucleation theory; the free energy barrier to nucleation was determined to be ˜18 kBT and the critical nucleus comprised ˜85 ice particles. Growth from the supercooled liquid gives clusters that are predominantly cubic, whilst starting with a pre-formed subcritical nucleus of cubic or hexagonal ice results in the growth of predominantly that phase of ice only.

  5. Homogeneous versus heterogeneous crystal nucleation in Li2O-2SiO2 glass

    NASA Technical Reports Server (NTRS)

    Weinberg, M. C.; Neilson, G. F.; Uhlmann, D. R.

    1984-01-01

    When analyzing crystal nucleation in glasses, it is difficult to distinguish between homogeneous and heterogeneous nucleation. A method is proposed to investigate the nature of crystal nucleation in Li2O-2SiO2, and calculations are performed to determine under which conditions saturation effects help ascertain the nature of the nucleation. The capability of detecting impurity particles in unheated glass via standard micrographic techniques (SEM or REM) and small angle X-ray scattering (SAXS) is explored. Results indicate that if the maximum impurity particle densities do not exceed 2 x 10 to the 7th per cu cm then heterogeneous nucleation may be excluded and most impurity particles with densities in excess of 10 to the 10th per cu cm are detectable by SAXS. It is concluded that crystal nucleation in this system most probably occurs homogeneously.

  6. Influence of Aerosol Chemical Composition on Heterogeneous Ice Formation under Mid-Upper Troposphere Conditions

    NASA Astrophysics Data System (ADS)

    Kanji, Z. A.; Niemand, M.; Saathoff, H.; Möhler, O.; Chou, C.; Abbatt, J.; Stetzer, O.

    2011-12-01

    Aerosols are involved in cooling/warming the atmosphere directly via interaction with incoming solar radiation (aerosol direct effect), or via their ability to act as cloud condensation or ice nuclei (IN) and thus play a role in cloud formation (indirect effect). In particular, the physical properties of aerosols such as size and solubility and chemical composition can influence their behavior and fate in the atmosphere. Ice nucleation taking place via IN is termed as heterogeneous ice nucleation and can take place with via deposition (ice forming on IN directly from the vapor phase), condensation/immersion (freezing via formation of the liquid phase on IN) or condensation (IN colliding with supercooled liquid drops). This presentation shows how the chemical composition and surface area of various tropospherically relevant aerosols influence conditions of temperature (T) and relative humidity (RH) required for heterogeneous ice formation conditions in the mid-upper troposphere regime (253 - 220K)? Motivation for this comes first from, the importance of being able to predict ice formation accurately so as to understand the hydrological cycle since the ice is the primary initiator of precipitation forming clouds. Second, the tropospheric budget of water vapour, an especially active greenhouse gas is strongly influenced by ice nucleation and growth. Third, ice surfaces in the atmosphere act as heterogeneous surfaces for chemical reactions of trace gases (e.g., SO2, O3, NOx and therefore being able to accurately estimate ice formation rates and quantify ice surface concentrations will allow a more accurate calculation of trace gas budgets in the troposphere. Ice nucleation measurements were conducted using a self-developed continuous flow diffusion chamber and static chamber. A number of tropospherically relevant particulates with naturally-varying and laboratory-modified surface chemistry/structure were investigated for their ice formation efficiency based on highest

  7. Ice nucleation by electric surface fields of varying range and geometry.

    PubMed

    Yan, J Y; Patey, G N

    2013-10-14

    Molecular dynamics simulations are employed to show that electric field bands acting only over a portion of a surface can function as effective ice nuclei. Field bands of different geometry (rectangular, triangular, and semicircular cross sectional areas are considered) all nucleate ice, provided that the band is sufficiently large. Rectangular bands are very efficient if the width and thickness are ≳0.35 nm, and ≳0.15 nm, respectively, and the necessary dimensions are comparable for other geometries. From these simulations we also learn more about the ice nucleation and growth process. Careful analysis of different systems reveals that ice strongly prefers to grow at (111) planes of cubic ice. This agrees with an earlier theoretical deduction based on considerations of water-ice interfacial energies. We find that ice nucleated by field bands usually grows as a mixture of cubic and hexagonal ice, consistent with other simulations of ice growth, and with experiment. This contrasts with simulations carried out with nucleating fields that span the entire surface area, where cubic ice dominates, and hexagonal layers are very rarely observed. We argue that this discrepancy is a simulation artifact related to finite sample size and periodic boundary conditions.

