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1

Structure Of Ice Crystallized From Supercooled Water: Stacking Disordered Ice  

NASA Astrophysics Data System (ADS)

At atmospheric pressures ice is thought to exist in two well defined crystalline forms: stable hexagonal ice and metastable cubic ice. A metastable form of ice is thought to form in the atmosphere [1] Using X-ray diffraction data and Monte Carlo simulations; we show that ice that crystallizes both homogeneously and heterogeneously from supercooled water adopts neither of these two phases. The resulting ice is disordered in one dimension and consequently does not possess either cubic or hexagonal symmetry. It is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I (ice Isd ) [2]. While similar stacking disorder has been reported before, such observations have been restricted to either samples re-crystallised from high-pressure ice phases [3] or ice formation in mesopores [4]. Review of the literature reveals that almost all ice previously identified as cubic ice in diffraction studies, which have used an array of methodologies to generate the ice, were most likely stacking-disordered ice I with varying degrees of stacking disorder. Our results suggest that the initial phase of ice formed when water freezes is the metastable stacking-disordered ice I which forms independent of the method of nucleation. Stacking-disordered ice may be the kinetic product, i.e. the material which forms fastest. Accordingly, we suggest that stacking-disordered ice is always the phase to crystallise when water freezes. In many situations it will relax to the stable hexagonal phase with time. Stacking-disordered ice may persist in the colder parts of the atmosphere and form irregular or rough crystals similar to many smaller quasi spherical ice crystals observed in the earth's atmosphere. [1] B. J. Murray et al., Nature, 2005, 434, 202-205 [2] T. L. Malkin et al., PNAS, 2012, 109 (4): 1041 - 1045 [3] T. C. Hansen et al., J. Phys. Condens. Matter, 2008, 20, 285105. [4] K. Morishige et al., J. Phys. Chem. C, 2009, 113, 3056-3061.

Malkin, T. L.; Murray, B. J.; Brukhno, A.; Anwar, J.; Salzmann, C.

2012-12-01

2

Snow Ice Crystals  

NSDL National Science Digital Library

This article from Physics Today by Yoshinori Furukawa and John S. Wettlaufer and John S. Wettlaufer describes how ice crystals form on the earth. The resource includes graphics depicting how different shapes of ice crystals are formed.

Furukawa, Y.; Wettlaufer, John S., 1963-

2010-03-12

3

Ice Crystal Terminal Velocities  

Microsoft Academic Search

Terminal velocities of different ice crystal forms were calculated using the most recent ice crystal drag coefficients, aspect ratios and densities. The equations derived were primarily for use in calculating precipitation rates by sampling particles with an aircraft in cirrus clouds, and determining particle size in cirrus clouds by Doppler radar. However, the equations are sufficiently general for determining particle

Andrew Heymsfield

1972-01-01

4

Sublimation of Ice Crystals  

Microsoft Academic Search

Recent experiments on the sublimation of single crystals of ice in an atmosphere of air indicate that the sublimation rate is diffusion limited and initially solid prismatic crystals evolve into time-independent shapes similar to confocal ellipses rotated about their major or minor axis (prolate or oblate spheroids). Step formation at crystal edges and vapor diffusion easily explain these observations.

Jon Nelson

1998-01-01

5

Ice crystal ingestion by turbofans  

NASA Astrophysics Data System (ADS)

This Thesis will present the problem of inflight icing in general and inflight icing caused by the ingestion of high altitude ice crystals produced by high energy mesoscale convective complexes in particular, and propose a new device to prevent it based on dielectric barrier discharge plasma. Inflight icing is known to be the cause of 583 air accidents and more than 800 deaths in more than a decade. The new ice crystal ingestion problem has caused more than 100 flights to lose engine power since the 1990's, and the NTSB identified it as one of the causes of the Air France flight 447 accident in 1-Jun2008. The mechanics of inflight icing not caused by ice crystals are well established. Aircraft surfaces exposed to supercooled liquid water droplets will accrete ice in direct proportion of the droplet catch and the freezing heat transfer process. The multiphase flow droplet catch is predicted by the simple sum of forces on each spherical droplet and a droplet trajectory calculation based on Lagrangian or Eulerian analysis. The most widely used freezing heat transfer model for inflight icing caused by supercooled droplets was established by Messinger. Several computer programs implement these analytical models to predict inflight icing, with LEWICE being based on Lagrangian analysis and FENSAP being based on Eulerian analysis as the best representatives among them. This Thesis presents the multiphase fluid mechanics particular to ice crystals, and explains how it differs from the established droplet multiphase flow, and the obstacles in implementing the former in computational analysis. A new modification of the Messinger thermal model is proposed to account for ice accretion produced by ice crystal impingement. Because there exist no computational and experimental ways to fully replicate ice crystal inflight icing, and because existing ice protections systems consume vast amounts of energy, a new ice protection device based on dielectric barrier discharge plasma is proposed and built in this Thesis, called DBDAIS, with a complete description of the anti-ice cycle. Contrary to existing ice protection systems, which either heat the aircraft surfaces, or mechanically remove the accreted ice, the DBDAIS employs non-thermal plasma discharges to prevent ice accretion. A new apparatus that mimics inflight icing based on combining the liquid sprays of liquid nitrogen and water was designed and fabricated, named LNITA. The apparatus produces ice similar to glaze ice and rime ice, the two characteristic types of ice from inflight icing, at the cost of 1% of similar tests in icing wind tunnels. Nineteen experiments of the DBDAIS were performed in the LNITA. The results from the experiments point to 32 kV and 4 kHz being adequate to prevent ice accretion, with a power consumption of 1 W/cm2. This compares favorably to existing ice protection systems, which typically run at 10 W/cm2, and to the power consumption of a typical electric stove burner at maximum power, which is 5 W/cm2. To complete this Thesis, a design and development project is proposed to implement the DBDAIS in Unmanned Aircraft Systems (UAS), with the selection of standard FAA inflight icing conditions, the run of 240 LEWICE simulations, and an analysis of the run results. The computational results lead to the design of a wing boot covering the airfoil from 20% of the lower pressure surface to 4% of the upper suction surface as the optimal protection for a UAS.

Rios Pabon, Manuel A.

6

Quasi-Spherical Light Cones of the Kerr Geometry  

E-print Network

Quasi-spherical light cones are lightlike hypersurfaces of the Kerr geometry that are asymptotic to Minkowski light cones at infinity. We develop the equations of these surfaces and examine their properties. In particular, we show that they are free of caustics for all positive values of the Kerr radial coordinate r. Useful applications include the propagation of high-frequency waves, the definition of Kruskal-like coordinates for a spinning black hole and the characteristic initial-value problem.

Frans Pretorius; Werner Israel

1998-03-25

7

Modeling Commercial Turbofan Engine Icing Risk With Ice Crystal Ingestion  

NASA Technical Reports Server (NTRS)

The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to ice crystal ingestion, partially melting, and ice accretion on the compression system components. The result was degraded engine performance, and one or more of the following: loss of thrust control (roll back), compressor surge or stall, and flameout of the combustor. As ice crystals are ingested into the fan and low pressure compression system, the increase in air temperature causes a portion of the ice crystals to melt. It is hypothesized that this allows the ice-water mixture to cover the metal surfaces of the compressor stationary components which leads to ice accretion through evaporative cooling. Ice accretion causes a blockage which subsequently results in the deterioration in performance of the compressor and engine. The focus of this research is to apply an engine icing computational tool to simulate the flow through a turbofan engine and assess the risk of ice accretion. The tool is comprised of an engine system thermodynamic cycle code, a compressor flow analysis code, and an ice particle melt code that has the capability of determining the rate of sublimation, melting, and evaporation through the compressor flow path, without modeling the actual ice accretion. A commercial turbofan engine which has previously experienced icing events during operation in a high altitude ice crystal environment has been tested in the Propulsion Systems Laboratory (PSL) altitude test facility at NASA Glenn Research Center. The PSL has the capability to produce a continuous ice cloud which are ingested by the engine during operation over a range of altitude conditions. The PSL test results confirmed that there was ice accretion in the engine due to ice crystal ingestion, at the same simulated altitude operating conditions as experienced previously in flight. The computational tool was utilized to help guide a portion of the PSL testing, and was used to predict ice accretion could also occur at significantly lower altitudes. The predictions were qualitatively verified by subsequent testing of the engine in the PSL. The PSL test has helped to calibrate the engine icing computational tool to assess the risk of ice accretion. The results from the computer simulation identified prevalent trends in wet bulb temperature, ice particle melt ratio, and engine inlet temperature as a function of altitude for predicting engine icing risk due to ice crystal ingestion.

Jorgenson, Philip C. E.; Veres, Joseph P.

2013-01-01

8

Supernumerary ice-crystal halos?  

PubMed

Geometric-optics singularities in the intensity profiles of refraction halos formed by randomly oriented ice crystals are softened by diffraction and decorated with fine supernumerary fringes. If the crystals have a fixed symmetry axis (as in parhelia), the geometric singularity is a square-root divergence, as in the rainbow. However, the universal curve that describes diffraction is different from the rainbow's Airy function, with weak maxima (supernumerary fringes) on the geometrically dark region inside the halo (and even fainter fringes outside); these are much smaller than their counterparts on the light side of rainbows. If the crystals have no preferred orientation (as in the 22° halo), the geometric singularity is a step. In this case the universal diffraction function has no maxima, and its supernumeraries are shoulders rather than maxima. The low contrast of the fringes is probably the main reason why supernumerary halos are rarely if ever seen. PMID:20935824

Berry, M V

1994-07-20

9

Retardation of ice crystallization by short peptides  

Microsoft Academic Search

The effect of short peptides on the growth of ice crystals is studied using molecular dynamics simulations. The simulations focus on two sequences (Gly-Pro-Ala-Gly and Gly-Gly-Ala-Gly) that are found in collagen hydrolysate, a substance that is known to retard crystal growth. In the absence of peptides, the growth of ice crystal in the solution with the ice\\/water interface is observed

Jun Soo Kim; Arun Yethiraj

2009-01-01

10

An Overview of NASA Engine Ice-Crystal Icing Research  

NASA Technical Reports Server (NTRS)

Ice accretions that have formed inside gas turbine engines as a result of flight in clouds of high concentrations of ice crystals in the atmosphere have recently been identified as an aviation safety hazard. NASA s Aviation Safety Program (AvSP) has made plans to conduct research in this area to address the hazard. This paper gives an overview of NASA s engine ice-crystal icing research project plans. Included are the rationale, approach, and details of various aspects of NASA s research.

Addy, Harold E., Jr.; Veres, Joseph P.

2011-01-01

11

Quasi-Spherical Implosions on ZR as a Novel Source for Effects Testing  

Microsoft Academic Search

Summary form only given. Quasi-spherical Z-pinch loads may be formed by an array of wires laid down on an appropriate path along the surface of a quasi-sphere. A 2-cm diameter quasi-spherical 18-mg, copper 160-wire-array or wire-basket has been designed as a load for ZR at 28-MA. Internal to this load is 4-mg of foam at a 1-cm diameter. 1D hydrodynamic

Thomas J. Nash; Christopher Deeney

2005-01-01

12

Impurities in Spin Ice Crystals  

NASA Astrophysics Data System (ADS)

Spin ice crystals (and pyrochlore oxides in general) have raised a lot of interest of late thanks to their exotic properties, including emergent gauge symmetries, possible spin liquid behavior, and magnetic monopole excitations. Theoretical and experimental efforts in the study of these materials have benefited from the relative ease of growth of large clean single crystals. Even in such clean systems, however, impurities can play a crucial role in determining the properties at very low temperatures (see e.g., C. Henley, http://arxiv.org/abs/1210.8137). Here we investigate this issue both experimentally and theoretically. We study how controlled non-magnetic Y-dilution in Dy2Ti2O7 gradually alters the effective monopole description and the thermodynamic properties of the system at low temperature (extending earlier work by other authors to regimes that have not been investigated so far). We also study how oxygen deficiency affects spin ice samples, and we discuss how the oxygen stoichiometry can be quantified and controlled experimentally.

Sala, Gabriele; Castelnovo, Claudio; Goff, Jon; Gutmann, Matthias; Dharmalingam, Prabhakaran

2013-03-01

13

Structure of ice crystallized from supercooled water  

PubMed Central

The freezing of water to ice is fundamentally important to fields as diverse as cloud formation to cryopreservation. At ambient conditions, ice is considered to exist in two crystalline forms: stable hexagonal ice and metastable cubic ice. Using X-ray diffraction data and Monte Carlo simulations, we show that ice that crystallizes homogeneously from supercooled water is neither of these phases. The resulting ice is disordered in one dimension and therefore possesses neither cubic nor hexagonal symmetry and is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I. Stacking disorder and stacking faults have been reported earlier for metastable ice I, but only for ice crystallizing in mesopores and in samples recrystallized from high-pressure ice phases rather than in water droplets. Review of the literature reveals that almost all ice that has been identified as cubic ice in previous diffraction studies and generated in a variety of ways was most likely stacking-disordered ice I with varying degrees of stacking disorder. These findings highlight the need to reevaluate the physical and thermodynamic properties of this metastable ice as a function of the nature and extent of stacking disorder using well-characterized samples. PMID:22232652

Malkin, Tamsin L.; Murray, Benjamin J.; Brukhno, Andrey V.; Anwar, Jamshed; Salzmann, Christoph G.

2012-01-01

14

Design, simulation, and application of quasi-spherical z-pinch implosions driven by tens of mega-amperes.  

SciTech Connect

A quasi-spherical z-pinch may directly compress foam or deuterium and tritium in three dimensions as opposed to a cylindrical z-pinch, which compresses an internal load in two dimensions only. Because of compression in three dimensions the quasi-spherical z-pinch is more efficient at doing pdV work on an internal fluid than a cylindrical pinch. Designs of quasi-spherical z-pinch loads for the 28 MA 100 ns driver ZR, results from zero-dimensional (0D) circuit models of quasi-spherical implosions, and results from 1D hydrodynamic simulations of quasi-spherical implosions heating internal fluids will be presented. Applications of the quasi-spherical z-pinch implosions include a high radiation temperature source for radiation driven experiments, a source of neutrons for treating radioactive waste, and a source of fusion energy for a power generator.

Struve, Kenneth William; Deeney, Christopher D.; Leeper, Ramon Joe; McDaniel, Dillon Heirman; Nash, Thomas J.; DeGroot, John Stacey; Sanford, Thomas W. L.

2004-08-01

15

Retardation of ice crystallization by short peptides  

NASA Astrophysics Data System (ADS)

The effect of short peptides on the growth of ice crystals is studied using molecular dynamics simulations. The simulations focus on two sequences (Gly-Pro-Ala-Gly and Gly-Gly-Ala-Gly) that are found in collagen hydrolysate, a substance that is known to retard crystal growth. In the absence of peptides, the growth of ice crystal in the solution with the ice/water interface is observed in at a rate comparable to the experimental data. When peptides are present in the liquid phase, the crystal growth is retarded to a significant extent compared to the pure water. It is found that Gly-Pro-Ala-Gly is more effective (crystallization is up to 5 times slower than in its absence) than Gly-Gly-Ala-Gly (up to 3 times slower) implying that the role of the proline residue is important. The mechanism can be understood in the nature of binding of the peptides to the growing crystal.

Kim, Jun Soo; Yethiraj, Arun

2009-03-01

16

Adiabatic Quasi-Spherical Compressions Driven by Magnetic Pressure for Inertial Confinement Fusion  

SciTech Connect

The magnetic implosion of a high-Z quasi-spherical shell filled with DT fuel by the 20-MA Z accelerator can heat the fuel to near-ignition temperature. The attainable implosion velocity on Z, 13-cm/{micro}s, is fast enough that thermal losses from the fuel to the shell are small. The high-Z shell traps radiation losses from the fuel, and the fuel reaches a high enough density to reabsorb the trapped radiation. The implosion is then nearly adiabatic. In this case the temperature of the fuel increases as the square of the convergence. The initial temperature of the fuel is set by the heating of an ion acoustic wave to be about 200-eV after a convergence of 4. To reach the ignition temperature of 5-keV an additional convergence of 5 is required. The implosion dynamics of the quasi-spherical implosion is modeled with the 2-D radiation hydrodynamic code LASNEX. LASNEX shows an 8-mm diameter quasi-spherical tungsten shell on Z driving 6-atmospheres of DT fuel nearly to ignition at 3.5-keV with a convergence of 20. The convergence is limited by mass flow along the surface of the quasi-spherical shell. With a convergence of 20 the final spot size is 400-{micro}m in diameter.

NASH,THOMAS J.

2000-11-01

17

A quasi-spherical gravitational wave solution in Kaluza-Klein theory  

E-print Network

An exact solution of the source-free Kaluza-Klein field equations is presented. It is a 5D generalization of the Robinson-Trautman quasi-spherical gravitational wave with a cosmological constant. The properties of the 5D solution are briefly described.

Zareyan, M

1996-01-01

18

A Convection Chamber for Measuring Ice Crystal Growth Dynamics  

E-print Network

A Convection Chamber for Measuring Ice Crystal Growth Dynamics Kenneth G. Libbrecht1 and Helen C the growth of ice crystals from water vapor in the presence of a background gas. Crystals grow in free fall the growth and morphology of ice crystals over a broad range of conditions, as a function of temperature

Libbrecht, Kenneth G.

19

Aggregation of ice crystals in cirrus  

NASA Technical Reports Server (NTRS)

Results are given from analysis of the aggregation of thick plate, columnar, and bullet rosette ice crystals in cirrus. Data were obtained from PMS 2D-C images, oil coated slides, and aircraft meteorological measurements. Crystal size ranged from 100 to 900 microns in temperatures from -30 to -45 C. The results indicate that the ratio of the sizes of aggregating crystals and the difference of their terminal velocities are important in aggregation. The collection efficiency was calculated for the thick plate crystals from the same data.

Kajikawa, Masahiro; Heymsfield, Andrew J.

1989-01-01

20

Dynamics of quasi-spherical Z-pinch implosions with mass redistribution and displacement modification  

NASA Astrophysics Data System (ADS)

Implosions of (quasi-)spherical loads with mass redistribution and displacement modification are investigated numerically. Both methods can theoretically counterbalance the nonuniformity of magnetic pressure along the load surface and realize quasi-spherical Z-pinch implosions. Mass redistribution is feasible for spherical loads with large radius and weight, while the displacement modification is more suitable for light loads, such as those composed of wire arrays. Simulation results suggest that, for mass redistributed spherical loads, wall instabilities induced by polar mass flows will deform the imploding shell. For prolate spherical loads, in which the wall instability cannot develop, the kinetic energy distribution is disturbed at high latitude. These passive behaviors and their possible mitigation methods, such as reshaping the electrode, are investigated numerically in this paper.

Zhang, Yang; Ding, Ning; Li, Zheng-Hong; Sun, Shun-Kai; Xue, Chuang; Ning, Cheng; Xiao, De-Long; Huang, Jun

2012-12-01

21

Carbon dioxide enhances fragility of ice crystals  

NASA Astrophysics Data System (ADS)

Ice caps and glaciers cover 7% of the Earth, greater than the land area of Europe and North America combined, and play an important role in global climate. The small-scale failure mechanisms of ice fracture, however, remain largely elusive. In particular, little understanding exists about how the presence and concentration of carbon dioxide molecules, a significant component in the atmosphere, affects the propensity of ice to fracture. Here we use atomic simulations with the first-principles based ReaxFF force field capable of describing the details of chemical reactions at the tip of a crack, applied to investigate the effects of the presence of carbon dioxide molecules on ice fracture. Our result shows that increasing concentrations of carbon dioxide molecules significantly decrease the fracture toughness of the ice crystal, making it more fragile. Using enhanced molecular sampling with metadynamics we reconstruct the free energy landscape in varied chemical microenvironments and find that carbon dioxide molecules affect the bonds between water molecules at the crack tip and decrease their strength by altering the dissociation energy of hydrogen bonds. In the context of glacier dynamics our findings may provide a novel viewpoint that could aid in understanding the breakdown and melting of glaciers, suggesting that the chemical composition of the atmosphere can be critical to mediate the large-scale motion of large volumes of ice.

Qin, Zhao; Buehler, Markus J.

2012-11-01

22

Sensitivity of Cirrus Bidirectional Reflectance at MODIS Bands to Vertical Inhomogeneity of Ice Crystal Habits and Size Distribution  

NASA Technical Reports Server (NTRS)

A common assumption in satellite imager-based cirrus retrieval algorithms is that the radiative properties of a cirrus cloud may be represented by those associated with a specific ice crystal shape (or habit) and a single particle size distribution. However, observations of cirrus clouds have shown that the shapes and sizes of ice crystals may vary substantially with height within the clouds. In this study we investigate the sensitivity of the top-of-atmosphere bidirectional reflectances at two MODIS bands centered at 0.65 micron and 2.11 micron to the cirrus models assumed to be either a single homogeneous layer or three distinct but contiguous, layers. First, we define the single- and three-layer cirrus cloud models with respect to ice crystal habit and size distribution on the basis of in situ replicator data acquired during the First ISCCP Regional Experiment (FIRE-II), held in Kansas during the fall of 1991. Subsequently, fundamental light scattering and radiative transfer theory is employed to determine the single scattering and the bulk radiative properties of the cirrus cloud. Regarding the radiative transfer computations, we present a discrete form of the adding/doubling principle by introducing a direct transmission function, which is computationally straightforward and efficient an improvement over previous methods. For the 0.65 micron band, at which absorption by ice is negligible, there is little difference between the bidirectional reflectances calculated for the one- and three-layer cirrus models, suggesting that the vertical inhomogeneity effect is relatively unimportant. At the 2.11 micron band, the bidirectional reflectances computed for both optically thin (tau = 1) and thick (tau = 10) cirrus clouds show significant differences between the results for the one- and three-layer models. The reflectances computed for the three-layer cirrus model are substantially larger than those computed for the single-layer cirrus. Finally, we find that cloud reflectance is very sensitive to the optical properties of the small crystals that predominate in the top layer of the three-layer cirrus model. It is critical to define the most realistic geometric shape for the small "quasi-spherical" ice crystals in the top layer for obtaining reliable single-scattering parameters and bulk radiative properties of cirrus.

Yang, P.; Gao, B.-C.; Baum, B. A.; Wiscombe, W.; Hu, Y.; Nasiri, S. L.; Soulen, P. F.; Heymsfield, A. J.; McFarquhar, G. M.; Miloshevich, L. M.

2000-01-01

23

Atmospheric Ice Crystals over the Antarctic Plateau in Winter  

Microsoft Academic Search

Falling ice crystals were collected daily on a gridded glass slide at South Pole Station, Antarctica, during the Antarctic winter of 1992 and were photographed through a microscope. Nine types of ice crystals are identified, which fall into three main categories: `diamond dust,' blowing snow, and snow grains. The dimensions of about 20 000 crystals were measured on scanned images

Von P. Walden; Stephen G. Warren; Elizabeth Tuttle

2003-01-01

24

Atmospheric Ice Crystals over the Antarctic Plateau in Winter  

Microsoft Academic Search

Falling ice crystals were collected daily on a gridded glass slide at South Pole Station, Antarctica, during the Antarctic winter of 1992 and were photographed through a microscope. Nine types of ice crystals are identified, which fall into three main categories: ''diamond dust,'' blowing snow, and snow grains. The dimensions of about 20 000 crystals were measured on scanned images

Von P. Walden; Stephen G. Warren; Elizabeth Tuttle

2003-01-01

25

The Microscopic Features of Heterogeneous Ice Nucleation May Affect the Macroscopic Morphology of Atmospheric Ice Crystals  

E-print Network

The Microscopic Features of Heterogeneous Ice Nucleation May Affect the Macroscopic Morphology of Atmospheric Ice Crystals Stephen J. Cox,1, 2 Zamaan Raza,1 Shawn M. Kathmann,3 Ben Slater,1 and Angelos ice that forms under "mild" conditions (temperatures > -40 C) requires the presence of a nucleating

Alavi, Ali

26

Time-dependent Evolution of Quasi-spherical, Self-gravitating Accretion Flow  

NASA Astrophysics Data System (ADS)

A self-similar solution for the time evolution of quasi-spherical, self-gravitating accretion flows is obtained under the assumption that the heat generated by viscosity is retained in the flow. The solutions are parameterized by the ratio of the mass of the accreting gas to the central object mass and the viscosity coefficient. While the density and the pressure are obtained simply by solving a set of ordinary differential equations, the radial and the rotational velocities are presented analytically. Profiles of the density and the rotational velocities show two distinct features. A low-density outer accreting flow with a relatively flat rotation velocity surrounds an inner high-density region. In the inner part, the rotational velocity increases from the center to a transition radius that separates the inner and outer portions. We show that the behavior of the solutions in the inner region depends on the ratio of the heat capacities, ?, and on the viscosity coefficient, ?.

Shadmehri, Mohsen

2004-09-01

27

On the global visibility of singularity in quasi-spherical collapse  

E-print Network

We analyze here the issue of local versus the global visibility of a singularity that forms in gravitational collapse of a dust cloud, which has important implications for the weak and strong versions of the cosmic censorship hypothesis. We find conditions as to when a singularity will be only locally naked, rather than being globally visible, thus preseving the weak censorship hypothesis. The conditions for formation of a black hole or naked singularity in the Szekeres quasi-spherical collapse models are worked out. The causal behaviour of the singularity curve is studied by examining the outgoing radial null geodesics, and the final outcome of collapse is related to the nature of the regular initial data specified on an initial hypersurface from which the collapse evolves. An interesting feature that emerges is the singularity in Szekeres spacetimes can be ``directionally naked''.

S. S. Deshingkar; S. Jhingan; P. S. Joshi

1998-06-11

28

Ice-Crystal Fallstreaks from Supercooled Liquid Water Parent Clouds  

NASA Technical Reports Server (NTRS)

On 31 December 2001, ice-crystal fallstreaks (e.g., cirrus uncinus, or colloquially "Mare's Tails") from supercooled liquid water parent clouds were observed by ground-based lidars pointed vertically from the Atmospheric Radiation Measurement Southern Great Plains (SGP) facility near Lamont, Oklahoma. The incidence of liquid phase cloud with apparent ice-phase precipitation is investigated. Scenarios for mixed-phase particle nucleation, and fallstreak formation and sustenance are discussed. The observations are unique in the context of the historical reverence given to the commonly observed c h s uncinus fallstreak (wholly ice) versus this seemingly contradictory coincidence of liquid water begetting ice-crystal streaks.

Campbell, James R.; O'C. Starr, David; Welton, Ellsworth J.; Spinhirne, James D.; Ferrare, Richard A.

2003-01-01

29

Ice crystallization in water's "no-man's land".  

PubMed

The crystallization of water at 180 K is studied through large-scale molecular dynamics simulations with the monatomic water model mW. This temperature is in the middle of water's "no-man's land," where rapid ice crystallization prevents the elucidation of the structure of liquid water and its transformation into ice with state of the art experimental methods. We find that critical ice nuclei (that contain less than ten water molecules) form in a time scale shorter than the time required for the relaxation of the liquid, suggesting that supercooled liquid water cannot be properly equilibrated in this region. We distinguish three stages in the crystallization of water at 180 K: concurrent nucleation and growth of ice, followed by consolidation that decreases the number density of ice nuclei, and finally, slow growth of the crystallites without change in their number density. The kinetics of the transformation along the three stages is well described by a single compacted exponential Avrami equation with n approximately 1.7. This work confirms the coexistence of ice and liquid after water is crystallized in "no-man's land": the formation of ice plateaus when there is still 15%-20% of liquid water in the systems, thinly dispersed between ice I crystals with linear dimensions ranging from 3 to 10 nm. We speculate that the nanoscopic size of the crystallites decreases their melting point and slows their evolution toward the thermodynamically most stable fully crystalline state. PMID:20590203

Moore, Emily B; Molinero, Valeria

2010-06-28

30

The effect of ice crystal surface roughness on the retrieval of ice cloud microphysical and optical properties  

E-print Network

The effect of the surface roughness of ice crystals is not routinely accounted for in current cloud retrieval algorithms that are based on pre-computed lookup libraries. In this study, we investigate the effect of ice crystal surface roughness...

Xie, Yu

2007-09-17

31

Diagnosing the Ice Crystal Enhancement Factor in the Tropics  

NASA Technical Reports Server (NTRS)

Recent modeling studies have revealed that ice crystal number concentration is one of the dominant factors in the effect of clouds on radiation. Since the ice crystal enhancement factor and ice nuclei concentration determine the concentration, they are both important in quantifying the contribution of increased ice nuclei to global warming. In this study, long-term cloud-resolving model (CRM) simulations are compared with field observations to estimate the ice crystal enhancement factor in tropical and midlatitudinal clouds, respectively. It is found that the factor in tropical clouds is 10 3-104 times larger than that of mid-latitudinal ones, which makes physical sense because entrainment and detrainment in the Tropics are much stronger than in middle latitudes. The effect of entrainment/detrainment on the enhancement factor, especially in tropical clouds, suggests that cloud microphysical parameterizations should be coupled with subgrid turbulence parameterizations within CRMs to obtain a more accurate depiction of cloud-radiative forcing.

Zeng, Xiping; Tao, Wei-Kuo; Matsui, Toshihisa; Xie, Shaocheng; Lang, Stephen; Zhang, Minghua; Starr, David O'C; Li, Xiaowen; Simpson, Joanne

2009-01-01

32

A Critical Look at Ice Crystal Growth Data KENNETH G. LIBBRECHT1  

E-print Network

A Critical Look at Ice Crystal Growth Data KENNETH G. LIBBRECHT1 Norman Bridge Laboratory. I review published data relating to the growth of ice crystals from water vapor under various of the crystal growth dynamics of ice. 1 Introduction The growth of ice crystals from the vapor phase

Libbrecht, Kenneth G.

33

Effect of the inhomogeneity of ice crystals on retrieving ice cloud optical thickness and effective particle size  

Microsoft Academic Search

Spherical or spheroidal air bubbles are often trapped in rapidly growing ice crystals. In this study, the single-scattering properties of inhomogeneous ice crystals containing air bubbles are investigated. Specifically, a combination of the ray-tracing technique and the Monte Carlo method is used to simulate the scattering of light by randomly oriented large hexagonal ice crystals containing spherical or spheroidal air

Yu Xie; Ping Yang; George W. Kattawar; Patrick Minnis; Yong X. Hu

2009-01-01

34

How big should hexagonal ice crystals be to produce halos?  

PubMed

It has been hypothesized that the frequent lack of halos in observations of cirrus and contrails and laboratory measurements is caused by small ice crystal sizes that put the particles outside the geometrical optics domain of size parameters. We test this hypothesis by exploiting a strong similarity of ray tracing phase functions for finite hexagonal and circular ice cylinders and using T-matrix computations of electromagnetic scattering by circular cylinders with size parameters up to 180 in the visible. We conclude that well-defined halos should be observable for ice crystal size parameters of the order of 100 and larger and discuss remote-sensing implications of this result. PMID:18305781

Mishchenko, M I; Macke, A

1999-03-20

35

Synthesis of monodisperse, quasi-spherical silver nanoparticles with sizes defined by the nature of silver precursors.  

PubMed

Monodisperse, quasi-spherical silver nanoparticles (Ag NPs) with controlled sizes have been produced directly in water via adding the aqueous solutions of the mixtures of AgNO3 and sodium citrate to boiling aqueous solutions of ascorbic acid (AA). Different compounds, including NaCl, NaBr, KI, Na2SO4, Na2CO3, Na2S, and Na3PO4, are added to the AgNO3/citrate mixture solutions to form new silver compounds with fairly low solubility in water, which are used as precursors instead of soluble Ag(+) ions to synthesize Ag NPs via AA/citrate reduction. This enables us not only to produce monodisperse, quasi-spherical Ag NPs but also to tune the sizes of the resulting NPs from 16 to 30 nm according to the potential of new silver precursors as well as the concentrations of anions. PMID:24528373

Li, Houshen; Xia, Haibing; Ding, Wenchao; Li, Yijing; Shi, Qiurong; Wang, Dayang; Tao, Xutang

2014-03-11

36

Zn2+-A?40 Complexes Form Metastable Quasi-spherical Oligomers That Are Cytotoxic to Cultured Hippocampal Neurons*  

PubMed Central

The roles of metal ions in promoting amyloid ?-protein (A?) oligomerization associated with Alzheimer disease are increasingly recognized. However, the detailed structures dictating toxicity remain elusive for A? oligomers stabilized by metal ions. Here, we show that small Zn2+-bound A?1–40 (Zn2+-A?40) oligomers formed in cell culture medium exhibit quasi-spherical structures similar to native amylospheroids isolated recently from Alzheimer disease patients. These quasi-spherical Zn2+-A?40 oligomers irreversibly inhibit spontaneous neuronal activity and cause massive cell death in primary hippocampal neurons. Spectroscopic and x-ray diffraction structural analyses indicate that despite their non-fibrillar morphology, the metastable Zn2+-A?40 oligomers are rich in ?-sheet and cross-? structures. Thus, Zn2+ promotes A?40 neurotoxicity by structural organization mechanisms mediated by coordination chemistry. PMID:22528492

Solomonov, Inna; Korkotian, Eduard; Born, Benjamin; Feldman, Yishay; Bitler, Arkady; Rahimi, Farid; Li, Huiyuan; Bitan, Gal; Sagi, Irit

2012-01-01

37

Zn2+-A?40 complexes form metastable quasi-spherical oligomers that are cytotoxic to cultured hippocampal neurons.  

PubMed

The roles of metal ions in promoting amyloid ?-protein (A?) oligomerization associated with Alzheimer disease are increasingly recognized. However, the detailed structures dictating toxicity remain elusive for A? oligomers stabilized by metal ions. Here, we show that small Zn(2+)-bound A?1-40 (Zn(2+)-A?40) oligomers formed in cell culture medium exhibit quasi-spherical structures similar to native amylospheroids isolated recently from Alzheimer disease patients. These quasi-spherical Zn(2+)-A?40 oligomers irreversibly inhibit spontaneous neuronal activity and cause massive cell death in primary hippocampal neurons. Spectroscopic and x-ray diffraction structural analyses indicate that despite their non-fibrillar morphology, the metastable Zn(2+)-A?40 oligomers are rich in ?-sheet and cross-? structures. Thus, Zn(2+) promotes A?40 neurotoxicity by structural organization mechanisms mediated by coordination chemistry. PMID:22528492

Solomonov, Inna; Korkotian, Eduard; Born, Benjamin; Feldman, Yishay; Bitler, Arkady; Rahimi, Farid; Li, Huiyuan; Bitan, Gal; Sagi, Irit

2012-06-01

38

Ice Crystal Growth Rates Under Upper Troposphere Conditions  

NASA Technical Reports Server (NTRS)

Atmospheric conditions for growth of ice crystals (temperature and ice supersaturation) are often not well constrained and it is necessary to simulate such conditions in the laboratory to investigate such growth under well controlled conditions over many hours. The growth of ice crystals from the vapour in both prism and basal planes was observed at temperatures of -60 C and -70 C under ice supersaturation up to 100% (200% relative humidity) at pressures derived from the standard atmosphere in a static diffusion chamber. Crystals grew outward from a vertical glass filament, thickening in the basal plane by addition of macroscopic layers greater than 2 m, leading to growth in the prism plane by passing of successive layers conveniently viewed by time lapse video.

Peterson, Harold S.; Bailey, Matthew; Hallett, John

2010-01-01

39

Visual Simulation of Ice Crystal Growth  

Microsoft Academic Search

The beautiful, branching structure of ice is one of the most striking visual phenomena of the winter landscape. Yet there is little study about modeling this effect in computer graphics. In this paper, we present a novel approach for visual simulation of ice growth. We use a numerical simulation technique from computational physics, the \\

Theodore Kim; Ming C. Lin

2003-01-01

40

Superheating of ice crystals in antifreeze protein solutions  

PubMed Central

It has been argued that for antifreeze proteins (AFPs) to stop ice crystal growth, they must irreversibly bind to the ice surface. Surface-adsorbed AFPs should also prevent ice from melting, but to date this has been demonstrated only in a qualitative manner. Here we present the first quantitative measurements of superheating of ice in AFP solutions. Superheated ice crystals were stable for hours above their equilibrium melting point, and the maximum superheating obtained was 0.44?°C. When melting commenced in this superheated regime, rapid melting of the crystals from a point on the surface was observed. This increase in melting temperature was more appreciable for hyperactive AFPs compared to the AFPs with moderate antifreeze activity. For each of the AFP solutions that exhibited superheating, the enhancement of the melting temperature was far smaller than the depression of the freezing temperature. The present findings clearly show that AFPs adsorb to ice surfaces as part of their mechanism of action, and this absorption leads to protection of ice against melting as well as freezing. PMID:20215465

Celik, Yeliz; Graham, Laurie A.; Mok, Yee-Foong; Bar, Maya; Davies, Peter L.; Braslavsky, Ido

2010-01-01

41

Scattering Properties of Oriented Hexagonal Ice Crystals  

E-print Network

To interpret the data from spaceborn lidar measurements, one must have a basic understanding of the backscattering of oriented ice particles. The conventional raytracing method is not applicable to the scattering of light by oriented particles...

Zhang, Feng

2010-01-14

42

Ice Growth Measurements from Image Data to Support Ice Crystal and Mixed-Phase Accretion Testing  

NASA Technical Reports Server (NTRS)

This paper describes the imaging techniques as well as the analysis methods used to measure the ice thickness and growth rate in support of ice-crystal icing tests performed at the National Research Council of Canada (NRC) Research Altitude Test Facility (RATFac). A detailed description of the camera setup, which involves both still and video cameras, as well as the analysis methods using the NASA Spotlight software, are presented. Two cases, one from two different test entries, showing significant ice growth are analyzed in detail describing the ice thickness and growth rate which is generally linear. Estimates of the bias uncertainty are presented for all measurements. Finally some of the challenges related to the imaging and analysis methods are discussed as well as methods used to overcome them.

Struk, Peter M.; Lynch, Christopher J.

2012-01-01

43

Ice-binding proteins that accumulate on different ice crystal planes produce distinct thermal hysteresis dynamics  

PubMed Central

Ice-binding proteins that aid the survival of freeze-avoiding, cold-adapted organisms by inhibiting the growth of endogenous ice crystals are called antifreeze proteins (AFPs). The binding of AFPs to ice causes a separation between the melting point and the freezing point of the ice crystal (thermal hysteresis, TH). TH produced by hyperactive AFPs is an order of magnitude higher than that produced by a typical fish AFP. The basis for this difference in activity remains unclear. Here, we have compared the time dependence of TH activity for both hyperactive and moderately active AFPs using a custom-made nanolitre osmometer and a novel microfluidics system. We found that the TH activities of hyperactive AFPs were time-dependent, and that the TH activity of a moderate AFP was almost insensitive to time. Fluorescence microscopy measurement revealed that despite their higher TH activity, hyperactive AFPs from two insects (moth and beetle) took far longer to accumulate on the ice surface than did a moderately active fish AFP. An ice-binding protein from a bacterium that functions as an ice adhesin rather than as an antifreeze had intermediate TH properties. Nevertheless, the accumulation of this ice adhesion protein and the two hyperactive AFPs on the basal plane of ice is distinct and extensive, but not detectable for moderately active AFPs. Basal ice plane binding is the distinguishing feature of antifreeze hyperactivity, which is not strictly needed in fish that require only approximately 1°C of TH. Here, we found a correlation between the accumulation kinetics of the hyperactive AFP at the basal plane and the time sensitivity of the measured TH. PMID:25008081

Drori, Ran; Celik, Yeliz; Davies, Peter L.; Braslavsky, Ido

2014-01-01

44

Crystallization of CO2 ice and the absence of amorphous CO2 ice in space  

PubMed Central

Carbon dioxide (CO2) is one of the most relevant and abundant species in astrophysical and atmospheric media. In particular, CO2 ice is present in several solar system bodies, as well as in interstellar and circumstellar ice mantles. The amount of CO2 in ice mantles and the presence of pure CO2 ice are significant indicators of the temperature history of dust in protostars. It is therefore important to know if CO2 is mixed with other molecules in the ice matrix or segregated and whether it is present in an amorphous or crystalline form. We apply a multidisciplinary approach involving IR spectroscopy in the laboratory, theoretical modeling of solid structures, and comparison with astronomical observations. We generate an unprecedented highly amorphous CO2 ice and study its crystallization both by thermal annealing and by slow accumulation of monolayers from the gas phase under an ultrahigh vacuum. Structural changes are followed by IR spectroscopy. We also devise theoretical models to reproduce different CO2 ice structures. We detect a preferential in-plane orientation of some vibrational modes of crystalline CO2. We identify the IR features of amorphous CO2 ice, and, in particular, we provide a theoretical explanation for a band at 2,328 cm?1 that dominates the spectrum of the amorphous phase and disappears when the crystallization is complete. Our results allow us to rule out the presence of pure and amorphous CO2 ice in space based on the observations available so far, supporting our current view of the evolution of CO2 ice. PMID:23858474

Escribano, Rafael M.; Munoz Caro, Guillermo M.; Cruz-Diaz, Gustavo A.; Rodriguez-Lazcano, Yamilet; Mate, Belen

2013-01-01

45

Ice-binding proteins that accumulate on different ice crystal planes produce distinct thermal hysteresis dynamics.  

PubMed

Ice-binding proteins that aid the survival of freeze-avoiding, cold-adapted organisms by inhibiting the growth of endogenous ice crystals are called antifreeze proteins (AFPs). The binding of AFPs to ice causes a separation between the melting point and the freezing point of the ice crystal (thermal hysteresis, TH). TH produced by hyperactive AFPs is an order of magnitude higher than that produced by a typical fish AFP. The basis for this difference in activity remains unclear. Here, we have compared the time dependence of TH activity for both hyperactive and moderately active AFPs using a custom-made nanolitre osmometer and a novel microfluidics system. We found that the TH activities of hyperactive AFPs were time-dependent, and that the TH activity of a moderate AFP was almost insensitive to time. Fluorescence microscopy measurement revealed that despite their higher TH activity, hyperactive AFPs from two insects (moth and beetle) took far longer to accumulate on the ice surface than did a moderately active fish AFP. An ice-binding protein from a bacterium that functions as an ice adhesin rather than as an antifreeze had intermediate TH properties. Nevertheless, the accumulation of this ice adhesion protein and the two hyperactive AFPs on the basal plane of ice is distinct and extensive, but not detectable for moderately active AFPs. Basal ice plane binding is the distinguishing feature of antifreeze hyperactivity, which is not strictly needed in fish that require only approximately 1°C of TH. Here, we found a correlation between the accumulation kinetics of the hyperactive AFP at the basal plane and the time sensitivity of the measured TH. PMID:25008081

Drori, Ran; Celik, Yeliz; Davies, Peter L; Braslavsky, Ido

2014-09-01

46

Geometric-opticsintegral-equation method for light scattering by nonspherical ice crystals  

E-print Network

Geometric-optics­integral-equation method for light scattering by nonspherical ice crystals Ping-scattering and polar- ization properties for arbitrarily oriented hexagonal ice crystals. The model uses the ray-tracing tech- nique to solve the near field on the ice crystal surface, which is then transformed to the far

Liou, K. N.

47

Critical Supersaturation for Ice Crystal Growth: Laboratory Measurements and Atmospheric Modeling Implications  

Microsoft Academic Search

An improved understanding of ice crystal growth, particularly at low temperatures, is much in demand for the advancement of numerical modeling of atmospheric processes. Cirrus models must contend with the complexity of ice crystals growing in cold temperatures, low pressures, low supersaturations, and with multiple nucleation mechanisms. Recent observations have allowed increasingly realistic parameterizations of cirrus ice crystal microphysics, but

N. Magee; A. Moyle; D. Lamb

2003-01-01

48

Supernumerary ice-crystal halos? Michael V. Berry  

E-print Network

profiles of refraction halos formed by randomly oriented ice crystals are softened by diffraction), the geometric singularity is a square-root divergence, as in the rainbow. However, the universal curve that describes diffraction is different from the rainbow's Airy function, with weak maxima (supernumerary fringes

Berry, Michael Victor

49

Ice nucleation: elemental identification of particles in snow crystals.  

PubMed

A scanning field-emission electron microscope combined with an x-ray analyzer is used to locate the ice nucleus within a three-dimensional image of a snow crystal and determine the chemical composition of the nucleus. This makes it possible to better understand the effect of nuclei in cloud seeding. PMID:17806581

Parungo, F P; Pueschel, R F

1973-06-01

50

Ice crystal growth in a dynamic thermal diffusion chamber  

NASA Technical Reports Server (NTRS)

Ice crystals were grown in a supersaturated environment produced by a dynamic thermal diffusion chamber, which employed two horizontal plates separated by a distance of 2.5 cm. Air was circulated between and along the 1.2 m length of the plates past ice crystals which nucleated and grew from a fiber suspended vertically between the two plates. A zoom stereo microscope with a magnification which ranged from 3X to 80X and both 35 mm still photographs and 16 mm time lapse cine films taken through the microscope were used to study the variation of the shape and linear growth rate of ice crystals as a function of the ambient temperature, the ambient supersaturation, and the forced ventilation velocity. The ambient growth conditions were varied over the range of temperature 0 to -40 C, over the range of supersaturation 4% to 50% with respect to ice, and over the range of forced ventilation velocities 0 cm/s to 20 cm/s.

Keller, V. W.

1980-01-01

51

Laboratory Investigation of Direct Measurement of Ice Water Content, Ice Surface Area, and Effective Radius of Ice Crystals Using a Laser-Diffraction Instrument  

NASA Technical Reports Server (NTRS)

The aircraft microphysics probe, PVM-100A, was tested in the Colorado State University dynamic cloud chamber to establish its ability to measure ice water content (IWC), PSA, and Re in ice clouds. Its response was compared to other means of measuring those ice-cloud parameters that included using FSSP-100 and 230-X 1-D optical probes for ice-crystal concentrations, a film-loop microscope for ice-crystal habits and dimensions, and an in-situ microscope for determining ice-crystal orientation. Intercomparisons were made in ice clouds containing ice crystals ranging in size from about 10 microns to 150 microns diameter, and ice crystals with plate, columnar, dendritic, and spherical shapes. It was not possible to determine conclusively that the PVM accurately measures IWC, PSA, and Re of ice crystals, because heat from the PVM evaporated in part the crystals in its vicinity in the chamber thus affecting its measurements. Similarities in the operating principle of the FSSP and PVM, and a comparison between Re measured by both instruments, suggest, however, that the PVM can make those measurements. The resolution limit of the PVM for IWC measurements was found to be on the order of 0.001 g/cubic m. Algorithms for correcting IWC measured by FSSP and PVM were developed.

Gerber, H.; DeMott, P. J.; Rogers, D. C.

1995-01-01

52

Study of the implosion characteristics of quasi-spherical wire arrays on the Angara-5-1 facility at currents of up to 4 MA  

SciTech Connect

Results are presented from experimental studies of the spatial distribution of the density of matter in the central part of the discharge gap and the formation of the temporal profile of the X-ray power in the course of implosion of quasi-spherical wire arrays at discharge currents of up to 4 MA. The spatial distribution of the X-ray intensity in the central part of the discharge gap and the temporal profile of the X-ray power are used as implosion characteristics of quasi-spherical wire arrays. The quasi-spherical arrays were formed by the radial stretching of unstrained wires of initially cylindrical and conical wire arrays under the action of the electrostatic field. The temporal profile of the output X-ray pulse in the photon energy range of 0.1-1 keV is shown to depend on both the geometrical parameters of the quasi-spherical array and the longitudinal distribution of its mass. It is found that a 40% increase in the wire mass due to deposition of an additional mass in the equatorial region of a quasi-spherical array leads to a 15% increase in the average current radius of the pinch and a 30% decrease in the X-ray yield. Experiments with quasi-spherical arrays made of kapron fibers with deposited Al and Bi conducting layers were also carried out. It is demonstrated that application of such arrays makes it possible to control the profile and duration of the generated X-ray pulse by varying the mass, material, and location of the deposited layer. It is found that deposition of an additional mass in the form of a thin Bi stripe on tungsten wires near the cathode end of the array allows one to mitigate the influence of the cathode zipper effect on the pinch compression and formation of the X-ray pulse in tungsten arrays.

Aleksandrov, V. V.; Volkov, G. S.; Grabovski, E. V.; Gribov, A. N.; Gritsuk, A. N.; Laukhin, Ya. N.; Mitrofanov, K. N.; Oleinik, G. M.; Sasorov, P. V.; Frolov, I. N. [Troitsk Institute for Innovation and Fusion Research (Russian Federation)

2012-04-15

53

The microphysical properties of small ice particles measured during MACPEX  

NASA Astrophysics Data System (ADS)

During the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) field campaign, the Small Ice Detector version 3 (SID-3) and the NCAR Video Ice Particle Sampler (VIPS) probes were operated onboard the NASA WB-57 aircraft to measure the microphysical properties of small ice particles in midlatitude cirrus clouds. The VIPS was optimized to measure the particle size distribution and projected area properties of ice particles between 20 and 200 microns and measurements agreed well with other microphysical probes. SID-3 measures the forward light scattering pattern from ice particles in the 1 to 100 micron size range. Forward scattering patterns can be used to characterize ice particle shape as well as surface roughness. Scattering patterns appear to be 'speckled' when particles have surface roughness and/or are polycrystalline. Scattering patterns can be used to identify quasi-spherical ice particles as well as particles which are sublimating. Sublimating crystals, spherical ice particles, and particles with surface roughness were all observed by SID-3 during MACPEX. Observed particle properties will be correlated to concurrent atmospheric observations. Measurements from the controlled environment of the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber will be related to atmospheric particle measurements.

Schmitt, C. G.; Schnaiter, M.; Heymsfield, A.; Bansemer, A.; Hirst, E.

2012-12-01

54

Optical Properties of Small Ice Crystals with Black Carbon Inclusions  

NASA Astrophysics Data System (ADS)

The optical properties of ice crystals play a fundamental role in modeling atmospheric radiation and hydrological cycle, which are critical in monitoring climate change. While Black Carbon (BC) is recognized as the dominant absorber with positive radiative forcing (warming) (Ramanathan & Carmichael, 2008), in-situ observations (Cappa, et al, 2012) indicate that the characterization of the mixing state of BC with ice crystals and other non-BC particles in global climate models (Ghan & Schwartz, 2007) needs further investigation. The limitation in the available mixing models is due to the drastically different absorbing properties of BC compared to other aerosols. We explore the scattering properties of ice crystals (in shapes commonly found in cirrus clouds and contrails - Yang, et al. 2012) with the inclusion of BC particles. The Discrete Dipole Approximation (DDA) (Yurkin & Hoekstra, 2011) is utilized to directly calculate the optical properties of the crystals with multiple BC inclusions, modeled as a distribution of spheres. The results are then compared with the most popular models of internal and external mixing (Liou, et al. 2011). The DDA calculations are carried out over a broad range of BC particle sizes and volume fractions within the crystal at the 532 nm wavelength and for ice crystals smaller than 50 ?m. The computationally intensive database generated in this study is critical for understanding the effect of different types of BC inclusions on the atmosphere radiative forcing. Examples will be discussed to illustrate the modification of BC optical properties by encapsulation in ice crystals and how the parameterization of the BC mixing state in global climate models can be improved. Acknowledgements Support by Sandia National Laboratories' LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. Cappa, C.D., Onasch, T.B., Massoli, et al. (2012). Radiative absorption enhancements due to the mixing state of atmospheric black carbon. Science, 337(6098), 1078-1081. Ghan, S.J., & Schwartz, S.E. (2007). Aerosol properties and processes: A path from field and laboratory measurements to global climate models. Bulletin of the American Meteorological Society, 88(7), 1059-1083. Liou, K.N., Takano, Y., & Yang, P. (2011). Light absorption and scattering by aggregates: Application to black carbon and snow grains. Journal of Quantitative Spectroscopy and Radiative Transfer, 112(10), 1581-1594. Ramanathan, V., & Carmichael, G. (2008). Global and regional climate changes due to black carbon. Nature Geoscience, 1(4), 221-227. Yang, P., Bi, L., Baum, B.A., et al. (2013). Spectrally Consistent Scattering, Absorption, and Polarization Properties of Atmospheric Ice Crystals at Wavelengths from 0.2 to 100 ? m. Journal of the Atmospheric Sciences, 70(1), 330-347. Yurkin, M.A., & Hoekstra, A.G. (2011). The discrete-dipole-approximation code ADDA: capabilities and known limitations. Journal of Quantitative Spectroscopy and Radiative Transfer, 112(13), 2234-2247.

Yang, X.; Geier, M.; Arienti, M.

2013-12-01

55

Geometrical-optics solution to light scattering by droxtal ice crystals  

E-print Network

Geometrical-optics solution to light scattering by droxtal ice crystals Zhibo Zhang, Ping Yang crystals. At the 11- m wavelength, the phase functions for droxtals are essentially featureless because- in . Radiative transfer modeling efforts have been hampered by the nonspherical nature of observed ice crystals

Baum, Bryan A.

56

Observations of an Impurity-driven Hysteresis Behavior in Ice Crystal Growth at Low Pressure  

E-print Network

Observations of an Impurity-driven Hysteresis Behavior in Ice Crystal Growth at Low Pressure Abstract. We describe observations of a novel hysteresis behavior in the growth of ice crystals under near the growth velocity vn normal to the surface of a crystal facet in terms of the Hertz-Knudsen formula vn

Libbrecht, Kenneth G.

57

Identification of a Novel "Fishbone" Structure in the Dendritic Growth of Columnar Ice Crystals  

E-print Network

Identification of a Novel "Fishbone" Structure in the Dendritic Growth of Columnar Ice Crystals will be an interesting challenge in understanding diffusion-limited crystal growth in the presence of highly anisotropic branching along growth directions that are not aligned with respect to the ice crystal lattice. Examples

Libbrecht, Kenneth G.

58

Precision Measurements of Ice Crystal Growth Rates Kenneth G. Libbrecht1  

E-print Network

Precision Measurements of Ice Crystal Growth Rates Kenneth G. Libbrecht1 Department of Physics precise measurements of the growth rates of the principal facets of ice crystals. Particular attention Introduction The growth of snow crystals from water vapor in air is governed by a number of factors, with vapor

Libbrecht, Kenneth G.

59

Optical detection and characterization of ice crystals in LACIS  

NASA Astrophysics Data System (ADS)

Tropospheric ice and mixed phase clouds are an integral part of the earth system and their microphysical and radiative properties are strongly coupled e.g. through the complexities of the ice nucleation process. Therefore the investigation of influences of different aerosol particles which act as ice nuclei (IN) on the freezing behaviour of cloud droplets is important and still poses unresolved questions. The Leipzig Aerosol and Cloud Interaction Simulator (LACIS) is used to investigate the IN activity of different natural and artificial aerosol particles (mineral dust, soot etc.) in heterogeneous freezing processes (immersion or deposition freezing). A critical part of LACIS is the particle detection system allowing for size-resolved counting of activated seed particles and discrimination between ice crystals and water droplets. Recently, two instruments have been developed to provide these measurements at the LACIS facility. The Thermally-stabilized Optical Particle Spectrometer (TOPS) is measuring the particle size based on the intensity of light scattered by individual particles into a near-forward (15° to 45°) direction. Two symmetrical forward scattering channels allow for optical determination of the sensing volume, thus reducing the coincidence counting error and the edge zone effect. The backscatter channel (162° to 176°) equipped with a rotatable cross polarizer allows for establishing the change in linear polarization state of the scattered light. The backscatter elevation angle is limited so that the linear depolarization of light scattered by spherical particles of arbitrary size is zero. Any detectable signal in the depolarization channel can be therefore attributed to non-spherical particles (ice crystals). With consideration of the signal in the backscatter channel the separate counting of water drops and ice particle is possible. The Leipzig Ice Scattering Apparatus (LISA) is a modified version of the Small Ice Detector (SID3), developed at the Science and Technology Research Institute at the University of Hertfordshire, UK. The SID instruments have been developed primarily as wing-mounted systems for airborne studies of cloud ice particles. SID3 records the forward scattered light pattern with high angular resolution using an intensified CCD (780 by 582 pixels) at a rate of 20 images per second. In addition to the SID3 capabilities, LISA is able to measure the circular depolarization ratio in the range of scattering angles from 166° to 172°. Whereas particle size, shape and orientation are characterized by the angular distribution of forward-scattered light, the measured value of the circular depolarization can be used to validate the existing theoretical models of light scattering by irregular particles (RTDF, GSVM, T-Matrix, DDA). The first measurements done at the LACIS facility have demonstrated a promising sensitivity of LISA's depolarization channel to the shape of ice crystals. Results showed an increase of the mean circular depolarization ratio from 1.5 (characteristic for the liquid water droplets above 3 µm) to 2.5 for the "just frozen" almost-spherical droplets in the same size range. The presentation will describe details of instruments set up and present some exemplary results from experiments carried out at LACIS and AIDA (KIT) facilities.

Kiselev, Alexei; Clauß, Tina; Niedermeier, Dennis; Hartmann, Susan; Wex, Heike; Stratmann, Frank

2010-05-01

60

Numerical Simulation of Three-Dimensional Unsteady Flow past Ice Crystals  

Microsoft Academic Search

The unsteady flow fields around falling columnar ice crystals, hexagonal ice plates, and broad-branch crystals are simulated by numerically solving the time-dependent Navier-Stokes equations appropriate for these geometries in the primitive equation form. A predictor-corrector method and a quadratic interpolation for convective kinematics (QUICK) scheme are applied on nonuniform grids to determine the velocity fields. The ice crystals are held

Pao K. Wang; Wusheng Ji

1997-01-01

61

Fluidized bed heat exchangers to prevent fouling in ice slurry systems and industrial crystallizers  

Microsoft Academic Search

Ozon layer depletion and global warming by synthetic refrigerants forces refrigeration industries to switch over to natural but hazardous refrigerants like ammonia and hydrocarbons. A promising technology to safely use the latter refrigerants is the application of indirect refrigeration systems with ice slurry as heat transfer fluid. Ice slurry, a suspension of aqueous solution and small ice crystals, has a

P. Pronk

2006-01-01

62

Strain history of ice shells of the Galilean satellites from radar detection of crystal orientation fabric  

E-print Network

Strain history of ice shells of the Galilean satellites from radar detection of crystal orientation of determining the subsurface thermal and physical structure of the outer ice I shells of the Galilean satellites. At radar frequencies, the dielectric permittivity of single and polycrystalline water ice I is anisotropic

Stillman, David E.

63

Using polarimetric remote sensing measurements to estimate ice particle size, optical depth and ice water path during CRYSTAL-FACE  

Microsoft Academic Search

In situ observations made during the CRYSTAL-FACE field experiment have indicated that ice crystals have smaller sizes and are more reflective than is commonly assumed in most current climate models. The size of the particles appears to be principally determined by temperature with the smallest particles being found at the coldest temperatures. Previous analyses of polarimetric measurements in non-absorbing bands

I. Geogdzhayev; B. Cairns; M. I. Mishchenko; L. D. Travis

2006-01-01

64

Parameterization of Tropical Cirrus Ice Crystal Size Distributions and Implications for Radiative Transfer: Results from CEPEX  

Microsoft Academic Search

ABSTRACT Average ice crystal size distributions are parameterized,as functions of temperature,and ice water content (IWC), based on observations in cirrus produced as outflows of deep convection made during the Central Equatorial Pacific Experiment (CEPEX), as the sum of a first-order gamma function, describing ice crystals with melted equivalent diameters (Dm) less than 100 mm, and a lognormal function, describing larger

Greg M. McFarquhar; Andrew J. Heymsfield

1997-01-01

65

75 FR 8116 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-Ice Crystal...  

Federal Register 2010, 2011, 2012, 2013

...National Cooperative Research and Production Act of 1993--Ice Crystal Consortium Notice is hereby given that, on December 31, 2009...15 U.S.C. 4301 et seq. (``the Act''), the Ice Crystal Consortium (``ICC'') has filed written...

2010-02-23

66

Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth  

PubMed Central

Antifreeze proteins (AFPs) are a subset of ice-binding proteins that control ice crystal growth. They have potential for the cryopreservation of cells, tissues, and organs, as well as for production and storage of food and protection of crops from frost. However, the detailed mechanism of action of AFPs is still unclear. Specifically, there is controversy regarding reversibility of binding of AFPs to crystal surfaces. The experimentally observed dependence of activity of AFPs on their concentration in solution appears to indicate that the binding is reversible. Here, by a series of experiments in temperature-controlled microfluidic devices, where the medium surrounding ice crystals can be exchanged, we show that the binding of hyperactive Tenebrio molitor AFP to ice crystals is practically irreversible and that surface-bound AFPs are sufficient to inhibit ice crystal growth even in solutions depleted of AFPs. These findings rule out theories of AFP activity relying on the presence of unbound protein molecules. PMID:23300286

Celik, Yeliz; Drori, Ran; Pertaya-Braun, Natalya; Altan, Aysun; Barton, Tyler; Bar-Dolev, Maya; Groisman, Alex; Davies, Peter L.; Braslavsky, Ido

2013-01-01

67

Bioprospecting for microbial products that affect ice crystal formation and growth  

Microsoft Academic Search

At low temperatures, some organisms produce proteins that affect ice nucleation, ice crystal structure, and\\/or the process\\u000a of recrystallization. Based on their ice-interacting properties, these proteins provide an advantage to species that commonly\\u000a experience the phase change from water to ice or rarely experience temperatures above the melting point. Substances that bind,\\u000a inhibit or enhance, and control the size, shape,

Brent C. Christner

2010-01-01

68

Anchor ice and benthic disturbance in shallow Antarctic waters: interspecific variation in initiation and propagation of ice crystals.  

PubMed

Sea ice typically forms at the ocean's surface, but given a source of supercooled water, an unusual form of ice--anchor ice--can grow on objects in the water column or at the seafloor. For several decades, ecologists have considered anchor ice to be an important agent of disturbance in the shallow-water benthic communities of McMurdo Sound, Antarctica, and potentially elsewhere in polar seas. Divers have documented anchor ice in the McMurdo communities, and its presence coincides with reduced abundance of the sponge Homaxinella balfourensis, which provides habitat for a diverse assemblage of benthic organisms. However, the mechanism of this disturbance has not been explored. Here we show interspecific differences in anchor-ice formation and propagation characteristics for Antarctic benthic organisms. The sponges H. balfourensis and Suberites caminatus show increased incidence of formation and accelerated spread of ice crystals compared to urchins and sea stars. Anchor ice also forms readily on sediments, from which it can grow and adhere to organisms. Our results are consistent with, and provide a potential first step toward, an explanation for disturbance patterns observed in shallow polar benthic communities. Interspecific differences in ice formation raise questions about how surface tissue characteristics such as surface area, rugosity, and mucus coating affect ice formation on invertebrates. PMID:22042434

Denny, Mark; Dorgan, Kelly M; Evangelista, Dennis; Hettinger, Annaliese; Leichter, James; Ruder, Warren C; Tuval, Idan

2011-10-01

69

Light scattering by absorbing hexagonal ice crystals in cirrus clouds  

NASA Astrophysics Data System (ADS)

An improved ray-optics theory for single scattering and polarization of hexagonal columns and plates randomly oriented in space has been developed by considering absorption and by using the Chebyshev solution for diffraction integrals. The vector-tracing method and statistics technique of random sampling are employed. The equivalent forms of Snell's law and Fresnel formulas for absorbing ice crystals are derived, and two equivalent optical constants, m` and m", are obtained. Comparison is made of the computed results of our model and the Takano and Liou model for asymmetry factors, single-scattering albedos, and scattering phase matrix elements. Some characteristics of our model are discussed, and these analyses demonstrate that our ray-optics model is practical and much improved.

Zhang, Jianyun; Xu, Lisheng

1995-09-01

70

Enhanced high-temperature ice nucleation ability of crystallized aerosol particles after preactivation at low temperature  

NASA Astrophysics Data System (ADS)

cloud chamber experiments with crystallized aqueous ammonium sulfate, oxalic acid, and succinic acid solution droplets, we have studied a preactivation mechanism that markedly enhances the particles' heterogeneous ice nucleation ability. 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 preactivated particles occurred via depositional and deliquescence-induced ice growth, with ice active fractions ranging from 1 to 4% and from 4 to 20%, respectively. Preactivation 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.

Wagner, Robert; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin

2014-07-01

71

Direct Visualization of Spruce Budworm Antifreeze Protein Interacting with Ice Crystals: Basal Plane Affinity Confers Hyperactivity  

PubMed Central

Antifreeze proteins (AFPs) protect certain organisms from freezing by adhering to ice crystals, thereby preventing their growth. All AFPs depress the nonequilibrium freezing temperature below the melting point; however AFPs from overwintering insects, such as the spruce budworm (sbw) are 10–100 times more effective than most fish AFPs. It has been proposed that the exceptional activity of these AFPs depends on their ability to prevent ice growth at the basal plane. To test the hypothesis that the hyperactivity of sbwAFP results from direct affinity to the basal plane, we fluorescently tagged sbwAFP and visualized it on the surface of ice crystals using fluorescence microscopy. SbwAFP accumulated at the six prism plane corners and the two basal planes of hexagonal ice crystals. In contrast, fluorescently tagged fish type III AFP did not adhere to the basal planes of a single-crystal ice hemisphere. When ice crystals were grown in the presence of a mixture of type III AFP and sbwAFP, a hybrid crystal shape was produced with sbwAFP bound to the basal planes of truncated bipyramidal crystals. These observations are consistent with the blockage of c-axial growth of ice as a result of direct interaction of sbwAFP with the basal planes. PMID:18339740

Pertaya, Natalya; Marshall, Christopher B.; Celik, Yeliz; Davies, Peter L.; Braslavsky, Ido

2008-01-01

72

Ice Growth Measurements from Image Data to Support Ice-Crystal and Mixed-Phase Accretion Testing  

NASA Technical Reports Server (NTRS)

This paper describes the imaging techniques as well as the analysis methods used to measure the ice thickness and growth rate in support of ice-crystal icing tests performed at the National Research Council of Canada (NRC) Research Altitude Test Facility (RATFac). A detailed description of the camera setup, which involves both still and video cameras, as well as the analysis methods using the NASA Spotlight software, are presented. Two cases, one from two different test entries, showing significant ice growth are analyzed in detail describing the ice thickness and growth rate which is generally linear. Estimates of the bias uncertainty are presented for all measurements. Finally some of the challenges related to the imaging and analysis methods are discussed as well as methods used to overcome them.

Struk, Peter, M; Lynch, Christopher, J.

2012-01-01

73

Ikaite crystal distribution in Arctic winter sea ice and implications for CO2 system dynamics  

NASA Astrophysics Data System (ADS)

The precipitation of ikaite (CaCO3·6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1 m thick land-fast ice site and a 0.3 m thick polynya site, both in the Young Sound area (74° N, 20° W) of NE Greenland. Ikaite crystals, ranging in size from a few µm to 700 µm were observed to concentrate in the interstices between the ice platelets in both granular and columnar sea ice. In vertical sea-ice profiles from both locations, ikaite concentration determined from image analysis, decreased with depth from surfaceice values of 700-900 µmol kg-1 ice (~ 25 × 106 crystals kg-1) to bottom-layer values of 100-200 µmol kg-1 ice (1-7 × 106 kg-1), all of which are much higher (4-10 times) than those reported in the few previous studies. Direct measurements of total alkalinity (TA) in surface layers fell within the same range as ikaite concentration whereas TA concentrations in bottom layers were twice as high. This depth-related discrepancy suggests interior ice processes where ikaite crystals form in surface sea ice layers and partly dissolved in bottom layers. From these findings and model calculations we relate sea ice formation and melt to observed pCO2 conditions in polar surface waters, and hence, the air-sea CO2 flux.

Rysgaard, S.; Søgaard, D. H.; Cooper, M.; Pu?ko, M.; Lennert, K.; Papakyriakou, T. N.; Wang, F.; Geilfus, N. X.; Glud, R. N.; Ehn, J.; McGinnnis, D. F.; Attard, K.; Sievers, J.; Deming, J. W.; Barber, D.

2012-12-01

74

Using polarimetric remote sensing measurements to estimate ice particle size, optical depth and ice water path during CRYSTAL-FACE  

NASA Astrophysics Data System (ADS)

In situ observations made during the CRYSTAL-FACE field experiment have indicated that ice crystals have smaller sizes and are more reflective than is commonly assumed in most current climate models. The size of the particles appears to be principally determined by temperature with the smallest particles being found at the coldest temperatures. Previous analyses of polarimetric measurements in non-absorbing bands have suggested that either bubble inclusions (inhomogeneous hexagonal mono-crystals) or distortions of the hexagonal crystal shape (distorted chain aggregates) are responsible for the observed general absence of haloes, smooth angular variation of reflectance and brightness of ice clouds. In this paper we use multi-angle measurements made by the Research Scanning Polarimeter (RSP) to examine the polarized and unpolarized reflectance of cirrus clouds in bands where ice is non-absorbing (670 and 865 nm) and absorbing (1590, 1880 and 2250 nm). During CRSYTAL-FACE the RSP scan was biased so that the view angle range was from 0 to 75 degrees to the rear of the Proteus aircraft and from 0 to 45 degrees to the front and was oriented to scan along the groundtrack of the aircraft. This allowed observations of a single target over a wide scattering angle range particularly when consecutive flight legs could be combined which allows for basic discrimination of crystal habit using the non-absorbing bands, similar to previous studies (at least in the gross sense of being able to separate columns from plates from distorted crystals from spheroidal shapes). However, compared with non-absorbing bands, the reflectance in absorbing bands is different depending on whether ice particles are geometrically distorted or contain air bubble inclusions because the path length of light inside an ice crystal is quite short which limits scattering off the bubble inclusions. Consequently the retrieved particle size is also sensitive to whether ice crystals are modeled as being distorted or containing air bubbles. We examine how the RSP size retrievals, with an appropriate vertical weighting determined by Green's function calculations, compare with in situ measurements and examine the angular and spectral polarized and unpolarized residuals from the retrievals. This allows us to identify the most appropriate crystal habit for use in the remote sensing of cirrus clouds formed by convection over land, such as those observed during CRYSTAL-FACE, and provide best estimates for the particle size, optical depth and ice water path determined using solar reflectance measurements.

Geogdzhayev, I.; Cairns, B.; Mishchenko, M. I.; Travis, L. D.

2006-12-01

75

A renewed argument for crystal size control of ice sheet strain rates  

NASA Astrophysics Data System (ADS)

At present, it is generally believed that crystal size has no direct influence on strain rate in the ice sheets and that the fraction of strain rate enhancement there which is not ascribable to c axis fabric is due to impurity content. Here we challenge this view because it is not consistent with recent results from analyses of deformation at Meserve Glacier and instead ascribe residual enhancement in the ice sheets to variations in crystal size. We resurrect the idea that variations of crystal size can be an important part of the total shear enhancement in the ice sheets, though agree with Paterson that this effect is generally dominated by variations of crystal fabric. We propose that the enhanced shear strain rate of ice age ice in southern Greenland, as inferred from tilt of the Dye 3 borehole, can be explained as a result of combined fabric variations and crystal size variations, with these two ice properties accounting for roughly 70% and 30% of the average enhancement, respectively. Permitting a grain size dependence of ice viscosity also resolves the quandary concerning closure and tilt of the Agassiz Ice Cap borehole.

Cuffey, K. M.; Thorsteinsson, T.; Waddington, E. D.

2000-12-01

76

On the scattering phase-function of non-symmetric ice-crystals  

NASA Astrophysics Data System (ADS)

Theoretical phase-functions representing randomly oriented fractal ice-crystals, bullet-rosettes, ice aggregates, and an ensemble of ice crystals are compared to measured phase-functions using a Polar Nephelometer located in the Antarctic. The Polar Nephelometer operated at a wavelength of 0.80 ?m and measured the scattering phase-functions of individual ice-crystals between the scattering angles of 5.86° and 167°. The Polar Nephelometer was operated in tandem with a Cloud Particle Imager (supplied by SPEC Inc.) both were situated at the South Pole Amundsen Scott base station during January 2002. In this paper we report on a sample of Polar Nephelometer data obtained over a time interval of 2000 seconds consisting of 3256 phase-functions measured from individual ice-crystals. The 3256 measured phase-functions were averaged to produce an ensemble-averaged phase-function. The theoretical phase-functions have been compared to the measured ensemble-averaged phase-function. The paper demonstrates that phase functions representing single ice-crystal geometries do not reproduce the measured data well. However, the theoretical phase-function representing scattering from an ensemble of ice crystals is found to be the best description of the measured phase-function over all scattering angles.

Baran, Anthony. J.; Shcherbakov, V. N.; Baker, B. A.; Gayet, J. F.; Lawson, R. P.

2005-10-01

77

Stability relationship for water droplet crystallization with the NASA Lewis icing spray  

NASA Technical Reports Server (NTRS)

In order to produce small droplets for icing cloud simulation, high pressure air atomizing nozzles are used. For certain icing testing applications, median drop sizes as small as 5 mm are needed, which require air atomizing pressures greater than 3000 kPa. Isentropic expansion of the ambient temperature atomizing air to atmospheric pressure can result in air stream temperatures of -160 C which results in ice crystals forming in the cloud. To avoid such low temperatures, it is necessary to heat the air and water to high initial temperatures. An icing spray research program was conducted to map the temperatures below which ice crystals form. A soot slide technique was used to determine the presence of crystals in the spray.

Marek, C. John; Bartlett, C. Scott

1987-01-01

78

Crystal Structure, Dielectric Relaxation and Rheology of the High Pressure Phases of Ice  

NASA Astrophysics Data System (ADS)

Knowledge of the rheological properties of the high pressure polymorphs of ice is important for discussing the tectonic and cratering histories of the icy satellites, and their internal structure. Several research groups have made measurements of the viscous flow properties of these ices. There are striking rheological contrasts between the different ice phases, with some phases being notably stiffer or softer than others. Here we discuss these rheological contrasts in relation to dislocation motion in the different ice phases. The mobility of dislocations is related to the dielectric properties of the different phases, and these are ultimately related to crystal structure, the bending of hydrogen bonds and the presence of proton disorder in some of the ice phases. Special note will be made of the important contributions Barclay Kamb to these studies - from the details of crystal structure to ice flow.

Echelmeyer, K. A.

2001-12-01

79

Doppler lidar measurements of oriented planar ice crystals falling from supercooled and glaciated layer clouds  

E-print Network

The properties of planar ice crystals settling horizontally have been investigated using a vertically-pointing Doppler lidar. Strong specular reflections were observed from their oriented basal facets, identified by comparison with a second lidar pointing 4 degrees from zenith. Analysis of 17 months of continuous high-resolution observations reveal that these pristine crystals are frequently observed in ice falling from mid-level mixed-phase layer clouds (85% of the time for layers at -15C). Detailed analysis of a case study indicates that the crystals are nucleated and grow rapidly within the supercooled layer, then fall out, forming well-defined layers of specular reflection. Polarimetric radar measurements confirmed that a substantial fraction of the crystal population was well oriented. As the crystals fall into subsaturated air, specular reflection is observed to switch off as the crystal faces become rounded and lose their faceted structure. Specular reflection in ice falling from supercooled layers col...

Westbrook, CD; O'Connor, EJ; Hogan, RJ

2009-01-01

80

Ice crystal nucleation and growth in contrails forming at low ambient temperatures  

NASA Astrophysics Data System (ADS)

A model of ice crystal nucleation and growth in a diluting aircraft exhaust plume is used to evaluate the physical processes responsible for the ice number densities and size distributions measured on May 4, 1996. Predicted ice crystal size distributions are compared with observations at about 70 seconds plume age. The simulated crystals grow to about 2 µm radius within 2-3 seconds, then remain approximately constant in size until 30-60 seconds plume age when crystal sublimations begins. The calculated crystal size distribution has approximately the same volume mode radius as the observed size distribution (1-2 µm) however, the model does not predict as many crystals larger than 2 µm radius as indicated by the measurements. Due to the low ambient temperature (-61°C), large ice supersaturations are generated in the plume, and all exhaust soot particles and ambient aerosols entrained into the plume before about 1 second plume age are activated to ice nuclei. The simulations indicate that if the soot particle emission index is on the order of 2×1012 particles (kg fuel)-1 or lower and freshly nucleated sulfate aerosols are too small to freeze in the young plume, then the majority of the contrail ice crystals may be nucleated on ambient aerosols entrained into the exhaust plume.

Jensen, E. J.; Toon, O. B.; Pueschel, R. F.; Goodman, J.; Sachse, G. W.; Anderson, B. E.; Chan, K. R.; Baumgardner, D.; Miake-Lye, R. C.

81

Effect of Antifreeze Glycoprotein in contact with ice interface on the growth mechanism of an ice crystal  

NASA Astrophysics Data System (ADS)

We study the effect of Antifreeze Glycoprotein in contact with ice interface on pattern formation of an ice crystal growing from AFGP solution. AFGP effects on ice crystal growth are completely opposite for basal and prismatic faces. Basal face of ice in pure water is governed by slow molecular rearrangements on the basal plane and is expressed as a second power of the supercooling at the interface. In the presence of AFGP molecules on the surface, the kinetic roughening transition from a smooth surface to a rough one occurs, and the growth rate is enhanced. Prismatic faces in pure water are controlled by transport of latent heat and are proportional to the supercooling at the interface. In the presence of AFGP molecules, the kinetic smoothing transition from a rough surface to smooth one occurs, and the growth rate is reduced. The effects relate to the anisotropic adsorption properties of AFGP molecules. In this study, we proposed a new model for the ice growth kinetics, in which a change of structure of water molecules near ice interface, i.e., hydrophobic interaction is taken into account instead of Gibbs-Thomson Effect caused by the pinning of a step by AFGP molecules.

Yokoyama, Etsuro; Furukawa, Yohsinori

2005-03-01

82

Oscillatory Growth of Ice Crystals Observed in a Solution of Antifreeze Glycoprotein  

NASA Astrophysics Data System (ADS)

One-directional growth experiments of ice crystals in an aqueous solution of antifreeze glycoprotein (AFGP) were carried out using a growth cell made of thin glass capillaries. When the interface tips of ice crystals were constructed by prismatic planes, the interface position changed periodically with time. These phenomena were not observed for the growth of basal planes in the AFGP solution or for the growth of ice crystals in pure water. We first observed the oscillatory growth of ice crystals in the AFGP solution. Fluorescent labeled AFGP molecules were also used to observe the diffusion, incorporation, and segregation of the solute at the interface, in the solid and in solution. The periodic incorporation of AFGP molecules were clearly observed in conjunction with the growth rate changes.

Furukawa, Yoshinori; Nishimura, Yoshihiro; Zepeda, Salvador; Nakaya, Hiroyuki; Yokoyama, Etsuro

2007-03-01

83

Optical detection and characterization of ice crystals in LACIS  

Microsoft Academic Search

Tropospheric ice and mixed phase clouds are an integral part of the earth system and their microphysical and radiative properties are strongly coupled e.g. through the complexities of the ice nucleation process. Therefore the investigation of influences of different aerosol particles which act as ice nuclei (IN) on the freezing behaviour of cloud droplets is important and still poses unresolved

Alexei Kiselev; Tina Clauß; Dennis Niedermeier; Susan Hartmann; Heike Wex; Frank Stratmann

2010-01-01

84

A Theoretical Study of the Variation of Ice Crystal Habits with Temperature  

Microsoft Academic Search

A theory is presented to explain the temperature dependence of the velocity of step-growth and the interaction distance between two approaching steps on the basal plane of ice. Numerical calculations based on this theory are shown to be in reasonable agreement with experimental results. It is suggested that an ice crystal grows from the vapor phase by steps being nucleated

P. V. Hobbs; W. D. Scott

1965-01-01

85

Radiative influences on ice crystal and droplet growth within mixed-phase stratus clouds  

Microsoft Academic Search

This study uses a box model and a Lagrangian microphysical parcel model to investigate the influences of radiative heating and cooling on the vapor diffusional growth of liquid drops and ice crystals within mixed-phase clouds. Without radiative effects, the combined influences of drop and ice vapor diffusion lead to slight supersaturations with respect to liquid despite the rapid growth of

Z. J. Lebo; N. C. Johnson; J. Y. Harrington

2008-01-01

86

The characteristics of mid-latitude and low-latitude ice cloud crystals  

NASA Astrophysics Data System (ADS)

An accurate understanding of the dimensional characteristics of atmospheric ice crystals is important for weather and climate models. Ice crystal fall speed which partially governs cloud lifetime is dependent on crystal mass and projected area. Ice cloud radiative properties are dependent on crystal shape as well as cloud optical thickness which can vary widely depending on local conditions and cloud formation mechanisms. These are some of the reasons that cirrus clouds are considered to be one of the most uncertain elements in the earth's climate system. This thesis addresses some of these uncertainties. Mid-latitude cirrus clouds are frequently composed of bullet rosette shaped ice crystals. Bullet rosettes can grow with hollow ends which affects their radiative properties. In chapter 2, the frequency of occurrence of bullet rosettes with hollows ends is investigated. The radiative properties of hollow crystals are investigated in Chapter 3. For a thin cloud (optical depth of unity) with hollow crystals would lead to a difference of 5 W/m2 in short wave radiation at the surface compared to solid crystals. The properties of low latitude sub-visible cirrus cloud particles have been poorly investigated due to the difficulty of reaching them with instrumented aircraft. The properties of sub-visible cirrus clouds are investigated through the analysis of a large dataset of aircraft observations in chapter 4. Parameterizations for particle area, mass, size distributions and mass weighted fall speeds are developed. Mass weighted fall speeds were found to be lower than predicted by previous parameterizations due to the lack of large particles compared to previous studies. Most atmospheric ice cloud particles are irregular in shape. The final two research topics addressed in this thesis investigate the dimensional characteristics of irregularly shaped ice particles. In chapter 5, the total surface area of irregular ice crystals is investigated. Knowledge of particle surface area is important for atmospheric chemistry applications. In Chapter 6, ice crystal projected area and mass are investigated using fractal geometry techniques. Ice crystal aggregation was simulated to investigate the structure of ice crystal aggregates. The fractal analysis allows the determination of mass dimensional relationships from particle projected area measurements.

Schmitt, Carl George

87

Tropical tropopause ice clouds: A new approach to answer the mystery of low crystal numbers  

NASA Astrophysics Data System (ADS)

Water vapour is the most important natural green house gas. However, in the stratosphere an increase in water vapour would possibly result in a net cooling of the earth-atmosphere system. The major entrance pathway of trace substances into the stratosphere is the tropical tropopause layer (TTL). The TTL water vapor budget, and thus the exchange between troposphere and stratosphere, depends crucially on the occurrence and properties of ice clouds in this cold region (T < 200 K). New observations indicate that very low ice crystal numbers frequently occur in the TTL. This phenomenon is not yet understood and is not compatible with the idea that homogeneous freezing of solution droplets is the major pathway of ice formation. These low ice number concentrations are consistent with observed persistent high ice supersaturations inside cold TTL cirrus clouds, which in turn control the exchange of water vapor with the stratosphere. Here, we reproduce in-situ measurements of frequencies of occurrence of ice crystal concentrations by extensive model simulations, driven by the special dynamical conditions in the TTL, namely the superposition of slow large-scale updrafts with high-frequency short waves. The simulations show that about 80% of the observed incidences of low ice crystal concentrations can be explained by 'classical' homogeneous ice nucleation in the very slow updrafts (< 1cm/s), about 19% stem from heterogeneous freezing, while the remaining of about 1% originates from homogeneous freezing in slightly faster updrafts (> 1cm/s). The mechanism limiting the ice crystal production from homogeneous freezing in an environment full of gravity waves is that freezing events are stalled -due to the shortness of the gravity waves- before a higher number concentration of ice crystals can be formed.