  8. Stimulated Heterogeneous Nucleation of Supercooled Liquid H2 Droplets

    NASA Astrophysics Data System (ADS)

    Knuth, E. L.; Schaper, S.; Toennies, J. P.

    2000-07-01

    The properties of H(2) droplets formed by condensation in a supersonic freejet were probed by the capture and coagulation of CO molecules for the purpose of determining whether the droplets are liquid or solid. The CO was introduced into the H(2) droplets by passing the droplet beam through a scattering chamber containing CO at room temperature and various pressures. Reduction of droplet size as a result of droplet collisions with CO molecules was determined by measuring the droplet size downstream from the scattering region for several different values of the CO pressure. The size of the embedded clusters formed by coagulation of the captured CO molecules was determined from the mass spectra measured for several values of CO pressure in the scattering chamber. A comparison of (a) the observed dramatic loss of about 7% of the H(2) molecules from a droplet after between 2 and 8 collisions with (b) the loss predicted due to evaporation/sublimation in the event of solidification is taken to be compelling evidence that the H(2) droplets were liquid prior to their collisions with the CO scattering gas. The observed dependence of the maximum CO cluster size on the collision frequency appears to indicate that a sufficiently high collision frequency will liquify a droplet which otherwise would be solid. This observation supports the conclusion that the H(2) droplets are solidified as a consequence of heterogeneous nucleation induced by the captured CO molecules. The evidence in favor of a liquid state. coupled with the estimated 4K droplet temperature, suggest strongly that the supercooled H(2) droplets are superfluid.

  9. Stimulated heterogeneous nucleation of supercooled liquid H2 droplets

    NASA Astrophysics Data System (ADS)

    Knuth, E. L.; Schaper, S.; Toennies, J. P.

    2001-08-01

    The properties of H2 droplets formed by condensation in a supersonic freejet were probed by the capture and coagulation of CO molecules for the purpose of determining whether the droplets are liquid or solid. The CO was introduced into the H2 droplets by passing the droplet beam through a scattering chamber containing CO at room temperature and various pressures. Reduction of droplet size as a result of droplet collisions with CO molecules was determined by measuring the droplet size downstream from the scattering region for several different values of the CO pressure. The size of the embedded clusters formed by coagulation of the captured CO molecules was determined from the mass spectra measured for several values of CO pressure in the scattering chamber. A comparison of (a) the observed dramatic loss of about 7% of the H2 molecules from a droplet after between 2 and 8 collisions with (b) the loss predicted due to evaporation/sublimation in the event of solidification is taken to be compelling evidence that the H2 droplets were liquid prior to their collisions with the CO scattering gas. The observed dependence of the maximum CO cluster size on the collision frequency appears to indicate that a sufficiently high collision frequency will liquify a droplet which otherwise would be solid. This observation supports the conclusion that the H2 droplets are solidified as a consequence of heterogeneous nucleation induced by the captured CO molecules. The evidence in favor of a liquid state, coupled with the estimated 4K droplet temperature, suggest strongly that the supercooled H2 droplets are superfluid.

  10. Direct calculation of ice homogeneous nucleation rate for a molecular model of water

    PubMed Central

    Haji-Akbari, Amir; Debenedetti, Pablo G.