Spichtinger, Peter; Krämer, Martina

2013-04-01

88

A new experimental setup to investigate nucleation, dynamic growth and surface properties of single ice crystals  

NASA Astrophysics Data System (ADS)

The nucleation and growth of atmospheric ice particles is of importance for both, weather and climate. However, knowledge is still sparse, e.g. when considering the influences of ice particle surface properties on the radiative properties of clouds. Therefore, based on the experiences with our laminar flow tube chamber LACIS (Leipzig Aerosol Cloud Interaction Simulator, Stratmann et al., 2004), we developed a new device to characterize nucleation, dynamic growth and light scattering properties of a fixed single ice crystal in dependence on the prevailing thermodynamic conditions. Main part of the new setup is a thermodynamically controlled laminar flow tube with a diameter of 15 mm and a length of 1.0 m. Connected to the flow tube is a SID3-type (Small Ice Detector, Kaye et al., 2008) instrument called LISA (Leipzig Ice Scattering Apparatus), equipped with an additional optical microscope. For the investigations, a single ice nucleus (IN) with a dry size of 2-5 micrometer is attached to a thin glass fiber and positioned within the optical measuring volume of LISA. The fixed particle is exposed to the thermodynamically controlled air flow, exiting the flow tube. Two mass flow controllers adjusting a dry and a humidified gas flow are applied to control both, the temperature and the saturation ratio over a wide range. The thermodynamic conditions in the experiments were characterized using a) temperature and dew-point measurements, and b) computational fluid dynamics (CFD) calculations. Dependent on temperature and saturation ratio in the measuring volume, ice nucleation and ice crystal growth/shrinkage can occur. The optical microscope allows a time dependent visualization of the particle/ice crystal, and the LISA instrument is used to obtain 2-D light scattering patterns. Both devices together can be applied to investigate the influence of thermodynamic conditions on ice crystal growth, in particular its shape and surface properties. We successfully performed deposition nucleation experiments considering kaolinite and SnowmaxTM (Johnson Controls Snow, Colorado, USA) particles. Different temperatures and saturation ratios were considered resulting in different growth rates and ice crystal shapes. We have proven the feasibility of the setup for investigating ice particle nucleation and growth. Further investigations and data evaluation concerning the quantification of the ice particle's surface properties are ongoing. Kaye, P., Hirst, E., Greenaway, R., Ulanowski, Z., Hesse, E., DeMott, P., Saunders, C., Conolly, P.: Classifying atmospheric ice crystals by spatial light scattering, Optics Letters, 33, 1545-1547, 2008. Stratmann, F., Kiselev, A., Wurzler, S., Wendisch, M., Heintzenberg, J., Charlson, R. J., Diehl, K., Wex, H., Schmidt, S.: Laboratory studies and numerical simulations of cloud droplet formation under realistic supersaturation conditions., J. Atmos. Ocean. Tech., 21, 876-887, 2004

Voigtlaender, Jens; Bieligk, Henner; Niedermeier, Dennis; Clauss, Tina; Chou, Cédric; Ulanowski, Zbigniew; Stratmann, Frank

2013-04-01

89

Critical Supersaturation for Ice Crystal Growth: Laboratory Measurements and Atmospheric Modeling Implications  

NASA Astrophysics Data System (ADS)

An improved understanding of ice crystal growth, particularly at low temperatures, is much in demand for the advancement of numerical modeling of atmospheric processes. Cirrus models must contend with the complexity of ice crystals growing in cold temperatures, low pressures, low supersaturations, and with multiple nucleation mechanisms. Recent observations have allowed increasingly realistic parameterizations of cirrus ice crystal microphysics, but these observations need to be supplemented by a fundamental understanding of growth processes affecting low-temperature crystals. Several experimental studies have demonstrated that certain ice crystals require a minimum "critical" supersaturation before exhibiting detectable growth. These crystals are presumed to be essentially defect-free, preventing vicinal hillock growth at the site of crystal dislocations. In the case of crystal growth by spiral dislocation, advancement of faces begins as soon as supersaturation is present. The finding of conditional critical supersaturations have analogies in other materials (metals, semiconductors, potassium dihydrogen phosphate) and are thermodynamically predicted given a two-dimensional nucleation growth mechanism. Previous measurements have determined the critical supersaturation for ice as a function of temperature and crystallographic face from 0 to --15° C with extrapolation to --30° C. For both basal and prism faces, critical supersaturation is seen to increase with decreasing temperature, suggesting that low-temperature, low-supersaturation processes are most likely to be affected by this critical contingency. We present laboratory results to verify and extend prior critical supersaturation measurements using a novel approach for supersaturation generation, control, and measurement. The crystals are grown on the tip of a fine glass fiber ( ˜10 microns in diameter) under varying conditions of temperature, pressure, and saturation. Supersaturation is generated when a pre-saturated airflow passes over a coil of ice warmed by electrical resistance upstream from the growing crystal. Supersaturation is determined by a system of differential thermocouples calibrated to sulfuric acid drop size measurements. Measurements follow those made in earlier studies, but also extend to temperatures of --45° C, mimicking conditions found in some high altitude clouds.

Magee, N.; Moyle, A.; Lamb, D.

2003-12-01

90

Development of Measurement System for Three-Dimensional Structure of Ice Crystals in Raw Beef Samples  

NASA Astrophysics Data System (ADS)

Micro-Slicer Image Processing System (MSIPS) has been developed for measuring the three-dimensional(3-D) structure and distribution of ice crystals formed in biological materials. The system has functions to reconstruct the 3-D image based on the image data of exposed cross sections obtained by multi-slicing of a frozen sample with the minimum thickness of 1?m and to display the internal structure as well as an arbitrary cross section of the sample choosing observation angles. The effects of freezing conditions on the morphology and distribl1tion of ice crystals were demonstrated quantitatively from the observations of raw beef stained by fluorescent indicator. The 3-D image of the sample demonstrated that the growth of ice columns was restricted by the intrinsic structure of muscle fibers. The proposed method provided a new tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.

Do, Gab-Soo; Sagara, Yasuyuki; Tabata, Mizuho; Kudoh, Ken-Ichi; Higuchi, Toshiro

91

Three-Dimensional Visualization of Ice Crystals in Frozen Materials by Near-Infrared Imaging Spectroscopy  

NASA Astrophysics Data System (ADS)

Micro Slicer Spectral Imaging System (MSSIS) has been applied to observe the three-dimensional(3-D) structure and distribution of ice crystals formed in biological materials. MSSIS is composed of a micro-slicer, near-infrared (NIR) illuminator and spectral imaging system. NIR Spectroscopic analysis using MSSIS confirmed that there are a water absorption band around 965 nm and an ice absorption band around 1025 nm. Spectroscopic images of a frozen agar gel and a piece of raw beef at 1,025 nm were obtained by the MSSIS. These images showed the ice crystals could be clearly distinguished from the other components by the different absorbance. The average area of ice crystals was 6,253 ?m2, and the average distances of major and minor axis were 111?m and 62?m respectively. In addition, the 3-D re-constructed image of the ice crystal morphology revealed that they were formed along with the direction of heat transfer. The proposed method provided a novel tool to investigate the effects of freezing conditions on the size, morphology and distribution of ice crystals.

Do, Gab-Soo; Ueno, Shigeaki; Sagara, Yasuyuki; Tsuta, Mizuki; Sugiyama, Junichi

92

A laboratory study of the effects of a kerosene-burner exhaust on ice nucleation and the evaporation rate of ice crystals  

NASA Astrophysics Data System (ADS)

Laboratory experiments are described during which the influence of gases and particles from the exhaust of a kerosene burner on microphysical processes were studied. In one experimental investigation the evaporation rates of ice crystals polluted with the kerosene-burner exhaust were compared with the evaporation rates of pure ice crystals. During another experimental investigation the ice nucleating ability of the exhaust particles was studied in terms of the efficiency of the exhaust particles to act as deposition and condensation freezing nuclei, as immersion freezing nuclei, and as contact nuclei. The results of our experiments showed that the evaporation rate of ice crystals polluted with the kerosene-burner exhaust was significantly reduced compared to the evaporation rate of pure ice crystals, implying an increased lifetime of aircraft contrails in comparison to a cloud of pure ice crystals. We also found that the kerosene-burner exhaust particles act as ice nuclei in all studied modes of ice formation at temperatures as high as -20°C, particulary freezing between 20 and 70% of the drops at temperatures warmer than -28°C in the immersion mode. Since the temperature at the level of the contrails is typically below -30°C our result allows the speculation that drop formation at the cruising altitude of air planes is immediately followed by ice crystal formation via heterogeneous nucleation.

Diehl, K.; Mitra, S. K.

93

Photonic crystal fiber monitors for intracellular ice formation  

NASA Astrophysics Data System (ADS)

An all-silica steering wheel photonic crystal fiber (SW-PCF) device with real-time analysis for cellular temperature sensing is presented. Results are provided for water-filled SW-PCF fibers experiencing cooling down near -40°C. Cellular temperature sensors with fast response times are of interest particularly to the study of cryopreservation, which has been influential in applications such as tissue preservation, food quality control, genetic engineering, as well as drug discovery and in- vitro toxin testing. Results of this investigation are relevant to detection of intracellular ice formation (IIF) and better understanding cell freezing at very low temperatures. IIF detection is determined as a function of absorption occurring within the core of the SW-PCF. The SW-PCF has a 3.3?m core diameter, 125?m outer diameter and steering wheel-like air hole pattern with triangular symmetry, with a 20?m radius. One end of a 0.6m length of the SW-PCF is placed between two thermoelectric coolers, filled with ~0.1?L water. This end is butt coupled to a 0.5m length of single mode fiber (SMF), the distal end of the fiber is then inserted into an optical spectrum analyzer. A near-IR light source is guided through the fiber, such that the absorption of the material in the core can be measured. Spectral characteristics demonstrated by the optical absorption of the water sample were present near the 1300-1700nm window region with strongest peaks at 1350, 1410 and 1460nm, further shifting of the absorption peaks is possible at cryogenic temperatures making this device suitable for IIF monitoring applications.

Battinelli, Emily; Reimlinger, Mark; Wynne, Rosalind

2012-04-01

94

Antifreeze Effect of Carboxylated ?-Poly-l-lysine on the Growth Kinetics of Ice Crystals.  

PubMed

Some biological substances control the nucleation and growth of inorganic crystals. Antifreeze proteins, which prohibit ice crystal growth in living organisms, promise are also important as biological antifreezes for medical applications and in the frozen food industries. In this work, we investigated the crystallization of ice in the presence of a new cryoprotector, carboxylated ?-poly-l-lysine (COOH-PLL). In order to reveal the characteristics and the mechanism of its antifreeze effect, free-growth experiments of ice crystals were carried out in solutions with various COOH-PLL concentrations and degrees of supercooling, and the depression of the freezing point and growth rates of the tips of ice dendrites were obtained using optical microscopy. Hysteresis of growth rates and depression of the freezing point was revealed in the presence of COOH-PLL. The growth-inhibition effect of COOH-PLL molecules could be explained on the basis of the Gibbs-Thomson law and the use of Langmuir's adsorption isotherm. Theoretical kinetic curves for hysteresis calculated on the basis of Punin-Artamonova's model were in good agreement with experimental data. We conclude that adsorption of large biological molecules in the case of ice crystallization has a non-steady-state character and occurs more slowly than the process of embedding of crystal growth units. PMID:25113284

Vorontsov, Dmitry A; Sazaki, Gen; Hyon, Suong-Hyu; Matsumura, Kazuaki; Furukawa, Yoshinori

2014-08-28

95

Ultrasonically triggered freezing of aqueous solutions: Influence of initial oxygen content on ice crystals' size distribution  

NASA Astrophysics Data System (ADS)

Samples of mannitol's aqueous solution at various contents of dissolved oxygen were frozen with the help of ultrasound and the ice crystals size distributions were measured by optical microscopy. Increasing the oxygen content led to a fair decreasing of the average crystals size and an increasing of the homogeneity of the size of crystals within the sample. The average size appeared simply as inversely proportional to the oxygen content in the initial liquid solution.

Jabbari-Hichri, Amira; Peczalski, Roman; Laurent, Pierre

2014-09-01

96

Investigation of nucleation, dynamic growth and surface properties of single ice crystals  

NASA Astrophysics Data System (ADS)

Nucleation, dynamic growth and optical light scattering properties of a fixed single ice crystal have been experimentally characterized in dependence of both, the type of the ice nucleus (IN) and the prevailing thermodynamic conditions. The set up was developed based on the laminar flow tube LACIS (Leipzig Aerosol Cloud Interaction Simulator, Stratmann et al., 2004; Hartmann et al., 2011). The flow tube is equipped with a SID3-type (Small Ice Detector, Kaye et al., 2008) instrument called LISA (LACIS Ice Scattering Apparatus) and an additional optical microscope. For the investigations, a single (IN with a dry size of 2-10 micrometer is attached to a thin glass fiber and positioned within the optical measuring volume of LISA. The fixed particle is exposed to the thermodynamically controlled air flow, exiting the flow tube. Temperature and saturation ratio in the measuring volume can be varied on a time scale of 1-2 s by adjusting the humidified gas flow. Dependent on the thermodynamic conditions, ice nucleation and ice particle growth/shrinkage occur and can be studied. Thereby, the LISA instrument is applied to obtain 2-D light scattering patterns, and the additional optical microscope allows a time dependent visualization of the ice crystal. Both devices together allow to investigate the influence of the thermodynamic conditions on ice particle growth, the particle shape and its surface properties (i.e., its surface roughness, Ulanowski et al., 2011; Ulanowski et al., 2012; Ulanowski et al., 2013)). The thermodynamic conditions in the optical measuring volume have been extensively characterized using a) computational fluid dynamics (CFD) calculations, b) temperature and dew-point measurements, and c) evaluation of droplet and ice particle growth data. Furthermore, we successfully performed condensation freezing and deposition nucleation experiments with ATD (Arizona Test Dust), kaolinite, illite and SnomaxTM (Johnson Controls Snow, Colorado, USA) particles. In the experiments we could prove that different types of IN, as well as different temperatures and saturation ratios result in different growth rates and ice crystal shapes, but also in different surface properties. Regarding on single ice crystal, the surface roughness can also be modified by varying the prevailing thermodynamic conditions. Thereby, the surface roughness tends to increase for growing and to decrease for shrinking particles. Here, we will present current results of the thermodynamic characterization measurements and the ongoing ice crystal growth experiments.

Voigtlaender, Jens; Herenz, Paul; Chou, Cédric; Bieligk, Henner; Clauss, Tina; Niedermeier, Dennis; Ritter, Georg; Ulanowski, Joseph Z.; Stratmann, Frank

2014-05-01

97

A model of self-oscillatory growth of ice crystals in antifreeze glycoprotein solutions  

NASA Astrophysics Data System (ADS)

We discuss that an oscillatory crystal growth is observed not only in the growth of an ice crystal from AFGP solution but also in the motion of steps on the surface of ice crystals in the presence of AFGP molecules. Our model of the oscillatory growth of crystals accounts for two elementary processes relevant to the growth: 1) an interface kinetic processes for transformation into a crystalline phase at the interface, and 2) a diffusion process for the transport of latent heat liberated at the growing interface. In this talk, we propose the hypothesis of a hysteresis behavior of growth rate to explain the formation of periodic structures of a growing crystal without a change of external conditions. The self-oscillatory growth in the presence of AFGP adsorbed molecules can occur because of the coupling of interface kinetics to the transport of latent heat under constant growth conditions.

Yokoyama, Etsuro; Furukawa, Yoshinori

2007-03-01

98

Theoretical analysis of the ice crystal size distribution in frozen aqueous specimens.  

PubMed Central

To estimate theoretically how suited different freezing techniques are for freezing of freeze-etch specimens, it is necessary to know the relationship between specimen cooling rate and the resulting average ice crystal size. Using a somewhat simplified theoretical analysis, we have derived the approximate ice crystal size distribution of nonvitrified frozen aqueous specimens frozen at different cooling rates. The derived size distribution was used to calculate the relationship between relative change in average ice crystal size, (delta l/l), and relative change in specimen cooling rate delta (dT/dt)/(dT/dt). We found this relationship to be (delta l/l) = -k X delta (dT/dt)/(dT/dt) where k = 1.0 when specimen solidification takes place at about -6 degrees C, and k congruent to 1.3 when it takes place at about -40 degrees C. Images FIGURE 6 PMID:7171711

Kopstad, G; Elgsaeter, A

1982-01-01

99

The crystal fabric of ice from full-waveform borehole sonic logging  

NASA Astrophysics Data System (ADS)

In an ice sheet, a preferred crystal orientation fabric affects deformation rates because ice crystals are strongly anisotropic: shear along the basal plane is significantly easier than shear perpendicular to the basal plane. The effect of fabric can be as important as temperature in defining deformation rates. Fabric is typically measured using analysis of thin sections under the microscope with co-polarized light. Due to the time-consuming and destructive nature of these measurements, however, it is difficult to capture the spatial variation in fabric necessary for evincing ice sheet flow patterns. Because an ice crystal is similarly elastically anisotropic, the speed of elastic waves through ice can be used as a proxy for quantify anisotropy. We use borehole sonic logging measurements and thin section data from Dome C, East Antarctica to define the relations between apparent fabric and borehole measured elastic speeds (compressionalVP and vertically polarized shear VSV). These relations, valid for single maximum fabrics, allow in-situ, depth-continuous fabric estimates of unimodal fabric strength from borehole sonic logging. We describe the single maximum fabric usinga1: the largest eigenvalue of the second-order orientation tensor. For ice at -16°C anda1in the 0.7-1 range the relations areVP = 248 a13.7 + 3755 m s-1 and VSV = -210a17.3 + 1968 m s-1.

Gusmeroli, Alessio; Pettit, Erin C.; Kennedy, Joseph H.; Ritz, Catherine

2012-09-01

100

DISCOVERY OF CRYSTALLIZED WATER ICE IN A SILHOUETTE DISK IN THE M43 REGION  

SciTech Connect

We present the 1.9-4.2 {mu}m spectra of the five bright (L {<=} 11.2) young stars associated with silhouette disks with a moderate to high inclination angle of 39 Degree-Sign -80 Degree-Sign in the M42 and M43 regions. The water ice absorption is seen toward d121-1925 and d216-0939, while the spectra of d182-316, d183-405, and d218-354 show no water ice feature around 3.1 {mu}m within the detection limits. By comparing the water ice features toward nearby stars, we find that the water ice absorption toward d121-1925 and d216-0939 most likely originates from the foreground material and the surrounding disk, respectively. The angle of the disk inclination is found to be mainly responsible for the difference of the optical depth of the water ice among the five young stars. Our results suggest that there is a critical inclination angle between 65 Degree-Sign and 75 Degree-Sign for the circumstellar disk where the water ice absorption becomes strong. The average density at the disk surface of d216-0939 was found to be 6.38 Multiplication-Sign 10{sup -18} g cm{sup -3}. The water ice absorption band in the d216-0939 disk is remarkable in that the maximum optical depth of the water ice band is at a longer wavelength than detected before. It indicates that the primary carrier of the feature is purely crystallized water ice at the surface of the d216-0939 disk with characteristic size of {approx}0.8 {mu}m, which suggests grain growth. This is the first direct detection of purely crystallized water ice in a silhouette disk.

Terada, Hiroshi [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720 (United States); Tokunaga, Alan T., E-mail: terada@subaru.naoj.org [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu 96822 (United States)

2012-07-01

101

Structural transformation in supercooled water controls the crystallization rate of ice  

E-print Network

One of water's unsolved puzzles is the question of what determines the lowest temperature to which it can be cooled before freezing to ice. The supercooled liquid has been probed experimentally to near the homogeneous nucleation temperature TH{\\approx}232 K, yet the mechanism of ice crystallization - including the size and structure of critical nuclei - has not yet been resolved. The heat capacity and compressibility of liquid water anomalously increase upon moving into the supercooled region according to a power law that would diverge at Ts{\\approx}225 K,(1,2) so there may be a link between water's thermodynamic anomalies and the crystallization rate of ice. But probing this link is challenging because fast crystallization prevents experimental studies of the liquid below TH. And while atomistic studies have captured water crystallization(3), the computational costs involved have so far prevented an assessment of the rates and mechanism involved. Here we report coarse-grained molecular simulations with the mW water model(4) in the supercooled regime around TH, which reveal that a sharp increase in the fraction of four-coordinated molecules in supercooled liquid water explains its anomalous thermodynamics and also controls the rate and mechanism of ice formation. The simulations reveal that the crystallization rate of water reaches a maximum around 225 K, below which ice nuclei form faster than liquid water can equilibrate. This implies a lower limit of metastability of liquid water just below TH and well above its glass transition temperature Tg{\\approx}136 K. By providing a relationship between the structural transformation in liquid water, its anomalous thermodynamics and its crystallization rate, this work provides a microscopic foundation to the experimental finding that the thermodynamics of water determines the rates of homogeneous nucleation of ice.(5)

Emily B. Moore; Valeria Molinero

2011-07-06

102

Crystallization of CO2 ice at astronomical conditions  

NASA Astrophysics Data System (ADS)

Carbon dioxide is, after water and comparable to carbon monoxide, one of the most abundant frozen molecular species observed in the lines of sight towards many astrophysical media. We present here an experimental and theoretical investigation on carbon dioxide ices, generated in the lab in a range of temperature, density, amorphicity, and growing conditions (1), and simulated via high level theoretical calculations. Amorphous CO2 ice was generated at CAB by deposition onto a CsI substrate at 8 K under ultrahigh vacuum conditions in the 10-11 mbar range. The pressure increase used for the deposition of CO2 was very low, 10-9 mbar, to enable the formation of highly amorphous CO2 ice, at very low deposition rate. The transmittance infrared spectra, collected at several stages of sample growth, from 20 to 360 monolayers, are shown in the Figure. In a different set of experiments performed at IEM, the morphology of the amorphous CO2 ice has been studied using reflexion-absorption infrared (RAIR) spectroscopy. Calculated spectra of amorphous CO2 ice are obtained using the SIESTA code (2). In a first step, crystalline structures are processed by molecular dynamics to generate amorphous samples, which are subsequently relaxed until an equilibrium configuration is reached. The vibrational spectra of the amorphous solids are then calculated. The spectra of amorphous ice can change significantly depending on the density of the sample. An IR band, red-shifted with respect to ?3, has been identified as a witness of pure and amorphous CO2 ice. It vanishes when the sample becomes crystalline, either by temperature increase or by accumulation of increasing number of layers. The absence of this band in the observed spectra of solid CO2 is an indication that there is no pure and amorphous CO2 ice in inter- and circumstellar mantles References 1. Escribano, R., Muñoz Caro, G., Cruz-Díaz, G.A. Rodríguez-Lazcano, Y. and Maté, B., PNAS, accepted for publication, July 2013.. 2. Ordejón, P., Artacho, E., Soler, J.M., Phys. Rev. B, 53, R10441 (1996). Transmission spectra of CO2 ice samples deposited at 8 K, for increasing thickness expressed as monolayer coverage. Spectral regions of ?3 (stretching mode) and ?2 (bending mode), are shown on the left- and right-hand panels, respectively.

Escribano, R. M.; Munoz-Caro, G.; Cruz-Diaz, G.; Mate, B.; Rodriguez-Lazcano, Y.

2013-12-01

103

Crystal alignments in the fast ice of Arctic Alaska  

SciTech Connect

Field observations at 60 sites located in the fast or near-fast ice along a 1200-km stretch of the north coast of Alaska between the Bering Strait and Barter Island have shown that the great majority of the ice samples (95%) exhibit striking c axis alignments within the horizontal plane. In all cases the degree of preferred orientation increased with depth in the ice. Representative standard deviations around a mean direction in the horizontal plane are commonly less than +- 10/sup 0/ for samples collected near the bottom of the ice. At a given site the mean c axis direction X-bar/sub 0/ may vary as much as 20/sup 0/ with vertical location in the ice sheet. The c axis allignments in the nearshore region generally parallel the coast, with strong alignments occurring in the lagoon systems between the barrier islands and the coast and seaward of the barrier islands. In passes between islands and in entrances such as the opening to Kotzebue Sound the alignment is parallel to the channel. Only limited observations are available farther seaward over the inner (10- to 50-m isobaths) and outer (50-m isobath to shelf break) shelf regions. These indicate Ne-SW and E-W alignments, respectively, in the Beaufort Sea north of Prudhoe Bay.

Weeks, W.F.; Gow, A.J.

1980-02-20

104

Formation of gas hydrate during crystallization of ethane-saturated amorphous ice  

NASA Astrophysics Data System (ADS)

Layers of ethane-saturated amorphous ice were prepared by depositing molecular beams of water and gas on a substrate cooled with liquid nitrogen. The heating of the layers was accompanied by vitrification (softening) followed by spontaneous crystallization. Crystallization of condensates under the conditions of deep metastability proceeded with gas hydrate formation. The vitrification and crystallization temperatures of the condensates were determined from the changes in their dielectric properties on heating. The thermal effects of transformations were recorded by differential thermal analysis. The crystallization of the amorphous water layers was studied by electron diffraction. Formation of a metastable packing with elements of a cubic diamond-like structure was noted.

Faizullin, M. Z.; Vinogradov, A. V.; Skokov, V. N.; Koverda, V. P.

2014-10-01

105

Experimental and theoretical study of model food freezing. Part II. Characterization and modelling of the ice crystal size  

Microsoft Academic Search

Frozen gelatin gels were freeze-dried, then sliced, microphotographed and analyzed with image analysis software. A mean ice crystal size was determined at different locations inside the gel for many operating conditions and different gelatin concentrations with or without ionic solute (sodium chloride). It was observed that the mean ice crystal size grew proportionally with the distance from the cold plate.

B. Woinet; J. Andrieu; M. Laurent; S. G. Min

1998-01-01

106

Elemental composition and morphology of ice-crystal residual particles in cirrus clouds and contrails  

Microsoft Academic Search

Aircraft sampling of residual particles from evaporated ice crystals was performed using a Counterflow Virtual Impactor. Samples of crystals taken in both contrails and cirrus clouds were compared with interstitial aerosols found in natural cirrus. The samples were analyzed with a scanning electron microscope which was equipped with a windowless energy-dispersive X-ray detector (SEM\\/EDX). In the contrail and cirrus cases

A Petzold; J Ström; S Ohlsson; F. P Schröder

1998-01-01

107

From parallel to single crystallization kinetics in high-density amorphous ice  

NASA Astrophysics Data System (ADS)

The isobaric transformation behavior of unannealed (uHDA) and expanded (eHDA) high-density amorphous ice at pressures up to 0.20 GPa is compared using powder x-ray diffraction and dilatometry. eHDA shows high thermal stability and crystallizes to a single ice phase only, whereas uHDA shows much lower thermal stability and always crystallizes to a mixture of ice phases. Unexpectedly, at low temperatures hexagonal ice grows first from uHDA, whereas this phase never crystallizes from eHDA. This leads us to conclude that hidden structural order in the form of nanocrystalline domains is present in uHDA, which triggers growth of hexagonal ice. By contrast, these ordered domains are absent in eHDA, which appears to be a homogeneous material and, thus, could be considered as a candidate for the low-temperature proxy of the proposed high-density liquid phase of water. The present work provides the basis for further experimental studies aiming at investigating this possibility since it establishes that the well-studied uHDA is not the right material to be studied in this context, whereas the more recently discovered eHDA is.

Seidl, Markus; Amann-Winkel, Katrin; Handle, Philip H.; Zifferer, Gerhard; Loerting, Thomas

2013-11-01

108

Seismic wave propagation in anisotropic ice - Part 2: Effects of crystal anisotropy in geophysical data  

NASA Astrophysics Data System (ADS)

We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded traveltimes. Velocities calculated from the polycrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from a vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monocrystal elasticity tensor used for the calculation of the polycrystal properties. With this validation of seismic velocities we make use of abrupt changes in COF as common reflection mechanism for seismic and radar data below the firn-ice transition to investigate their occurrence by comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic deployment to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous viscosity from preferred crystal orientations.

Diez, A.; Eisen, O.; Hofstede, C.; Lambrecht, A.; Mayer, C.; Miller, H.; Steinhage, D.; Binder, T.; Weikusat, I.

2014-08-01

109

A Model to Assess the Risk of Ice Accretion Due to Ice Crystal Ingestion in a Turbofan Engine and its Effects on Performance  

NASA Technical Reports Server (NTRS)

The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that were attributed to ice crystal ingestion, partially melting, and ice accretion on the compression system components. The result was one or more of the following anomalies: degraded engine performance, engine roll back, compressor surge and stall, and flameout of the combustor. The main focus of this research is the development of a computational tool that can estimate whether there is a risk of ice accretion by tracking key parameters through the compression system blade rows at all engine operating points within the flight trajectory. The tool has an engine system thermodynamic cycle code, coupled with a compressor flow analysis code, and an ice particle melt code that has the capability of determining the rate of sublimation, melting, and evaporation through the compressor blade rows. Assumptions are made to predict the complex physics involved in engine icing. Specifically, the code does not directly estimate ice accretion and does not have models for particle breakup or erosion. Two key parameters have been suggested as conditions that must be met at the same location for ice accretion to occur: the local wet-bulb temperature to be near freezing or below and the local melt ratio must be above 10%. These parameters were deduced from analyzing laboratory icing test data and are the criteria used to predict the possibility of ice accretion within an engine including the specific blade row where it could occur. Once the possibility of accretion is determined from these parameters, the degree of blockage due to ice accretion on the local stator vane can be estimated from an empirical model of ice growth rate and time spent at that operating point in the flight trajectory. The computational tool can be used to assess specific turbine engines to their susceptibility to ice accretion in an ice crystal environment.

Jorgenson, Philip C. E.; Veres, Joseph P.; Wright, William B.; Struk, Peter M.

2013-01-01

110

NASA Glenn Propulsion Systems Lab: 2012 Inaugural Ice Crystal Cloud Calibration Procedure and Results  

NASA Technical Reports Server (NTRS)

The inaugural calibration of the ice crystal and supercooled liquid water clouds generated in NASA Glenn's engine altitude test facility, the Propulsion Systems Lab (PSL) is reported herein. This calibration was in support of the inaugural engine ice crystal validation test. During the Fall of 2012 calibration effort, cloud uniformity was documented via an icing grid, laser sheet and cloud tomography. Water content was measured via multi-wire and robust probes, and particle sizes were measured with a Cloud Droplet Probe and Cloud Imaging Probe. The environmental conditions ranged from 5,000 to 35,000 ft, Mach 0.15 to 0.55, temperature from +50 to -35 F and relative humidities from less than 1 percent to 75 percent in the plenum.

VanZante, Judith F.; Rosine, Bryan M.

2014-01-01

111

arXiv:1110.5828v1[cond-mat.mtrl-sci]26Oct2011 Measurements of Growth Rates of (0001) Ice Crystal Surfaces  

E-print Network

arXiv:1110.5828v1[cond-mat.mtrl-sci]26Oct2011 Measurements of Growth Rates of (0001) Ice Crystal plays an important role in the growth dy- namics of ice crystals from water vapor [1, 2, 3]. Although holds that temperature-dependent effects of premelting on ice crystal growth are responsible for the ob

Libbrecht, Kenneth G.

112

Scattering phase matrix for hexagonal ice crystals computed from ray optics  

E-print Network

properties for ice crystals have been devel- oped by several researchers.1- 5 They used the geo- metric ray-6935/85/193254-10$02.00/0. © 1985 Optical Society of America. asymmetry factor for randomly oriented hexagonal plates with vertical angle X= r/2 - a and azimuth angle measured with respect to the coordinate system fixedto the cylinder

Takano, Yoshihide

113

Photon conservation in scattering by large ice crystals with the SASKTRAN radiative transfer model  

E-print Network

Photon conservation in scattering by large ice crystals with the SASKTRAN radiative transfer model direction. We introduce a technique that ensures numerical conservation of photons in any radiative transfer of models [1], which employ plane­parallel geo- metry. In such models, photon conservation is analytically

Martin, Randall

114

Photon Conservation in Scattering by Large Ice Crystals with the SASKTRAN Radiative Transfer Model  

E-print Network

Photon Conservation in Scattering by Large Ice Crystals with the SASKTRAN Radiative Transfer Model conser- vation of photons in any radiative transfer model and that quantifies the integration error . . . . . 4 1.2 Transport Approximation . . . . . . . . . . . . . . . . . . . . 5 1.3 Photon Conservation

Martin, Randall

115

laboratory studies on the uptake of organic compounds by ice crystals  

Microsoft Academic Search

Anthropogenic aerosols produced from biomass burning are known to increase the number of cloud condensation nuclei in the atmosphere at most latitudes. This reduces cloud droplet size, which prevents raindrop formation at shallower levels in the atmosphere. Vertical convection processes force particles and water vapor to rise up to the upper troposphere. At lower temperatures, ice crystals are formed via

E. Fries; W. Jaeschke

2003-01-01

116

Depolarization of lidar returns by small ice crystals: An application to contrails  

Microsoft Academic Search

Measurements of the lidar linear depolarization ratio delta can be a powerful remote sensing technique for characterizing the microphysics of contrail particles. Since young contrails often consist of relatively small ice crystals, the quantitative interpretation of lidar measurements requires accurate theoretical computations of delta for polydisperse, randomly oriented nonspherical particles with size parameters ranging from zero to at least several

Michael I. Mishchenko; Kenneth Sassen

1998-01-01

117

Validation and determination of ice water content-radar reflectivity relationships during CRYSTAL-  

E-print Network

scatter and absorb radiation is determined by the microphysical and geometric structure of the cloudValidation and determination of ice water content- radar reflectivity relationships during CRYSTAL with remote sensing data made by the Cloud Radar System instrument in order to derive and validate

118

Investigations of the differential affinity of antifreeze glycoprotein for single crystals of ice  

NASA Astrophysics Data System (ADS)

Two distinctively different experiments showing the differential affinity of antifreeze glycoproteins (AFGP) for the facets of ice crystals are presented. In free growth studies of single seed crystals of ice into solutions of AFGP, clear distinction between crystals growing into the AFGP solution and similar crystals growing into pure water is found. Immediately upon going below the temperature of freezing depression, crystals grow along the c-axis as long spicules, not dendrites within the basal plane as is the case of growth into pure water. The rates of growth of the spicules are higher than growth velocity of dendrites in pure water. As the supercooling is increased, both morphology and rate become more like that of growth in pure water. We also conducted dynamic light scattering studies of the ice-solution interface. In these experiments, the local concentration of AFGP in the neighborhood of the interface was monitored by the effect of these molecules on microbubbles present near the growing interface; AFGP molecules showed preference towards the prismatic facets. All of these experimental observations support the idea of a dynamic adsorption/desorption equilibrium that is facet dependent.

Feeney, R. E.; Fink, W. H.; Hallet, J.; Harrison, K.; Osuga, D. T.; Vesenka, J. P.; Yeh, Y.

1991-09-01

119

Quantum Simulation of Collective Proton Tunneling in Hexagonal Ice Crystals  

NASA Astrophysics Data System (ADS)

The effect of proton tunneling on many-body correlated proton transfer in hexagonal ice is investigated by quantum simulation. Classical single-particle hopping along individual hydrogen bonds leads to charge defects at high temperature, whereas six protons in ringlike topologies can move concertedly as a delocalized quasiparticle via collective tunneling at low temperature, thus preventing the creation of high-energy topological defects. Our findings rationalize many-body quantum tunneling in hydrogen-bonded networks and suggest that this phenomenon might be more widespread than previously thought.

Drechsel-Grau, Christof; Marx, Dominik

2014-04-01

120

Quantum simulation of collective proton tunneling in hexagonal ice crystals.  

PubMed

The effect of proton tunneling on many-body correlated proton transfer in hexagonal ice is investigated by quantum simulation. Classical single-particle hopping along individual hydrogen bonds leads to charge defects at high temperature, whereas six protons in ringlike topologies can move concertedly as a delocalized quasiparticle via collective tunneling at low temperature, thus preventing the creation of high-energy topological defects. Our findings rationalize many-body quantum tunneling in hydrogen-bonded networks and suggest that this phenomenon might be more widespread than previously thought. PMID:24766024

Drechsel-Grau, Christof; Marx, Dominik

2014-04-11

121

Artificial multimers of the type III antifreeze protein. Effects on thermal hysteresis and ice crystal morphology.  

PubMed

A variant of antifreeze protein (AFP) named RD3 from antarctic eel pout (Lycodichthys dearborni) comprises the type III AFP intramolecular dimer, which is known to exhibit a significant enhancement of thermal hysteresis when compared with the type III AFP monomer (Miura, K., Ohgiya, S., Hoshino, T, Nemoto, N., Suetake, T., Miura, A, Spyracopoulos, L., Kondo, H., and Tsuda, S. (2001) J. Biol. Chem. 276, 1304-1310). Here we genetically synthesized intramolecular dimer, trimer, and tetramer of the type III AFP, for which we utilize the genes encoding the primary sequences of the N-domain, the C-domain, and the 9-residue linker of RD3, and we examined the AFP multimerization effects on thermal hysteresis and ice crystal morphology. Significantly, (i) the thermal hysteresis increases in proportion with the size of the multimers, (ii) a larger size of the multimer exerts the maximum activity at lower concentration, (iii) every multimer changes the morphology of a single ice crystal into a unique shape that is similar but not identical to the ordinary hexagonal bipyramid, and (iv) the size of ice crystal becomes dramatically small with increasing the concentration of the multimer. The thermal hysteresis enhancement of the multimer was detected in both molar and domain bases. These results suggest that a molecule comprising the multiple AFP domains connected in tandem acquires an enhanced affinity for the ice binding. PMID:12805364

Nishimiya, Yoshiyuki; Ohgiya, Satoru; Tsuda, Sakae

2003-08-22

122

MODELING COLLECTIVE DISLOCATION DYNAMICS IN ICE SINGLE CRYSTALS  

E-print Network

. VESPIGNANI \\Lambda , and S. ZAPPERI \\Lambda\\Lambda \\Lambda The Abdus Salam International Centre. Dislocations may be incorporated into a crystal in the growth process, affecting the topology of the whole rise to a rather complex and heterogeneous slip process. Dislocations move in groups to form slip bands

Miguel-Lopez, Carmen

123

The physical-optics approximation and its application to light backscattering by hexagonal ice crystals  

NASA Astrophysics Data System (ADS)

The physical-optics approximation in the problem of light scattering by large particles is so defined that it includes the classical physical optics concerning the problem of light penetration through a large aperture in an opaque screen. In the second part of the paper, the problem of light backscattering by quasi-horizontally oriented atmospheric ice crystals is considered where conformity between the physical-optics and geometric-optics approximations is discussed. The differential scattering cross section as well as the polarization elements of the Mueller matrix for quasi-horizontally oriented hexagonal ice plates has been calculated in the physical-optics approximation for the case of vertically pointing lidars.

Borovoi, A.; Konoshonkin, A.; Kustova, N.

2014-10-01

124

Preliminary electron crystallographic analysis of ice-embedded tropomyosin crystals.  

PubMed

Electron images and diffraction patterns of ice-embedded tropomyosin crystalline sheets have been recorded at 100 and 400 kV. Optical diffractograms from the images indicated an elongated, centered unit cell with a = 799.2 +/- 10.6 A, b = 55.1 +/- 3.5 A. Evaluation of the phases in the computed Fourier transforms up to 7 A resolution revealed the presence of symmetry axes consistent with two-dimensional space group cmm. Electron diffraction patterns show diffuse arcs and discrete sampling at a resolution of 5.1 A, arising from the alpha-helical coiled-coil features of the molecule. These results demonstrate that tropomyosin thin sheets are highly ordered and suggest that retrieval of its high-resolution three-dimensional structure may be feasible by electron crystallography. PMID:8494673

Avila-Sakar, A J; Schmid, M F; Li, L S; Whitby, F G; Phillips, G N; Chiu, W

1993-01-01

125

A modified scheme that parameterizes depositional growth of ice crystal: A modeling study of pre-summer torrential rainfall case over Southern China  

NASA Astrophysics Data System (ADS)

Depositional growth of cloud ice is estimated and its parameterization schemes are compared through the two-dimensional cloud-resolving modeling analysis of pre-summer heavy rainfall over southern China. Hsie et al. (1980) and Krueger et al. (1995) developed parameterization schemes to calculate depositional growth of cloud ice by estimating the growth timescale under the assumption that the ice crystal concentration is independent of crystal size. A new scheme is proposed by Zeng et al. (2008) under the assumption that the ice crystal concentration is proportional to the mass of ice crystal. Hsie's and Krueger's schemes produce small amount of cloud ice similar to what Zeng's scheme with low ice crystal concentration does. When ice crystal concentration is increased to a high value in Zeng's scheme, the simulation generates anomalous depositional growth of cloud ice and thus anomalous area expansion of stratiform rainfall. Zeng's scheme is modified by changing radius of base ice crystal from 0 to 40 ?m in the calculation of depositional growth of cloud ice. The modified scheme with high ice crystal concentration greatly reduces growth of cloud ice and thus fractional coverage of stratiform rainfall.

Shen, Xinyong; Huang, Wei; Qing, Tao; Huang, Wenyan; Li, Xiaofan

2014-03-01

126

The application of time-dependent ice crystal trajectory and growth model for the evaluation of cloud seeding experiment using liquid carbon dioxide  

NASA Astrophysics Data System (ADS)

This study evaluated the results of cloud seeding experiment conducted on 17th January, 2008, in western Kyushu, Japan, using simplified time-dependent ice crystal growth and trajectory cloud model, which is characterized by 1) depositional diffusion growth process only of an ice crystal, and 2) the pursuit of the growing ice crystal based on wind field and ice crystal terminal velocity. For the estimation of the ice crystal growth and trajectory, the model specifies ice supersaturation ratio that expresses the degree of competition growth among ice crystals formed by LC seeding for existing water vapor, assuming no effect of natural ice crystals. The model is based on ice crystal growth along a- and c-axes depending on air temperature and ice supersatuation, according to Chen and Lamb (1994). The cloud seeding experiment was conducted by applying homogeneous nucleation (rapid cooling of air mass and subsequent formation of many ice crystals~1013/g LC) of Liquid Carbon (LC) dioxide seeding under typical winter-type snowfall-inducing weather situation characterized by the outbreak of cold air masses from the Siberia. The result of aircraft horizontally-penetrating seeding of LC into lower layer (-2 degree C) of supercooled convective cloud with 1km thickness above the freezing level led to the formation of an artificially-induced 'isolated' radar echo (the left figures of Fig. 1) in dominant 'no-natural radar echo region'. In other words, natural biases were eliminated by the formation of the isolated radar echo. This fact provides the shortcut for evaluating the result of cloud seeding experiment. In the next, the observed cloud seeding results were evaluated by estimating the trajectory of artificially-induced growing ice crystal. The results show that the trajectory of artificial ice crystals depends on the degree of completion growth mode. Free growth brings rapid growth of an ice crystal and, therefore, the ice crystal falls into lower layers for a short time. On the other hand, as the degree of competition is higher, ice crystal growth and falling are slower. The result (the right figure of Fig. 1) showed that the movement of observed isolated radar echo formed after LC cloud seeding is closely related to the trajectories of artificially-induced ice crystals depending on the specification of ice supersaturation. Therefore, it was found that time-dependent ice crystal growth and trajectory model is a useful tool for the evaluation of cloud seeding results regardless of its simplification and many uncertain factors. Fig.1 The left figure shows the movement of isolated radar echo formed by LC seeding. The right figure shows the comparison between observed radar echo location and estimated ice crystal location.

Nishiyama, K.; Wakimizu, K.; Maki, T.; Suzuki, Y.; Morita, O.; Tomine, K.

2012-12-01

127

General equations for the motions of ice crystals and water drops in gravitational and electric fields  

NASA Technical Reports Server (NTRS)

General equations for the Reynolds number of a variety of types of ice crystals and water drops are given in terms of the Davies, Bond, and Knudsen numbers. The equations are in terms of the basic physical parameters of the system and are valid for calculating velocities in gravitational and electric fields over a very wide range of sizes and atmospheric conditions. The equations are asymptotically matched at the bottom and top of the size spectrum, useful when checking large computer codes. A numerical system for specifying the dimensional properties of ice crystals is introduced. Within the limits imposed by such variables as particle density, which have large deviations, the accuracy of velocities appears to be within 10 percent over the entire range of sizes of interest.

Nisbet, John S.

1989-01-01

128

A model predicting the evolution of ice particle size spectra and radiative properties of cirrus clouds. Part 2: Dependence of absorption and extinction on ice crystal morphology  

NASA Technical Reports Server (NTRS)

This study builds upon the microphysical modeling described in Part 1 by deriving formulations for the extinction and absorption coefficients in terms of the size distribution parameters predicted from the micro-physical model. The optical depth and single scatter albedo of a cirrus cloud can then be determined, which, along with the asymmetry parameter, are the input parameters needed by cloud radiation models. Through the use of anomalous diffraction theory, analytical expressions were developed describing the absorption and extinction coefficients and the single scatter albedo as functions of size distribution parameters, ice crystal shapes (or habits), wavelength, and refractive index. The extinction coefficient was formulated in terms of the projected area of the size distribution, while the absorption coefficient was formulated in terms of both the projected area and mass of the size distribution. These properties were formulated as explicit functions of ice crystal geometry and were not based on an 'effective radius.' Based on simulations of the second cirrus case study described in Part 1, absorption coefficients predicted in the near infrared for hexagonal columns and rosettes were up to 47% and 71% lower, respectively, than absorption coefficients predicted by using equivalent area spheres. This resulted in single scatter albedos in the near-infrared that were considerably greater than those predicted by the equivalent area sphere method. Reflectances in this region should therefore be underestimated using the equivalent area sphere approach. Cloud optical depth was found to depend on ice crystal habit. When the simulated cirrus cloud contained only bullet rosettes, the optical depth was 142% greater than when the cloud contained only hexagonal columns. This increase produced a doubling in cloud albedo. In the near-infrared (IR), the single scatter albedo also exhibited a significant dependence on ice crystal habit. More research is needed on the geometrical properties of ice crystals before the influence of ice crystal shape on cirrus radiative properties can be adequately understood. This study provides a way of coupling the radiative properties of absorption, extinction, and single scatter albedo to the microphysical properties of cirrus clouds. The dependence of extinction and absorption on ice crystal shape was not just due to geometrical differences between crystal types, but was also due to the effect these differences had on the evolution of ice particle size spectra. The ice particle growth model in Part 1 and the radiative properties treated here are based on analytical formulations, and thus represent a computationally efficient means of modeling the microphysical and radiative properties of cirrus clouds.

Mitchell, David L.; Arnott, W. Patrick

1994-01-01

129

Effects of arctic sulphuric acid aerosols on wintertime low-level atmospheric ice crystals, humidity and temperature at Alert, Nunavut  

Microsoft Academic Search

The effect of pollution-derived sulphuric acid aerosols on wintertime arctic lower atmospheric ice crystals is investigated. These anthropogenic aerosols differ from natural background aerosols by their number concentration, strong solubility and reduced homogeneous freezing temperature when internally mixed with other compounds. Furthermore, observations suggest that the ice-forming nuclei concentration is reduced by one to four orders of magnitude when the

Eric Girard; Jean-Pierre Blanchet; Yves Dubois

2005-01-01

130

Hydrohalite in cold sea ice: Laboratory observations of single crystals, surface accumulations, and migration rates under a temperature  

E-print Network

, and migration rates under a temperature gradient, with application to ``Snowball Earth'' Bonnie Light,1 Richard of single crystals, surface accumulations, and migration rates under a temperature gradient the fractional volumes of ice, gas, brine, and precipitated salt. [3] Temperatures within sea ice exhibit a wide

Warren, Stephen

131

Exploration of NVE classical trajectories as a tool for molecular crystal structure prediction, with tests on ice polymorphs  

NASA Astrophysics Data System (ADS)

Following an initial Communication [Buch et al., J. Chem. Phys. 123, 051108 (2005)], a new molecular-dynamics-based approach is explored to search for candidate crystal structures of molecular solids corresponding to minima of the enthalpy. The approach is based on the observation of phase transitions in an artificial periodic system with a small unit cell and relies on the existence of an optimal energy range for observing freezing to low-lying minima in the course of classical trajectories. Tests are carried out for O structures of nine H2O-ice polymorphs. NVE trajectories for a range of preimposed box shapes display freezing to the different crystal polymorphs whenever the box dimensions approximate roughly the appropriate unit cell; the exception is ice II for which freezing requires unit cell dimensions close to the correct ones. In an alternate version of the algorithm, an initial box shape is picked at random and subsequently readjusted at short trajectory intervals by enthalpy minimization. Tests reveal the existence of ice forms which are ``difficult'' and ``easy'' to locate in this way. The former include ice IV, which is also difficult to crystallize experimentally from the liquid, and ice II, which does not interface with the liquid in the phase diagram. On the other hand, the latter crystal search procedure located successfully the remaining seven ice polymorphs, including ice V, which corresponds to the most complicated structure of all ice phases, with a monoclinic cell of 28 molecules.

Buch, V.; Marto?ák, R.; Parrinello, M.

2006-05-01

132

Preparation for Scaling Studies of Ice-Crystal Icing at the NRC Research Altitude Test Facility  

NASA Technical Reports Server (NTRS)

This paper describes experiments conducted at the National Research Council (NRC) of Canadas Research Altitiude Test Facility between March 26 and April 11, 2012. The tests, conducted collaboratively between NASA and NRC, focus on three key aspects in preparation for later scaling work to be conducted with a NACA 0012 airfoil model in the NRC Cascade rig: (1) cloud characterization, (2) scaling model development, and (3) ice-shape profile measurements. Regarding cloud characterization, the experiments focus on particle spectra measurements using two shadowgraphy methods, cloud uniformity via particle scattering from a laser sheet, and characterization of the SEA Multi-Element probe. Overviews of each aspect as well as detailed information on the diagnostic method are presented. Select results from the measurements and interpretation are presented which will help guide future work.

Struk, Peter M.; Bencic, Timothy J.; Tsao, Jen-Ching; Fuleki, Dan; Knezevici, Daniel C.

2013-01-01

133

The mystery of low ice crystal numbers in the TTL and implications for the UTLS water vapor budget  

NASA Astrophysics Data System (ADS)

Water vapour is the most important natural green house gas. However, in the stratosphere an increase in water vapour would possibly result in a net cooling of the earth-atmosphere system. The major entrance pathway of trace substances into the stratosphere is the tropical tropopause layer (TTL). The TTL water vapor budget, and thus the exchange between troposphere and stratosphere, depends crucially on the occurrence and properties of ice clouds in this cold region (T < 200 K). New observations indicate that very low ice crystal numbers frequently occur in the TTL. This phenomenon is not yet understood and is not compatible with the idea that homogeneous freezing of solution droplets is the major pathway of ice formation. These low ice number concentrations are consistent with observed persistent high ice supersaturations inside cold TTL cirrus clouds, which in turn control the exchange of water vapor with the stratosphere. Here, we reproduce in-situ measurements of frequencies of occurrence of ice crystal concentrations by extensive model simulations, driven by the special dynamical conditions in the TTL, namely the superposition of slow large-scale updrafts with high-frequency short waves. The simulations show that about 80% of the observed incidences of low ice crystal concentrations can be explained by 'classical' homogeneous ice nucleation in the very slow updrafts (< 1cm/s), about 19% stem from heterogeneous freezing, while the remaining of about 1% originates from homogeneous freezing in slightly faster updrafts (> 1cm/s). The mechanism limiting the ice crystal production from homogeneous freezing in an environment full of gravity waves is that freezing events are stalled -due to the shortness of the gravity waves- before a higher number concentration of ice crystals can be formed. Furthermore, the very few ice crystals cannot efficiently reduce the gas phase water vapor inside of the cirrus. As a result, high supersaturations can last for many hours thus hindering the downward transport of water by sedimenting ice crystals. Based on our new insights in both the low ice crystal numbers and subsequent persistent high supersatuartions, we propose to reasses the water transport to the stratosphere in the TTL.

Kraemer, M.; Spichtinger, P.

2012-12-01

134

A LiDAR study of the effective size of cirrus ice crystals over Chung-Li, Taiwan  

NASA Astrophysics Data System (ADS)

In this paper, we estimated the effective size of ice crystals in cirrus clouds using fall velocity derived from LiDAR (light detection and ranging) measurements at Chung-Li (24.58°N, 121.1°E), Taiwan. Nine shapes of the ice crystals, viz. hexagonal plates, hexagonal columns, rimed long columns, crystals with sector-like branches, broad-branched crystals, stellar crystal with broad arms, side planes, bullet rosettes and assemblages of planar poly-crystals of specific dimensions have been analyzed. The results show that the lidar derived most probable mean effective size of ice crystals is 340±180 [mu]m with a dominant size range of 200-300 [mu]m. The lidar derived mean effective size of cirrus crystals are parameterized in terms of cloud mid-height temperature as well as optical depth. The discussed method will be useful to study the most probable effective size distribution of ice crystals in cirrus cloud.

Kumar Das, Subrata; Nee, Jan-Bai; Chiang, Chih-Wei

2010-06-01

135

A new method for producing artificial snow crystals using a mixture of salt and ice  

NASA Astrophysics Data System (ADS)

It has been found that artificial snow crystals can be produced by a simple method using a mixture of salt and ice crushed into sherbet as the cooling material. The freezing mixture of about 100 g was contained in a small styrene cup (85 mm varnothing, 50 mm height). A black acrylic plate (25 mm varnothing, 2 mm thickness) was placed on the freezing mixture in the cup. The cup was placed in a closed plastic box (130×130×65 mm). The water vapour in the air trapped in the plastic box crystallized onto the surface of the acrylic plate and made a crystal 1-2 mm in size in 20 minutes. The artificial crystal is quite similar to natural snow crystals with excellent hexagonal symmetry. A model to explain the process of producing the artificial snow crystal has been proposed, insisting that the electric field due to the static electricity from the acrylic plate plays an important role in making the seeds for the crystal growth.

Suwa, Y.; Myint, H. H.; Kurniawan, H.; Ito, F.; Kagawa, K.

2001-07-01

136

Studying Cirrus Mean Effective Ice Crystal Sizes Using Satellite Tiros-n Operational Vertical Sounder (tovs) Observations  

NASA Astrophysics Data System (ADS)

The Improved Initialization Inversion (3I) algorithm converts TIROS-N Operational Vertical Sounder (TOVS) observations from the NOAA Polar Orbiting Environmen- tal Satellites into atmospheric temperature and water vapor profiles, as well as into cloud and surface properties at a spatial resolution of 1. Within the framework of the NOAA/NASA Pathfinder Program, eight years (1987-1995) of TOVS data have already been processed. Due to their relatively high spectral resolution, IR vertical sounders are especially useful for the identification of cirrus clouds (day and night). Cloud-top pressure and effective IR cloud emissivity are computed from the CO2- band radiances by a weighted c2 method. The empirical weights have been developed to take into account the effect of the brightness temperature uncertainty within an air- mass on these radiances at the various cloud levels. Mean effective ice crystal sizes are retrieved for large-scale cirrus clouds with an IR emissivity between 0.4 and 0.8. Therefore, cloud emissivities at 8 mm and 11 mm are computed from the measured brightness temperatures, the cloud-top temperature and the surface temperature. The difference between emissivities at these wavelengths is sensitive to the mean ice crys- tal size of the cirrus cloud. However, the exact correlation depends on the theoretical approach to express the absorption coefficients, single scattering albedo and asymme- try parameter of ice crystals explicitly in dependence of their shape and size distribu- tion. At present, we have compared two different sets of ice crystal single scattering properties and their effect on ice crystal size retrieval: randomly oriented planar poly- crystals and hexagonal columns. Cirrus emissivities are simulated at 8 mm and 11 mm in dependence of mean effective ice crystal size by integrating these single scattering properties into a radiative transfer model. Mean effective ice crystal sizes of large- scale cirrus are studied using NOAA-10 observations from 1987 to 1991. On average, effective ice crystal diameters lie between 35 and 45 mm. In winter midlatitudes, with lower humidity, mean ice crystal sizes are smaller than in summer midlatitudes and in the tropics. Mean cirrus ice crystal sizes slightly increase with cloud-top temperature, and we will study effects of the Mount Pinatubo eruption.

Stubenrauch, C. J.; Radel, G.; Eddounia, F.; Scott, N.; Mitchell, D.

137

Measurements of Ice Crystal Growth Rates in Air at -5C and -10C K. G. Libbrecht and H. M. Arnold  

E-print Network

Measurements of Ice Crystal Growth Rates in Air at -5C and -10C K. G. Libbrecht and H. M. Arnold to: kgl@caltech.edu Abstract. We present experiments investigating the growth of ice crystals from understand the surface molecular dynamics that determine crystal growth rates and morphologies. [The figures

Libbrecht, Kenneth G.

138

Self-oscillatory ice crystal growth in antifreeze protein (AFP) and glycoprotein (AFGP) solutions  

NASA Astrophysics Data System (ADS)

AFPs and AFGPs allow many organisms including fish, plants and insects to survive sub-freezing environments. They occur in a wide range of compositions and structure, but to some extent they all accomplish the same functions: they suppress the freezing temperature, inhibit recrystallization, and modify ice crystal growth. A complete description of the AFGP/AFP surface mechanism as well as other ice surface phenomenon has eluded scientists primarily due to a lack of direct surface studies. We study ice crystal growth in AFGP and AFP solutions with phase contrast microscopy during free solution growth under various conditions including microgravity. Free-solution growth experiments show an anisotropic self-oscillatory growth mode of the steps and interface near the freezing temperature and enhancement of the growth rates in the c-axis. These results contradict the previous ?tight-binding? mechanism thought to be responsible for antifreeze function. To study the effects of temperature driven convective flows on the interface kinetics, microgravity experiments were performed in a jet airplane during a parabolic flight path. Step propagation on the basal plane slows down considerably when entering the microgravity condition and reaches a critical condition just below 0.2g.

Zepeda, Salvador; Nakaya, Hiroyuki; Uda, Yukihiro; Yokoyama, Etsuro; Furukawa, Yoshinori

2006-03-01

139

Calorimetric determination of inhibition of ice crystal growth by antifreeze protein in hydroxyethyl starch solutions.  

PubMed Central

Differential scanning calorimetry and cryomicroscopy were used to investigate the effects of type I antifreeze protein (AFP) from winter flounder on 58% solutions of hydroxyethyl starch. The glass, devitrification, and melt transitions noted during rewarming were unaffected by 100 micrograms/ml AFP. Isothermal annealing experiments were undertaken to detect the effects of AFP-induced inhibition of ice crystal growth using calorimetry. A premelt endothermic peak was detected during warming after the annealing procedure. Increasing the duration or the temperature of the annealing for the temperature range from -28 and -18 degrees C resulted in a gradual increase in the enthalpy of the premelt endotherm. This transition was unaffected by 100 micrograms/ml AFP. Annealing between -18 and -10 degrees C resulted in a gradual decrease in the premelt peak enthalpy. This process was inhibited by 100 micrograms/ml AFP. Cryomicroscopic examination of the samples revealed that AFP inhibited ice recrystallization during isothermal annealing at -10 degrees C. Annealing at lower temperatures resulted in minimal ice recrystallization and no visible effect of AFP. Thus, the 100 micrograms/ml AFP to have a detectable influence on thermal events in the calorimeter, conditions must be used that result in significant ice growth without AFP and visible inhibition of this process by AFP. Images FIGURE 8 PMID:7690257

Hansen, T N; Carpenter, J F

1993-01-01

140

Calorimetric study of crystal growth of ice in hydrated methemoglobin and of redistribution of the water clusters formed on melting the ice.  

PubMed Central

Calorimetric studies of the melting patterns of ice in hydrated methemoglobin powders containing between 0.43 and 0.58 (g water)/(g protein), and of their dependence on annealing at subzero temperatures and on isothermal treatment at ambient temperature are reported. Cooling rates were varied between approximately 1500 and 5 K min-1 and heating rate was 30 K min-1. Recrystallization of ice during annealing is observed at T > 228 K. The melting patterns of annealed samples are characteristically different from those of unannealed samples by the shifting of the melting temperature of the recrystallized ice fraction to higher temperatures toward the value of "bulk" ice. The "large" ice crystals formed during recrystallization melt on heating into "large" clusters of water whose redistribution and apparent equilibration is followed as a function of time and/or temperature by comparison with melting endotherms. We have also studied the effect of cooling rate on the melting pattern of ice with a methemoglobin sample containing 0.50 (g water)/(g protein), and we surmise that for this hydration cooling at rates of > or = approximately 150 K min-1 preserves on the whole the distribution of water molecules present at ambient temperature. PMID:7819504

Sartor, G; Mayer, E

1994-01-01

141

Collecting, shipping, storing, and imaging snow crystals and ice grains with low-temperature scanning electron microscopy  

USGS Publications Warehouse

Methods to collect, transport, and store samples of snow and ice have been developed that enable detailed observations of these samples with a technique known as low-temperature scanning electron microscopy (LTSEM). This technique increases the resolution and ease with which samples of snow and ice can be observed, studied, and photographed. Samples are easily collected in the field and have been shipped to the electron microscopy laboratory by common air carrier from distances as far as 5,000 miles. Delicate specimens of snow crystals and ice grains survive the shipment procedures and have been stored for as long as 3 years without undergoing any structural changes. The samples are not subjected to the melting or sublimation artifacts. LTSEM allows individual crystals to be observed for several hours with no detectable changes. Furthermore, the instrument permits recording of photographs containing the parallax information necessary for three-dimensional imaging of the true shapes of snowflakes, snow crystals, snow clusters, ice grains, and interspersed air spaces. This study presents detailed descriptions of the procedures that have been used successfully in the field and the laboratory to collect, ship, store, and image snow crystals and ice grains. Published 2003 Wiley-Liss, Inc.

Erbe, E.F.; Rango, A.; Foster, J.; Josberger, E.G.; Pooley, C.; Wergin, W.P.

2003-01-01

142

Accurate simulation of the optical properties of atmospheric ice crystals with the invariant imbedding T-matrix method  

NASA Astrophysics Data System (ADS)

The invariant imbedding T-matrix method (II-TM) is employed to compute the optical properties of randomly oriented ice crystals of various shapes including hexagonal columns, hollow columns, droxtals, bullet rosettes and aggregates. The II-TM is shown to be numerically stable and capable of obtaining the single-scattering properties of hexagonal ice crystals with size parameters up to 150. The 22° and 46° halo peaks in the phase function of compact hexagonal ice crystals begin to emerge at a size parameter of approximately 80 and tend to become insensitive to particle size as the corresponding size parameter approaches 150. Furthermore, the II-TM solutions are shown to be in agreement with their counterparts based on the discrete dipole approximation (DDA) method and the pseudo-spectral time-domain (PSTD) method. In addition, the accuracy of the improved geometric-optics method (IGOM) is examined for randomly oriented hexagonal ice crystal cases over a wide size-parameter range from the resonant to geometric-optics regimes. The II-TM is also used to study the effects of particle surface roughness and internal inclusions on the single-scattering properties of ice particles.

Bi, Lei; Yang, Ping

2014-05-01

143

162 J. Opt. Soc. Am. A/Vol. 12, No. 1/January 1995 P. Yang and K. N. Liou Light scattering by hexagonal ice crystals  

E-print Network

, scattering properties for more complex ice crystal shapes have also been determined by the geometric ray by hexagonal ice crystals: comparison of finite-difference time domain and geometric optics models Ping Yang and K. N. Liou Department of Meteorology/Center for Atmospheric and Remote Sounding Studies, University

Liou, K. N.

144

Detection of ice crystal particles preferably oriented in the atmosphere by use of the specular component of scattered light.  

PubMed

A new method to retrieve sizes and flutter of ice crystals in the atmosphere when they reveal their preferably horizontal orientation is proposed and realized. The method consists of the measurement of angular width for the specular component of scattered light in the bistatic sounding scheme. The technique is realized with a floodlight beam and a CCD camera as a detector. PMID:18545469

Borovoi, Anatoli; Galileiskii, Victor; Morozov, Alexander; Cohen, Ariel

2008-05-26

145

T-1020 NaI crystal test for DM-Ice  

SciTech Connect

This is a memorandum of understanding between the Fermi National Accelerator Laboratory (Fermilab) and the experiments of the NaI Crystal Test for DM-Ice from the University of Wisconsin who have committed to participate in detector tests to be carried out during the 2011-2012 Fermilab Neutrino program. The memorandum is intended primarily for the purpose of recording expectations for budget estimates and work allocations for Fermilab, the funding agencies and the participating institutions. It reflects an arrangement that currently is satisfactory to the parties; however, it is recognized and anticipated that changing circumstances of the evolving research program will necessitate revisions. The parties agree to modify this memorandum to reflect such required adjustments. Actual contractual obligations will be set forth in separate documents. The DM-Ice collaboration is designing a sodium-iodide (NaI) based detector for a direct dark matter search. The detectors should have low readout noise and background levels to carry out a sensitive search. A 17-kg version of the experiment is running at the South Pole, 2500 m deep in the Antarctic ice, and a large scale experiment is currently being designed. One of the keys to the success of the experiment is to have a good understanding of the background levels intrinsic in the NaI detectors. To measure the background level, the detectors have to be shielded against cosmic rays. The lead shielding used for DAMIC in the Minos Underground Areas is a well-suited location for this test since it offers enough overburden to shield against cosmic rays, lead shielding, and experimental infrastructure. The goal of the test is to assess the background levels in the detector and to assess the characteristics of phosphorescence induced by muons and 100 keV-3 MeV gamma rays.

Maruyama, Reina; Heeger, Karsten; Pierpoint, Zachary; Pettus, Walter; Broerman, Benjamin; Hilgenberg, Chris; Webber, David; /Wisconsin U., Madison

2011-11-03

146

Estimation of Cirrus Cloud Effective Ice Crystal Shapes using Visible Reflectances from Dual-Satellite Measurements  

NASA Technical Reports Server (NTRS)

This study develops and examines a multiangle, multisatellite method for determining effective cloud particle shapes from reflectances observed at visible wavelengths. The technique exploits the significant differences in the various cloud particle shape phase functions near the backscatter direction to infer particle shape from a combination of views from a near-backscatter angle and a side scattering angle. Adding-doubling calculations confirm that the optimal viewing combinations include one near-backscatter angle and another between 60" and 150". Sensitivity to shape increases with solar zenith angle. A total of 28 collocated, visible images from pairs of currently operating meteorological satellites with the desired viewing combinations were analyzed for particle shape. Matching reflectances from images with optimal viewing angles clearly separates water droplet from ice crystal clouds. Reflectance pairs from matched pixels containing ice crystals can be explained by the range of selected microphysical models. The most common retrieved shapes correspond to combinations of hexagonal compacts (aspect ratio of unity), hexagonal columns, and bullet rosettes. Although no single microphysical model can account for the observed variability, taken together, the models used for retrieving cloud particle size by the Clouds and the Earth's Radiant Energy System and the Moderate Resolution Imaging Spectroradiometer Projects can account for most of the reflectance variability observed in this limited data set. Additional studies are needed to assess the uncertainties in retrieved shapes due to temporal and spatial mismatches, anisotropic and bright background reflectances, and calibration errors and to validate the retrieved shapes. While applicable to a limited number of dual-satellite viewing combinations for current research and operational meteorological satellites, this approach could be used most extensively to derive effective particle size, shape, and optical depth from a combination of an imaging satellite in an L1 orbit, like Triana, and any other lower Earth orbiting Satellites.

Chepfer, Helene; Minnis, Patrick; Young, David; Nguyen, Louis; Arduini, Robert F.

2002-01-01

147

How Does a Raindrop Grow?: Precipitation in natural clouds may develop from ice crystals or from large hygroscopic aerosols.  

PubMed

On the basis of presently available data, combined with present-day knowledge of the physics and chemistry of cloud particle development, it is possible to make the following generalizations about the mode of precipitation in natural clouds. 1) The all-water mechanism begins to operate as soon as a parcel of cloud air is formed and continues to operate throughout the life of the cloud. The ice-crystal mechanism, on the other hand, can begin to operate only after the top of the cloud has reached levels where ice nuclei can be effective (about -15 degrees C). Some clouds never reach this height; any precipitation from them must be through the all-water mechanism. In cold climates and at high levels in the atmosphere, the cloud bases may be very close to this critical temperature. In the tropics, approximately 25,000 feet separate the bases of low clouds from the natural ice level. 2) The number of large hygroscopic nuclei in maritime air over tropical oceans is entirely adequate to rain-out any cloud with a base below about 10,000 feet, provided the cloud duration and cloud depth is sufficient for the precipitation process to operate. Extensive trajectories over land will decrease the number of sea-salt particles, both because of sedimentation and removal in rain. Measurements show an order-of-magnitude decrease in the number of large particles as maritime air moves from the Gulf of Mexico to the vicinity of St. Louis, during the summer months. Measurements in Arizona and New Mexico show even smaller chloride concentrations, presumably because of the long overland trajectories required in reaching these areas. The maritime particles lost in overland trajectories apparently are more than replaced by particles of land origin. The latter are usually of mixed composition and are less favorable for the formation of outsized solution droplets. 3) Ice nuclei, required for the formation of ice crystals and for droplet freezing, are rather rare at temperatures higher than about -10 degrees C. This, of course, accounts for the fact that natural clouds undergo extensive undercooling. Because of the scarcity of suitable nuclei, precipitation through the ice phase usually is not found in clouds warmer than about -15 degrees to -20 degrees C. Natural cirrus clouds might provide ice nuclei for precipitation at somewhat higher temperatures, but this possibility has not been extensively studied. 4) Precipitation in tropical clouds invariably first develops through the all-water mechanism; points discussed in paragraphs 1, 2, and 3 above all work toward this end. Tropical clouds which reach to heights above about 25,000 feet also develop precipitation through snow pellets. The data for mid-latitude clouds are conflicting. Some measurements suggest that summer clouds in the central United States and in the semiarid Southwest develop rain largely through the all-water process; existing theories support such a suggestion. However, flight measurements indicate that there is considerably more ice and snow in the clouds than can be accounted for by present theory; as a consequence, one must be careful in ruling out the ice mechanism in these areas. It appears to me, however, that the ice particles in these clouds are best accounted for through the hypothesis of freezing of drops which have grown to fairly large size through diffusion of vapor. Thus, the ice would be only incidental to the precipitation development. Winter clouds in the central United States and almost all of the clouds of northern United States and Canada appear to precipitate largely through the ice-crystal mechanism. The relatively cold cloud bases and the continental sources of air masses in these regions appear to retard the warm-rain mechanism to the point where the ice mechanism dominates. But here again, a great deal of research must be completed before a firm conclusion can be drawn (18). PMID:17745322

Braham, R R

1959-01-16

148

Layers of quasi-horizontally oriented ice crystals in cirrus clouds observed by a two-wavelength polarization lidar.  

PubMed

Layers of quasi-horizontally oriented ice crystals in cirrus clouds are observed by a two-wavelength polarization lidar. These layers of thickness of several hundred meters are identified by three attributes: the backscatter reveals a sharp ridge while the depolarization ratio and color ratio become deep minima. These attributes have been justified by theoretical calculations of these quantities within the framework of the physical-optics approximation. PMID:25322032

Borovoi, Anatoli; Balin, Yurii; Kokhanenko, Grigorii; Penner, Iogannes; Konoshonkin, Alexander; Kustova, Natalia

2014-10-01

149

Ice crystallization and freeze tolerance in embryonic stages of the tardigrade Milnesium tardigradum.  

PubMed

In tardigrades, tolerance to low temperature is well known and allows them to cope with subzero temperatures in their environment. Although the ability to tolerate freezing body water has been demonstrated in some tardigrades, freeze tolerance of embryonic stages has been little studied, although this has ecological significance. In this study, we evaluated the subzero temperature survival of five different developmental stages of the eutardigrade species Milnesium tardigradum after freezing to -30 degrees C. Embryos were exposed to five different cooling rates between room temperature and -30 degrees C at 1 degrees C/h, 3 degrees C/h, 5 degrees C/h, 7 degrees C/h, and 9 degrees C/h followed by a warming period at 10 degrees C/h. The results showed that the developmental stage and the cooling rate have a significant effect on the hatching rate. Less developed embryonic stages were more sensitive to freezing at higher freezing rates than more developed stages. Differential Scanning Calorimetry (DSC) was used to determine the temperature of crystallization (Tc) in single embryos of the different developmental stages and revealed no differences between the stages. Based on the calorimetric data, we also conclude that the ice nucleation is homogeneous in embryonic stages in tardigrades, as also recently shown for fully developed tardigrades, and not triggered by nucleating agents. PMID:20116441

Hengherr, S; Reuner, A; Brümmer, F; Schill, R O

2010-05-01

150

The effects of small ice crystals on the infrared radiative properties of cirrus clouds. Semiannual status report, 1 October 1989-31 March 1990  

SciTech Connect

To be successful in the development of satellite retrieval methodologies for the determination of cirrus cloud properties, fundamental scattering and absorption data on nonspherical ice crystals that are found in cirrus clouds must be available. Recent aircraft observations (Platt et al.) reveal that there is a large amount of small ice particles, on the order of 10 micron, in cirrus clouds. Thus it is important to explore the potential differences in the scattering and absorption properties of ice crystals with respect to their sizes and shapes. In this study the effects of nonspherical small ice crystals on the infrared radiative properties of cirrus clouds are investigated using light scattering properties of spheroidal particles. In Section 2, using the anomalous diffraction theory for spheres and results from the exact spheroid scattering program, efficient parameterization equations are developed for calculations of the scattering and absorption properties for small ice crystals. Parameterization formulas are also developed for large ice crystals using results computed from the geometric ray-tracing technique and the Fraunhofer diffraction theory for spheroids and hexagonal crystals. This is presented in Section 3. Finally, applications to the satellite remote sensing are described in Section 4.

Takano, Y.; Liou, K.N.; Asano, S.; Heymsfield, A.; Minnis, P.

1990-04-01

151

Midlatitude Cirrus Clouds Derived from Hurricane Nora: A Case Study with Implications for Ice Crystal Nucleation and Shape  

NASA Technical Reports Server (NTRS)

Hurricane Nora traveled up the Bala Peninsula coast in the unusually warm El Nino waters of September 1997, until rapidly decaying as it approached Southern California on 24 September. The anvil cirrus blowoff from the final surge of tropical convection became embedded in subtropical flow that advected the cirrus across the western US, where it was studied from the Facility for Atmospheric Remote Sensing (FARS) in Salt Lake City, Utah. A day later, the cirrus shield remnants were redirected southward by midlatitude circulations into the Southern Great Plains, providing a case study opportunity for the research aircraft and ground-based remote sensors assembled at the Clouds and Radiation Testbed (CART) site in northern Oklahoma. Using these comprehensive resources and new remote sensing cloud retrieval algorithms, the microphysical and radiative cloud properties of this unusual cirrus event are uniquely characterized. Importantly, at both the FARS and CART sites the cirrus generated spectacular optical displays, which acted as a tracer for the hurricane cirrus, despite the limited lifetimes of individual ice crystals. Lidar polarization data indicate widespread regions of uniform ice plate orientations, and in situ particle masticator data show a preponderance of pristine, solid hexagonal plates and columns. It is suggested that these unusual aspects are the result of the mode of cirrus particle nucleation, presumably involving the lofting of sea-salt nuclei in thunderstorm updrafts into the upper troposphere. This created a reservoir of haze particles that continued to produce halide-saltcontaminated ice crystals during the extended period of cirrus cloud maintenance. The reference that marine microliters are embedded in the replicas of ice crystals collected over the CART site points to the longevity of marine effects. Various nucleation scenarios proposed for cirrus clouds based on this and other studies, and the implications for understanding cirrus radiative properties or a global scale, are discussed.

Sassen, Kenneth; Arnott, W. Patrick; OCStarr, David; Mace, Gerald G.; Wang, Zhien; Poellot, Michael R.

2002-01-01

152

Reversible pressure-induced crystal-amorphous structural transformation in ice Ih  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) simulation of depressurised high-density amorphous ice (HDA) at 80 K and at negative pressures has been performed. Over several attempts, HDA recrystallised to a form close to hexagonal ice Ih, albeit with some defects. The results support the hypothesis that compression of ice-Ih to HDA is a reversible first-order phase transition, with a large hysteresis. Therefore, it would appear that LDA is not truly amorphous. The elastic energy estimated from the area of the hysteresis loop is ca. 4.5 kJ/mol, in some way consistent with experimentally-determined accumulated successive heats of transformations from recovered HDA ? ice Ih.

English, Niall J.; Tse, John S.

2014-08-01

153

Testing the influence of small crystals on ice size spectra using Doppler lidar observations  

E-print Network

of Doppler velocity varies strongly with temperature, with mean velocities of 0.2ms�1 at �40°C, increasing. Introduction [2] There has been much controversy over the number of small sub-60mm particles in ice clouds diagnosed as a function of temperature T or deduced from the model ice water content (IWC), while

Reading, University of

154

Trehalose solution viscosity at low temperatures measured by dynamic light scattering method: Trehalose depresses molecular transportation for ice crystal growth  

NASA Astrophysics Data System (ADS)

The inhibitory effects of trehalose on ice crystal growth were discussed on the basis of the viscosity measurements of aqueous solutions via the dynamic light-scattering method. The temperature and concentration conditions of the solution were ranged between 268 and 343 K and up to 50 wt%, respectively, which were feasible for applying this novel technique and were useful in the indirect measurement of the macroscopic dynamic properties of the trehalose solutions. A comparison of the viscosity data with those reported in the literatures indicated the validity of this method for measuring the viscosity. The nonlinearity of the temperature and concentration dependences of the trehalose solutions suggested that two different hydrogen-bonding networks exist in the solutions within the investigated range. Dilute solutions of less than 10 wt% of trehalose exhibited properties very similar to those of pure water. Higher concentration solutions had large viscosities with large temperature and concentration dependences. This was caused by the decrease in the free water in the solution and the development of hydrogen-bonding networks with hydrated trehalose clusters. Sucrose and maltose solutions had the same properties, so this would be the dominant inhibitory process of disaccharides on ice crystal growth.

Uchida, Tsutomu; Nagayama, Masafumi; Gohara, Kazutoshi

2009-12-01

155

Influence of local surface albedo variability and ice crystal shape on passive remote sensing of thin cirrus  

NASA Astrophysics Data System (ADS)

Airborne measurements of solar spectral radiance reflected by cirrus are performed with the HALO-Solar Radiation (HALO-SR) instrument onboard the High Altitude and Long Range Research Aircraft (HALO) in November 2010. The data are used to quantify the influence of surface albedo variability on the retrieval of cirrus optical thickness and crystal effective radius. The applied retrieval of cirrus optical properties is based on a standard two-wavelength approach utilizing measured and simulated reflected radiance in the visible and near-infrared spectral region. Frequency distributions of the surface albedos from Moderate resolution Imaging Spectroradiometer (MODIS) satellite observations are used to compile surface-albedo-dependent lookup tables of reflected radiance. For each assumed surface albedo the cirrus optical thickness and effective crystal radius are retrieved as a function of the assumed surface albedo. The results for the cirrus optical thickness are compared to measurements from the High Spectral Resolution Lidar (HSRL). The uncertainty in cirrus optical thickness due to local variability of surface albedo in the specific case study investigated here is below 0.1 and thus less than that caused by the measurement uncertainty of both instruments. It is concluded that for the retrieval of cirrus optical thickness the surface albedo variability is negligible. However, for the retrieval of crystal effective radius, the surface albedo variability is of major importance, introducing uncertainties up to 50%. Furthermore, the influence of the bidirectional reflectance distribution function (BRDF) on the retrieval of crystal effective radius was investigated and quantified with uncertainties below 10%, which ranges below the uncertainty caused by the surface albedo variability. The comparison with the independent lidar data allowed for investigation of the role of the crystal shape in the retrieval. It is found that if assuming aggregate ice crystals, the HSRL observations fit best with the retrieved optical thickness from HALO-SR.

Fricke, C.; Ehrlich, A.; Jäkel, E.; Bohn, B.; Wirth, M.; Wendisch, M.

2014-02-01

156

Supercooled Droplets and Ice Crystals in Mixed-Phase Clouds: Numerical Simulations Considering Isotropic Turbulence of the Ambient Flow Field  

NASA Astrophysics Data System (ADS)

In midlatitudes the formation and evolution of precipitation is the result of a chain of processes taking place in mixed-phase clouds. Due to the coexistence of supercooled water drops and ice particles in such clouds mutual interactions by collisions, i.e. riming and aggregation, take place leading to ice hydrometeors of a large precipitation size. In the past these collision mechanisms have been investigated - besides laboratory measurements - by numerical simulations of the collision process where trajectories of the participating hydrometeors have been calculated as occurring in an environment at rest (Pruppacher and Klett, Kluwer Academic Publishers, Dordrecht, 1997). However, as it is well-known the flow field in clouds is almost always turbulent (Siebert et al., Atmos. Res. 97 (2010) 426-437) except in undiluted updrafts of single strong convective clouds. And it has been argued that turbulence may enhance precipitation formation. As a consequence turbulence effects on the collisional interaction of cloud and other heavy particles came into focus during the last decade and gave rise to the description in terms of radial distribution function, mean radial relative velocity and the collection efficiency all derived from numerical simulations. Up to now mostly the turbulence influence on cloud droplet/cloud droplet collisions has been investigated (Ayala et al., New J. Phys. 10 (2008) 075015), (Bec et al., J. Fluid Mech. 646 (2010) 527-536). Much less is known about the influence of turbulence on particles in mixed phase clouds. This is mainly due to the various and complex shapes of the ice particles depending on the temperature, the supersaturation, and their life time. Hence, our knowledge about the behavior of ice crystals in turbulence is based on wind tunnel experiments. In the early stage ice crystals often have the shape of hexagonal plates or needles. In theoretical and numerical studies these are commonly approximated by ellipsoids. However, except in (Pinsky and Khain, Atmos. Res. 47-48 (1998) 69-86) only laminar flows have been considered so far. Therefore we have developed a numerical experiment with a novel setup (Kunnen et al., under review in Atmos. Res. (2013)). Therein synthetic turbulence is generated at the inflow and is then advected by a mean flow through the domain. The full Navier-Stokes equations are solved using a DNS method on an Eulerian Cartesian grid. The evolving decaying turbulence shares similarities with the grid-generated turbulence of wind tunnels. In this flow several million particle spheres as well as ellipsoids are advanced in a Lagrangian manner in order to represent the supercooled droplets and ice crystals out of a small region of a mixed-phase cloud. Statistics will be gathered about the orientation, the sedimentation velocities, the clustering, and the relative velocities of these particles. From this basis collision kernels can be calculated. These are input parameters for cloud models estimating the evolution of precipitation.

Siewert, Christoph; Kunnen, Rudie; Meinke, Matthias; Schröder, Wolfgang; Beheng, Klaus

2013-04-01

157

Cloud Resolving Simulations of Mixed-Phase Arctic Stratus Observed during BASE: Sensitivity to Concentration of Ice Crystals and Large-Scale Heat and Moisture Advection  

Microsoft Academic Search

The authors' previous idealized, two-dimensional cloud resolving model (CRM) simulations of Arctic stratus revealed a surprising sensitivity to the concentrations of ice crystals. In this paper, simulations of an actual case study observed during the Beaufort and Arctic Seas Experiment are performed and the results are compared to the observed data. It is again found in the CRM simulations that

Hongli Jiang; William R. Cotton; James O. Pinto; Judy A. Curry; Michael J. Weissbluth

2000-01-01

158

Crystal structure and encapsulation dynamics of ice II-structured neon hydrate.  

PubMed

Neon hydrate was synthesized and studied by in situ neutron diffraction at 480 MPa and temperatures ranging from 260 to 70 K. For the first time to our knowledge, we demonstrate that neon atoms can be enclathrated in water molecules to form ice II-structured hydrates. The guest Ne atoms occupy the centers of D2O channels and have substantial freedom of movement owing to the lack of direct bonding between guest molecules and host lattices. Molecular dynamics simulation confirms that the resolved structure where Ne dissolved in ice II is thermodynamically stable at 480 MPa and 260 K. The density distributions indicate that the vibration of Ne atoms is mainly in planes perpendicular to D2O channels, whereas their distributions along the channels are further constrained by interactions between adjacent Ne atoms. PMID:25002464

Yu, Xiaohui; Zhu, Jinlong; Du, Shiyu; Xu, Hongwu; Vogel, Sven C; Han, Jiantao; Germann, Timothy C; Zhang, Jianzhong; Jin, Changqing; Francisco, Joseph S; Zhao, Yusheng

2014-07-22

159

Magnetic vortex crystal formation in the antidot complement of square artificial spin ice  

NASA Astrophysics Data System (ADS)

We have studied ferromagnetic nickel thin films patterned with square lattices of elongated antidots that are negative analogues of square artificial spin ice. Micromagnetic simulations and direct current magnetic moment measurements reveal in-plane anisotropy of the magnetic hysteresis loops, and the formation of a dense array of magnetic vortices with random polarization and chirality. These multiply-connected antidot arrays could be superior to lattices of disconnected nanodisks for investigations of vortex switching by applied electric current.

de Araujo, C. I. L.; Silva, R. C.; Ribeiro, I. R. B.; Nascimento, F. S.; Felix, J. F.; Ferreira, S. O.; Mól, L. A. S.; Moura-Melo, W. A.; Pereira, A. R.

2014-03-01

160

Isothermal Ice-Crystallization Kinetics in the Gas-Diffusion Layer of a Proton-Exchange-Membrane Fuel Cell  

SciTech Connect

Nucleation and growth of ice in the fibrous gas-diffusion layer (GDL) of a proton-exchange membrane fuel cell (PEMFC) are investigated using isothermal differential scanning calorimetry (DSC). Isothermal crystallization rates and pseudo-steady-state nucleation rates are obtained as a function of subcooling from heat-flow and induction-time measurements. Kinetics of ice nucleation and growth are studied at two polytetrafluoroethylene (PTFE) loadings (0 and 10 wt %) in a commercial GDL for temperatures between 240 and 273 K. A nonlinear icecrystallization rate expression is developed using Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, in which the heat-transfer-limited growth rate is determined from the moving-boundary Stefan problem. Induction times follow a Poisson distribution and increase upon addition of PTFE, indicating that nucleation occurs more slowly on a hydrophobic fiber than on a hydrophilic fiber. The determined nucleation rates and induction times follow expected trends from classical nucleation theory. A validated rate expression is now available for predicting icecrystallization kinetics in GDLs.

Dursch, Thomas J.; Ciontea, Monica A.; Radke, Clayton J.; Weber, Adam Z.

2011-11-11

161

Ice rule correlations in stuffed spin ice  

NASA Astrophysics Data System (ADS)

Stuffed spin ice is a chemical variation of a spin ice material like Ho2Ti2O7 in which extra magnetic ions are inserted into the crystal structure. Previous studies have shown that the degree of stuffing has very little effect on the residual entropy in the system, which takes a value very close to the spin ice entropy. We argue, however, that the observation of this entropy does not imply long range coherence of the ice rules, that determine the local spin configurations. We have characterized deviations from the ice rules by means of a polarized neutron diffraction study of a single crystal of Ho2+?Ti2-?O7-?/2 with ? = 0.3. Our results demonstrate that the ice rules in stuffed spin ice are strictly valid only over a relatively short range, and that at longer range stuffed spin ice exhibits some characteristics of a ‘cluster glass’, with a tendency to more conventional ferromagnetic correlations.

Aldus, R. J.; Fennell, T.; Deen, P. P.; Ressouche, E.; Lau, G. C.; Cava, R. J.; Bramwell, S. T.

2013-01-01

162

Hypergravity as a crystallization tool.  