    2015-01-01

    Ice formation is ubiquitous in nature, with important consequences in a variety of environments, including biological cells, soil, aircraft, transportation infrastructure, and atmospheric clouds. However, its intrinsic kinetics and microscopic mechanism are difficult to discern with current experiments. Molecular simulations of ice nucleation are also challenging, and direct rate calculations have only been performed for coarse-grained models of water. For molecular models, only indirect estimates have been obtained, e.g., by assuming the validity of classical nucleation theory. We use a path sampling approach to perform, to our knowledge, the first direct rate calculation of homogeneous nucleation of ice in a molecular model of water. We use TIP4P/Ice, the most accurate among existing molecular models for studying ice polymorphs. By using a novel topological approach to distinguish different polymorphs, we are able to identify a freezing mechanism that involves a competition between cubic and hexagonal ice in the early stages of nucleation. In this competition, the cubic polymorph takes over because the addition of new topological structural motifs consistent with cubic ice leads to the formation of more compact crystallites. This is not true for topological hexagonal motifs, which give rise to elongated crystallites that are not able to grow. This leads to transition states that are rich in cubic ice, and not the thermodynamically stable hexagonal polymorph. This mechanism provides a molecular explanation for the earlier experimental and computational observations of the preference for cubic ice in the literature. PMID:26240318

  11. Direct calculation of ice homogeneous nucleation rate for a molecular model of water.

    PubMed

    Haji-Akbari, Amir; Debenedetti, Pablo G

    2015-08-25

    Ice formation is ubiquitous in nature, with important consequences in a variety of environments, including biological cells, soil, aircraft, transportation infrastructure, and atmospheric clouds. However, its intrinsic kinetics and microscopic mechanism are difficult to discern with current experiments. Molecular simulations of ice nucleation are also challenging, and direct rate calculations have only been performed for coarse-grained models of water. For molecular models, only indirect estimates have been obtained, e.g., by assuming the validity of classical nucleation theory. We use a path sampling approach to perform, to our knowledge, the first direct rate calculation of homogeneous nucleation of ice in a molecular model of water. We use TIP4P/Ice, the most accurate among existing molecular models for studying ice polymorphs. By using a novel topological approach to distinguish different polymorphs, we are able to identify a freezing mechanism that involves a competition between cubic and hexagonal ice in the early stages of nucleation. In this competition, the cubic polymorph takes over because the addition of new topological structural motifs consistent with cubic ice leads to the formation of more compact crystallites. This is not true for topological hexagonal motifs, which give rise to elongated crystallites that are not able to grow. This leads to transition states that are rich in cubic ice, and not the thermodynamically stable hexagonal polymorph. This mechanism provides a molecular explanation for the earlier experimental and computational observations of the preference for cubic ice in the literature.

  12. Rate of Homogenous Nucleation of Ice in Supercooled Water.

    PubMed

    Atkinson, James D; Murray, Benjamin J; O'Sullivan, Daniel

    2016-08-25

    The homogeneous freezing of water is of fundamental importance to a number of fields, including that of cloud formation. However, there is considerable scatter in homogeneous nucleation rate coefficients reported in the literature. Using a cold stage droplet system designed to minimize uncertainties in temperature measurements, we examined the freezing of over 1500 pure water droplets with diameters between 4 and 24 μm. Under the assumption that nucleation occurs within the bulk of the droplet, nucleation rate coefficients fall within the spread of literature data and are in good agreement with a subset of more recent measurements. To quantify the relative importance of surface and volume nucleation in our experiments, where droplets are supported by a hydrophobic surface and surrounded by oil, comparison of droplets with different surface area to volume ratios was performed. From our experiments it is shown that in droplets larger than 6 μm diameter (between 234.6 and 236.5 K), nucleation in the interior is more important than nucleation at the surface. At smaller sizes we cannot rule out a significant contribution of surface nucleation, and in order to further constrain surface nucleation, experiments with smaller droplets are necessary. Nevertheless, in our experiments, it is dominantly volume nucleation controlling the observed nucleation rate.

  13. Airborne measurement of tropospheric ice nuclei aerosols using the Portable Ice Nucleation Chamber (PINC)

    NASA Astrophysics Data System (ADS)

    Chou, C.; Stetzer, O.; Sierau, B.; Lohmann, U.

    2009-04-01

    Ice clouds and mixed phase clouds have different microphysical and radiative properties that need to be assessed in order to understand their impact on the climate. Indeed, on one hand ice crystals found in the ice phase have the ability to scatter incoming solar radiation and absorb terrestrial radiation. On the other hand, about 70% of the tropical precipitation forms via the ice-phase, this means an impact on the hydrological cycle. Investigation of the ability of an aerosol to act as Ice Nuclei (IN) requires knowledge of the thermodynamics conditions, i.e. relative humidity and temperature at which this aerosol form ice crystal. The PerformPINC project was a research campaign within the Education & Training program of the EUropean Fleet for Airborne Research (EUFAR). The project objectives were to measure the number concentration of IN in free and upper troposphere using the Portable Ice Nucleation Chamber (PINC) recently developed by the Institute for Atmospheric Climate Sciences at the ETH Zürich, and thus as a primary objective, testing the technical performance of the instrument during in-situ airborne measurements at different conditions within the chamber. The PINC is the portable version of the Zurich Ice Nucleation Chamber (ZINC) (Stetzer et al., 2008) and is meant for in-situ measurements. Both ZINC and PINC follow the same principle as the Continuous Flow Diffusion Chamber of the Colorado University (Rogers, 1988) that has proven to be of good performance in previous airborne in-situ campaigns (DeMott et al., 2003a). Unlike the CFDC, the PINC has a flat design composed of a main chamber, and an evaporation part. The cooling system of the PINC is also different and consists for the warm side of two BD120 compressors mounted in parallel. For the cold side, it is four BD120 compressors in parallel mounted to another BD120 compressor in serial, thus allowing us to reach lower temperature than the warm side. Aerosols are collected through an inlet where

  14. Airborne measurement of tropospheric ice nuclei aerosols using the Portable Ice Nucleation Chamber (PINC)

    NASA Astrophysics Data System (ADS)

    Chou, C.; Stetzer, O.; Sierau, B.; Lohmann, U.

    2009-04-01

    Ice clouds and mixed phase clouds have different microphysical and radiative properties that need to be assessed in order to understand their impact on the climate. Indeed, on one hand ice crystals found in the ice phase have the ability to scatter incoming solar radiation and absorb terrestrial radiation. On the other hand, about 70% of the tropical precipitation forms via the ice-phase, this means an impact on the hydrological cycle. Investigation of the ability of an aerosol to act as Ice Nuclei (IN) requires knowledge of the thermodynamics conditions, i.e. relative humidity and temperature at which this aerosol form ice crystal. The PerformPINC project was a research campaign within the Education & Training program of the EUropean Fleet for Airborne Research (EUFAR). The project objectives were to measure the number concentration of IN in free and upper troposphere using the Portable Ice Nucleation Chamber (PINC) recently developed by the Institute for Atmospheric Climate Sciences at the ETH Zürich, and thus as a primary objective, testing the technical performance of the instrument during in-situ airborne measurements at different conditions within the chamber. The PINC is the portable version of the Zurich Ice Nucleation Chamber (ZINC) (Stetzer et al., 2008) and is meant for in-situ measurements. Both ZINC and PINC follow the same principle as the Continuous Flow Diffusion Chamber of the Colorado University (Rogers, 1988) that has proven to be of good performance in previous airborne in-situ campaigns (DeMott et al., 2003a). Unlike the CFDC, the PINC has a flat design composed of a main chamber, and an evaporation part. The cooling system of the PINC is also different and consists for the warm side of two BD120 compressors mounted in parallel. For the cold side, it is four BD120 compressors in parallel mounted to another BD120 compressor in serial, thus allowing us to reach lower temperature than the warm side. Aerosols are collected through an inlet where

  15. Ice-nucleating bacteria control the order and dynamics of interfacial water.

    PubMed

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A; Fischer, Sean A; Pfaendtner, Jim; Backus, Ellen H G; Nagata, Yuki; Fröhlich-Nowoisky, Janine; Schmüser, Lars; Mauri, Sergio; Scheel, Jan F; Knopf, Daniel A; Pöschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-04-01

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice-active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. The freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.

  16. Ice-nucleating bacteria control the order and dynamics of interfacial water

    SciTech Connect

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; Fischer, Sean A.; Pfaendtner, Jim; Backus, Ellen H. G.; Nagata, Yuki; Frohlich-Nowoisky, Janine; Schmuser, Lars; Mauri, Sergio; Scheel, Jan F.; Knopf, Daniel A.; Poschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-04-22

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. Finally, the freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.