PubMed

The centrifugal increase of concentration is nondestructive, rapid, and simple technology. Therefore it is used to create a higher supersaturation that is required for crystal nucleation, as the one that is appropriate for the subsequent growth. Crystal nucleation is evoked in glass capillary tubes filled with protein solutions. The couple ferritin/ apoferritin is used as model proteins in the present article. Although differing in their masses the two (quasi) spherical molecules have exactly the same size and surface properties. Together with the temperature-independent solubility this makes them very convenient for our investigations. Decoupling nucleation and growth, for example, by means of hypergravity makes it possible to grow quasi-equidimensional crystals. The use of monodisperse crystalline forms of therapeutic agents can ensure constant time-release of protein-based medications. PMID:17124122

Nanev, Christo N; Dimitrov, I; Hodjaoglu, F

2006-09-01

163

Using MODIS data to detect the presence of ice crystals in and above super-cooled liquid water clouds over the Arctic  

NASA Astrophysics Data System (ADS)

Determining cloud properties from satellite data over the Arctic is difficult due to low solar elevation angles and the large extent of snow and ice cover. Although it is well established that ice clouds can be discriminated from those having a liquid phase, the mixed-phase clouds represent a problem since they appear nearly identical to liquid phase clouds in satellite data. This is due to the liquid-dominant top found in many mixed-phase stratus clouds. The Terra MODIS particle size ratio between 1.6 and 3.7 ?m for super-cooled liquid water (SLW) clouds is useful for determining ice crystal presence. Since the 1.6 ?m channel detects radiation from deeper inside the clouds, particle size retrievals using this channel are expected to be larger than 3.7 ?m retrievals if ice crystals are embedded inside the cloud. A technique utilizing the MODIS 6.7, 7.3, 8.5, 11 and 12 ?m channels is also used to determine ice crystal presence in SLW clouds. After determining the phase occurring at the cloud top, the internal cloud phase is parameterized in terms of the thermal and water vapor structure above the cloud. This method is useful since it can be applied to nighttime and twilight scenes in addition to daytime scenes. Although the focus of this study is on single layer cloud systems, a multilayer cloud algorithm, which discriminates thin, high ice crystal clouds from low level SLW clouds, is also run. Microwave radiometer, cloud radar and rawinsonde data collected at the Atmospheric Radiation Measurement DOE site in Barrow, Alaska and surface observations from the National Weather Service collected at the Barrow airport are used to evaluate MODIS cloud phase, and to determine whether MODIS can detect differences in the amount of ice embedded in SLW clouds. Accurately assigning cloud phase over large areas of the remote Arctic will benefit the aviation community for aircraft icing detection. Also, since mixed-phase clouds usually precipitate, the likely occurrence of snowfall can be determined remotely. The assignment of cloud phase is also critical in retrieving a cloud’s optical depth, height, particle size, and water path.

Spangenberg, D.; Minnis, P.; Palikonda, R.; Chang, F.; Shupe, M.

2010-12-01

164

On the characterization of crystallization and ice adhesion on smooth and rough surfaces using molecular dynamics  

NASA Astrophysics Data System (ADS)

Coarse-grained molecular dynamics is utilized to quantify the behavior of a supercooled water drop on smooth and rough surfaces. Crystallization on rough surface is characterized based on wetting states. Freezing temperature and work of adhesion of water droplet are linearly associated with roughness parameters corresponding to the Cassie-Baxter and Wenzel states. The behavior is insensitive to different surface-fluid affinity. We show in general, for Wenzel states, work of adhesion is higher than that of Cassie-Baxter state for surfaces that have identical freezing temperatures.

Singh, Jayant K.; Müller-Plathe, Florian

2014-01-01

165

Multiferroicity in spin ice Ho2Ti2O7: An investigation on single crystals  

NASA Astrophysics Data System (ADS)

The single crystals of rare-earth titanate pyrochlore compound Ho2Ti2O7 are grown and their multiferroicity along the [110] and [111] directions is investigated. The ferroelectricity below ˜28 K, with a polarization of ˜2.50 ?C/m2 along the ?111? direction at 2 K, qualitatively fitting with the theoretical scenario proposed by Khomskii (Nat. Commun. 3, 904 (2012)), is revealed. The magnetoelectric responses along both the [110] and [111] directions are observed, but different underlying mechanisms associated with the specific spin configurations are suggested.

Liu, D.; Lin, L.; Liu, M. F.; Yan, Z. B.; Dong, S.; Liu, J.-M.

2013-05-01

166

Hot ice computer  

Microsoft Academic Search

We experimentally demonstrate that supersaturated solution of sodium acetate, commonly called ‘hot ice’, is a massively-parallel unconventional computer. In the hot ice computer data are represented by a spatial configuration of crystallization induction sites and physical obstacles immersed in the experimental container. Computation is implemented by propagation and interaction of growing crystals initiated at the data-sites. We discuss experimental prototypes

Andrew Adamatzky

2009-01-01

167

Crystal shape-dependent magnetic susceptibility and Curie law crossover in the spin ices Dy2Ti2O7 and Ho2Ti2O7  

NASA Astrophysics Data System (ADS)

We present an experimental determination of the isothermal magnetic susceptibility of the spin ice materials Dy2Ti2O7 and Ho2Ti2O7 in the temperature range 1.8-300 K. The use of spherical crystals has allowed accurate correction for demagnetizing fields and allowed the true bulk isothermal susceptibility ?T(T) to be estimated. This has been compared against a theoretical expression based on a Husimi tree approximation to the spin ice model. Agreement between experiment and theory is excellent at T > 10 K, but systematic deviations occur below that temperature. Our results largely resolve an apparent disagreement between neutron scattering and bulk measurements that has been previously noted. They also show that the use of non-spherical crystals in magnetization studies of spin ice may introduce very significant systematic errors, although we note some interesting—and possibly new—systematics concerning the demagnetizing factor in cuboidal samples. Finally, our results show how experimental susceptibility measurements on spin ices may be used to extract the characteristic energy scale of the system and the corresponding chemical potential for emergent magnetic monopoles.

Bovo, L.; Jaubert, L. D. C.; Holdsworth, P. C. W.; Bramwell, S. T.

2013-09-01

168

Crystal shape-dependent magnetic susceptibility and Curie law crossover in the spin ices Dy2Ti2O7 and Ho2Ti2O7.  

PubMed

We present an experimental determination of the isothermal magnetic susceptibility of the spin ice materials Dy2Ti2O7 and Ho2Ti2O7 in the temperature range 1.8-300 K. The use of spherical crystals has allowed accurate correction for demagnetizing fields and allowed the true bulk isothermal susceptibility ?T(T) to be estimated. This has been compared against a theoretical expression based on a Husimi tree approximation to the spin ice model. Agreement between experiment and theory is excellent at T > 10 K, but systematic deviations occur below that temperature. Our results largely resolve an apparent disagreement between neutron scattering and bulk measurements that has been previously noted. They also show that the use of non-spherical crystals in magnetization studies of spin ice may introduce very significant systematic errors, although we note some interesting--and possibly new--systematics concerning the demagnetizing factor in cuboidal samples. Finally, our results show how experimental susceptibility measurements on spin ices may be used to extract the characteristic energy scale of the system and the corresponding chemical potential for emergent magnetic monopoles. PMID:23988470

Bovo, L; Jaubert, L D C; Holdsworth, P C W; Bramwell, S T

2013-09-25

169

Incorporation of Frazil Ice into a Sea Ice/Ocean Model Nikhil Radia1  

E-print Network

ice consists of millimetre-sized crystals which are formed through supercooling of the sea is needed, usually in the form of an foreign crystal. Fig 1. Frazil Ice. Fig 2. Example of a polynya (left in the ocean cavity beneath an ice shelf. The model categorizes ice crystals into different size classes

170

Ice as a matrix for IR-matrix-assisted laser desorption/ionization: mass spectra from a protein single crystal.  

PubMed Central

Lasers emitting in the ultraviolet wavelength range of 260-360 nm are almost exclusively used for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of macromolecules. Reports about the use of lasers emitting in the infrared first appeared in 1990/1991. In contrast to MALDI in the ultraviolet, a very limited number of reports on IR-MALDI have since been published. Several matrices have been identified for infrared MALDI yielding spectra of a quality comparable to those obtained in the ultraviolet. Water (ice) was recognized early as a potential matrix because of its strong O-H stretching mode near 3 microm. Interest in water as matrix derives primarily from the fact that it is the major constituent of most biological tissues. If functional as matrix, it might allow the in situ analysis of macromolecular constituents in frozen cell sections without extraction or exchanging the water. We present results that show that IR-MALDI of lyophilized proteins, air dried protein solutions, or protein crystals up to a molecular mass of 30 kDa is possible without the addition of any separate matrix. Samples must be frozen to retain a sufficient fraction of the water of hydration in the vacuum. The limited current sensitivity, requiring at least 10 pmol of protein for a successful analysis needs to be further improved. Images Fig. 5 PMID:8692933

Berkenkamp, S; Karas, M; Hillenkamp, F

1996-01-01

171

MEAT, POULTRY, Still contains ice  

E-print Network

MEAT, POULTRY, SEAFOOD Still contains ice crystals and feels as cold, there will be some texture and Clavor loss. Discard DAIRY Still contains ice crystals and feels Ice cream, frozen yogurt Discard Discard Cheese (soft and semi-soft) Refreeze. May

Liskiewicz, Maciej

172

Ice is a Mineral  

NSDL National Science Digital Library

This is a lesson about the characteristics of ice as a mineral and how it compares to other minerals with respect to hardness. Learners will observe ice crystals, develop a hardness scale and position ice on it. Learners will also practice working collaboratively in a team. Activities include small group miming, speaking, drawing, and/or writing. This is lesson 3 of 12 in the unit, Exploring Ice in the Solar System.

173

Ice crystal concentrations in wave clouds: dependencies on temperature, D>0.5 ?m aerosol particle concentration and duration of cloud processing  

NASA Astrophysics Data System (ADS)

Model equations used to either diagnose or prognose the concentration of heterogeneously nucleated ice crystals depend on combinations of cloud temperature, aerosol properties, and elapsed time of supersaturated-vapor or supercooled-liquid conditions. The validity of these equations is questioned. For example, there is concern that practical limitations on aerosol particle time-of-exposure to supercooled-liquid conditions, within ice nucleus counters, can bias model equations that have been constrained by ice nuclei (IN) measurements. In response to this concern, this work analyzes airborne measurements of crystals made within the downwind glaciated portions of middle-tropospheric wave clouds. A streamline model is used to connect a measurement of aerosol concentration, made upwind of a cloud, to a downwind ice crystal (IC) concentration. Four parameters were derived for 80 streamlines: (1) minimum cloud temperature along the streamline, (2) aerosol particle concentration (diameter, D>0.5 ?m) measured within ascending air, upwind of the cloud, (3) IC concentration measured in descending air downwind, and (4) the duration of water-saturated conditions along the streamline. The latter are between 38 to 507 s and the minimum temperatures are between -34 to -14 °C. Values of minimum temperature, D>0.5 ?m aerosol concentration and IC concentration were fitted using the equation developed for IN by DeMott et al. (2010; D10). Overall, there is reasonable agreement among measured IC concentrations, IN concentrations derived using D10's fit equation, and IC concentrations derived by fitting the wave cloud measurements with the equation developed by D10.

Peng, L.; Snider, J. R.; Wang, Z.

2014-10-01

174

Ice Tank Experiments Highlight Changes in Sea Ice Types  

NASA Astrophysics Data System (ADS)

With the current and likely continuing reduction of summer sea ice extent in the Arctic Ocean, the predominant mechanism of sea ice formation in the Arctic is likely to change in the future. Although substantial new ice formation occurred under preexisting ice in the past, the fraction of sea ice formation in open water likely will increase significantly. In open water, sea ice formation starts with the development of small ice crystals, called frazil ice, which are suspended in the water column [World Meteorological Organization, 1985]. Under quiescent conditions, these crystals accumulate at the surface to form an unbroken ice sheet known in its early stage as nilas. Under turbulent conditions, caused by wind and waves, frazil ice continues to grow and forms into a thick, soupy mixture called grease ice. Eventually the frazil ice will coalesce into small, rounded pieces known as pancake ice, which finally consolidate into an ice sheet with the return of calm conditions. This frazil/pancake/ice sheet cycle is currently frequently observed in the Antarctic [Lange et al., 1989]. The cycle normally occurs in regions that have a significant stretch of open water, because this allows for the formation of larger waves and hence increased turbulence. Given the increase of such open water in the Arctic Ocean caused by retreating summer sea ice, the frazil/pancake/ice sheet cycle may also become the dominant ice formation process during freezeup in the Arctic.

Wilkinson, Jeremy P.; DeCarolis, Giacomo; Ehlert, Iris; Notz, Dirk; Evers, Karl-Ulrich; Jochmann, Peter; Gerland, Sebastian; Nicolaus, Marcel; Hughes, Nick; Kern, Stefan; de la Rosa, Sara; Smedsrud, Lars; Sakai, Shigeki; Shen, Hayley; Wadhams, Peter

2009-03-01

175

Detection of the Impact of Ice Crystal Accretion in an Aircraft Engine Compression System During Dynamic Operation  

NASA Technical Reports Server (NTRS)

The accretion of ice in the compression system of commercial gas turbine engines operating in high ice water content conditions is a safety issue being studied by the aviation community. While most of the research focuses on the underlying physics of ice accretion and the meteorological conditions in which accretion can occur, a systems-level perspective on the topic lends itself to potential near-term operational improvements. Here a detection algorithm is developed which has the capability to detect the impact of ice accretion in the Low Pressure Compressor of an aircraft engine during steady flight as well as during changes in altitude. Unfortunately, the algorithm as implemented was not able to distinguish throttle changes from ice accretion and thus more work remains to be done.

May, Ryan D.; Simon, Donald L.; Guo, Ten-Huei

2014-01-01

176

Diffusion-controlled metabolism for long-term survival of single isolated microorganisms trapped within ice crystals  

PubMed Central

Two known habitats for microbial metabolism in ice are surfaces of mineral grains and liquid veins along three-grain boundaries. We propose a third, more general, habitat in which a microbe frozen in ice can metabolize by redox reactions with dissolved small molecules such as CO2, O2, N2, CO, and CH4 diffusing through the ice lattice. We show that there is an adequate supply of diffusing molecules throughout deep glacial ice to sustain metabolism for >105 yr. Using scanning fluorimetry to map proteins (a proxy for cells) and F420 (a proxy for methanogens) in ice cores, we find isolated spikes of fluorescence with intensity consistent with as few as one microbial cell in a volume of 0.16 ?l with the protein mapper and in 1.9 ?l with the methanogen mapper. With such precise localization, it should be possible to extract single cells for molecular identification. PMID:17940052

Rohde, Robert A.; Price, P. Buford

2007-01-01

177

Flow in Polycrystalline Ice  

NSDL National Science Digital Library

This is a virtual journal article about polycrystalline ice. It focuses on plastic deformation, specific flow characteristics and crystallographic preferred orientations associated with polycrystalline ice within glaciers. Part I covers Polycrystalline aggregates deformed in pure-shear; Dynamic recrystallisation; Grain shape and preferred orientation change; Fabric; Evolution of glacial ice during deformation. Part II covers: Time lapse photography; Glaciers; Dislocations; Bernal-Fowler rule; Generation of defect structures; Crystal structure; Ice; Basal glide; Strain rate for glide on basal systems; Critical resolved shear stress; Non-basal glide; Diffusional flow; Plastic deformation; Primary creep; Secondary creep; Tertiary creep; Deformation maps; Grain growth; Grain size reduction; Anisotropic flow law for ice.

Wilson, Chris

178

Influence of particle size and shape on the backscattering linear depolarisation ratio of small ice crystals - cloud chamber measurements in the context of contrail and cirrus microphysics  

NASA Astrophysics Data System (ADS)

The article presents the laser scattering and depolarisation instrument SIMONE that is installed at the large aerosol and cloud chamber facility AIDA of the Karlsruhe Institute of Technology. SIMONE uses a 488 nm cw laser to probe simulated atmospheric clouds by measuring the scattered light from the 1.8° and 178.2° directions. At 178.2°, the scattered light is analysed for the linear polarisation state to deduce the linear depolarisation ratio ?l which is a common measurement parameter of atmospheric LIDAR applications. The optical setup and the mathematical formalism of the depolarisation detection concept are given. SIMONE depolarisation measurements in spheroidal hematite aerosol and supercooled liquid clouds are used to validate the instrument. SIMONE data from a series of AIDA ice nucleation experiments at temperatures between 195 and 225 K were analysed in terms of the impact of the ice particle microphysics on ?l. We found strong depolarisation values of up to 0.4 in case of small growing and sublimating ice particles with volume equivalent diameters of only a few micrometers. Modelling runs with the T-matrix method showed that the measured depolarisation ratios can be accurately reproduced assuming spheroidal and cylindrical particles with a size distribution that has been constrained by IR extinction spectroscopy. Based on the T-matrix modelling runs, we demonstrate that in case of small ice crystals the SIMONE depolarisation results are representative for the LIDAR depolarisation ratio which is measured at exact backscattering direction of 180°. The relevance of our results for the interpretation of recent LIDAR observations in cirrus and contrails is discussed. In view of our results, the high depolarisation ratios observed by the spaceborne LIDAR CALIOP in the tropical upper troposphere might be a hint for the presence of small (sublimating) ice particles in the outflows of deep convective systems.

Schnaiter, M.; Büttner, S.; Möhler, O.; Skrotzki, J.; Vragel, M.; Wagner, R.

2012-06-01

179

Influence of particle size and shape on the backscattering linear depolarisation ratio of small ice crystals - cloud chamber measurements in the context of contrail and cirrus microphysics  

NASA Astrophysics Data System (ADS)

The article presents the laser scattering and depolarisation instrument SIMONE that is installed at the large aerosol and cloud chamber facility AIDA of the Karlsruhe Institute of Technology. SIMONE uses a 488 nm cw laser to probe simulated atmospheric clouds by measuring the scattered light from the 1.8° and 178.2° directions. At 178.2°, the scattered light is analysed for the linear polarisation state to deduce the particle linear depolarisation ratio ?p which is a common measurement parameter of atmospheric lidar applications. The optical setup and the mathematical formalism of the depolarisation detection concept are given. SIMONE depolarisation measurements in spheroidal hematite aerosol and supercooled liquid clouds are used to validate the instrument. SIMONE data from a series of AIDA ice nucleation experiments at temperatures between 195 and 225 K were analysed in terms of the impact of the ice particle microphysics on ?p. We found strong depolarisation values of up to 0.4 in case of small growing and sublimating ice particles with volume equivalent diameters of only a few micrometers. Modelling runs with the T-matrix method showed that the measured depolarisation ratios can be accurately reproduced assuming spheroidal and cylindrical particles with a size distribution that has been constrained by IR extinction spectroscopy. Based on the T-matrix modelling runs, we demonstrate that in case of small ice crystals the SIMONE depolarisation results are representative for the lidar depolarisation ratio which is measured at exact backscattering direction of 180°. The relevance of our results for the interpretation of recent lidar observations in cirrus and contrails is discussed. In view of our results, the high depolarisation ratios observed by the spaceborne lidar CALIOP in the tropical upper troposphere might be a hint for the presence of small (sublimating) ice particles in the outflows of deep convective systems.

Schnaiter, M.; Büttner, S.; Möhler, O.; Skrotzki, J.; Vragel, M.; Wagner, R.

2012-11-01

180

Extinction coefficients from lidar observations in ice clouds compared to in-situ measurements from the Cloud Integrating Nephelometer during CRYSTAL-FACE  

NASA Technical Reports Server (NTRS)

This paper presents a comparison of volume extinction coefficients in tropical ice clouds retrieved from two instruments : the 532-nm Cloud Physics Lidar (CPL), and the in-situ probe Cloud Integrating Nephelometer (CIN). Both instruments were mounted on airborne platforms during the CRYSTAL-FACE campaign and took measurements in ice clouds up to 17km. Coincident observations from three cloud cases are compared : one synoptically-generated cirrus cloud of low optical depth, and two ice clouds located on top of convective systems. Emphasis is put on the vertical variability of the extinction coefficient. Results show small differences on small spatial scales (approx. 100m) in retrievals from both instruments. Lidar retrievals also show higher extinction coefficients in the synoptic cirrus case, while the opposite tendency is observed in convective cloud systems. These differences are generally variations around the average profile given by the CPL though, and general trends on larger spatial scales are usually well reproduced. A good agreement exists between the two instruments, with an average difference of less than 16% on optical depth retrievals.

Noel, Vincent; Winker, D. M.; Garrett, T. J.; McGill, M.

2005-01-01

181

Comparison of CALIPSO-Like, LaRC, and MODIS Retrievals of Ice Cloud Properties over SIRTA in France and Florida during CRYSTAL-FACE  

NASA Technical Reports Server (NTRS)

This study compares cirrus particle effective radius retrieved by a CALIPSO-like method with two similar methods using MODIS, MODI Airborne Simulator (MAS), and GOES imagery. The CALIPSO-like method uses lidar measurements coupled with the split-window technique that uses the infrared spectral information contained at the 8.65-micrometer, 11.15-micrometer and 12.05-micrometer bands to infer the microphysical properties of cirrus clouds. The two other methods, sing passive remote sensing at visible and infrared wavelengths, are the operational MODIS cloud products (referred to by its archival product identifier MOD06 for MODIS Terra) and MODIS retrievals performed by the CERES team at LaRC (Langley Research Center) in support of CERES algorithms; the two algorithms will be referred to as MOD06- and LaRC-method, respectively. The three techniques are compared at two different latitudes: (i) the mid-latitude ice clouds study uses 18 days of observations at the Palaiseau ground-based site in France (SIRTA: Site Instrumental de Recherche par Teledetection Atmospherique) including a ground-based 532 nm lidar and the Moderate Resolution Imaging Spectrometer (MODIS) overpasses on the Terra Platform, (ii) the tropical ice clouds study uses 14 different flight legs of observations collected in Florida, during the intensive field experiment CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and cirrus Layers-Florida Area Cirrus Experiment), including the airborne Cloud Physics Lidar (CPL) and the MAS. The comparison of the three methods gives consistent results for the particle effective radius and the optical thickness, but discrepancies in cloud detection and altitudes. The study confirms the value of an active remote-sensing method (CALIPSO-like) for the study of sub-visible ice clouds, in both mid-latitudes and tropics. Nevertheless, this method is not reliable in optically very thick tropical ice clouds.

Chiriaco, M.; Chepfer, H.; Haeffelin, M.; Minnis, P.; Noel, V.; Platnick, S.; McGill, M.; Baumgardner, D.; Dubuisson, P.; Pelon, J.; Spangenberg, D.; Sun-Mack, S.; Wind, G.

2007-01-01

182

The Spectral Signature of Mixed-Phase Clouds Composed of Non-Spherical Ice Crystals and Spherical Liquid Droplets in the Terrestrial Window Region  

SciTech Connect

An outstanding problem facing the cloud modeling and remote sensing community is to improve satellite-derived cloud microphysical and macrophysical properties when a single cloud layer exists within a temperature range for which a combination of water and ice particles may be present. This is typically known as a ''mixed-phase'' cloud condition, and is prevalent when the cloud-top temperature lies between -40C and 0C. In this paper, we report on a sensitivity study of the spectral signature of mixed-phase clouds in the infrared terrestrial window (8-13 um). Mixed clouds are assumed to be a vertically uniform cloud layer composed of a mixture of pristine hexagonal crystals and spherical water droplets. Unlike the conventional approach that derives the bulk scattering properties of the mixed-phase clouds by a linear weighting of the contributions of ice and water components, the bulk single-scattering properties of mixed-phase clouds are formulated on the basis of fundamental physics. With the aid of a line-by-line radiative transfer model and a discrete ordinates radiative transfer (DISORT) computational program, we investigate the high-resolution spectral signature, expressed in terms of brightness temperature, of mixed-phase clouds with various effective sizes, ice fraction ratios, and optical thicknesses. Small particles are found to have a significant impact on the infrared spectral signature of mixed-phase clouds when the size discrepancy between the ice and water particles is large. Furthermore, the simulation results show that the infrared radiative spectrum associated with cirrus clouds can be quite different from their mixed-phase counterparts even if only a small amount of water droplets exist in the mixed-phase cloud layer.

Yang, P.; Wei, H.- L.; Bryan, B. A.; Huang, H.- L.; Heymsfield, Andrew J.; Hu, Yong X.; Gao, B.- C.; Turner, David D.

2003-06-01

183

Remote sensing estimates of cirrus particle size for tropical and midlatitude cirrus: Hexagonal crystals and ice spheres  

NASA Technical Reports Server (NTRS)

A large discrepancy exists in current estimates of a mean cirrus particle size appropriate for calculations of the effects of these ice clouds on solar and thermal infrared radiative fluxes. For spheres with large size parameter (x = (2 pi r / lambda) is greater than 30, where r is particle radius), and moderate absorption (n(sup i) x less than 1, where n(sup i) is imaginary index of refraction for ice), the optimal effective particle radius is given by: r(sub e) = integral of r(exp 3)n(r)dr / integral of r(exp 2)n(r)dr. For the remote sensing of cirrus particle size at wavelengths of 0.83, 1.65, and 2.21 mu m, a 50 mu m ice sphere would have a size parameter of about 200, and values of n(sup i) x of 0, 0.045, and 0.06, satisfying the above conditions. However, while r(sub e) is a well-defined parameter for spheres, this cross-section area-weighted particle radius can only be extended to non-spherical particles by defining some equivalent sphere, typically an equivalent volume or equivalent cross-section area sphere. Using equivalent volume spheres, values of r(sub e) obtained over Lake Michigan on October 28, 1986, during FIRE phase I varied from 200 mu m (King Air 2D Imaging probes) to 60 mu m (Landsat reflectances at 0.83, 1.65, and 2.2 mu m), to 25 mu m (HIS spectrometer thermal emission between 8 and 12 mu m). Three major uncertainties were identified in this comparison: small ice particles missed by the 2D-C aircraft probes, uncertain ice refractive index, and uncertainties in the single scatter albedos and scattering phase functions used in the radiative calculations. Since the first FIRE cirrus results, advances have been made in all three areas. The present paper reports on improvements in the radiative modeling of ice particles at 0.83, 1.65, and 2.21 mu m wavelengths appropriate for comparisons to Landsat Thematic Mapper data. The paper also includes new results for Landsat observations of ice clouds in the eastern and western tropical Pacific.

Wielicki, Bruce A.; Minnis, Patrick; Arduini, Robert; Parker, Lindsay; Tsay, Si-Chee; Takano, Yoshihide; Liou, Kuo-Nan

1993-01-01

184

Aircraft Icing Sensor  

NASA Technical Reports Server (NTRS)

Simmonds Precision's ice system consists of an ultrasonic sensor and a signal conditioner. The sensor has a piezoelectric ceramic crystal (PCC) that sends an ultrasonic pulse into an ice layer and detects an echo returning from the ice; the time elapsed in the pulse-echo round trip provides a basis for calculating ice thickness. Simmonds offers an alternative system with two PCCs, one a transmitter and the other a receiver for picking up the return echo. This technique offers detection of ice at much smaller thickness values, but at the cost of some ability to detect thicker ice. Among the advantages of the system are the small size of the sensor, which allows its placement in areas previously inaccessible. Other sensor advantages include high accuracy and insensitivity to salt spray, fog, chemicals and abrasion. Both sensor and signal conditioner offer high reliability, light weight and low power consumption.

1990-01-01

185

Retrieval of ice crystal effective diameters from ground-based near-infrared spectra of optically thin cirrus  

Microsoft Academic Search

The microphysical properties of an optically thin (? ? 0.12) cirrus layer formed by dispersing contrails above Boulder, Colorado, have been examined in a ground-based study. Backscatter and depolarization lidar measurements at 0.532 ?m were used to characterize the cloud morphology, while near-infrared (0.9 to 1.7 ?m) spectroscopy was used to measure zenith scattered sunlight from the ice particles. The

A. O. Langford; R. W. Portmann; J. S. Daniel; H. L. Miller; C. S. Eubank; S. Solomon; E. G. Dutton

2005-01-01

186

Classification of Particle Shapes from Lidar Depolarization Ratios in Convective Ice Clouds Compared to in situ Observations During CRYSTAL-FACE  

NASA Technical Reports Server (NTRS)

This manuscript describes a method to class@ cirrus cloud ice particle shape using lidar depolarization measurements as a basis for segregating different particle shape regimes. Measurements from the ER-2 Cloud Physics Lidar (CPL) system during CRYSTAL-FACE provide the basis for this work. While the CPL onboard the ER-2 aircraft was providing remote sensing measurements of cirrus clouds, the Cloud Particle Imager (CPI) onboard the WB-57 aircraft was flying inside those same clouds to sample particle sizes. The results of classifying particle shapes using the CPL data are compared to the in situ measurements made using the CPI , and there is found to be good agreement between the particle shape inferred from the CPL data and that actually measured by the CPI. If proven practical, application of this technique to spaceborne observations could lead to large-scale classification of cirrus cloud particle shapes.

Noel, Vincent; Winker, David; McGill, Matthew; Lawson, Paul

2004-01-01

187

Methods for Validation and Intercomparison of Remote Sensing and In situ Ice Water Measurements: Case Studies from CRYSTAL-FACE and Model Results  

NASA Technical Reports Server (NTRS)

Remote sensing observations, such as those from AURA, are necessary to understand the role of cirrus in determining the radiative and humidity budgets of the upper troposphere. Using these measurements quantitatively requires comparisons with in situ measurements that have previously been validated. However, a direct comparison of remote and in situ measurements is difficult due to the requirement that the spatial and temporal overlap be sufficient in order to guarantee that both instruments are measuring the same air parcel. A difficult as this might be for gas phase intercomparisons, cloud inhomogeneities significantly exacerbate the problem for cloud ice water content measurements. The CRYSTAL-FACE mission provided an opportunity to assess how well such intercomparisons can be performed and to establish flight plans that will be necessary for validation of future satellite instruments. During CRYSTAL-FACE, remote and in situ instruments were placed on different aircraft (NASA's ER-2 and WB-59, and the two planes flew in tandem so that the in situ payload flew in the field of view of the remote instruments. We show here that, even with this type of careful flight planning, it is not always possible to guarantee that remote and in situ instruments are viewing the same air parcel. We use ice water data derived from the in situ Harvard Total Water (HV-TW) instrument, and the remote Goddard Cloud Radar System (CRS) and show that agreement between HV-TW and CRS is a strong function of the horizontal separation and the time delay between the aircraft transects. We also use a cloud model to simulate possible trajectories through a cloud and evaluate the use of statistical analysis in determining the agreement between the two instruments. This type of analysis should guide flight planning for future intercomparison efforts, whether for aircraft or satellite-borne instrumentation.

Sayres, D.S.; Pittman, J. V.; Smith, J. B.; Weinstock, E. M.; Anderson, J. G.; Heymsfield, G.; Li, L.; Fridlind, A.; Ackerman, A. S.

2004-01-01

188

Characterization of ice binding proteins from sea ice algae.  

PubMed

Several polar microalgae are able to live and thrive in the extreme environment found within sea ice, where growing ice crystals may cause mechanical damage to the cells and reduce the organisms' living space. Among the strategies adopted by these organisms to cope with the harsh conditions in their environment, ice binding proteins (IBPs) seem to play a key role and possibly contribute to their success in sea ice. IBPs have the ability to control ice crystal growth. In nature they are widespread among sea ice microalgae, and their mechanism of function is of interest for manifold potential applications. Here we describe methods for a classical determination of the IBP activity (thermal hysteresis, recrystallization inhibition) and further methods for protein characterization (ice pitting assay, determination of the nucleating temperature). PMID:24852640

Bayer-Giraldi, Maddalena; Jin, EonSeon; Wilson, Peter W

2014-01-01

189

crystal  

NASA Astrophysics Data System (ADS)

A Nd3+:Na2La4(WO4)7 crystal with dimensions of ? 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for ?-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for ?-polarization. The emission cross sections are 3.19 × 10-20 cm2 for ?-polarization and 2.67 × 10-20 cm2 for ?-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

2014-07-01

190

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

Microsoft Academic Search

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:

Cédric Chou

2010-01-01

191

crystal  

NASA Astrophysics Data System (ADS)

The polarized absorption, emission spectra and decay time measurements of Pr3+-doped CaYAlO4 single crystal have been performed at room temperature. Based on the Judd-Ofelt theory, the spectroscopic parameters , radiative transition probabilities, radiative lifetimes and branching ratios were obtained. The stimulated emission cross-section, fluorescence lifetimes and the quantum efficiency of the promising laser transition were also calculated and compared with other reported crystals. The results show that Pr3+:CaYAlO4 is a promising candidate for visible solid-state laser emission.

Lv, Shaozhen; Wang, Yan; Zhu, Zhaojie; You, Zhenyu; Li, Jianfu; Gao, Shufang; Wang, Hongyan; Tu, Chaoyang

2014-07-01

192

A comparison of heterogeneous ice nucleation parameterizations using a parcel model framework  

Microsoft Academic Search

A liquid-phase Lagrangian parcel model was expanded to include nucleation and growth of ice crystals. Intercomparisons between three heterogeneous ice nucleation parameterizations that link aerosol type and number to ice crystal concentration were conducted. Results indicate large differences in the prediction of ice formation in modestly supercooled clouds and in the susceptibility of cirrus to heterogeneous ice nucleation for the

Trude Eidhammer; Paul J. DeMott; Sonia M. Kreidenweis

2009-01-01

193

Snow Crystals  

NSDL National Science Digital Library

This site describes snow crystals and snowflakes. Although a common meteorological phenomenon, snow crystal growth is a fascinating and poorly understood process, in which remarkably complex and beautifully symmetric structures appear, quite literally, out of thin air. The many facets of snow crystals are described here, along with the attempts to understand their formation. Site highlights include research on creating designer snow crystals in the laboratory, the history of early snow crystal observations, snow crystal photography, properties of frozen precipitation, and a snow crystal primer for a short course in snow crystal physics - what snow crystals are, how they form, and why they form the way they do. Information is offered on snow crystal classification, preservation, and unusual crystal forms. An extensive image gallery of lab-created crystal forms is available, with enlargeable thumbnail images. There are even instructions for users on how to create crystals. This could be made into a classroom activity, as the science of the growth is explained. Snowflake Physics discusses diffusion, dendrite growth, ice surface physics, electric growth, and ice properties. A vast list of related links is also provided.

Libbrecht, Kenneth

194

Ice/hydrohalite crystallization structures in sub-eutectic freezing experiments in the system NaCl-H20 and possible implications for the properties of frozen brines in Europa: A preliminary report  

NASA Astrophysics Data System (ADS)

Sulfates are likely to be the most abundant solutes in the subsurface Europan liquid ocean. NaCl may also be a significant component of such liquids based on the compositions of stony meteorites like those thought to be among the source materials for the silicates in Europa's interior. The system NaCl-H20 exhibits a eutectic at -20.8°C and 23.3 weight percent NaCl between ice Ih and hydrohalite (NaCl.2H20). This low eutectic temperature compared to Mg and Na sulfate hydrate/ice eutectics indicates that hydrohalite should be among the last salts to crystallize in brine upwellings along rifts and other places where resurfacing by melt extrusion occurs on Europa. We conducted a suite of freezing experiments on NaCl brines with 20.3, 23.3, and 26.6 (saturated) weight percent NaCl by holding these liquids at a few degrees below the eutectic temperature. These runs produced ice-rich, eutectic and hydrohalite-rich aggregates of both phases, respectively, as confirmed by cryogenic x-ray diffraction and x-ray fluorescence spectroscopy. Based on direct observations of crystals forming at the tops and bottoms of the sample chambers and on refractive index measurements of subsequently melted sample material, marked fractional crystallization and segregation by density of ice, hydrohalite, and residual liquids occurred in the 20.3 and 26.6% samples and less so in for the eutectic composition. Crystallization of very fine grained eutectic intergrowths was recognized in cryogenic SEM images of all these samples and they were especially prominent in samples frozen from saturated brine. These samples were very difficult to cleave compared to pure polycrystalline ice, and hence are likely to have high fracture toughness. Direct measurements of this property and also the effects of partial melting on ductile flow rates are planned on such samples. Refracturing of such regions of fine eutectoid ice/hydrohalite intergrowths is likely to be inhibited in refrozen rifts compared to more ice-rich regions on Europa.

Rieck, K.; Kirby, S. H.; Stern, L. A.

2005-12-01

195

9422 Stratospheric ice catalyzes chlorine reactions 9428 Fusing silk and silica  

E-print Network

of hydrochloric acid form a quasiliquid layer on the surface of stratospheric ice crystals. The quasiliquid layer deteriorates with age CHEMISTRY Stratospheric ice catalyzes chlorine reactions To explain how ice crystals can nitrate and promoted the adsorption of acetic acid onto the ice crystals. The effects were observed

McFadden, Geoff

196

Icing instrumentation  

NASA Technical Reports Server (NTRS)

The types and usage categories of icing instrumentation are discussed. The state-of-the-art for the technology governing the use of icing instrumentation is reported with particular emphasis on ground based facilities for icing tests.

Olsen, W.

1980-01-01

197

Development of an ice crystal scattering database for the global change observation mission/second generation global imager satellite mission: investigating the refractive index grid system and potential retrieval error.  

PubMed

Computing time and retrieval error of the effective particle radius are important considerations when developing an ice crystal scattering database to be used in radiative transfer simulation and satellite remote sensing retrieval. Therefore, the light scattering database should be optimized based on the specifications of the satellite sensor. In this study, the grid system of the complex refractive index in the 1.6 ?m (SW3) channel of the Global Change Observation Mission/Second Generation Global Imager satellite sensor is investigated for optimizing the ice crystal scattering database. This grid system is separated into twelve patterns according to the step size of the real and imaginary parts of the refractive index. Specifically, the LIght Scattering solver Applicable to particles of arbitrary Shape/Geometrical-Optics Approximation technique is used to simulate the scattering of light by randomly oriented large hexagonal ice crystals. The difference of radiance with different step size of the refractive index is calculated from the developed light scattering database using the radiative transfer (R-STAR) solver. The results indicated that the step size of the real part is a significant factor in difference of radiance. PMID:22945165

Letu, Husi; Nakajima, Takashi Y; Matsui, Takashi N

2012-09-01

198

Chemical characterization of individual particles and residuals of cloud droplets and ice crystals collected on board research aircraft in the ISDAC 2008 study  

NASA Astrophysics Data System (ADS)

Ambient particles and the dry residuals of mixed-phase cloud droplets and ice crystals were collected during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) near Barrow, Alaska, in spring of 2008. The collected particles were analyzed using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy to identify physico-chemical properties that differentiate cloud-nucleating particles from the total aerosol population. A wide range of individually mixed components was identified in the ambient particles and residuals including organic carbon compounds, inorganics, carbonates, and black carbon. Our results show that cloud droplet residuals differ from the ambient particles in both size and composition, suggesting that both properties may impact the cloud-nucleating ability of aerosols in mixed-phase clouds. The percentage of residual particles which contained carbonates (47%) was almost four times higher than those in ambient samples. Residual populations were also enhanced in sea salt and black carbon and reduced in organic compounds relative to the ambient particles. Further, our measurements suggest that chemical processing of aerosols may improve their cloud-nucleating ability. Comparison of results for various time periods within ISDAC suggests that the number and composition of cloud-nucleating particles over Alaska can be influenced by episodic events bringing aerosols from both the local vicinity and as far away as Siberia.

Hiranuma, N.; Brooks, S. D.; Moffet, R. C.; Glen, A.; Laskin, A.; Gilles, M. K.; Liu, P.; MacDonald, A. M.; Strapp, J. W.; McFarquhar, G. M.

2013-06-01

199

A direct evidence of vibrationally delocalized response at ice surface.  

PubMed

Surface-specific vibrational spectroscopic responses at isotope diluted ice and amorphous ice are investigated by molecular dynamics (MD) simulations combined with quantum mechanics/molecular mechanics calculations. The intense response specific to the ordinary crystal ice surface is predicted to be significantly suppressed in the isotopically diluted and amorphous ices, demonstrating the vibrational delocalization at the ordinary ice surface. The collective vibration at the ice surface is also analyzed with varying temperature by the MD simulation. PMID:25399168

Ishiyama, Tatsuya; Morita, Akihiro

2014-11-14

200

A direct evidence of vibrationally delocalized response at ice surface  

NASA Astrophysics Data System (ADS)

Surface-specific vibrational spectroscopic responses at isotope diluted ice and amorphous ice are investigated by molecular dynamics (MD) simulations combined with quantum mechanics/molecular mechanics calculations. The intense response specific to the ordinary crystal ice surface is predicted to be significantly suppressed in the isotopically diluted and amorphous ices, demonstrating the vibrational delocalization at the ordinary ice surface. The collective vibration at the ice surface is also analyzed with varying temperature by the MD simulation.

Ishiyama, Tatsuya; Morita, Akihiro

2014-11-01

201

Geomicrobiology of Vostok Ice: Implications for Life in Lake Vostok  

NSDL National Science Digital Library

This abstract introduces newly discovered microbe assemblages within Lake Vostok and the research it has inspired. Current studies hope to gain insight into the following areas: physical stresses in deep glacial and accretion ice; the role of clathrates on gas dynamics within the lake; the origin of microbes in accretion ice; the physiological state of ice-bound microbes; the geochemistry of the ice column; and living microbes in ice veins that form at triple junctions in the ice crystal matrix.

Priscu, John

2011-09-15

202

Meth (Crank, Ice) Facts  

MedlinePLUS

Listen to this page Meth (Crank, Ice) Facts Methamphetamine—meth for short—is a white, bitter powder. Sometimes it's made into a white pill or ... clear or white shiny rock (called a crystal). Meth powder can be eaten or snorted up the ...

203

Method of forming clathrate ice  

DOEpatents

A method of forming clathrate ice in a supercooled water-based liquid contained in a vessel is disclosed. Initially, an oscillator device is located in the liquid in the vessel. The oscillator device is then oscillated ultrasonically so that small crystals are formed in the liquid. These small crystals serve as seed crystals for ice formation in the liquid and thereby prevent supercooling of the liquid. Preferably, the oscillating device is controlled by a thermostat which initiates operation of the oscillator device when the temperature of the liquid is lowered to the freezing point. Thereafter, the operation of the oscillator device is terminated when ice is sensed in the liquid by an ice sensor.

Hino, Toshiyuki (Tokyo, JP); Gorski, Anthony J. (Lemont, IL)

1987-01-01

204

Modelling Sea Ice Growth Mark J. McGuinness  

E-print Network

Modelling Sea Ice Growth Mark J. McGuinness Received Day December 2007; revised Day Month Year flux, and slowing ice growth. 1 Introduction The temperature at which sea-water freezes depends on its #12;When cold air causes open sea-water to begin to freeze, many small ice crystals (frazil ice) form

McGuinness, Mark

205

Pack-Ice Studies in the Arctic Ocean  

Microsoft Academic Search

The annual stratification of pack ice has been examined. Summer layers are formed either by arrested growth or by thin layers of fresh-water ice. The crystal structure and the salt content of the ice reflect the seasonal cycle. During the growth of ice a pro- nounced orientation of crystalline structure develops; it is determined by vertical as well as by

W. Schwarzacher

1959-01-01

206

Formation of frazil ice in leads and polynyas  

NASA Astrophysics Data System (ADS)

Areas of open ocean within the sea ice cover, known as leads and polynyas, expose ocean water directly to the cold atmosphere. In winter, these are re- gions of high sea ice production, and they play an important role in the mass balance of sea ice and the salt budget of the ocean. Sea ice formation is a complex process which starts with frazil ice crystals which grow and form pancake ice, and eventually consolidate and turn into a layer of solid sea ice. This study will look at all three phases, concentrating on the first. Frazil ice are millimetre-sized crystals of ice which form in supercooled, turbulent water. They initially form through a process of seeding, and then grow and multiply through secondary nucleation, which is where smaller crystals break off from larger ones to create new nucleii for further growth. The increase in volume of frazil ice will continue to occur until there is no longer supercooling in the water. The crystals eventually precipitate to the surface and pile up to form pancake ice. The presence of pancakes at the surface dampens the effects of waves and turbulence, which allows them to consolidate into a solid layer of ice. The ice then mostly grows through congelation ice forming beneath the layer of ice. Desalination of the sea ice cover due to brine drainage is modelled. The model consists of conservation equation for mass and heat, with an imposed momentum budget. Simulations appear to be realistic.