  17. Ice-nucleating bacteria control the order and dynamics of interfacial water

    PubMed Central

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; Fischer, Sean A.; Pfaendtner, Jim; Backus, Ellen H. G.; Nagata, Yuki; Fröhlich-Nowoisky, Janine; Schmüser, Lars; Mauri, Sergio; Scheel, Jan F.; Knopf, Daniel A.; Pöschl, Ulrich; Bonn, Mischa; Weidner, Tobias

    2016-01-01

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice-active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. The freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy. PMID:27152346

  18. Ice-nucleating bacteria control the order and dynamics of interfacial water

    DOE PAGES

    Pandey, Ravindra; Usui, Kota; Livingstone, Ruth A.; ...

    2016-04-22

    Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering onmore » the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. Finally, the freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.« less

  19. Ice nucleation by cellulose and its potential impact on clouds and climate

    NASA Astrophysics Data System (ADS)

    Hiranuma, Naruki; Möhler, Ottmar; Yamashita, Katsuya; Tajiri, Takuya; Saito, Atsushi; Kiselev, Alexei; Hoose, Corinna; Murakami, Masataka

    2014-05-01

    Biological aerosol particles have recently been accentuated by their efficient ice nucleating activity as well as potential impact on clouds and global climate. Despite their potential importance, little is known about the abundance of biological particles in the atmosphere and their role compared to non-biological material and, consequently, their potential role in the cloud-hydrology and climate system is also poorly constrained. However, field observations show that the concentration of airborne cellulose, which is one of the most important derivatives of glucose and atmospherically relevant biopolymers, is consistently prevalent (>10 ng per cubic meter) throughout the whole year even at remote- and elevated locations. Here we use a novel cloud simulation chamber in Tsukuba, Japan to demonstrate that airborne cellulose of biological origin can act as efficient ice nucleating particles in super-cooled clouds of the lower and middle troposphere. In specific, we measured the surface-based ice nucleation activity of microcrystalline cellulose particles immersed in cloud droplets, which may add crucial importance to further quantify the role of biological particles as ice nuclei in the troposphere. Our results suggest that the concentration of ice nucleating cellulose to become significant (>0.1 per liter) below about -17 °C and nearly comparable to other known ice nucleating clay mineral particles (e.g., illite rich clay mineral - INUIT comparisons are also presented). An important and unique characteristic of microcrystalline cellulose compared to other particles of biological origin is its high molecular packing density, enhancing resistance to hydrolysis degradation. More in-depth microphysical understandings as well as quantitative observations of ice nucleating cellulose particles in the atmosphere are necessary to allow better estimates of their effects on clouds and the global climate. Acknowledgement: We acknowledge support by German Research Society (Df

  20. Isolation and identification of an ice-nucleating bacterium from the gills of the intertidal bivalve mollusc Geukensia demissa.

    PubMed

    Loomis, S H.; Zinser, M

    2001-07-01

    In the fall, freeze tolerant intertidal invertebrates usually produce ice-nucleating proteins that are secreted into the hemolymph. These proteins help protect against freeze damage by insuring that ice formation is limited to extracellular spaces. Geukensia demissa, a freeze tolerant, salt marsh bivalve mollusc was examined for the presence of ice nucleating proteins. The ice-nucleating temperature (INT) of the hemolymph was not significantly different from artificial seawater of the same salinity indicating the lack of an ice nucleating protein in the hemolymph. The palial fluid did have an elevated INT, indicating the presence of an ice nucleator. The INT of the palial fluid was significantly reduced by boiling and filtration through a 0.45-&mgr;m filter. High INT was also observed in the seawater associated with the bivalves, and was demonstrated in water samples collected from salt marshes but not sand and pebble beaches. Moreover, the INT of water samples collected from a salt marsh decreased in the summer. All of these data suggest that the ice-nucleating agents in the hemolymph and the seawater are ice-nucleating bacteria. One species of ice-nucleating bacteria, Pseudomonas fulva was isolated from the gills of Geukensia. These bacteria could perform the same function as hemolymph ice-nucleating proteins by limiting ice formation to extracellular compartments.

  1. Nucleation in Synoptically Forced Cirrostratus

    NASA Technical Reports Server (NTRS)

    Lin, R.-F.; Starr, D. OC.; Reichardt, J.; DeMott, P. J.

    2004-01-01

    Formation and evolution of cirrostratus in response to weak, uniform and constant synoptic forcing is simulated using a one-dimensional numerical model with explicit microphysics, in which the particle size distribution in each grid box is fully resolved. A series of tests of the model response to nucleation modes (homogeneous-freezing-only/heterogeneous nucleation) and heterogeneous nucleation parameters are performed. In the case studied here, nucleation is first activated in the prescribed moist layer. A continuous cloud-top nucleation zone with a depth depending on the vertical humidity gradient and one of the nucleation parameters is developed afterward. For the heterogeneous nucleation cases, intermittent nucleation zones in the mid-upper portion of the cloud form where the relative humidity is on the rise, because existent ice crystals do not uptake excess water vapor efficiently, and ice nuclei (IN) are available. Vertical resolution as fine as 1 m is required for realistic simulation of the homogeneous-freezing-only scenario, while the model resolution requirement is more relaxed in the cases where heterogeneous nucleation dominates. Bulk microphysical and optical properties are evaluated and compared. Ice particle number flux divergence, which is due to the vertical gradient of the gravity-induced particle sedimentation, is constantly and rapidly changing the local ice number concentration, even in the nucleation zone. When the depth of the nucleation zone is shallow, particle number concentration decreases rapidly as ice particles grow and sediment away from the nucleation zone. When the depth of the nucleation zone is large, a region of high ice number concentration can be sustained. The depth of nucleation zone is an important parameter to be considered in parametric treatments of ice cloud generation.

  2. The inhibition of ice nucleators by insect antifreeze proteins is enhanced by glycerol and citrate.

    PubMed

    Duman, J G

    2002-02-01

    Antifreeze proteins depress the freezing point of water while not affecting the melting point, producing a characteristic difference in freezing and melting points termed thermal hysteresis. Larvae of the beetle Dendroides canadensis accumulate potent antifreeze proteins (DAFPs) in their hemolymph and gut, but to achieve high levels of thermal hysteresis requires enhancers, such as glycerol. DAFPs have previously been shown to inhibit the activity of bacterial and hemolymph protein ice nucleators, however, the effect was not large and therefore the effectiveness of the DAFPs in promoting supercooling of the larvae in winter was doubtful. However, this study demonstrates that DAFPs, in combination with the thermal hysteresis enhancers glycerol (1 M) or citrate (0.5 M), eliminated the activity of hemolymph protein ice nucleators and Pseudomonas syringae ice-nucleating active bacteria, and lowered the supercooling points (nucleation temperatures) of aqueous solutions containing these ice nucleators to those of water or buffer alone. This shows that the DAFPs, along with glycerol, play a critical role in promoting hemolymph supercooling in overwintering D. canadensis. Also, DAFPs in combination with enhancers may be useful in applications which require inhibition of ice nucleators.

  3. Perturbation of bacterial ice nucleation activity by a grass antifreeze protein.

    PubMed

    Tomalty, Heather E; Walker, Virginia K

    2014-09-26

    Certain plant-associating bacteria produce ice nucleation proteins (INPs) which allow the crystallization of water at high subzero temperatures. Many of these microbes are considered plant pathogens since the formed ice can damage tissues, allowing access to nutrients. Intriguingly, certain plants that host these bacteria synthesize antifreeze proteins (AFPs). Once freezing has occurred, plant AFPs likely function to inhibit the growth of large damaging ice crystals. However, we postulated that such AFPs might also serve as defensive mechanisms against bacterial-mediated ice nucleation. Recombinant AFP derived from the perennial ryegrass Lolium perenne (LpAFP) was combined with INP preparations originating from the grass epiphyte, Pseudomonas syringae. The presence of INPs had no effect on AFP activity, including thermal hysteresis and ice recrystallization inhibition. Strikingly, the ice nucleation point of the INP was depressed up to 1.9°C in the presence of LpAFP, but a recombinant fish AFP did not lower the INP-imposed freezing point. Assays with mutant LpAFPs and the visualization of bacterially-displayed fluorescent plant AFP suggest that INP and LpAFP can interact. Thus, we postulate that in addition to controlling ice growth, plant AFPs may also function as a defensive strategy against the damaging effects of ice-nucleating bacteria. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

  4. The unstable ice nucleation properties of Snomax® bacterial particles

    NASA Astrophysics Data System (ADS)

    Polen, Michael; Lawlis, Emily; Sullivan, Ryan C.