Radia, N. V.; Feltham, D. L.; Morales Maqueda, M.

2011-12-01

207

crystals  

NASA Astrophysics Data System (ADS)

A novel combined interferometric-mask method for the formation of micro- and nanometric scale three-dimensional (3D) rotational symmetry quasi-crystalline refractive lattice structures in photorefractive materials is demonstrated experimentally. The method is based on micrometric scale spatial modulation of the light by amplitude mask in the radial directions and along the azimuthal angle and the use of counter-propagating beam geometry building up Gaussian standing wave, which defines the light modulation in the axial direction with half-wavelength periodicity. 3D intensity pattern can be represented as numerous mask-generated 2D quasi-periodic structures located in each anti-node of the standing wave. The formed 3D intensity distributions of the optical beams can be imparted into the photorefractive medium thus creating the micro- and sub-micrometric scale 3D refractive index volume lattices. The used optical scheme allows also the formation of 2D lattices by removing the back-reflecting mirror. 2D and 3D refractive lattices were recorded with the use of 532 nm laser beam and rotational symmetry mask in doped lithium niobate crystals and were tested by the probe beam far-field diffraction pattern imaging and direct observation by phase microscope. The formed rotational symmetry 3D refractive structures have the periods of 20-60 ?m in the radial directions, 60 ?m along the azimuthal angle and half-wavelength 266 nm in the axial direction.

Badalyan, A.; Hovsepyan, R.; Mantashyan, P.; Mekhitaryan, V.; Drampyan, R.

2014-07-01

208

Sea Ice  

NASA Technical Reports Server (NTRS)

Sea ice covers vast areas of the polar oceans, with ice extent in the Northern Hemisphere ranging from approximately 7 x 10(exp 6) sq km in September to approximately 15 x 10(exp 6) sq km in March and ice extent in the Southern Hemisphere ranging from approximately 3 x 10(exp 6) sq km in February to approximately 18 x 10(exp 6) sq km in September. These ice covers have major impacts on the atmosphere, oceans, and ecosystems of the polar regions, and so as changes occur in them there are potential widespread consequences. Satellite data reveal considerable interannual variability in both polar sea ice covers, and many studies suggest possible connections between the ice and various oscillations within the climate system, such as the Arctic Oscillation, North Atlantic Oscillation, and Antarctic Oscillation, or Southern Annular Mode. Nonetheless, statistically significant long-term trends are also apparent, including overall trends of decreased ice coverage in the Arctic and increased ice coverage in the Antarctic from late 1978 through the end of 2003, with the Antarctic ice increases following marked decreases in the Antarctic ice during the 1970s. For a detailed picture of the seasonally varying ice cover at the start of the 21st century, this chapter includes ice concentration maps for each month of 2001 for both the Arctic and the Antarctic, as well as an overview of what the satellite record has revealed about the two polar ice covers from the 1970s through 2003.

Parkinson, Claire L.; Cavalieri, Donald J.

2005-01-01

209

The Influence of Platelet Ice and Snow on Antarctic Land-fast Sea Ice  

NASA Astrophysics Data System (ADS)

Sea ice fastened to coasts, icebergs and ice shelves is of crucial importance for climate- and ecosystems. Near Antarctic ice shelves, this land-fast sea ice exhibits two unique characteristics that distinguish it from most other sea ice: a sub-ice layer of ice platelets and a highly stratified and thick snow cover. Ice platelets are flat, plate-like ice crystals forming and growing in a layer of super-cooled water which originates from ice shelf cavities. During growth, heat is lost to the super-cooled ocean rather than conducted to the atmosphere. The crystals accumulate beneath the solid sea-ice cover, forming a layer of loose platelets and eventually becoming incorporated into the sea-ice fabric as platelet ice. Considering the fact that the amount of platelet ice contributes between 10 and 60% to the mass of the land-fast sea ice around Antarctica, very little is known about its spatial and temporal variability. A thick and partly multi-year snow cover develops on top of the Antarctic fast ice, ultimately altering the sea-ice surface and affecting the sea-ice thermodynamics and mass balance. It typically leads to snow-ice formation, surface flooding, and the development of superimposed ice from snow melt water. In order to investigate the role of platelet ice and snow for Antarctic fast ice, we have initiated a regular observation program on the land-fast sea ice of Atka Bay as part of the international Antarctic Fast Ice Network (AFIN). We performed manual measurements of sea-ice and snow thicknesses from June to December 2010 and 2011. Additionally, a mass balance buoy and an automatic weather station were deployed in 2011 and ice cores were taken. Our measurements will reveal insight into the spatial and temporal variability of sea-ice and snow thickness distributions on Atka Bay fast ice. First results show that sea-ice thickness is lowest in the eastern part of the Bay, where a thick snow cover leads to extensive surface flooding. In the West, dynamic conditions lead to high thickness and high local variability. Ice platelets were observed regularly in the boreholes, but measurement techniques have to be improved to assess the thickness of the platelet layer.

Hoppmann, M.; Nicolaus, M.

2011-12-01

210

Airborne measurement of tropospheric ice nuclei aerosols using the Portable Ice Nucleation Chamber (PINC)  

Microsoft Academic Search

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

C. Chou; O. Stetzer; B. Sierau; U. Lohmann

2009-01-01

211

Antarctica Ice  

NSDL National Science Digital Library

This short video examines the recent melting ice shelves in the Antarctica Peninsula; the potential collapse of West Antarctic ice shelf; and how global sea levels, coastal cities, and beaches would be affected.

Geographic, National

212

Sea Ice, an Antarctic Habitat  

NSDL National Science Digital Library

A 'click-and-learn' sub site hosted by the Alfred Wegener Institute Foundation for Polar and Marine Research (AWI), this is a succinct, educational tour of sea-ice and its associated ecological communities. Short synopses introduce the dynamics of sea-ice formation, the microstructure of sea-ice (including crystal structure, brine channels, and ice algae), the effects of ice melt on resident organisms, the logistics of sea-ice research, and _land fast-ice_ and platelet ice habitats. Introductions also exist for the following organisms: krill; whales (i.e., Orcas, southern bottlenosesd dolphins, minke whales); sea birds (i.e., skuas and snow petrals), penguins (i.e., emperor, adelie, and chinstraps), and seals (i.e., weddell, crabeater, leopard, and ross.) Enlargeable thumbnail images accompany the habitat and inhabitant descriptions. Further investigations (at an accelerated level) are prompted with the inclusion of bibliographic references and scientific research presentations (in PDF format) on fast-ice and platelet ice, as well as links to the main site for the AWI.

213

Extreme Ice  

NSDL National Science Digital Library

This activity students through the ways scientists monitor changes in Earth's glaciers, ice caps, and ice sheets. Students investigate about glacier locations, glacial movement, and impacts of climate change on glaciers depending on the depth of research. It is linked to 2009 PBS Nova program entitled Extreme Ice.

Kuntz, Margy; Teachers, Pbs

214

Hot Ice  

Microsoft Academic Search

BEING a reader of NATURE, I have become quite interested in Mr. Thos. Carnelley's experiments with hot ice. Although Mr. Carnelley's experiments would seem to be sufficiently accurate to prove that the ice was in a heated condition, I would still like to offer an additional method to heat the ice, and also a method to test for heat in

George B. Richmond

1881-01-01

215

Melting Ice  

NSDL National Science Digital Library

Monitor the temperature of a melting ice cube and use temperature probes to electronically plot the data on graphs. Investigate what temperature the ice is as it melts in addition to monitoring the temperature of liquid the ice is submerged in.

Consortium, The C.

2011-12-13

216

Basal ice facies and supraglacial melt-out till of the Laurentide Ice Sheet, Tuktoyaktuk Coastlands, western Arctic Canada  

NASA Astrophysics Data System (ADS)

Glacially-deformed massive ice and icy sediments (MI-IS) in the Eskimo Lakes Fingerlands and Summer Island area of the Tuktoyaktuk Coastlands, western Arctic Canada, show, in the same stratigraphic sequences, features characteristic of both basal glacier ice and intrasedimental ice. Basal-ice features comprise (1) ice facies and facies groupings similar to those from the basal ice layers of contemporary glaciers and ice sheets in Alaska, Greenland and Iceland; (2) ice crystal fabrics similar to those from basal ice in Antarctica and ice-cored moraines on Axel Heiberg Island, Canada; and (3) a thaw or erosional unconformity along the top of the MI-IS, buried by glacigenic or aeolian sediments. Intrasedimental ice consists of pore ice and segregated ice formed within Pleistocene sands deposited before glacial overriding. The co-existence of basal and intrasedimental ice within the MI-IS records their occurrence within the basal ice layer of the Laurentide Ice Sheet. Stagnation of the ice sheet and melt-out of till from the ice surface allowed burial and preservation of the basal ice layer on a regional scale. The widespread occurrence of supraglacial melt-out till with clast fabrics similar to those in the underlying ice suggests that such till can be well preserved during partial thaw of a continental ice sheet in lowlands underlain by continuous permafrost.

Murton, J. B.; Whiteman, C. A.; Waller, R. I.; Pollard, W. H.; Clark, I. D.; Dallimore, S. R.

2005-03-01

217

The strength anisotropia of sea ice  

SciTech Connect

The hydraulic-engineering structure calculations of sea ice formation force require the sea ice strength data. The strength characteristics values and the types of sea ice formations in view of water depth define the type and the design of future structures in each particular region of supposed construction. The most objective information on the sea ice physical and technical properties can be obtained by field investigations ad the existing methods of their calculations refer to a great number of errors. The accumulated bank of data on studying the sea ice formation strength properties show one that ice as a natural material is of great crystalline structure variety. The level ice fields have a number of particularities. The crystal sizes increase in ice thickness. The crystals consist of fresh-water thin plates 0.5--0.6 mm in thickness oriented by pickle-water interlayers. Difference in thickness of the sea ice cover structure is one of the main causes of the changes strength characteristics layer. Besides that the sea ice strength depends upon the destroying force direction in reference to crystal orientation which characterizes the sea ice anisotropia as a material.

Evdokimov, G.N.; Rogachko, S.I. [Moscow State Univ. of Civil Engineering (Russian Federation)

1994-12-31

218

Ice Ages  

NSDL National Science Digital Library

During most of the last one billion years the globe had no permanent ice. However, sometimes large areas of the globe were covered with vast ice sheets. Users can read and view pictures which help explain what ice ages are, when they occurred, and why they occur. This site, sponsored by the Illinois State Museum, has links to web pages on paleontology of the midwestern United States during the last ice age and to an animation showing the advance and retreat of the ice sheet in North America 20,000 years ago.

219

Spin Ice  

NASA Astrophysics Data System (ADS)

Pauling's model of hydrogen disorder in water ice represents the prototype of a frustrated system. Over the years it has spawned several analogous models, including Anderson's model antiferromagnet and the statistical "vertex" models. Spin Ice is a sixteen vertex model of "ferromagnetic frustration" that is approximated by real materials, most notably the rare earth pyrochlores Ho2Ti2O7, Dy2Ti2O7 and Ho2Sn2O7. These "spin ice materials" have the Pauling zero point entropy and in all respects represent almost ideal realisations of Pauling's model. They provide experimentalists with unprecedented access to a wide variety of novel magnetic states and phase transitions that are located in different regions of the field-temperature phase diagram. They afford theoreticians the opportunity to explore many new features of the magnetic interactions and statistical mechanics of frustrated systems. This chapter is a comprehensive review of the physics -- both experimental and theoretical -- of spin ice. It starts with a discussion of the historic problem of water ice and its relation to spin ice and other frustrated magnets. The properties of spin ice are then discussed in three sections that deal with the zero field spin ice state, the numerous field-induced states (including the recently identified "kagomé ice") and the magnetic dynamics. Some materials related to spin ice are briefly described and the chapter is concluded with a short summary of spin ice physics.

Bramwell, Steven T.; Gingras, Michel J. P.; Holdsworth, Peter C. W.

2013-03-01

220

UARS/MLS Cloud Ice Measurements: Implications for H2O Transport near the Tropopause  

E-print Network

to ice (RHi) at 100 hPa during both the dry (January­ March) and moist (July­September) periods. 1UARS/MLS Cloud Ice Measurements: Implications for H2O Transport near the Tropopause D. L. WU AND W ice clouds and are sensitive to ice crystals of convective origin. Rough ice water content (IWC

Sherwood, Steven

221

Mystery of ice multiplication in warm-based precipitating shallow cumulus clouds  

Microsoft Academic Search

High concentrations of ice crystals exceeding those of background ice nuclei have often been observed in warm-based precipitating shallow cumulus clouds. Laboratory experiments reveal that such ice multiplication can occur when large ice particles collide with cloud droplets (Hallett-Mossop mechanism). Further studies suggested that this mechanism is unable to account for the exceedingly high ice concentrations in those kinds of

Jiming Sun; Parisa A. Ariya; Henry G. Leighton; M. K. Yau

2010-01-01

222

Ice binding, recrystallization inhibition, and cryoprotective properties of ice-active substances associated with Antarctic sea ice diatoms.  

PubMed

Extracellular macromolecules associated with Antarctic sea ice diatoms were previously shown to have ice-binding activities. The function of these ice-active substances (IASs) has not been identified. Here we show that two of the IASs have a strong ability to inhibit the recrystallization of ice, possibly signifying a cryoprotectant function. To test this possibility, two species of marine diatom (one Antarctic and one temperate) were subjected to a single freeze-thaw cycle (approximately 20h at -4 or -5 degrees C) in the presence or absence of IAS. Viability, based on a double staining technique, was 15-29% higher in the presence of IAS. Etching of single crystal ice hemispheres grown from dilute IAS solutions indicated that the IASs bind to specific faces of ice and are incorporated into the ice lattice. Together, these results suggest that the IASs acts as a cryoprotectant, probably through some ice-binding mechanism. PMID:12686207

Raymond, James A; Knight, Charles A

2003-04-01

223

Modelling ice-ocean interaction in ice shelf crevasses  

NASA Astrophysics Data System (ADS)

Ocean freezing within ice shelf basal crevasses could potentially act as a stabilising influence on ice shelves, however ice-ocean interaction and ocean dynamics within these crevasses are as yet poorly understood. To this end, an idealised two-dimensional model of an ice shelf basal crevasse has been developed using Fluidity-ICOM, a finite element ocean model using an unstructured mesh. A model of frazil ice formation and deposition has been incorporated into Fluidity-ICOM to better represent the freezing process. Model results show that freezing at the top of crevasses leads to the formation of an unstable overturning circulation due to the rejection of dense, salty water. The strength of this circulation, which is increased by the formation of frazil ice, is found to be the dominant factor influencing the total freezing rate. Frazil ice precipitation is found to be responsible for roughly one sixth of ice formation on the top of the basal crevasse, with direct freezing, enhanced by the complex dynamics of the overturning circulation, responsible for the rest. Increasing the frazil crystal radii used in the model has little impact on the amount of frazil ice deposition but does increase the amount of direct freezing. Significant melting and freezing was found to occur on the walls of the crevasse due to the strong overturning circulation. With previous modelling approaches it has not been possible to simulate this strong circulation, with water rising up one side of the crevasse and down the other.

Jordan, J. R.; Holland, P.; Piggott, M. D.; Jenkins, A.; Kimura, S.

2013-12-01

224

Optical Properties of Ice Particles in Young Contrails  

NASA Technical Reports Server (NTRS)

The single-scattering properties of four types of ice crystals (pure ice crystals, ice crystals with an internal mixture of ice and black carbon, ice crystals coated with black carbon, and soot coated with ice) in young contrails are investigated at wavelengths 0.65 and 2.13 micrometers using Mie codes from coated spheres. The four types of ice crystals have distinct differences in their single-scattering properties because of the embedded black carbon. The bulk scattering properties of young contrails consisting of the four types of ice crystals are further investigated by averaging their single-scattering properties over a typical ice particle size distribution found in young contrails. The effect of the radiative properties of the four types of ice particles on the Stokes parameters I, Q, U, and V is also investigated for different viewing zenith angles and relative azimuth angles with a solar zenith angle of 30 degrees using a vector radiative transfer model based on the adding-doubling technique. The Stokes parameters at a wavelength of 0.65 micrometers show pronounced differences for the four types of ice crystals. Those at a wavelength of 2.13 micrometers show similar variations with the viewing zenith angle and relative azimuth angle, but their values are noticeably different.

Hong, Gang; Feng, Qian; Yang, Ping; Kattawar, George; Minnis, Patrick; Hu, Yong X.

2008-01-01

225

Iced Coffee Iced Chai Tea Latte  

E-print Network

Iced Coffee Iced Chai Tea Latte Iced Americano Iced Cappuccino Iced Latte Iced Mocha Iced White.74 $0.70 $0.99 $2.00 $1.39 Coffee By the Pound Organic Espresso Sierra Organic Mexican $9.50 $9.50 Listed prices do not include applicable sales tax. #12;Brewed Coffee Cafe au Lait Hot Tea Chai Tea Latte

226

Sea ice terminology  

SciTech Connect

A group of definitions of terms related to sea ice is presented, as well as a graphic representation of late winter ice zonation of the Beaufort Sea Coast. Terms included in the definition list are belt, bergy bit, bight, brash ice, calving, close pack ice, compacting, compact pack ice, concentration, consolidated pack ice, crack, diffuse ice edge, fast ice, fast-ice boundary, fast-ice edge, first-year ice, flaw, flaw lead, floe, flooded ice, fractured, fractured zone, fracturing, glacier, grey ice, grey-white ice, growler, hummock, iceberg, iceberg tongue, ice blink, ice boundary, ice cake, ice edge, ice foot, ice free, ice island, ice shelf, large fracture, lead, medium fracture, multiyear ice, nilas, old ice, open pack ice, open water, pack ice, polar ice, polynya, puddle, rafted ice, rafting, ram, ridge, rotten ice, second-year ice, shearing, shore lead, shore polynya, small fracture, strip, tabular berg, thaw holes, very close pack ice, very open pack ice, water sky, young coastal ice, and young ice.

Not Available

1980-09-01

227

Medical ice slurry production device  

DOEpatents

The present invention relates to an apparatus for producing sterile ice slurries for medical cooling applications. The apparatus is capable of producing highly loaded slurries suitable for delivery to targeted internal organs of a patient, such as the brain, heart, lungs, stomach, kidneys, pancreas, and others, through medical size diameter tubing. The ice slurry production apparatus includes a slurry production reservoir adapted to contain a volume of a saline solution. A flexible membrane crystallization surface is provided within the slurry production reservoir. The crystallization surface is chilled to a temperature below a freezing point of the saline solution within the reservoir such that ice particles form on the crystallization surface. A deflector in the form of a reciprocating member is provided for periodically distorting the crystallization surface and dislodging the ice particles which form on the crystallization surface. Using reservoir mixing the slurry is conditioned for easy pumping directly out of the production reservoir via medical tubing or delivery through other means such as squeeze bottles, squeeze bags, hypodermic syringes, manual hand delivery, and the like.

Kasza, Kenneth E. (Palos Park, IL); Oras, John (Des Plaines, IL); Son, HyunJin (Naperville, IL)

2008-06-24

228

Dust ice nuclei effects on cirrus clouds  

NASA Astrophysics Data System (ADS)

In order to study aerosol-cloud interactions in cirrus clouds, we apply a new multiple-mode ice microphysical scheme to the general circulation model ECHAM5-HAM. The multiple-mode ice microphysical scheme allows for analysis of the competition between homogeneous freezing of solution droplets, deposition nucleation of pure dust particles, and immersion freezing of coated dust particles and pre-existing ice. We base the freezing efficiencies of coated and pure dust particles on the most recent laboratory data. The effect of pre-existing ice, which has been neglected in previous ice nucleation parameterizations, is to deplete water vapour by depositional growth and thus prevent homogeneous and heterogeneous freezing from occurring. As a first step, we extensively tested the model and validated the results against in situ measurements from various aircraft campaigns. The results compare well with observations; properties such as ice crystal size and number concentration as well as supersaturation are predicted within the observational spread. We find that heterogeneous nucleation on mineral dust particles and the consideration of pre-existing ice in the nucleation process may lead to significant effects: globally, ice crystal number and mass are reduced by 10 and 5%, whereas the ice crystals' size is increased by 3%. The reductions in ice crystal number are most pronounced in the tropics and mid-latitudes in the Northern Hemisphere. While changes in the microphysical and radiative properties of cirrus clouds in the tropics are mostly driven by considering pre-existing ice, changes in the northern hemispheric mid-latitudes mainly result from heterogeneous nucleation. The so-called negative Twomey effect in cirrus clouds is represented in ECHAM5-HAM. The net change in the radiation budget is -0.94 W m-2, implying that both heterogeneous nucleation on dust and pre-existing ice have the potential to modulate cirrus properties in climate simulations and thus should be considered in future studies.

Kuebbeler, M.; Lohmann, U.; Hendricks, J.; Kärcher, B.

2014-03-01

229

Hot Ice  

Microsoft Academic Search

THAT the experiments of Dr. Carnelley on hot ice have excited much interest is not to be wondered at. His statement, however, that ice could be raised to a temperature of 180° without melting was so amazing that many a one could not accept it without repeating the experiments. Soon after the first short notice of Dr. Carnelley appeared in

C. J. E. Brutel de La Rivière; A. van Hasselt

1881-01-01

230

Hot Ice  

Microsoft Academic Search

As my name has been mentioned in NATURE in connection with Dr. Carnelley's experiments on hot ice it may possibly be convenient if I describe the experiments in which I have failed to raise the temperature of ice and camphor above their fusing-points when they are heated in vacuo.

Herbert McLeod

1881-01-01

231

Ice Floats  

NSDL National Science Digital Library

This is a lesson about displacement, buoyancy, and density. Learners will understand why ice floats. Includes background information, teacher notes, assessment criteria, and related resources; activities are differentiated for Pre-K-grade 2 and grades 3-5. This is lesson 4 of the unit Exploring Ice in the Solar System.

232

Climate Impacts of Ice Nucleation  

NASA Technical Reports Server (NTRS)

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).

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

2012-01-01

233

Shape and size of contrails ice particles  

Microsoft Academic Search

A NASA DC-8, equipped as an in-situ sampling aircraft, flew in the exhaust wake of a Boeing 757 on May 4, 1996 over Kansas. Ice crystal samples were collected by impaction technique and replicated twice about 8 to 17 km behind the aircraft at an altitude of 11.8 km. The ice crystals in the contrail (after about 1 minute of

J. Goodman; R. F. Pueschel; E. J. Jensen; S. Verma; G. V. Ferry; S. D. Howard; S. A. Kinne; D. Baumgardner

1998-01-01

234

Archimedean Ice  

E-print Network

The striking boundary dependency (the Arctic Circle phenomenon) exhibited in the ice model on the square lattice extends to other planar set-ups. We present these findings for the triangular and the Kagome lattices. Critical connectivity results guarantee that ice configurations can be generated using the simplest and most efficient local actions. Height functions are utilized throughout the analysis. At the end there is a surprise in store: on the remaining Archimedean lattice for which the ice model can be defined, the 3.4.6.4. lattice, the long range behavior is completely different from the other cases.

Kari Eloranta

2009-09-22

235

Melting Ice  

NSDL National Science Digital Library

In this lesson, students explore a discrepant event when they design an experiment to measure the rate that ice melts when in pure water versus salt water. It is designed to help students realize that a carefully-designed experiment may yield unexpected results, due to unseen events, even though the experiment is precisely planned and executed. The addition of a new technology may clarify factors in the experiment which were previously unknown. Note: the experiment requires advance preparation the day before: two buckets of water are set-up (one with plain tap water, the other with as much salt dissolved in it as possible), which need to be at room temperature. It also requires ice cubes of uniform shape (e.g., from an ice maker or ice trays filled to uniform capacity). This lesson is part of the Cosmic Times teachers guide and is intended to be used in conjunction with the 1993 Cosmic Times Poster.

236

Ice Ages  

NSDL National Science Digital Library

This online exhibit from the Illinois State Museum provides an introduction to glaciation in the midwestern United States since the last glacial advance 20,000 years ago. Topics include what ice ages are, when they occurred, and why. There is also an animation showing the advance and retreat if the ice sheet that covered much of North America from 18,000 to 8000 years ago.

237

Study of Ice Cloud Properties from Synergetic Use of Satellite Observations and Modeling Capabilities  

E-print Network

in comparison with the case of bubble-free ice crystals. Cloud reflectance look-up tables were generated at the wavelengths of 0.65 ?m and 2.13 ?m to examine the impact of accounting for air bubbles in ice crystal morphology on the retrieval of ice cloud optical...

Xie, Yu

2011-02-22

238

[Spectral features analysis of sea ice in the Arctic Ocean].  

PubMed

Sea ice in the Arctic Ocean plays an important role in the global climate change, and its quick change and impact are the scientists' focus all over the world. The spectra of different kinds of sea ice were measured with portable ASD FieldSpec 3 spectrometer during the long-term ice station of the 4th Chinese national Arctic Expedition in 2010, and the spectral features were analyzed systematically. The results indicated that the reflectance of sea ice covered by snow is the highest one, naked sea ice the second, and melted sea ice the lowest. Peak and valley characteristics of spectrum curves of sea ice covered by thick snow, thin snow, wet snow and snow crystal are very significant, and the reflectance basically decreases with the wavelength increasing. The rules of reflectance change with wavelength of natural sea ice, white ice and blue ice are basically same, the reflectance of them is medium, and that of grey ice is far lower than natural sea ice, white ice and blue ice. It is very significant for scientific research to analyze the spectral features of sea ice in the Arctic Ocean and to implement the quantitative remote sensing of sea ice, and to further analyze its response to the global warming. PMID:22715789

Ke, Chang-qing; Xie, Hong-jie; Lei, Rui-bo; Li, Qun; Sun, Bo

2012-04-01

239

A simulated Antarctic fast ice ecosystem  

NASA Technical Reports Server (NTRS)

A 2D numerical ecosystem model of Antarctic land fast ice is developed to elucidate the primary production with the Antarctic sea ice zone. The physical component employs atmospheric data to simulate congelation ice growth, initial brine entrapment, desalination, and nutrient flux. The biological component is based on the concept of a maximum temperature-dependent algal growth rate which is reduced by limitations imposed from insufficient light or nutrients, as well as suboptimal salinity. Preliminary simulations indicate that, during a bloom, microalgae are able to maintain their vertical position relative to the lower congelation ice margin and are not incorporated into the crystal matrix as the ice sheet thickens. It is inferred that land fast sea ice contains numerous microhabitats that are functionally distinct based upon the unique set of processes that control microalgal growth and accumulation within each.

Arrigo, Kevin R.; Kremer, James N.; Sullivan, Cornelius W.

1993-01-01

240

Determination of Ice Cloud Models Using MODIS and MISR Data  

NASA Technical Reports Server (NTRS)

Representation of ice clouds in radiative transfer simulations is subject to uncertainties associated with the shapes and sizes of ice crystals within cirrus clouds. In this study, we examined several ice cloud models consisting of smooth, roughened, homogeneous and inhomogeneous hexagonal ice crystals with various aspect ratios. The sensitivity of the bulk scattering properties and solar reflectances of cirrus clouds to specific ice cloud models is investigated using the improved geometric optics method (IGOM) and the discrete ordinates radiative transfer (DISORT) model. The ice crystal habit fractions in the ice cloud model may significantly affect the simulations of cloud reflectances. A new algorithm was developed to help determine an appropriate ice cloud model for application to the satellite-based retrieval of ice cloud properties. The ice cloud particle size retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) data, collocated with Multi-angle Imaging Spectroradiometer (MISR) observations, is used to infer the optical thicknesses of ice clouds for nine MISR viewing angles. The relative differences between view-dependent cloud optical thickness and the averaged value over the nine MISR viewing angles can vary from -0.5 to 0.5 and are used to evaluate the ice cloud models. In the case for 2 July 2009, the ice cloud model with mixed ice crystal habits is the best fit to the observations (the root mean square (RMS) error of cloud optical thickness reaches 0.365). This ice cloud model also produces consistent cloud property retrievals for the nine MISR viewing configurations within the measurement uncertainties.

Xie, Yu; Yang, Ping; Kattawar, George W.; Minnis, Patrick; Hu, Yongxiang; Wu, Dong L.

2012-01-01

241

CO2 (dry ice) cleaning system  

NASA Astrophysics Data System (ADS)

Tomco Equipment Company has participated in the dry ice (solid carbon dioxide, CO2) cleaning industry for over ten years as a pioneer in the manufacturer of high density, dry ice cleaning pellet production equipment. For over four years Tomco high density pelletizers have been available to the dry ice cleaning industry. Approximately one year ago Tomco introduced the DI-250, a new dry ice blast unit making Tomco a single source supplier for sublimable media, particle blast, cleaning systems. This new blast unit is an all pneumatic, single discharge hose device. It meters the insertion of 1/8 inch diameter (or smaller), high density, dry ice pellets into a high pressure, propellant gas stream. The dry ice and propellant streams are controlled and mixed from the blast cabinet. From there the mixture is transported to the nozzle where the pellets are accelerated to an appropriate blasting velocity. When directed to impact upon a target area, these dry ice pellets have sufficient energy to effectively remove most surface coatings through dry, abrasive contact. The meta-stable, dry ice pellets used for CO2 cleaning, while labeled 'high density,' are less dense than alternate, abrasive, particle blast media. In addition, after contacting the target surface, they return to their equilibrium condition: a superheated gas state. Most currently used grit blasting media are silicon dioxide based, which possess a sharp tetrahedral molecular structure. Silicon dioxide crystal structures will always produce smaller sharp-edged replicas of the original crystal upon fracture. Larger, softer dry ice pellets do not share the same sharp-edged crystalline structures as their non-sublimable counterparts when broken. In fact, upon contact with the target surface, dry ice pellets will plastically deform and break apart. As such, dry ice cleaning is less harmful to sensitive substrates, workers and the environment than chemical or abrasive cleaning systems. Dry ice cleaning system components include: a dry ice pellet supply, a non-reactive propellant gas source, a pellet and propellant metering device, and a media transport and acceleration hose and nozzle arrangement. Dry ice cleaning system operating parameters include: choice of propellant gas, its pressure and temperature, dry ice mass flow rate, dry ice pellet size and shape, and acceleration nozzle configuration. These parameters may be modified to fit different applications. ice cleaning industry will depend upon timely data acquisition of the effects that independent changes in these parameters have on cleaning rates, with respect to different surface coating and substrate combinations. &With this data, optimization of cleaning rates for particular applications will be possible. The analysis of the applicable range of modulation of these parameters, within system component mechanical constraints, has just begun.

Barnett, Donald M.

1995-03-01

242

Hot Ice  

Microsoft Academic Search

I VENTURE, in referring to Dr. Lodge's letter of this week, to put before your readers the meaning of the remarks made on Dr. Carnelley's experiment at the Chemical Society by Prof. Ayrton, who is now away from England. I understood him to say that as Dr. Carnelley's hot ice is obviously in a condition which cannot be represented within

John Perry; A. VAN HASSELT

1881-01-01

243

Hot Ice  

Microsoft Academic Search

THE announcement made some time since by Dr. Carnelley that ice in vacuo could be raised to a temperature far above its ordinary melting-point, seemed so thoroughly in opposition to the experience derived from the great work of Regnault on the tensions of vapours; and as it called for a complete change of ideas in a field in which I

J. B. Hannay

1881-01-01

244

Iced Tea  

NSDL National Science Digital Library

Dissolving things in the universal solvent water is an everyday experience for almost all of us. We don't have a lot of trouble dissolving honey in our hot tea, but when it comes to sweetening cold iced tea, it is quite a task, if not almost impossible. O

Konicek-Moran, Richard

2009-04-01

245

High density amorphous ice at room temperature  

PubMed Central

The phase diagram of water is both unusual and complex, exhibiting a wide range of polymorphs including proton-ordered or disordered forms. In addition, a variety of stable and metastable forms are observed. The richness of H2O phases attests the versatility of hydrogen-bonded network structures that include kinetically stable amorphous ices. Information of the amorphous solids, however, is rarely available especially for the stability field and transformation dynamics—but all reported to exist below the crystallization temperature of approximately 150–170 K below 4–5 GPa. Here, we present the evidence of high density amorphous (HDA) ice formed well above the crystallization temperature at 1 GPa—well inside the so-called “no-man’s land.” It is formed from metastable ice VII in the stability field of ice VI under rapid compression using dynamic-diamond anvil cell (d-DAC) and results from structural similarities between HDA and ice VII. The formation follows an interfacial growth mechanism unlike the melting process. Nevertheless, the occurrence of HDA along the extrapolated melt line of ice VII resembles the ice Ih-to-HDA transition, indicating that structural instabilities of parent ice VII and Ih drive the pressure-induced amorphization. PMID:21518902

Chen, Jing-Yin; Yoo, Choong-Shik

2011-01-01

246

Predominance of Homogeneous Ice nucleation during the Formation of Cirrus Clouds  

NASA Astrophysics Data System (ADS)

Cirrus cloud formation proceeds either by homogeneous freezing (HOM) of liquid droplets or by heterogeneous ice nucleation (HET) on ice nuclei. Liquid droplets are ubiquitous in the upper troposphere and HOM is commonly associated with high concentrations of ice crystals. On the other hand ice nuclei are very scarce in the upper troposphere and cirrus clouds produced by HET tend to have low ice crystal concentration. Recent studies have suggested that observed ice crystal concentration in cirrus is more consistent with a HET scenario than with cirrus clouds formed by HOM. Here we revised such picture and show that although heterogeneous ice nucleation has a significant influence on cirrus formation, when considered over a global basis homogeneous ice nucleation is the predominant mechanism of ice formation. Modeling experiments were carried out with NASA Global Observing System (GEOS). The ice nucleation parameterization in GEOS has been updated to account for the effect of competition between HOM and HET mechanisms, water vapor deposition onto preexisting ice crystals, and parcel history during cirrus cloud formation. When these factors are considered, the ice crystal concentration produced by HOM and HET become comparable. Moreover, over extended areas in the West coast of North and South America, as well as Central Asia HET becomes the predominant path of the ice crystal production. These regions are typically the focus of field campaigns and this may explain the predominance of heterogeneous ice nucleation observed in collected ice crystal residuals. However over the rest of the world, and particularly over most of the Southern Hemisphere, ice crystal production is dominated by HOM. This picture reconciles model results and field campaign observations.

Barahona, Donifan

2014-05-01

247

De-icing: recovery of diffraction intensities in the presence of ice rings.  

PubMed

Macromolecular structures are routinely determined at cryotemperatures using samples flash-cooled in the presence of cryoprotectants. However, sometimes the best diffraction is obtained under conditions where ice formation is not completely ablated, with the result that characteristic ice rings are superimposed on the macromolecular diffraction. In data processing, the reflections that are most affected by the ice rings are usually excluded. Here, an alternative approach of subtracting the ice diffraction is tested. High completeness can be retained with little adverse effect upon the quality of the integrated data. This offers an alternate strategy when high levels of cryoprotectant lead to loss of crystal quality. PMID:20516627

Chapman, Michael S; Somasundaram, Thayumanasamy

2010-06-01

248

De-icing: recovery of diffraction intensities in the presence of ice rings  

PubMed Central

Macromolecular structures are routinely determined at cryotemperatures using samples flash-cooled in the presence of cryoprotectants. However, sometimes the best diffraction is obtained under conditions where ice formation is not completely ablated, with the result that characteristic ice rings are superimposed on the macromolecular diffraction. In data processing, the reflections that are most affected by the ice rings are usually excluded. Here, an alternative approach of subtracting the ice diffraction is tested. High completeness can be retained with little adverse effect upon the quality of the integrated data. This offers an alternate strategy when high levels of cryoprotectant lead to loss of crystal quality. PMID:20516627

Chapman, Michael S.; Somasundaram, Thayumanasamy

2010-01-01

249

Numerical Modeling of Ice Fog in Interior Alaska Using the Weather Research and Forecasting Model  

NASA Astrophysics Data System (ADS)

An ice microphysics parameterization scheme has been modified to better describe and understand ice fog formation. The modeling effort is based on observations in the Sub-Arctic Region of Interior Alaska, where ice fog occurs frequently during the cold season due to abundant water vapor sources and strong inversions existing near the surface at extremely low air temperatures. The microphysical characteristics of ice fog are different from those of other ice clouds, implying that the microphysical processes of ice should be changed in order to generate ice fog particles. Ice fog microphysical characteristics were derived with the NCAR Video Ice Particle Sampler during strong ice fog cases in the vicinity of Fairbanks, Alaska, in January and February 2012. To improve the prediction of ice fog in the Weather Research and Forecasting model, observational data were used to change particle size distribution properties and gravitational settling rates, as well as to implement a homogeneous freezing process. The newly implemented homogeneous freezing process compliments the existing heterogeneous freezing scheme and generates a higher number concentration of ice crystals than the original Thompson scheme. The size distribution of ice crystals is changed into a Gamma distribution with the shape factor of 2.0, using the observed size distribution. Furthermore, gravitational settling rates are reduced for the ice crystals since the crystals in ice fog do not precipitate in a similar manner when compared to the ice crystals of cirrus clouds. The slow terminal velocity plays a role in increasing the time scale for the ice crystals to settle to the surface. Sensitivity tests contribute to understanding the effects of water vapor emissions as an anthropogenic source on the formation of ice fog.

Kim, Chang Ki; Stuefer, Martin; Schmitt, Carl G.; Heymsfield, Andrew; Thompson, Greg

2014-08-01

250

Effect of type III antifreeze protein dilution and mutation on the growth inhibition of ice.  

PubMed

Mutation of residues at the ice-binding site of type III antifreeze protein (AFP) not only reduced antifreeze activity as indicated by the failure to halt ice crystal growth, but also altered ice crystal morphology to produce elongated hexagonal bipyramids. In general, the c axis to a axis ratio of the ice crystal increased from approximately 2 to over 10 with the severity of the mutation. It also increased during ice crystal growth upon serial dilution of the wild-type AFP. This is in marked contrast to the behavior of the alpha-helical type I AFPs, where neither dilution nor mutation of ice-binding residues increases the c:a axial ratio of the ice crystal above the standard 3.3. We suggest that the ice crystal morphology produced by type III AFP and its mutants can be accounted for by the protein binding to the prism faces of ice and operating by step growth inhibition. In this model a decrease in the affinity of the AFP for ice leads to filling in of individual steps at the prism surfaces, causing the ice crystals to grow with a longer c:a axial ratio. PMID:8913575

DeLuca, C I; Chao, H; Sönnichsen, F D; Sykes, B D; Davies, P L

1996-11-01

251

Mars water-ice clouds and precipitation.  

PubMed

The light detection and ranging instrument on the Phoenix mission observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well mixed, up to heights of around 4 kilometers, by the summer daytime turbulence and convection. The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing. The interpretation is that water vapor mixed upward by daytime turbulence and convection forms ice crystal clouds at night that precipitate back toward the surface. PMID:19574386

Whiteway, J A; Komguem, L; Dickinson, C; Cook, C; Illnicki, M; Seabrook, J; Popovici, V; Duck, T J; Davy, R; Taylor, P A; Pathak, J; Fisher, D; Carswell, A I; Daly, M; Hipkin, V; Zent, A P; Hecht, M H; Wood, S E; Tamppari, L K; Renno, N; Moores, J E; Lemmon, M T; Daerden, F; Smith, P H

2009-07-01

252

Forces Generated by High Velocity Impact of Ice on a Rigid Structure  

NASA Technical Reports Server (NTRS)

Tests were conducted to measure the impact forces generated by cylindrical ice projectiles striking a relatively rigid target. Two types of ice projectiles were used, solid clear ice and lower density fabricated ice. Three forms of solid clear ice were tested: single crystal, poly-crystal, and "rejected" poly-crystal (poly-crystal ice in which defects were detected during inspection.) The solid ice had a density of approximately 56 lb/cu ft (0.9 gm/cu cm). A second set of test specimens, termed "low density ice" was manufactured by molding shaved ice into a cylindrical die to produce ice with a density of approximately 40 lb/cu ft (0.65 gm/cu cm). Both the static mechanical characteristics and the crystalline structure of the ice were found to have little effect on the observed transient response. The impact forces generated by low density ice projectiles, which had very low mechanical strength, were comparable to those of full density solid ice. This supports the hypothesis that at a velocity significantly greater than that required to produce fracture in the ice, the mechanical properties become relatively insignificant, and the impact forces are governed by the shape and mass of the projectile.

Pereira, J. Michael; Padula, Santo A., II; Revilock, Duane M.; Melis, Matthew E.

2006-01-01

253

Surface characteristics of lead ice  

NASA Astrophysics Data System (ADS)

Under cold conditions, ice growth in a lead occurs rapidly, giving young sea ice a high bulk salinity. The surface characteristics of this ice type are dominated by a thin, highly saline surface skim and often by the formation of frost flowers. These surface characteristics are of particular interest because of their significant temporal variability and large impact on the electromagnetic properties of sea ice. As part of the Lead Experiment held during March and April of 1991 and 1992 in the Alaskan Beaufort Sea, ice properties and surface conditions typical of springtime leads were monitored at three sites during the initial few days of growth. Observations indicate that once the ice thickness reached approximately 2 cm, a thin (˜1 mm), highly saline (˜100 parts per thousand (ppt)) skim of brine formed on the surface. After only a few hours of growth the initially smooth surface of the sea ice developed some small-scale roughness. Frost flowers, the result of ice grown from the vapor phase, quickly formed on the surface of the sea ice and continued to develop during the observations. Depending on the temperature, the frost flowers were composed of various ice crystal types, including clumps, stellar dendrites, and needles. The initially fresh frost flowers quickly became salty, reaching salinities as high as 100 ppt. The salinity of both the frost flowers and the surface skim decreased at night as temperatures dropped and additional hoarfrost accumulated on the surface. These decreases were also due in part to the accumulation of snow on the surface of the leads. Combining these observations with simple calculations, possible mechanisms for the development and evolution of the surface skim and frost flowers are discussed. They include the hypothesis that the source of the surface skim is brine expelled upward from the sea ice as it cools, that the surface protrusions serve as nucleation sites for the frost flowers, and that the source of the excess water vapor necessary for frost flower growth is the wet surface skim.

Perovich, Donald K.; Richter-Menge, Jacqueline A.