    2016-10-01

    Snomax® is often used as a surrogate for biological ice nucleating particles (INPs) and has recently been proposed as an INP standard for evaluating ice nucleation methods. We have found the immersion freezing properties of Snomax particles to be substantially unstable, observing a loss of ice nucleation ability over months of repeated droplet freezing measurements of the same batch of Snomax stored as dry pellets in a freezer. This reflects the fragility of the most ice active large protein aggregates and presents issues for the use of Snomax as an INP standard. The ice nucleation properties we determined using a fresh Snomax batch agreed well with the recent method intercomparison from the Ice Nucleation UnIT (UNIT) project, while an older batch did not. Using an oil immersion droplet freezing technique, repeated freezes of Snomax droplets resulted in a decrease in ice nucleation ability after successive refreezes. We attribute this to the disruption or displacement of the most ice active protein aggregates that are thought to contain the ice nucleants. Partitioning of the protein aggregates from the droplet into the immersion oil that is accelerated by droplet freezing events could explain the observed decrease in freezing ability. Droplets in mineral oil or low viscosity silicone oil experienced a smaller reduction in freezing temperature than when squalene oil was used. The effect of the immersion oil may be specific to proteinaceous biological particles, and we have not observed it in nonproteinaceous materials. Caution is warranted in the use of oil immersion droplet freezing methods to determine immersion freezing properties.

  5. Heterogeneous Nucleation of an n-Alkane on Tetrahedrally Coordinated Crystals.

    PubMed

    Bourque, Alexander J; Locker, C Rebecca; Rutledge, Gregory C

    2017-02-02

    Heterogeneous nucleation refers to the propensity for phase transformations to initiate preferentially on foreign surfaces, such as vessel walls, dust particles, or formulation additives. In crystallization, the form of the initial nucleus has ramifications for the crystallographic form, morphology, and properties of the resulting solid. Nevertheless, the discovery and design of nucleating agents remains a matter of trial and error because of the very small spatiotemporal scales over which the critical nucleus is formed and the extreme difficulty of examining such events empirically. Using molecular dynamics simulations, we demonstrate a method for the rapid screening of entire families of materials for activity as nucleating agents and for characterizing their mechanism of action. The method is applied to the crystallization of n-pentacontane, a model surrogate for polyethylene, on the family of tetrahedrally coordinated crystals, including diamond and silicon. A systematic variation of parameters in the interaction potential permits a comprehensive, physically based screening of nucleating agents in this class of materials, including both real and hypothetical candidates. The induction time for heterogeneous nucleation is shown to depend strongly on crystallographic registry between the nucleating agent and the critical nucleus, indicative of an epitaxial mechanism in this class of materials. Importantly, the severity of this registry requirement weakens with decreasing rigidity of the substrate and increasing strength of attraction to the surface of the nucleating agent. Employing this method, a high-throughput computational screening of nucleating agents becomes possible, facilitating the discovery of novel nucleating agents within a broad "materials genome" of possible additives.

  6. On the role of ice-nucleating aerosol in the formation of ice particles in tropical mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Ladino, Luis A.; Korolev, Alexei; Heckman, Ivan; Wolde, Mengistu; Fridlind, Ann M.; Ackerman, Andrew S.

    2017-02-01

    Over the decades, the cloud physics community has debated the nature and role of aerosol particles in ice initiation. The present study shows that the measured concentration of ice crystals in tropical mesoscale convective systems exceeds the concentration of ice nucleating particles (INPs) by several orders of magnitude. The concentration of INPs was assessed from the measured aerosol particle concentration in the size range of 0.5 to 1 µm. The observations from this study suggest that primary ice crystals formed on INPs make only a minor contribution to the total concentration of ice crystals in tropical mesoscale convective systems. This is found by comparing the predicted INP number concentrations with in situ ice particle number concentrations. The obtained measurements suggest that ice multiplication is the likely explanation for the observed high concentrations of ice crystals in this type of convective system.

  7. Direct Calculation of the Rate of Homogeneous Ice Nucleation for a Molecular Model of Water

    NASA Astrophysics Data System (ADS)

    Haji-Akbari, Amir; Debenedetti, Pablo

    Ice formation is ubiquitous in nature, with important consequences in many systems and environments. However, its intrinsic kinetics and mechanism are difficult to discern with experiments. Molecular simulations of ice nucleation are also challenging due to sluggish structural relaxation and the large nucleation barriers, and direct calculations of homogeneous nucleation rates have only been achieved for mW, a monoatomic coarse-grained model of water. For the more realistic molecular models, only indirect estimates have been obtained by assuming the validity of classical nucleation theory. Here, we use a coarse-grained variant of a path sampling approach known as forward-flux sampling to perform the first direct calculation of the homogeneous nucleation rate for TIP4P/Ice, which is the most accurate water model for studying ice polymorphs. By using a novel topological order parameter, we are able to identify a freezing mechanism that involves a competition between cubic and hexagonal ice polymorphs. In this competition, cubic ice wins as its growth leads to more compact crystallites

  8. Inhibition of ice nucleation by slippery liquid-infused porous surfaces (SLIPS).

    PubMed

    Wilson, Peter W; Lu, Weizhe; Xu, Haojun; Kim, Philseok; Kreder, Michael J; Alvarenga, Jack; Aizenberg, Joanna

    2013-01-14

    Ice repellent coatings have been studied and keenly sought after for many years, where any advances in the durability of such coatings will result in huge energy savings across many fields. Progress in creating anti-ice and anti-frost surfaces has been particularly rapid since the discovery and development of slippery, liquid infused porous surfaces (SLIPS). Here we use SLIPS-coated differential scanning calorimeter (DSC) pans to investigate the effects of the surface modification on the nucleation of supercooled water. This investigation is inherently different from previous studies which looked at the adhesion of ice to SLIPS surfaces, or the formation of ice under high humidity conditions. Given the stochastic nature of nucleation of ice from supercooled water, multiple runs on the same sample are needed to determine if a given surface coating has a real and statistically significant effect on the nucleation temperature. We have cycled supercooling to freezing and then thawing of deionized water in hydrophilic (untreated aluminum), hydrophobic, superhydrophobic, and SLIPS-treated DSC pans multiple times to determine the effects of surface treatment on the nucleation and subsequent growth of ice. We find that SLIPS coatings lower the nucleation temperature of supercooled water in contact with statistical significance and show no deterioration or change in the coating performance even after 150 freeze-thaw cycles.

  9. Effects Of Crystallographic Properties On The Ice Nucleation Properties Of Volcanic Ash Particles

    SciTech Connect

    Kulkarni, Gourihar R.; Nandasiri, Manjula I.; Zelenyuk, Alla; Beranek, Josef; Madaan, Nitesh; Devaraj, Arun; Shutthanandan, V.; Thevuthasan, Suntharampillai; Varga, Tamas

    2015-04-28

    Specific chemical and physical properties of volcanic ash particles that could affect their ability to induce ice formation are poorly understood. In this study, the ice nucleating properties of size-selected volcanic ash and mineral dust particles in relation to their surface chemistry and crystalline structure at temperatures ranging from –30 to –38 °C were investigated in deposition mode. Ice nucleation efficiency of dust particles was higher compared to ash particles at all temperature and relative humidity conditions. Particle characterization analysis shows that surface elemental composition of ash and dust particles was similar; however, the structural properties of ash samples were different.

  10. Effects of crystallographic properties on the ice nucleation properties of volcanic ash particles

    NASA Astrophysics Data System (ADS)

    Kulkarni, Gourihar; Nandasiri, Manjula; Zelenyuk, Alla; Beranek, Josef; Madaan, Nitesh; Devaraj, Arun; Shutthanandan, Vaithiyalingam; Thevuthasan, Suntharampillai; Varga, Tamas

    2015-04-01

    Specific chemical and physical properties of volcanic ash particles that could affe