1994-08-01

254

Ice crystals growth driving assembly of porous nitrogen-doped graphene for catalyzing oxygen reduction probed by in situ fluorescence electrochemistry  

NASA Astrophysics Data System (ADS)

In recent years, doped carbonaceous materials as alternative catalysts for oxygen reduction reaction (ORR) have received considerable attention due to the low cost and high CO tolerance capability. Different theoretical studies have suggested that oxygen is reduced in a rapid sequence intermediated by diverse oxygen-containing reactive intermediates (ORI). However, due to the short lifetimes of the possible ORI, direct experimental evidence is very difficult to be obtained. Here, we report the synthesis of an ultralight and porous nitrogen-doped graphene (NG) by annealing graphite oxide (GO)-melamine scaffold shaped in ice template. The resultant NG exhibits excellent electrocatalytic activity toward 4e-reduction of oxygen with the onset potential as low as -0.05 V vs. Ag/AgCl in alkaline media. Using this material as model study, sensitive in situ fluorescence spectroelectrochemistry is applied to demonstrate the presence the reactive ORI. The global ORR pathway is unraveled as stepwise electron transfer involving hydroxyl radical as the important intermediate via both inner- and outer-sphere process. This result would likely provide a new insight into the further understanding of ORR mechanism on those intrinsic carbonaceous materials.

Wang, Jiong; Wang, Huai-Song; Wang, Kang; Wang, Feng-Bin; Xia, Xing-Hua

2014-10-01

255

Ice crystals growth driving assembly of porous nitrogen-doped graphene for catalyzing oxygen reduction probed by in situ fluorescence electrochemistry.  

PubMed

In recent years, doped carbonaceous materials as alternative catalysts for oxygen reduction reaction (ORR) have received considerable attention due to the low cost and high CO tolerance capability. Different theoretical studies have suggested that oxygen is reduced in a rapid sequence intermediated by diverse oxygen-containing reactive intermediates (ORI). However, due to the short lifetimes of the possible ORI, direct experimental evidence is very difficult to be obtained. Here, we report the synthesis of an ultralight and porous nitrogen-doped graphene (NG) by annealing graphite oxide (GO)-melamine scaffold shaped in ice template. The resultant NG exhibits excellent electrocatalytic activity toward 4e-reduction of oxygen with the onset potential as low as -0.05?V vs. Ag/AgCl in alkaline media. Using this material as model study, sensitive in situ fluorescence spectroelectrochemistry is applied to demonstrate the presence the reactive ORI. The global ORR pathway is unraveled as stepwise electron transfer involving hydroxyl radical as the important intermediate via both inner- and outer-sphere process. This result would likely provide a new insight into the further understanding of ORR mechanism on those intrinsic carbonaceous materials. PMID:25335571

Wang, Jiong; Wang, Huai-Song; Wang, Kang; Wang, Feng-Bin; Xia, Xing-Hua

2014-01-01

256

Ice crystals growth driving assembly of porous nitrogen-doped graphene for catalyzing oxygen reduction probed by in situ fluorescence electrochemistry  

PubMed Central

In recent years, doped carbonaceous materials as alternative catalysts for oxygen reduction reaction (ORR) have received considerable attention due to the low cost and high CO tolerance capability. Different theoretical studies have suggested that oxygen is reduced in a rapid sequence intermediated by diverse oxygen-containing reactive intermediates (ORI). However, due to the short lifetimes of the possible ORI, direct experimental evidence is very difficult to be obtained. Here, we report the synthesis of an ultralight and porous nitrogen-doped graphene (NG) by annealing graphite oxide (GO)-melamine scaffold shaped in ice template. The resultant NG exhibits excellent electrocatalytic activity toward 4e-reduction of oxygen with the onset potential as low as ?0.05?V vs. Ag/AgCl in alkaline media. Using this material as model study, sensitive in situ fluorescence spectroelectrochemistry is applied to demonstrate the presence the reactive ORI. The global ORR pathway is unraveled as stepwise electron transfer involving hydroxyl radical as the important intermediate via both inner- and outer-sphere process. This result would likely provide a new insight into the further understanding of ORR mechanism on those intrinsic carbonaceous materials. PMID:25335571

Wang, Jiong; Wang, Huai-Song; Wang, Kang; Wang, Feng-Bin; Xia, Xing-Hua

2014-01-01

257

Interstellar ice  

NASA Astrophysics Data System (ADS)

The 3250/cm 'ice' band observed in absorption and polarization in interstellar spectra is studied in the laboratory in low-temperature solid mixtures of H2O and other molecules. General empirical rules are derived which relate the shape and relative intensity of the H2O infrared absorptions to the degree of H2O dilution and hydrogen-bonding capacity of the dilutant. The chemical composition of mantles accreting on interstellar grains inside dense (1000-100,000/cu cm) molecular clouds has been calculated numerically. The reaction scheme comprises gas-phase as well as grain surface reactions. The results show that in most circumstances grain mantles consist of the molecules H2O, H2CO, NH3, N2, O2, CO, and CO2. The expected infrared characteristics of the calculated grain mantles are discussed with an emphasis on the observed 3250/cm 'ice' band. Grain mantles accreted at a density of about 10,000/cu cm contain large concentrations of H2O (about 60 percent) and produce a broad 3250/cm 'ice' band.

Tielens, A. G. G. M.; Hagen, W.; Greenberg, J. M.

258

Heterogeneous Ice Nuclei Measurements in Monte Cimone, Italy  

NASA Astrophysics Data System (ADS)

Supercooled liquid droplets may coexist with ice crystals below the freezing point in mixed phase clouds. Although pure liquid droplets will not freeze spontaneously until the homogeneous freezing temperature -38°C, ice crystals exist at warmer temperatures due to the presence of ice nuclei (IN), that allow heterogeneous freezing on their surface. Only a small portion of the natural and anthropogenic aerosols serve as ice nuclei. Each aerosol type has its own ability to create and grow ice. IN ability varies with chemical and physical properties and with the environmental characteristics, as temperature and humidity. In this study, samples of aerosol particles were collected on a daily basis over a period of two weeks, on top of Monte Cimone in Italy (44.18°N, 10.70°E, 2165m asl), as part of the PEGASOS (Pan-European Gas-AeroSOl-climate interaction Study) project. The aerosols precipitated electrostatically onto a silicon wafer for an offline measurement of the ice nucleation ability, using the FRankfurt Ice Nuclei Deposition FreezinG Experiment (FRIDGE). The FRIDGE is a vacuum diffusion chamber that generates the sub-freezing temperatures and the supersaturations above ice, simulating conditions that exist inside a mixed phase cloud. On top of the chamber, a camera monitors the formation of ice crystals and a new counting algorithm reports the number concentration of ice crystals. During this campaign, a Saharan dust storm reached the sampling area and the ice nuclei concentrations were higher compared to the daily ice nuclei concentrations for the rest of the campaign. This result supports the previous findings that dust particles are among the most effective and important natural sources of ice nuclei.

Rudich, Y.; Reicher, N.; Schrod, J.; Bingemer, H. G.

2013-12-01

259

Parameterizing Size Distribution in Ice Clouds  

SciTech Connect

PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD). Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice cloud optical properties formulated in terms of PSD parameters in combination with remote measurements of thermal radiances to characterize the small mode. This is possible since the absorption efficiency (Qabs) of small mode crystals is larger at 12 µm wavelength relative to 11 µm wavelength due to the process of wave resonance or photon tunneling more active at 12 µm. This makes the 12/11 µm absorption optical depth ratio (or equivalently the 12/11 µm Qabs ratio) a means for detecting the relative concentration of small ice particles in cirrus. Using this principle, this project tested and developed PSD schemes that can help characterize cirrus clouds at each of the three ARM sites: SGP, NSA and TWP. This was the main effort of this project. These PSD schemes and ice sedimentation velocities predicted from them have been used to test the new cirrus microphysics parameterization in the GCM known as the Community Climate Systems Model (CCSM) as part of an ongoing collaboration with NCAR. Regarding the second problem, we developed and did preliminary testing on a passive thermal method for retrieving the total water path (TWP) of Arctic mixed phase clouds where TWPs are often in the range of 20 to 130 g m-2 (difficult for microwave radiometers to accurately measure). We also developed a new radar method for retrieving the cloud ice water content (IWC), which can be vertically integrated to yield the ice water path (IWP). These techniques were combined to determine the IWP and liquid water path (LWP) in Arctic clouds, and hence the fraction of ice and liquid water. We have tested this approach using a case study from the ARM field campaign called M-PACE (Mixed-Phase Arctic Cloud Experiment). This research led to a new satellite remote sensing method that appears promising for detecting low levels of liquid water in high clouds typically between -20 and -36 oC. We hope to develop this method in future research.

DeSlover, Daniel; Mitchell, David L.

2009-09-25

260

Ingredients: Vanilla ice cream  

E-print Network

Ingredients: Root beer Vanilla ice cream Tall glasses Straws and iced tea spoons Procedure:We are going to make an ice cream float. Experiment: Whathappensifyou... 1. Put the ice cream in the glass before adding the root beer? 2. Put the root beer in the glass before adding the ice cream? 3. Compare

261

Impact of surface nanostructure on ice nucleation  

NASA Astrophysics Data System (ADS)

Nucleation of water on solid surface can be promoted noticeably when the lattice parameter of a surface matches well with the ice structure. However, the characteristic length of the surface lattice reported is generally less than 0.5 nm and is hardly tunable. In this paper, we show that a surface with nanoscale roughness can also remarkably promote ice nucleation if the characteristic length of the surface structure matches well with the ice crystal. A series of surfaces composed of periodic grooves with same depth but different widths are constructed in molecular dynamics simulations. Water cylinders are placed on the constructed surfaces and frozen at constant undercooling. The nucleation rates of the water cylinders are calculated in the simulation using the mean first-passage time method and then used to measure the nucleation promotion ability of the surfaces. Results suggest that the nucleation behavior of the supercooled water is significantly sensitive to the width of the groove. When the width of the groove matches well with the specific lengths of the ice crystal structure, the nucleation can be promoted remarkably. If the width does not match with the ice crystal, this kind of promotion disappears and the nucleation rate is even smaller than that on the smooth surface. Simulations also indicate that even when water molecules are adsorbed onto the surface structure in high-humidity environment, the solid surface can provide promising anti-icing ability as long as the characteristic length of the surface structure is carefully designed to avoid geometric match.

Zhang, Xiang-Xiong; Chen, Min; Fu, Ming

2014-09-01

262

The spectrometer for ice nuclei (SPIN): An instrument for continuous measurements of ice nuclei  

NASA Astrophysics Data System (ADS)

Ice in clouds has major impacts on precipitation formation and cloud characteristics including cloud dynamics and radiation. Primary nucleation of ice crystals at temperatures warmer than about -38 C occurs through heterogeneous nucleation by aerosol particles via several possible mechanisms. Droplet Measurement Technologies is producing a commercial ice nuclei (IN) counter sensitive to deposition and immersion/condensation freezing that features a parallel plate diffusion chamber. A high efficiency refrigeration system allows control of the cold wall to temperatures as low as approximately -70 C and the warm wall to temperatures as low as approximately -40 C, allowing measurements of IN activity over a wide range of atmospherically-relevant temperatures and water/ice saturations. Newly formed ice crystals are detected using an optical particle counter that features detection of polarized scattered light to identify ice crystals and distinguish them from liquid droplets. An actively controlled evaporation section can be operated to remove liquid droplets from the chamber output to further aid discrimination between ice and water. The instrument's data system and electronics allow for binning of the data as well as particle-by-particle recording of the forward scattered signal intensity and the backward scattered P and S polarization intensities. Particle sizing is from 0.4 to 10 ?m.

McMeeking, Gavin; Sagan, Frank; Kok, Greg

2013-05-01

263

Ice Core Secrets  

NSDL National Science Digital Library

In this activity, students will explore the characteristics of ice and explain the influencing factors by using Internet connections to polar field experiences, making their own ice cores and taking a field trip for obtaining a local ice core. The students will practice scientific journaling to document their observations. They will assemble their findings, develop a poster of their ice core and explain their observations. The 'ice is ice' misconception will be dispelled. Students will explain what scientists learn from ice cores and define basic vocabulary associated with ice cores.

Kolb, Sandra

264

About the role of ice in the reconstruction of ice  

NASA Astrophysics Data System (ADS)

As part of the Molecules and Interstellar Ices project, we report the first theoretical results obtained on one of the possible mechanisms for the reconstruction of the ice mantle of interstellar grains after irradiation by the radiation field. In the ISM, the growth of the ice mantle is assumed to proceed more by radical recombination O + H + H than by direct condensation on the grain (Kouchi et al. A&A 1994). Due to the extremely small probability of finding these three species on the same site simultaneously, water formation is thought to be a two-step process: H + O ? OH (1) OH + H ? H2O (2a) Another mechanism has recently been found to operate in the cryogenic environments of noble gas matrices (Krim et al. in preparation) OH + OH ? H2O + O (2b) and the O:H2O complex has been characterized by FTIR spectroscopy. Reaction (2b) opens a new scenario that could be effective in the reconstruction of the ice by using the same OH radicals formed by the irradiation. Here we present a theoretical study of reaction (2b) in a model environment - in the presence of an increasing number of water molecules (DFT ; MP2 ; CCSD ; CCSD(T)) - in the presence of an ice surface extracted from the ice crystal (DFT) - in the presence of an ordered and periodic crystalline surface (periodic DFT/VASP) The first study performed in the gas phase shows that the reaction is exothermic (?H˜16 kcal/mol) with an activation barrier (?E˜2 kcal/mol) in such condition. In a second step, the OH + OH reaction is studied, taking into account the interaction of all species with the ice surface along the whole reaction path; The characteristic points on the potential energy surface, including adsorption sites and transition states, have been determined for each situation. It is found that the activation barrier vanishes as soon as an aggregate of three water molecules or more represents the surface. In addition to the formation of H2O, reaction (2b) provides atomic oxygen ready to take a hydrogen atom to form another OH radical to restart the process. The ice mantle could then be reformed by in situ recombination. Our results suggest also that the OH radical that is a very reactive species in the ice could be involved in a large number of processes implying complex organic molecules (see communication by Pernet et al).

Pauzat, F.; Redondo, P.; Markovits, A.; Ellinger, Y.

2011-05-01

265

Photos by D. Lamb Modeling Ice Growth In Clouds  

E-print Network

;Why is the problem difficult? Wide Variety of Ice Crystal Habits! #12;Capacitance: Captures strong and Harrington (2010) #12;Final Size Changing Aspect Ratio Faster Growth!! C(c,a) = L fs() #12;Aspect ratio Data too small too large #12;Bergeron Process: Rapid growth of ice, drops evaporate Depends on habit

Harrington, Jerry Y.

266

Subliming Ice Surfaces: Freeze-Etch Electron Microscopy  

Microsoft Academic Search

Vacuum sublimation of oriented single crystals of ice at temperatures from -110 to -60 degrees Celsius was studied by electron microscopy with the freeze-etch technique. Sublimation etches the ice surface to produce pits and asperities and above -85 degrees Celsius causes extreme surface roughening. The etch pits are ascribed to surface dislocations, and the extreme roughening is ascribed to the

J. Gordon Davy; Daniel Branton

1970-01-01

267

Ice Zones: Where We Look for Ice  

NSDL National Science Digital Library

In this activity, learners draw conclusions about where on a planetary body scientists might look for ice and why. They use a clay ball, ice cubes, and a heat lamp to model the permanently-shadowed polar regions of planets and moons that may harbor ice. They learn that our Moon, and even Mercury, may have areas with ice. This activity is part of Explore! To the Moon and Beyond! - a resource developed specifically for use in libraries.

268

Concentrated englacial shear over rigid basal ice, West Antarctica: implications for modelling and ice sheet flow  

NASA Astrophysics Data System (ADS)

Basal freeze-on, deformation and ice crystal fabric re-organisation have been invoked to explain thick, massive englacial units observed in the lower ice column of both the Antarctic and Greenland ice sheets. Whilst recognised as having very different rheological properties to overlying meteoric ice, studies assessing the impact of these basal units on the large-scale flow of an ice sheet have so far been limited. We report the discovery of a previously unknown, extensive (100 km long, more than 25 km wide, and up to 1 km thick) englacial unit of near-basal ice beneath the onset zone of the Institute Ice Stream, West Antarctica. Using radio-echo sounding observations, we describe the form and physical characteristics of this englacial unit, and its impact on the stratigraphy and internal deformation of the overlying ice. The lower englacial unit, characterised by a highly-deformed to massive structure, is inferred to be rheologically distinct from the overlying ice column. The overlying ice contains a series of englacial 'whirlwind' features, which are traceable and exhibit longitudinal continuity between flow-orthogonal radar lines. In our data, these whirlwinds are the representation of englacial layer buckling, and therefore provide robust evidence for enhanced ice flow. The interface between the primary ice units is sharp and abrupt, and at a macro-scale is characterised by a series of high-amplitude long-wavelength undulations. Immediately above this interface, whirlwind features are deformed and display evidence for flow-orthogonal horizontal shear, consistent with the deformation of the overlying ice across the basal ice unit. This phenomenon is not a local process, it is observed above the entirety of the currently mapped extent of the basal ice, nor is it dependent on flight orientation, the direction of shear is consistent regardless of flight orientation. These findings have clear significance for our understanding and ability to realistically model ice sheet flow. Our observations suggest that, in parts of the onset zone of the Institute Ice Stream, the flow of the ice sheet effectively ignores the basal topography. Instead, enhanced ice flow responds to a pseudo-bed, with internal deformation concentrated and terminating at an englacial rheological interface between the upper ice sheet column and the massive basal ice. Although we cannot entirely rule out basal accretion as the cause of the strong englacial interface and thick basal layer, discrete englacial shearing acting to realign ice crystals, may be the best explanation for the basal unit in this case. Our results demonstrate that we will, at the very least, need to adapt numerical models of those parts of the ice sheet with extensive and thick basal ice units, and that we may even need to carefully reconsider existing schematic models of ice flow, to incorporate processes associated with concentrated englacial shear.

Ross, Neil; Siegert, Martin

2014-05-01

269

Friction of ice on ice  

NASA Astrophysics Data System (ADS)

New measurements have been made of the friction coefficient of freshwater polycrystalline ice sliding slowly (5 × 10-8 to 1 × 10-3 m s-1) upon itself at temperatures from 98 to 263 K under low normal stresses (?98 kPa). Sliding obeys Coulomb's law: the shear stress is directly proportional to the normal stress across the interface, while cohesion offers little contribution to frictional resistance. The coefficient of kinetic friction of smooth surfaces varies from ?k = 0.15 to 0.76 and, at elevated temperatures (?223 K), exhibits both velocity strengthening at lower velocities (<10-5 to 10-4 m s-1) and velocity weakening at higher velocities. Strengthening and weakening are attributed to creep deformation of asperities and localized melting, respectively. At intermediate temperatures of 173 and 133 K, the kinetic coefficient appears to not exhibit significant dependence upon velocity. However, at the low temperature of 98 K the coefficient of kinetic friction exhibits moderate velocity strengthening at both the lowest and the highest velocities but velocity independence over the range of intermediate velocities. No effect was detected of either grain size or texture. Over the range of roughness 0.4 × 10-6 m ? Ra ? 12 × 10-6 m, a moderate effect was detected, where ?k ? Ra0.08. Slide-hold-slide experiments revealed that the coefficient of static friction increases by an amount that scales logarithmically with holding time. Implications of the results are discussed in relation to shearing across "tiger stripe" faults within the icy crust of Saturn's Enceladus, sliding of the arctic sea ice cover and brittle compressive failure of cold ice.

Schulson, Erland M.; Fortt, Andrew L.

2012-12-01

270

Ice clouds over Fairbanks, Alaska  

NASA Astrophysics Data System (ADS)

Arctic clouds have been recognized long ago as one of the key elements modulating the global climate system. They have gained much interest in recent years because the availability of new continuous datasets is opening doors to explore cloud and aerosol properties as never before. This is particularly important in the light of current climate change studies that predict changing weather scenarios around the world. This research investigates the occurrence and properties of a few types of ice clouds over the Arctic region with datasets available through the Arctic Facility for Atmospheric Remote Sensing (AFARS; 64.86° N, 147.84° W). This study exclusively focuses on ice clouds that form in the upper (cirrus clouds) and midlevels of the troposphere, and that are transparent to laser pulses (visible optical depth, tau < 3.0 -- 4.0). Cirrus clouds are ice-dominated clouds that are formed in the upper levels of the troposphere and are relatively thin such that their visual appearances range from bluish to gray in color. Mid-level ice clouds are those clouds primarily composed of ice crystals forming in the midlevels of the troposphere. It is hypothesized that unlike the basic midlevel cloud type (altostratus), other varieties of midlevel ice clouds exist at times over the Arctic region. The midlevel ice clouds studied here are also transparent to laser pulses and sometimes appear as a family of cirrus clouds to a surface observer. Because of their intermediate heights of occurrence in the troposphere, these could have microphysical properties and radiative effects that are distinct from those associated with upper level ice clouds in the troposphere. A ground-based lidar dataset with visual observations for identifying cloud types collected at AFARS over eight years is used to investigate this hypothesis. Cloud types over AFARS have been identified by a surface observer (Professor Kenneth Sassen) using established characteristics traits. Essential macrophysical properties of the clouds are derived from the lidar data, which serves as a climatological representation for the visually identified cirrus and mid-level ice clouds over a typical sub-Arctic location. Synoptic-scale weather patterns conducive for such cloud type formations are derived using a clustering technique applied to a re-analysis dataset. The cloud properties derived from ground-based lidar over AFARS are used to assess the cloud observations from the CALIPSO satellite.

Kayetha, Vinay Kumar

271

Scrambled Ice  

NASA Technical Reports Server (NTRS)

This complex area on the side of Europa which faces away from Jupiter shows several types of features which are formed by disruptions of Europa's icy crust. North is to the top of the image, taken by NASA's Galileo spacecraft, and the Sun illuminates the surface from the left. The prominent wide, dark bands are up to 20 kilometers (12 miles) wide and over 50 kilometers (30 miles) long. They are believed to have formed when Europa's icy crust fractured, separated and filled in with darker, 'dirtier' ice or slush from below. A relatively rare type of feature on Europa is the 15-kilometer-diameter (9.3-mile) impact crater in the lower left corner. The small number of impact craters on Europa's surface is an indication of its relatively young age. A region of chaotic terrain south of this impact crater contains crustal plates which have broken apart and rafted into new positions. Some of these 'ice rafts' are nearly 1 kilometer (about half a mile) across. Other regions of chaotic terrain are visible and indicate heating and disruption of Europa's icy crust from below. The youngest features in this scene are the long, narrow cracks in the ice which cut across all other features. One of these cracks is about 30 kilometers (18 miles) to the right of the impact crater and extends for hundreds of miles from the top to the bottom of the image.

The image, centered near 23 degrees south latitude and 179 degrees longitude, covers an area about 240 by 215 kilometers (150 by 130 miles) across. The finest details that can be discerned in this picture are about 460 meters (500 yards) across. The image was taken as Galileo flew by Europa on March 29, 1998. The image was taken by the onboard solid state imaging system camera from an altitude of 23,000 kilometers (14,000 miles).

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

1998-01-01

272

Physical characteristics of summer sea ice across the Arctic Ocean  

USGS Publications Warehouse

Sea ice characteristics were investigated during July and August on the 1994 transect across the Arctic Ocean. Properties examined from ice cores included salinity, temperature, and ice structure. Salinities measured near zero at the surface, increasing to 3-4??? at the ice-water interface. Ice crystal texture was dominated by columnar ice, comprising 90% of the ice sampled. Surface albedos of various ice types, measured with radiometers, showed integrated shortwave albedos of 0.1 to 0.3 for melt ponds, 0.5 for bare, discolored ice, and 0.6 to 0.8 for a deteriorated surface or snow-covered ice. Aerial photography was utilized to document the distribution of open melt ponds, which decreased from 12% coverage of the ice surface in late July at 76??N to almost none in mid-August at 88??N. Most melt ponds were shallow, and depth bore no relationship to size. Sediment was pervasive from the southern Chukchi Sea to the north pole, occurring in bands or patches. It was absent in the Eurasian Arctic, where it had been observed on earlier expeditions. Calculations of reverse trajectories of the sediment-bearing floes suggest that the southernmost sediment was entrained during ice formation in the Beaufort Sea while more northerly samples probably originated in the East Siberian Sea, some as far west as the New Siberian Islands.

Tucker, III, W. B.; Gow, A. J.; Meese, D. A.; Bosworth, H. W.; Reimnitz, E.

1999-01-01

273

Ice growth in supercooled solutions of antifreeze glycoproteins  

NASA Technical Reports Server (NTRS)

The effects of different degrees of supercooling on the habit and rates of growth of ice crystals from solutions of antifreeze glycoproteins are reported. To isolate the influence of different solutions and supercooling alone, a system was devised that nucleated crystals in the middle of a uniformly supercooled sample. Alternatively, single crystals of selected orientation were inserted into free liquid surface. A crystallization rate up to five times greater than that in pure water was found. A mechanism explaining these results is suggested.

Harrison, K.; Hallett, J.; Burcham, T. S.; Feeney, R. E.; Kerr, W. L.

1987-01-01

274

Color Reveals Translucent Seasonal Ice  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Figure 1

In a region near the south pole of Mars translucent carbon dioxide ice covers the ground seasonally. For the first time we can 'see' the translucent ice by the affect it has on the appearance of the surface below.

Dark fans of dust (figure 1) from the surface drape over the top of the seasonal ice. The surface would be the same color as the dust except that the seasonal ice affecting its appearance. Bright bluish streaks are frost that has re-crystallized from the atmosphere.

Sunlight can penetrate through the seasonal layer of translucent ice to warm the ground below. That causes the seasonal ice layer to sublime (evaporate) from the bottom rather than the top.

Observation Geometry Image PSP_002942_0935 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 13-Mar-2007. The complete image is centered at -86.4 degrees latitude, 99.2 degrees East longitude. The range to the target site was 245.4 km (153.4 miles). At this distance the image scale is 49.1 cm/pixel (with 2 x 2 binning) so objects 147 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel . The image was taken at a local Mars time of 06:41 PM and the scene is illuminated from the west with a solar incidence angle of 82 degrees, thus the sun was about 8 degrees above the horizon. At a solar longitude of 199.6 degrees, the season on Mars is Northern Autumn.

2007-01-01

275

Analysis of Stress Concentration Effects Around Triple Junctions in Lake Vostok Accretion Ice  

Microsoft Academic Search

Due to the thickness of the Antarctic ice cap, the accretion ice just above Lake Vostok Antarctica exists at temperatures close to the melting point. In addition, the large crystals making up this accretion ice are not highly aligned. Therefore, at triple junctions, substantial stress concentrations may exist. This enhanced stress state may subsequently produce additional melting beyond what would

R. L. Brown; E. E. Adams

2002-01-01

276

Tellus (1989), 41A, 132-147 The effect of parameterized ice microphysics on the  

E-print Network

the experimental basis for dynamic cloud seeding in which massive artificial ice nucleation in updraft regions and associated stratiform rainfall. In this paper, parameterized cloud ice and snow crystals are incorporated). In addition, many numerical simulations of individual clouds show that incorporation of ice- phase

Zhang, Da-Lin

277

A Snow Crystal Primer  

NSDL National Science Digital Library

This website, from Caltech, contains the basic facts about snowflakes and snow crystals, along with many images. The structure of ice, the basic form of a snowflake, the dependence of shape on temperature and humidity, and growing "designer snowflakes" in the lab are described. Links provide more information and image galleries.

Libbrecht, Kenneth

2008-01-23

278

Optimal convective brine drainage from sea ice and optimal brine channel spacing  

NASA Astrophysics Data System (ADS)

The drainage of brine from sea ice controls both the structural properties of sea ice, and forcing of the ocean thermohaline circulation. Sea ice consists of a porous array of ice crystals bathed in dense salty brine, which can be considered as a reactive porous medium or mushy layer. The buoyancy driven flow of brine leads to local dissolution of ice and the formation of brine channels: ice free conduits through which brine drains. It is observed that the spacing of brine channels and structure of the ice matrix evolve as sea ice grows. We consider nonlinear convection in a mushy layer undergoing steady state growth, applying a numerical model to investigate the mechanism controlling the spatial distribution of brine channels. The resulting dynamics yields insight into brine fluxes from young sea ice, and the consequent variations in sea ice microstructure.

Wells, Andrew; Orszag, Steven; Wettlaufer, John

2010-05-01

279

Global Ice Viewer  

NSDL National Science Digital Library

This website explores the sentinels of climate change with a 3D interactive global ice viewer. View the effects of climate change on glaciers, sea ice, and continental ice sheets worldwide, in Greenland, Arctic and Antarctica through time lapse movies of ice melt and trends, comparison photographs and maps. Links to NASA satellites and their missions are provided.

280

Examination of Icing Induced Loss of Control and Its Mitigations  

NASA Technical Reports Server (NTRS)

Factors external to the aircraft are often a significant causal factor in loss of control (LOC) accidents. In today s aviation world, very few accidents stem from a single cause and typically have a number of causal factors that culminate in a LOC accident. Very often the "trigger" that initiates an accident sequence is an external environment factor. In a recent NASA statistical analysis of LOC accidents, aircraft icing was shown to be the most common external environmental LOC causal factor for scheduled operations. When investigating LOC accident or incidents aircraft icing causal factors can be categorized into groups of 1) in-flight encounter with super-cooled liquid water clouds, 2) take-off with ice contamination, or 3) in-flight encounter with high concentrations of ice crystals. As with other flight hazards, icing induced LOC accidents can be prevented through avoidance, detection, and recovery mitigations. For icing hazards, avoidance can take the form of avoiding flight into icing conditions or avoiding the hazard of icing by making the aircraft tolerant to icing conditions. Icing detection mitigations can take the form of detecting icing conditions or detecting early performance degradation caused by icing. Recovery from icing induced LOC requires flight crew or automated systems capable of accounting for reduced aircraft performance and degraded control authority during the recovery maneuvers. In this report we review the icing induced LOC accident mitigations defined in a recent LOC study and for each mitigation describe a research topic required to enable or strengthen the mitigation. Many of these research topics are already included in ongoing or planned NASA icing research activities or are being addressed by members of the icing research community. These research activities are described and the status of the ongoing or planned research to address the technology needs is discussed

Reehorst, Andrew L.; Addy, Harold E., Jr.; Colantonio, Renato O.

2010-01-01

281

Icing: Accretion, Detection, Protection  

NASA Technical Reports Server (NTRS)

The global aircraft industry and its regulatory agencies are currently involved in three major icing efforts: ground icing; advanced technologies for in-flight icing; and tailplane icing. These three major icing topics correspondingly support the three major segments of any aircraft flight profile: takeoff; cruise and hold; and approach and land. This lecture addressess these three topics in the same sequence as they appear in flight, starting with ground deicing, followed by advanced technologies for in-flight ice protection, and ending with tailplane icing.

Reinmann, John J.

1994-01-01

282

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

NASA Astrophysics Data System (ADS)

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 with the ice crystals during the preceding homogeneous freezing cycle exhibit pre-activation: they may retain small ice embryos in pores, have footprints on their surface which match the ice lattice, or simply have a much greater surface area or different surface microstructure compared to the unprocessed glassy aerosol particles. Pre-activation must be considered for the correct interpretation of experimental results on the heterogeneous ice nucleation ability of glassy aerosol particles and may provide a mechanism of producing a population of extremely efficient ice nuclei in the upper troposphere.

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

2012-09-01

283

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

NASA Astrophysics Data System (ADS)

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 ice crystals during the preceding homogeneous freezing cycle exhibit pre-activation: they may retain small ice embryos in pores, have footprints on their surface which match the ice lattice, or simply have a much greater surface area or different surface microstructure compared to the unprocessed glassy aerosol particles. Pre-activation must be considered for the correct interpretation of experimental results on the heterogeneous ice nucleation ability of glassy aerosol particles and may provide a mechanism of producing a population of extremely efficient ice nuclei in the upper troposphere.

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

2012-04-01

284

Ice on waterfowl markers  

USGS Publications Warehouse

Wild and captive giant Canada geese (Branta canadensis maxima) and captive mallards (Anas platyrhynchos) accumulated ice on neck collars and/or nasal saddles during winter storm periods in 1971 and 1972. Weather conditions associated with icing were documented, and characteristics of icing are discussed. Severe marker icing occurred during subfreezing weather when the windchill reached approximately -37 deg.C. Birds appeared able to de-ice nasal saddles in most instances.

Greenwood, R. J.; Bair, W. C.

1974-01-01

285

Ice Formation in Gas-Diffusion Layers  

SciTech Connect

Under sub-freezing conditions, ice forms in the gas-diffusion layer (GDL) of a proton exchange membrane fuel cell (PEMFC) drastically reducing cell performance. Although a number of strategies exist to prevent ice formation, there is little fundamental understanding of the mechanisms of freezing within PEMFC components. Differential scanning calorimetry (DSC) is used to elucidate the effects of hydrophobicity (Teflon® loading) and water saturation on the rate of ice formation within three commercial GDLs. We find that as the Teflon® loading increases, the crystallization temperature decreases due to a change in internal ice/substrate contact angle, as well as the attainable level of water saturation. Classical nucleation theory predicts the correct trend in freezing temperature with Teflon® loading.

Dursch, Thomas; Radke, Clayton J.; Weber, Adam Z.

2010-07-10

286

Crystal Notes The Crystal  

E-print Network

Crystal Notes The Crystal The crystal is defined as an ordered set of atoms (molecules) arranged. Ordered crystals exist because in their formation they must disorder their surroundings more than they are ordered. The key to growing a crystal is to cause in the disorder of the surroundings to be more than

Meagher, Mary

287

A Laboratory Route to Interstellar Ice  

NASA Astrophysics Data System (ADS)

The formation of snow and ice has always intrigued humans and challenged them to study these phenomena. Every snowflake has its own unique history of formation, but no two are alike. Like snow-crystals, interstellar ices consist predominantly of water (H2O), but also contain significant fractions of other molecules such as carbon monoxide (CO), carbon dioxide (CO2), and methanol (CH3OH), and traces of dinitrogen (N2) and ammonia (NH3). The presence, or absence, of a molecule in the ice strongly depends on the environmental conditions. Vice versa, these molecules have an influence on their environment as well. Hence, the chemical composition and the structure of interstellar ices are thought to contain valuable information about the past and the future of interstellar regions, and it is for this reason that interstellar ices are simulated and studied under laboratory conditions. The present thesis contains a study of laboratory analogs of interstellar ices and presents a newly developed apparatus that provides a novel laboratory route to investigate the properties of these ices in more detail than has previously been possible.

van Broekhuizen, Fleur Antoinette

2005-06-01

288

Arctic ice islands  

SciTech Connect

The development of offshore oil and gas resources in the Arctic waters of Alaska requires offshore structures which successfully resist the lateral forces due to moving, drifting ice. Ice islands are floating, a tabular icebergs, up to 60 meters thick, of solid ice throughout their thickness. The ice islands are thus regarded as the strongest ice features in the Arctic; fixed offshore structures which can directly withstand the impact of ice islands are possible but in some locations may be so expensive as to make oilfield development uneconomic. The resolution of the ice island problem requires two research steps: (1) calculation of the probability of interaction between an ice island and an offshore structure in a given region; and (2) if the probability if sufficiently large, then the study of possible interactions between ice island and structure, to discover mitigative measures to deal with the moving ice island. The ice island research conducted during the 1983-1988 interval, which is summarized in this report, was concerned with the first step. Monte Carlo simulations of ice island generation and movement suggest that ice island lifetimes range from 0 to 70 years, and that 85% of the lifetimes are less then 35 years. The simulation shows a mean value of 18 ice islands present at any time in the Arctic Ocean, with a 90% probability of less than 30 ice islands. At this time, approximately 34 ice islands are known, from observations, to exist in the Arctic Ocean, not including the 10-meter thick class of ice islands. Return interval plots from the simulation show that coastal zones of the Beaufort and Chukchi Seas, already leased for oil development, have ice island recurrences of 10 to 100 years. This implies that the ice island hazard must be considered thoroughly, and appropriate safety measures adopted, when offshore oil production plans are formulated for the Alaskan Arctic offshore. 132 refs., 161 figs., 17 tabs.

Sackinger, W.M.; Jeffries, M.O.; Lu, M.C.; Li, F.C.

1988-01-01

289

Cirrus Uncinus Generating Cells and the Evolution of Cirrdorm Clouds. Part III: Numerical Computations of the Growth of the Ice Phase  

Microsoft Academic Search

Equations were developed to calculate the growth of the ice phase in cirrus clouds. Calculations indicated that nucleation of ice crystals in cirrus uncinus heads forming at temperatures lower than 35°C generally should occur near the upwind base of the head, and in cirrostratus clouds at the top of the cloud.The growth of ice crystals and the resulting shape of

Andrew Heymsneid

1975-01-01

290

Sea ice ecosystems.  

PubMed

Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters. PMID:24015900

Arrigo, Kevin R

2014-01-01

291

Physical and biological controls on DMS,P dynamics in ice shelf-influenced fast ice during a winter-spring and a spring-summer transitions  

NASA Astrophysics Data System (ADS)

report the seasonal and vertical variations of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in fast ice at Cape Evans, McMurdo Sound (Antarctica) during the spring-summer transition in 2011 and winter-spring transition in 2012. We compare the variations of DMS,P observed to the seasonal evolution of the ice algal biomass and of the physical properties of the ice cover, with emphasis on the ice texture and brine dynamics. Isolated DMS and DMSP maxima were found during both seasonal episodes in interior ice and corresponded to the occurrence of platelet crystals in the ice texture. We show that platelet crystals formation corresponded in time and depth to the incorporation of dinoflagellates (strong DMSP producers) in the ice cover. We also show that platelet crystals could modify the environmental stresses on algal cells and perturb the vertical redistribution of DMS,P concentrations. We show that during the winter-spring transition in 2012, the DMS,P profiles were strongly influenced by the development and decline of a diatom-dominated bloom in the bottom ice, with DMSP variations remarkably following chl a variations. During the spring-summer transition in 2011, the increase in brine volume fraction (influencing ice permeability) on warming was shown to trigger (1) an important release of DMS to the under-ice water through brine convection and (2) a vertical redistribution of DMSP across the ice.

Carnat, Gauthier; Zhou, Jiayun; Papakyriakou, Tim; Delille, Bruno; Goossens, Thomas; Haskell, Tim; Schoemann, Véronique; Fripiat, François; Rintala, Janne-Markus; Tison, Jean-Louis

2014-05-01

292

Digital-image processing and image analysis of glacier ice  

USGS Publications Warehouse

This document provides a methodology for extracting grain statistics from 8-bit color and grayscale images of thin sections of glacier ice—a subset of physical properties measurements typically performed on ice cores. This type of analysis is most commonly used to characterize the evolution of ice-crystal size, shape, and intercrystalline spatial relations within a large body of ice sampled by deep ice-coring projects from which paleoclimate records will be developed. However, such information is equally useful for investigating the stress state and physical responses of ice to stresses within a glacier. The methods of analysis presented here go hand-in-hand with the analysis of ice fabrics (aggregate crystal orientations) and, when combined with fabric analysis, provide a powerful method for investigating the dynamic recrystallization and deformation behaviors of bodies of ice in motion. The procedures described in this document compose a step-by-step handbook for a specific image acquisition and data reduction system built in support of U.S. Geological Survey ice analysis projects, but the general methodology can be used with any combination of image processing and analysis software. The specific approaches in this document use the FoveaPro 4 plug-in toolset to Adobe Photoshop CS5 Extended but it can be carried out equally well, though somewhat less conveniently, with software such as the image processing toolbox in MATLAB, Image-Pro Plus, or ImageJ.

Fitzpatrick, Joan J.

2013-01-01

293

Measurement of ice thickness (icing) in aeronautics  

NASA Technical Reports Server (NTRS)

Pulsed ultrasonic techniques have been used to measure the formation of ice in flight in an icing wind tunnel with a precision of + or - 0.5 mm. Two icing regimes, humid and dry, are identified. Both natural and artificial conditions are considered. On the basis of ice formation rates obtained by the ultrasound technique and the observed surface conditions, it is found that the heat transfer coefficients are larger in the wind tunnel tests than in actual flight, presumably due to the higher level of turbulence in the wind tunnel tests. Profiles obtained during flight under natural conditions are compared with mechanical-type measurements and with the results of stereographic analysis.

Hansman, R. John; Kirby, Mark S. JR.

1988-01-01

294

Slow wave dynamics stalls tropical tropopause ice clouds  

NASA Astrophysics Data System (ADS)

Water vapour is the most important natural green house gas. However, in the stratosphere an increase in water vapour would possibly result in a cooling. The major entrance of trace substances into the stratosphere is the tropical tropopause layer (TTL), localized between the main level of convective outflow, 150 hPa, and 70 hPa. The TTL water vapour budget, and thus the exchange with the stratosphere, depends crucially on the occurrence and properties of ice clouds in this cold region (T < 200 K). It is believed that homogeneous freezing of liquid solution particles, which predominate the particle population, is the preferred pathway of ice formation. High water vapour supersaturation with respect to ice is required to initiate homogeneous ice nucleation. The number of emerging ice crystals depends on temperature and the ambient relative humidity over ice (RHi). Strong increase in RHi due to rising vertical velocity will produce large amounts of ice crystals. In the TTL, very slow large-scale updraughts prevail (? 0.01 m/s), which would lead to low ice crystal concentrations (? 0.1cm-3). However, tropical deep convection initiates intrinsic gravity waves and consequently, we would expect much higher vertical velocities and therefore higher ice crystal number concentrations. Since the many ice crystals rapidly grow by water vapour diffusion it is also expected that the initially high ice supersaturation quickly reduces to saturation after ice formation. Contrarily, during the last years high and persistent ice supersaturations were observed in the cold TTL in several airborne field campaigns inside and outside of ice clouds (Peter et al., 2006), creating a discussion called the 'supersaturation puzzle'. A step forward in that discussion was made recently: Krämer et al. (2009) observed ice crystal concentrations much lower than expected (most often < 0.1cm-3), but consistent with the measured high supersaturations. These observations turned the 'supersaturation' into a 'nucleation puzzle'. The 'nucleation puzzle' is currently intensely discussed and other nucleation pathways suppressing, modifying or replacing homogeneous freezing are proposed. All these approaches to explain the TTL ice nucleation are of chemical or microphysical nature. Here, we present intense model studies of ice cloud formation under dynamical conditions typical for the TTL. From direct comparison of model simulations and observations we claim that the special TTL dynamics - namely a superposition of very slow large-scale updraughts with high-frequency short waves - can produce the observed low numbers of ice crystals solely by 'classical' homogeneous freezing. References: Krämer, M., Schiller, C., Afchine, A., Bauer, R., Gensch, I., Mangold, A., Schlicht, S., Spelten, N., Ebert, V., Möhler, O., Saathoff, H., Sitnikov, N., Borrman, S., de Reus, M. and P. Spichtinger, 2009: On Cirrus Cloud Supersaturations and Ice Crystal Numbers. Atmos. Chem. Phys., 9, 3505-3522. Peter T., Marcolli C., Spichtinger, P., Corti, T., Baker M.B., Koop, T., 2006: When dry air is too humid. Science 314 (5804), 1399-1402.

Spichtinger, Peter; Krämer, Martina; Borrmann, Stephan

2010-05-01

295

Simulation Tools Model Icing for Aircraft Design  

NASA Technical Reports Server (NTRS)

Here s a simple science experiment to try: Place an unopened bottle of distilled water in your freezer. After 2-3 hours, if the water is pure enough, you will notice that it has not frozen. Carefully pour the water into a bowl with a piece of ice in it. When it strikes the ice, the water will instantly freeze. One of the most basic and commonly known scientific facts is that water freezes at around 32 F. But this is not always the case. Water lacking any impurities for ice crystals to form around can be supercooled to even lower temperatures without freezing. High in the atmosphere, water droplets can achieve this delicate, supercooled state. When a plane flies through clouds containing these droplets, the water can strike the airframe and, like the supercooled water hitting the ice in the experiment above, freeze instantly. The ice buildup alters the aerodynamics of the plane - reducing lift and increasing drag - affecting its performance and presenting a safety issue if the plane can no longer fly effectively. In certain circumstances, ice can form inside aircraft engines, another potential hazard. NASA has long studied ways of detecting and countering atmospheric icing conditions as part of the Agency s efforts to enhance aviation safety. To do this, the Icing Branch at Glenn Research Center utilizes a number of world-class tools, including the Center s Icing Research Tunnel and the NASA 607 icing research aircraft, a "flying laboratory" for studying icing conditions. The branch has also developed a suite of software programs to help aircraft and icing protection system designers understand the behavior of ice accumulation on various surfaces and in various conditions. One of these innovations is the LEWICE ice accretion simulation software. Initially developed in the 1980s (when Glenn was known as Lewis Research Center), LEWICE has become one of the most widely used tools in icing research and aircraft design and certification. LEWICE has been transformed over the years from strictly a research tool to one used routinely by industry and other government agencies. Glenn contractor William Wright has been the architect of this development, supported by a team of researchers investigating icing physics, creating validation data, and ensuring development according to standard software engineering practices. The program provides a virtual simulation environment for determining where water droplets strike an airfoil in flight, what kind of ice would result, and what shape that ice would take. Users can enter geometries for specific, two-dimensional cross sections of an airfoil or other airframe surface and then apply a range of inputs - different droplet sizes, temperatures, airspeeds, and more - to model how ice would build up on the surface in various conditions. The program s versatility, ease of use, and speed - LEWICE can run through complex icing simulations in only a few minutes - have contributed to it becoming a popular resource in the aviation industry.

2012-01-01

296

The presence and quantification of splenic ice in the McMurdo Sound notothenioid fish, Pagothenia borchgrevinki (Boulenger, 1902).  

PubMed

Survival of some polar fishes is associated with high levels of circulating antifreeze glycoproteins (AFGPs). AFGP prevent ice growth giving rise to thermal hysteresis. The inhibiting action of AFGPs implies that polar fish contain ice to which AFGPs adsorb. Cryopelagic Pagothenia borchgrevinki, inhabiting the ice-laden waters of McMurdo Sound, Antarctica, were assayed for ice and ice was found on skin, gills, in the intestine, and in the spleen. Two methods used to assess the number of ice crystals in spleens gave comparable results (12.1+/-1.9 and 22+/-3.8 per spleen). Attempts were made to measure the rate of uptake of ice by P. borchgrevinki held in cages immediately beneath the sub-ice platelet layer in McMurdo Sound; uptake was sporadic. Introduction of ice into fish by spray freezing a small patch of the integument resulted in detection of splenic ice after 1h, illustrating that a mechanism exists for ice transport from the periphery to the spleen. Splenic ice did not seem to be eliminated from fish held in ice-free water at -1.6 degrees C for approximately two months. The relatively small number of splenic ice crystals and the slow rate of ice uptake suggest efficient ice barriers exist in P. borchgrevinki. PMID:19758576

Praebel, Kim; Hunt, Ben; Hunt, Luke H; DeVries, Arthur L

2009-12-01

297

Spectral properties of ice-particulate mixtures and implications for remote sensing. 1. Intimate mixtures.  

USGS Publications Warehouse

The spectral properties of water ice-partitioning mixtures are studied for the purpose of deriving the ice and particulate abundances from remotely obtained spectra (particulates referring to non-icy materials in the form of grains). Reflectance levels and ice absorption band depths are a complex function of the single scattering albedo of the particulates embedded in the ice. The ice absorption band depths are related to the mean optical path length of photons in ice through Beers law, Fresnel reflection from the ice-crystal faces on the surface, and ice absorption coefficient as a function of wavelength. Laboratory spectra of many ice- particulate mixtures are studied with high-, medium-, and low-albedo particulates.-from Authors

Clark, R. N.; Lucey, P. G.

1984-01-01

298

A Prolific Warm Rain Process and its Possible Influence on Ice Nucleation as Observed During ICE-T  

NASA Astrophysics Data System (ADS)

A particularly difficult, long-standing problem has been to explain observations in extra-tropical and tropical maritime clouds, made as early as the mid-1960's but also in later field studies, that exhibited far greater ice crystal number concentrations than expected from past ice nuclei measurements, especially when cloud top temperatures were greater than -10 °C. Some studies have implicated rime-splintering (Hallet-Mossop process) as an explanation for the unusually high number concentrations of ice crystals observed in warmer regions of the clouds. This process is likely active in maritime cumuli, but it cannot explain the first ice crystals formed, as it requires some ice (graupel) to already be present. A prolific warm rain process (i.e. converting much of the cloud water to precipitation-size drops) in these maritime clouds, spurred by the warm, humid environment and low droplet number concentrations, may provide the raindrops that later freeze to become the source of the graupel needed to initiate the Hallett-Mossop process. Recently, new observations in maritime cumuli relevant to ice nucleation were collected during the Ice in Cumulus Experiment -Tropical (ICE-T) field campaign, based in the Caribbean in July 2011. In-situ aircraft observations, in addition to remotely sensed data collected with aircraft-mounted radar and lidar, were collected on developing cumuli at temperatures of -12 °C and greater. The warm rain process and ice onset in the clouds were documented with observations of water mass and cloud particle (droplet and ice crystal) size distributions. The radar data placed these observations in the context of the cloud development. Aerosol data (cloud condensation nuclei and ice nuclei number concentrations) were collected to provide constraints on droplet and ice initiation processes. This presentation will consist of a preliminary analysis of these observations from several cases observed during ICE-T, to illustrate the impressive amount of supercooled water present in these clouds, and its possible influence on ice nucleation. Preliminary numerical modeling results constrained by these observations will also be presented to understand if raindrops formed by the warm rain process could be initiating the first ice, and if the cloud conditions and time scales of the microphysical processes are consistent with those observed.

Lasher-Trapp, S.; DeMott, P. J.; Heymsfield, A.; Hudson, J. G.; Jensen, J. B.; Johnson, A. V.; Leon, D.; McMeeking, G.; Rogers, D. C.; Toohey, D. W.; Twohy, C. H.

2011-12-01

299

Quantifying and Reducing Biases in Satellite Derived Ice Cloud Optical Thickness and Ice Effective Diameter by Simultaneous Retrievals of Ice Asymmetry Parameter  

NASA Astrophysics Data System (ADS)

The ice cloud optical thickness (COT) and the ice crystal effective diameter (Deff), defined as one-and-one-half times the bulk ice volume over the bulk ice projected area, are fundamental radiative properties of ice clouds and provide valuable constraints for cloud model simulations. These parameters can be retrieved from satellite, in situ or ground-based measurements, although COT and Deff derived from such sensors are known to differ significantly amongst each other and biases need to be better quantified. Here we focus on COT and Deff at cloud top derived from satellite measurements in the visible and shortwave infrared. For such retrievals, the leading source of uncertainty is related to the asymmetry parameter of the ice optical model assumed in the retrieval algorithm. We first quantify the biases in retrieved COT and Deff as a function of bias in assumed asymmetry parameter. We then present a method to retrieve ice cloud asymmetry parameter from multi-directional polarization measurements, which allows for subsequent retrievals of COT and Deff that are not biased by a preselected ice optical model. This method is applied to combined measurements of the POLDER and MODIS satellite instruments over deep convection observed during the TWP-ICE campaign. We show that retrieved ice crystal asymmetry parameter and Deff vary systematically with cloud-top temperature, but even more so with changes of monsoon activity. Using both TWP-ICE and global measurements, we show that our retrieved COT values are significantly smaller than current operational MODIS collection 5 retrievals, because our retrieved asymmetry parameters are systematically smaller than those assumed in the operational retrievals. Moreover, the retrieved Deff values are generally 20-50% larger than operational MODIS retrievals and show a significantly wider range. Based on these results, we note expected improvements and limitations of upcoming MODIS collection 6 retrievals. Finally, we briefly discuss the use of our retrievals for evaluating cloud-resolving model simulations.

van Diedenhoven, B.; Fridlind, A. M.; Ackerman, A. S.; Cairns, B.

2013-12-01

300

Impact of surface nanostructure on ice nucleation.  

PubMed

Nucleation of water on solid surface can be promoted noticeably when the lattice parameter of a surface matches well with the ice structure. However, the characteristic length of the surface lattice reported is generally less than 0.5 nm and is hardly tunable. In this paper, we show that a surface with nanoscale roughness can also remarkably promote ice nucleation if the characteristic length of the surface structure matches well with the ice crystal. A series of surfaces composed of periodic grooves with same depth but different widths are constructed in molecular dynamics simulations. Water cylinders are placed on the constructed surfaces and frozen at constant undercooling. The nucleation rates of the water cylinders are calculated in the simulation using the mean first-passage time method and then used to measure the nucleation promotion ability of the surfaces. Results suggest that the nucleation behavior of the supercooled water is significantly sensitive to the width of the groove. When the width of the groove matches well with the specific lengths of the ice crystal structure, the nucleation can be promoted remarkably. If the width does not match with the ice crystal, this kind of promotion disappears and the nucleation rate is even smaller than that on the smooth surface. Simulations also indicate that even when water molecules are adsorbed onto the surface structure in high-humidity environment, the solid surface can provide promising anti-icing ability as long as the characteristic length of the surface structure is carefully designed to avoid geometric match. PMID:25273463

Zhang, Xiang-Xiong; Chen, Min; Fu, Ming

2014-09-28

301

Martian Ice Caves  

NASA Astrophysics Data System (ADS)

Ice in Martian lava tube caves would have scientific and developmental value. These natural channels in rock may hold keys to Mars' past as well as potential resources for humanity's futures. Terrestrial lava tube caves are natural receptacles for accumulations of water. Often, due to lower temperatures coupled with the superior insulation properties of the surrounding rock, these accumulations are in the form of ice. Historically, ice was mined from some lava tube caves. Many of the lava tubes in the Central Oregon area sport such names as "Arnolds Ice Cave," "Surveyors Ice Cave," "South Ice Cave," etc. These caves are not caves in ice, but rather common lava tubes with seasonal, and sometimes perennial ice deposits. Locating and cataloging similar features on Mars, could be of value for the colonization of Mars and the search for life. Such features may also prove useful in helping to determine past climatic conditions on the Red Planet.

Frederick, R. D.; Billings, T. L.; McGown, R. D.; Walden, B. E.

2000-07-01

302

Greenland Ice Flow  

NASA Video Gallery

Greenland looks like a big pile of snow seen from space using a regular camera. But satellite radar interferometry helps us detect the motion of ice beneath the snow. Ice starts flowing from the fl...

303

Elaboration and characterization of a KCl single crystal doped with nanocrystals of a Sb2O3 semiconductor  

NASA Astrophysics Data System (ADS)

Undoped and doped KCl single crystals have been successfully elaborated via the Czochralski (Cz) method. The effects of dopant Sb2O3 nanocrystals on structural and optical properties were investigated by a number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis, UV-visible and photoluminescence (PL) spectrophotometers. An XRD pattern of KCl:Sb2O3 reveals that the Sb2O3 nanocrystals are in the well-crystalline orthorhombic phase. The broadening of diffraction peaks indicated the presence of a Sb2O3 semiconductor in the nanometer size regime. The shift of absorption and PL peaks is observed near 334 nm and 360 nm respectively due to the quantum confinement effect in Sb2O3 nanocrystals. Particle sizes calculated from XRD studies agree fairly well with those estimated from optical studies. An SEM image of the surface KCl:Sb2O3 single crystal shows large quasi-spherical of Sb2O3 crystallites scattered on the surface. The elemental analysis from EDAX demonstrates that the KCl:Sb2O3 single crystal is slightly rich in oxygen and a source of excessive quantities of oxygen is discussed.

Bouhdjer, L.; Addala, S.; Chala, A.; Halimi, O.; Boudine, B.; Sebais, M.

2013-04-01

304

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

NASA Astrophysics Data System (ADS)

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 undisturbed free troposphere, but is also influenced by the Planetary Boundary Layer (PBL) especially in summer. The probability of Saharan Dust Events (SDE) at the Jungfraujoch is usually high from March to July (Collaud Coen et al., 2004). Two campaigns have been performed during this period in order to investigate the influence of a SDE on the IN number concentration and properties: PINC II took place from February 23rd to March 16th, 2009 and PINC III from June 3rd to 17th, 2009. The operating conditions inside the chamber during both campaigns were -31°C with relative humidities with respect to ice and water of 127% and 91%, respectively. During the first campaign, no SDE were detected and the average number concentration of IN was <10 particles/liter. Two SDE of different intensity occurred during the second campaign on June 15th and 16th where significantly higher IN number concentrations have been observed. We found that the larger the particles are, the more efficient they are as IN especially during SDE. References: Collaud Coen M., Weingartner E., Schaub D., Hueglin C., Corrigan C., Henning S., Schwikowski M., and Baltensperger U. (2004). Saharan dust events at the Jungfraujoch: detection by wavelength dependence of the single scattering albedo and first climatology analysis. Atmos. Chem. Phys., 4, 2465-2480, 2004 Rogers, D. C. (1988), Development of a Continuous Flow Thermal Gradient Diffusion Chamber for Ice Nucleation Studies, Atmos. Res. 22:149-181. Stetzer, O., Baschek, B., Lueoend, F., Lohmann, U. (2008), The Zurich Ice Nucleation Chamber (ZINC)-A New Instrument to Investigate Atmospheric Ice Formation, Aerosol Science and Technology, 42:64-74, 2008

Chou, Cédric

2010-05-01

305

Ice electrode electrolytic cell  

DOEpatents

This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an ice layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the ice. The metal is then easily removed after melting the ice. In a second embodiment, the same ice-covered electrode can be employed to form powdered metals.

Glenn, David F. (Idaho Falls, ID); Suciu, Dan F. (Idaho Falls, ID); Harris, Taryl L. (Idaho Falls, ID); Ingram, Jani C. (Idaho Falls, ID)

1993-01-01

306

Ice electrode electrolytic cell  

DOEpatents

This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an ice layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the ice. The metal is then easily removed after melting the ice. In a second embodiment, the same ice-covered electrode can be employed to form powdered metals.

Glenn, D.F.; Suciu, D.F.; Harris, T.L.; Ingram, J.C.

1993-04-06

307

Diatom assemblages promote ice formation in large lakes  

PubMed Central

We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (Tc) as high as ?3?°C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world. PMID:23552624

D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Kocer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

2013-01-01

308

Ultrafast superheating and melting of bulk ice.  

PubMed

The superheating of a solid to a temperature beyond its melting point, without the solid actually melting, is a well-known phenomenon. It occurs with many substances, particularly those that can readily be produced as high-quality crystals. In principle, ice should also be amenable to superheating. But the complex three-dimensional network of hydrogen bonds that holds water molecules together and gives rise to unusual solid and liquid properties strongly affects the melting behaviour of ice; in particular, ice usually contains many defects owing to the directionality of its hydrogen bonds. However, simulations are readily able to 'create' defect-free ice that can be superheated. Here we show that by exciting the OH stretching mode of water, it is possible to superheat ice. When using an ice sample at an initial temperature of 270 K, we observe an average temperature rise of 20 +/- 2 K that persists over the monitored time interval of 250 ps without melting. PMID:16407948

Iglev, H; Schmeisser, M; Simeonidis, K; Thaller, A; Laubereau, A

2006-01-12

309

Technology for Ice Rinks  

NASA Technical Reports Server (NTRS)

Ron Urban's International Ice Shows set up portable ice rinks for touring troupes performing on temporary rinks at amusement parks, sports arenas, dinner theaters, shopping malls and civic centers. Key to enhanced rink portability, fast freezing and maintaining ice consistency is a mat of flexible tubing called ICEMAT, an offshoot of a solar heating system developed by Calmac, Mfg. under contract with Marshall.

1983-01-01

310

Aircraft icing: Introduction  

NASA Technical Reports Server (NTRS)

The objectives of the Workshop were as follows: (1) to assess the current understanding of fixed wing and rotorcraft operational icing environments and problems (2) to evaluate facilities requirements for R&D and certification purposes (3) to examine means of improving icing forecasts (4) to identify shortcomings in aeronautical icing knowledge which can be alleviated by new research and instrumentation development.

Enders, J. H.

1979-01-01

311

Ice on the Moon  

NSDL National Science Digital Library

This information about the Lunar Prospector mission to the Moon discusses the possibility that ice exists on the lunar surface. The article indicates that no native water ice has been found on the moon. If ice has been found, it most likely originated from meteors and meteorites which periodically bombard the lunar surface.

Williams, David

2003-01-22

312

Ice age paleotopography  

Microsoft Academic Search

A gravitationally self-consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the Last Glacial Maximum (LGM). The results show that LGM ice volume was approximately 35 percent lower than suggested by the CLIMAP reconstruction and the maximum heights of the main Laurentian and Fennoscandian ice complexes are inferred

W. R. Peltier

1994-01-01

313

Multi-year ice  

USGS Multimedia Gallery

ARCTIC OCEAN - A multi-year ice floe slides down the starboard side of the Coast Guard Cutter Healy Aug. 11, 2009, as the ship heads north into even thicker ice. "You can tell that this is a multi-year ice floe by the light blue melt ponds that have formed on top of the floe," said Pablo Clemente-Co...

2010-02-19

314

In situ observations of a high-pressure phase of H2O ice  

USGS Publications Warehouse

A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10??and 50??C. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.

Chou, I.-M.; Blank, J.G.; Goncharov, A.F.; Mao, H.-K.; Hemley, R.J.

1998-01-01

315

Black carbon enrichment in atmospheric ice particle residuals observed in lower trophospheric mixed phase clouds  

SciTech Connect

The enrichment of black carbon (BC) in residuals of small ice particles was investigated during intensive experiments in winter 2004 and 2005 at the high alpine research station Jungfraujoch (3580 m asl, Switzerland). Two inlets were used to sample the bulk aerosol (residuals of cloud droplets and ice crystals as well as non-activated aerosol particles) and the residual particles of small ice crystals (diameter 5 - 20 m). An enrichment of the BC mass fraction in the ice particle residuals was observed by investigating the measured BC mass concentration as a fraction of the bulk (submicrometer) aerosol mass concentration sampled by the two inlets. On average, the BC mass fraction was 5% for the bulk aerosol and 14% for the ice particle residuals. The observed enrichment of BC in ice particle residuals suggests that BC may act as ice nuclei, with important implications for the indirect aerosol effect via glaciation of clouds.

Cozic, J.; Mertes, S.; Verheggen, B.; Cziczo, Dan; Gallavardin, S. J.; Walter, S.; Baltensperger, Urs; Weingartner, E.

2008-08-15

316

Emergent ice rule and magnetic charge screening from vertex frustration in artificial spin ice  

NASA Astrophysics Data System (ADS)

Artificial spin ice comprises a class of frustrated arrays of interacting single-domain ferromagnetic nanostructures. Previous studies of artificial spin ice have focused on simple lattices based on natural frustrated materials. Here we experimentally examine artificial spin ice created on the shakti lattice, a structure that does not directly correspond to any known natural magnetic material. On the shakti lattice, none of the near-neighbour interactions is locally frustrated, but instead the lattice topology frustrates the interactions leading to a high degree of degeneracy. We demonstrate that the shakti system achieves a physical realization of the classic six-vertex model ground state. Furthermore, we observe that the mixed coordination of the shakti lattice leads to crystallization of effective magnetic charges and the screening of magnetic excitations, underscoring the importance of magnetic charge as the relevant degree of freedom in artificial spin ice and opening new possibilities for studies of its dynamics.

Gilbert, Ian; Chern, Gia-Wei; Zhang, Sheng; O'Brien, Liam; Fore, Bryce; Nisoli, Cristiano; Schiffer, Peter

2014-09-01

317

Diffusion, adsorption and incorporation of antifreeze glycoprotein molecules at the ice/water interface  

NASA Astrophysics Data System (ADS)

Antifreeze glycoproteins(AFGP) are known to inhibit ice crystal growth by adsorbing to the interface. But, there is no direct observation of the distribution of AFGP molecules around the interface of the growing ice crystal. In order to observe the growing ice/water interface, one-directional growth experiments of ice crystal growth were carried out in AFGP solution. AFGPs were labeled with fluorescent markers to see the distribution of AFGP molecules. We obtained video image of the distribution of AFGP molecules near the growing ice/water interface by using fluorescent microscopy. Incorporation and accumulation of AFGP molecules at the interface were clearly observed, and strongly depend on the growth rate of the ice crystal. We also observed the diffusion field of AFGP molecules from the ice interface and calculated diffusion and segregation coefficients. We found that AFGP molecules strongly adsorb to the growing ice crystal interface, and incorporate between grain boundaries, but found little evidence for incorporation into the crystal lattice. This is contrary to previous paradigms for AFGP function.

Nakaya, Hiroyuki; Zepeda, Salvador; Uda, Yukihiro; Matsumoto, Shuichiro; Yokoyama, Etsuro; Furukawa, Yoshinori

2006-03-01

318

The growth of ice particles in a mixed phase environment based on laboratory observations  

NASA Astrophysics Data System (ADS)

This paper describes new laboratory observations about the size evolution of ice crystals and cloud droplets immersed in a mixed-phase cloud. The experiments were performed by using a cloud chamber facility for three temperatures - 6 °C, - 10 °C and - 20 °C, in order to explore the basic crystal growth habits (columns and hexagonal plates). The sizes of the cloud droplets, ice-columns and hexagonal ice-plates were examined for growth times between 50 and 300 s. The results show evidence that after ice crystal nucleation, the cloud droplets reduce gradually their sizes by the evaporation process; while the ice crystals grow as a consequence of the water vapor diffusion process. The ice crystal growths at different temperatures were compared with the results reported by other authors. The experimental data were also compared with a theoretical model of the growth rate of ice crystals. It was observed that the numerical model provides a description of the ice columns' growth in fairly good agreement with the laboratory observations, while it predicts that the hexagonal plates evolve with maximum sizes larger than those observed in the experiments. In general, it has been noted that the results obtained from the model are very sensitive to the parameter that denotes the ratio between the condensation coefficient for the basal face and prism face. It is a critical coefficient that needs to be carefully addressed in cloud modeling.

Castellano, Nesvit E.; Ávila, Eldo E.; Bürgesser, Rodrigo E.; Saunders, Clive P. R.

2014-12-01

319

Ice-templated structures for biomedical tissue repair: From physics to final scaffolds  

NASA Astrophysics Data System (ADS)

Ice-templating techniques, including freeze-drying and freeze casting, are extremely versatile and can be used with a variety of materials systems. The process relies on the freezing of a water based solution. During freezing, ice nucleates within the solution and concentrates the solute in the regions between the growing crystals. Once the ice is removed via sublimation, the solute remains in a porous structure, which is a negative of the ice. As the final structure of the ice relies on the freezing of the solution, the variables which influence ice nucleation and growth alter the structure of ice-templated scaffolds. Nucleation, the initial step of freezing, can be altered by the type and concentration of solutes within the solution, as well as the set cooling rate before freezing. After nucleation, crystal growth and annealing processes, such as Ostwald ripening, determine the features of the final scaffold. Both crystal growth and annealing are sensitive to many factors including the set freezing temperature and solutes. The porous structures created using ice-templating allow scaffolds to be used for many diverse applications, from microfluidics to biomedical tissue engineering. Within the field of tissue engineering, scaffold structure can influence cellular behavior, and is thus critical for determining the biological stimulus supplied by the scaffold. The research focusing on controlling the ice-templated structure serves as a model for how other ice-templating systems might be tailored, to expand the applications of ice-templated structures to their full potential.

Pawelec, K. M.; Husmann, A.; Best, S. M.; Cameron, R. E.

2014-06-01

320

The anomalously high melting temperature of bilayer ice  

NASA Astrophysics Data System (ADS)

Confinement of water usually depresses its melting temperature. Here we use molecular dynamics simulations to determine the liquid-crystal equilibrium temperature for water confined between parallel hydrophobic or mildly hydrophilic plates as a function of the distance between the surfaces. We find that bilayer ice, an ice polymorph in which the local environment of each water molecule strongly departs from the most stable tetrahedral structure, has the highest melting temperature (Tm) of the series of l-layer ices. The melting temperature of bilayer ice is not only unusually high compared to the other confined ices, but also above the melting point of bulk hexagonal ice. Recent force microscopy experiments of water confined between graphite and a tungsten tip reveal the formation of ice at room temperature [K. B. Jinesh and J. W. M. Frenken, Phys. Rev. Lett. 101, 036101 (2008)]. Our results suggest that bilayer ice, for which we compute a Tm as high as 310 K in hydrophobic confinement, is the crystal formed in those experiments.

Kastelowitz, Noah; Johnston, Jessica C.; Molinero, Valeria

2010-03-01

321

Physical and structural properties of the Greenland Ice Sheet Project 2 ice core: A review  

NASA Astrophysics Data System (ADS)

Substantial data sets have been collected on the relaxation characteristics, density, grain size, c axis fabrics, and ultrasonic velocities of the Greenland Ice Sheet Project 2 (GISP2) core to its contact with bedrock at 3053.4 m. Changes in all these properties paralleled closely those found in cores from Byrd Station, Antarctica, and Dye 3, Greenland. Density increased progressively with depth to a maximum of 0.921 Mg/m3 at about 1400 m, at which depth the ice became bubble free. Below about 2000 m, in situ densities began to decrease in response to increasing ice sheet temperatures. Since drilling, much of the ice core has undergone significant volume expansion (relaxation) due to microcracking and the exsolving of enclathratized gases, especially in the brittle ice zone between 650 and 1400 m. Grain size increased linearly to about 1000 m, thereafter remaining fairly constant until the Younger Dryas event at 1678 m where a twofold to threefold decrease in grain size occurred. These grain size changes were accompanied by a progressive clustering of crystal c axes toward the vertical, including a small increase in c axis concentration across the Younger Dryas/Holocene boundary. Increased dust levels in the Wisconsin ice have contributed to the maintenance of a fine-grained texture which, with its strong vertical c axis fabric, persisted to nearly 3000 m. However, beginning at about 2800 m, layers of coarse-grained ice intermixed with the much finer-grained matrix ice are observed. Below 3000 m the ice became very coarse grained. This change, attributed to annealing recrystallization at elevated temperatures in the ice sheet, was accompanied by a dispersed or ring-like redistribution of the c axes about the vertical. Ultrasonic measurements of vertical and horizontal P wave velocities made at 10-m intervals along the entire length of the GISP2 core fully confirmed the results of the crystallo-optical observations. A return to fine-grained ice coincided with the first appearance of brown, silty ice 13 m above bedrock. Bedrock material consisted of 48 cm of till, including boulders and cobbles, overlying gray biotite granite comprising the true bedrock. There is evidence that disturbed structure in the GISP2 cores begins little more than 70% of the way through the ice sheet. This disturbance increases with depth until it becomes large enough to cast suspicion on features lasting centuries or more in the bottom 10% of the ice sheet.

Gow, A. J.; Meese, D. A.; Alley, R. B.; Fitzpatrick, J. J.; Anandakrishnan, S.; Woods, G. A.; Elder, B. C.

1997-11-01

322

Using ice cores from the East Antarctic Ice Sheet, scientists have been able to study  

E-print Network

Using ice cores from the East Antarctic Ice Sheet, scientists have been able to study ice's ice sheets. Ice sheets are huge areas of permanent ice. There are only three ice sheets on Earth: the Greenland Ice Sheet, the West Antarctic Ice Sheet, and the East Antarctic Ice Sheet. The Greenland Ice Sheet

323

Compression of Ice to 170 Gpa  

NASA Astrophysics Data System (ADS)

Studies on H2O have revealed a rich polymorphism of ice at low pressures. Bcc-structured ice VII is stable at room temperature above 2.2 GPa. Infrared spectroscopy measurements by Aoki et al. (Phys. Rev. B, 1996) and Goncharov et al. (Science, 1996) demonstrated that around 60 GPa the ice VII exhibits a phase transition to a structure with symmetric hydrogen bonds, which is so called symmetric ice. The x-ray diffraction measurement of single-crystal ice up to 170 GPa (Loubeyre et al., Nature, 1999) showed that the cubic ice is stable over the whole pressure range, while x-ray powder diffraction study by Wolanin et al. (Phys. Rev. B, 1997) reported that the ice VII becomes stiffer above 66 GPa. These studies, however, included large uncertainties on pressure determinations. Here we investigated the compressibility of H2O to 170 GPa based on x-ray diffraction (XRD) measurements with synchrotron radiation. High-pressure conditions were generated in a diamond-anvil cell (DAC). H2O was compressed together with Au powder that served as an internal pressure marker. The pressure was determined by applying the equation of state of Au, using (111), (200), and (220) lines. Angle-dispersive XRD spectra were collected using both CCD detector and imaging plate (IP) at BL10XU of SPring-8. The recorded intensities were uniform around the powder rings. The results were consistent with previous compression studies up to 70 GPa. Above 80 GPa, the ice became significantly less compressive than the phase at lower pressures. This has been also suggested in earlier studies, but our data demonstrated more considerable change in the compressibility.

Sugimura, E.; Hirose, K.; Sata, N.; Ohishi, Y.

2006-12-01

324

GIA Ice Models  

NASA Astrophysics Data System (ADS)

Defining the ice load in a way that avoids circularity is perhaps the most difficult aspect of GIA modeling. At any instant of past time the global land-supported ice load must honor the meltwater curve and the known edges of the ice, but within these constraints the ice mass can be swapped to a considerable extent between the various glacial systems and parts of those systems. In our models, ice thickness is controlled by the effective basal shear stress (EBSS). This parameter incorporates the sub-ice lithology (e.g., whether the ice rests on sediment of crystalline rock), the relative local snow accumulation rate, and the local basal shear strength (which presumably depends most strongly on sub-ice temperature). The effective basal shear stress can be fairly easily modified to construct an ice model. The ice model is evaluated by the geological reasonability of its changes in EBSS in space and time, and by how well it matches measured GIA data. The risk that an incorrect earth model can be forced to fit the GIA data by manipulating the ice model (the circularity mentioned above) can be minimized by evaluating the longest wavelength deformations (peripheral bulge behavior) before proceeding to the shorter wavelength deformations (local emergence variations). The poster will describe how we have proceeded in this fashion to develop a framework for interpreting GIA data in Norway. The poster will be augmented by computer software that compares emergence data to models at specific sites in Norway.

Kachuck, Samuel; Cathles, Larry; Amantov, Aleksey

2013-04-01

325

ICE SLURRY APPLICATIONS.  

PubMed

The role of secondary refrigerants is expected to grow as the focus on the reduction of greenhouse gas emissions increases. The effectiveness of secondary refrigerants can be improved when phase changing media are introduced in place of single phase media. Operating at temperatures below the freezing point of water, ice slurry facilitates several efficiency improvements such as reductions in pumping energy consumption as well as lowering the required temperature difference in heat exchangers due to the beneficial thermo-physical properties of ice slurry. Research has shown that ice slurry can be engineered to have ideal ice particle characteristics so that it can be easily stored in tanks without agglomeration and then be extractable for pumping at very high ice fraction without plugging. In addition ice slurry can be used in many direct contact food and medical protective cooling applications. This paper provides an overview of the latest developments in ice slurry technology. PMID:21528014

Kauffeld, M; Wang, M J; Goldstein, V; Kasza, K E

2010-12-01

326

ICE SLURRY APPLICATIONS  

PubMed Central

The role of secondary refrigerants is expected to grow as the focus on the reduction of greenhouse gas emissions increases. The effectiveness of secondary refrigerants can be improved when phase changing media are introduced in place of single phase media. Operating at temperatures below the freezing point of water, ice slurry facilitates several efficiency improvements such as reductions in pumping energy consumption as well as lowering the required temperature difference in heat exchangers due to the beneficial thermo-physical properties of ice slurry. Research has shown that ice slurry can be engineered to have ideal ice particle characteristics so that it can be easily stored in tanks without agglomeration and then be extractable for pumping at very high ice fraction without plugging. In addition ice slurry can be used in many direct contact food and medical protective cooling applications. This paper provides an overview of the latest developments in ice slurry technology. PMID:21528014

Kauffeld, M.; WANG, M. J.; Goldstein, V.; Kasza, K. E.

2011-01-01

327

Mechanisms of ice gouging  

SciTech Connect

Sea ice is carried to the cost of Hokkaido by wind and water currents every year. In low pressure systems or when there is much sea ice, it drifts out toward the Pacific Ocean. When sea ice moves in shallow water areas, the sandy subgrade on the sea bottom is gouged by the sea ice. This phenomenon is generally called ``ice gouging``. Substantial damage to sea food i.e. (shellfish) and to structures embedded in the seabed is reported every year. However, the mechanisms and behavior of ice gouging is not known sufficiently enough for discussion. Therefore, the authors have conducted a suitable experiment to clarify this phenomenon and have suggested formulas to measure ice gouging.

Kioka, Shinji; Saeki, Hiroshi [Hokkaido Univ., Sapporo (Japan)

1995-12-31

328

River Ice Processes  

NSDL National Science Digital Library

The âRiver Ice Processesâ module provides information on flooding associated with river ice jams. In this webcast, Dr. Kate White, nationally-recognized expert on river ice, explores basic river ice processes including the formation, growth, breakup, and transport of river ice and how it can become jammed, triggering floods. In addition, Dr. White covers the current, state-of-the-art ice jam forecasting, and current ice-modeling research and development being conducted by the U.S. Army Corps of Engineers. As a foundation topic for the Basic Hydrologic Science course, this module may be taken on its own, but it will also be available as a supporting topic providing factual scientific information to support students in completion of the case-based forecasting modules.

Comet

2006-11-10

329

Heterogeneous ice nucleation ability of crystalline sodium chloride dihydrate particles  

NASA Astrophysics Data System (ADS)

The aerosol and cloud chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) of the Karlsruhe Institute of Technology has been used to quantify the deposition mode ice nucleation ability of airborne crystalline sodium chloride dihydrate (NaCl • 2H2O) particles with median diameters between 0.06 and 1.1 µm. For this purpose, expansion cooling experiments with starting temperatures from 235 to 216 K were conducted. Recently, supermicron-sized NaCl • 2H2O particles deposited onto a surface have been observed to be ice-active in the deposition mode at temperatures below 238 K, requiring a median threshold ice saturation ratio of only 1.02 in the range from 238 to 221 K. In AIDA, heterogeneous ice nucleation by NaCl • 2H2O was first detected at a temperature of 227.1 K with a concomitant threshold ice saturation ratio of 1.25. Above that temperature, the crystallized salt particles underwent a deliquescence transition to form aqueous NaCl solution droplets upon increasing relative humidity. At nucleation temperatures below 225 K, the inferred threshold ice saturation ratios varied between 1.15 and 1.20. The number concentration of the nucleated ice crystals was related to the surface area of the seed aerosol particles to deduce the ice nucleation active surface site (INAS) density of the aerosol population as a function of the ice supersaturation. Maximum INAS densities of about 6 ? 1010 m-2 at an ice saturation ratio of 1.20 were found for temperatures below 225 K. These INAS densities are similar to those recently derived for deposition mode ice nucleation on mineral dust particles.

Wagner, Robert; MöHler, Ottmar

2013-05-01

330

Mountain of Ice: Secrets in the Ice  

NSDL National Science Digital Library

This classroom activity has students graph and analyze chemical concentrations from ice core data. They will be analyzing some of the actual data that United States International Trans-Antarctic Scientific Expedition (ITASE) scientists obtained from Antarctica when they drilled into the West Antarctic Ice Sheet to collect ice cores for data on past sulfate, sodium, and chloride ion concentrations. The data will eventually be used to help understand global climate change. This activity has a stated objective, a list of materials, procedure, activity answer, and links for more information.

331

A Scheme for Parameterizing Ice-Cloud Water Content in General Circulation Models.  

NASA Astrophysics Data System (ADS)

The optical properties of ice clouds are a primary issue for climate and climate change. Evaluating these optical properties in three-dimensional models for studying climate will require a method to calculate the ice water content of such clouds. A procedure is developed to parameterize ice water content as a function of large-scale meteorological characteristics for use in circulation models in which the ice water content is not calculated by means of a three-dimensional prognostic equation for condensed water. The technique identifies large-scale flows in which ice clouds exist and calculates their ice water content by reconstructing the trajectory associated with cloud formation. As the cloud forms, its ice content changes both by deposition of ice from water vapor and by ice removal by sedimentation. The sedimentation process is found to modify significantly the ice water content expected from deposition alone. Ice water contents predicted by the parameterization are compared with aircraft observations collected in the middle latitudes and the tropics, and show reasonable agreement over four orders-of-magnitude of ice water content. A parameterization for the sublimation of ice crystals settling into ice-subsaturated environments is also presented.

Heymsfield, Andrew J.; Donner, Leo J.

1990-08-01

332

Ice nucleation in the tropical tropopause layer  

NASA Astrophysics Data System (ADS)

We simulated homogeneous ice nucleation using temperature time series data collected at high temporal resolution by long duration balloon flights near the tropical tropopause. The observed temperatures contain perturbations from a spectrum of waves, whose periods range from days to minutes. With the temperature time series data that we used, the simulations show the full range of ice number concentrations as previously observed in the tropical tropopause layer (between 0.001 cm-3 and 100 cm-3). From our simulations we empirically found that the number of ice crystals formed in a nucleation event increases exponentially with the difference between the temperature at the beginning of the nucleation event and the minimum temperature during the event.

Dinh, T.; Legras, B.; Hertzog, A.; Plougonven, R.; Podglajen, A.

2013-12-01

333

Melting point of ice in aqueous saccharide solutions  

NASA Astrophysics Data System (ADS)

The melting point of ice in trehalose and sucrose solutions was measured by in situ observations of a minute ice crystal. It was found that the concentration dependence of the melting point of ice in both trehalose and sucrose solutions was identical. Such a concentration dependence of the melting point was in agreement with the equation of freezing point depression for dilute aqueous solutions up to about 1 molal. In addition, the measured values of the melting point decreased rapidly with an increase in the concentration. These experimental results for an equilibrium state were discussed by comparing them with the results for a nonequilibrium state, i.e., the results obtained for growing ice crystals in saccharide solutions.

Sei, Tadanori; Gonda, Takehiko

2006-07-01

334

Video Observations of Anchor Ice/Sediment Interactions in Two Rocky Mountain Streams  

NASA Astrophysics Data System (ADS)

Anchor ice is submerged ice that is attached or anchored to the bottom of rivers, lakes, and shallow seas. It forms in turbulent, supercooled water. In rivers, anchor ice usually forms at night and is released from the riverbed in the morning as the sun warms the water column. Released anchor ice often contains significant amounts of coarse-grained sediment. This entrained sediment can be transported (ice rafted) long distances downstream before it is released from the buoyant, floating ice back to the riverbed. Understanding sediment entrainment into anchor ice requires knowledge of the processes occurring at the sediment/ice interface. Viewing this interface through a freezing water column is a difficult task. Removing anchor ice from the water usually destroys the fragile contact between the ice and entrained sediment. In this study, we used an underwater video system to document anchor ice/sediment interactions in two small Rocky Mountain rivers. The video system allowed us to view: (1) the contact between attached anchor ice and the streambed; (2) the distribution of sediment in attached and released anchor ice masses; (3) the release of anchor ice from the bed; and (4) ice rafting of sediment in released anchor ice masses. One of the greatest benefits of the video system is the ability to see the in situ sediment distribution in attached and recently released anchor ice. Analysis of the video reveals that gravel concentrations are high on the top and bottom surfaces of anchor ice masses with relatively little gravel in the interior. The video system is not perfect for viewing ice underwater, however. The small difference between the refractive indices of ice and water makes it very difficult to discern ice crystal shapes and the exact nature of ice/sediment contacts. We are continuing to develop ways to enhance the image quality of ice crystals in water. Even with this shortcoming, the underwater video system is a very useful tool for observing in situ anchor ice/sediment relationships with minimal disturbance.

Kempema, E. W.; McGee, B. W.; Pueblitz, L.

2004-12-01

335

Preparing and Analyzing Iced Airfoils  

NASA Technical Reports Server (NTRS)

SmaggIce version 1.2 is a computer program for preparing and analyzing iced airfoils. It includes interactive tools for (1) measuring ice-shape characteristics, (2) controlled smoothing of ice shapes, (3) curve discretization, (4) generation of artificial ice shapes, and (5) detection and correction of input errors. Measurements of ice shapes are essential for establishing relationships between characteristics of ice and effects of ice on airfoil performance. The shape-smoothing tool helps prepare ice shapes for use with already available grid-generation and computational-fluid-dynamics software for studying the aerodynamic effects of smoothed ice on airfoils. The artificial ice-shape generation tool supports parametric studies since ice-shape parameters can easily be controlled with the artificial ice. In such studies, artificial shapes generated by this program can supplement simulated ice obtained from icing research tunnels and real ice obtained from flight test under icing weather condition. SmaggIce also automatically detects geometry errors such as tangles or duplicate points in the boundary which may be introduced by digitization and provides tools to correct these. By use of interactive tools included in SmaggIce version 1.2, one can easily characterize ice shapes and prepare iced airfoils for grid generation and flow simulations.

Vickerman, Mary B.; Baez, Marivell; Braun, Donald C.; Cotton, Barbara J.; Choo, Yung K.; Coroneos, Rula M.; Pennline, James A.; Hackenberg, Anthony W.; Schilling, Herbert W.; Slater, John W.; Burke, Kevin M.; Nolan, Gerald J.; Brown, Dennis

2004-01-01

336

Continuous Production of Ice Slurry by Control of Solute Concentration with Ultrasonic Vibration  

NASA Astrophysics Data System (ADS)

A method to making ice slurry is one of key technology for cold-energy Storage system. This study has been conducted to clarify continuous production of ice slurry by utilizing constitutional supercooling promoted by mixing of two aqueous solutions whose solute concentrations are different. In this technique, fine ice crystals are made under volume-catalyzed nucleation without heat transfer surface. In the experiments, cooled sucrose solution and water were mixed in the cylindrical vessel, and ultrasonic vibration was applied to promote nucleation in the supercooled solution. It was found that the ice making process is classified into three characteristic patterns; stable ice making, ice making in stratified concentration layer due to defect in solute-mixing, and no ice making due to no supercooling by mixing. The characteristics of ice making were discussed with the mixing ratio and total flow rate of solutions.

Tada, Yukio; Takimoto, Akira; Miyamoto, Tomoaki; Mikami, Hiroko; Hayashi, Yujiro

337

Ice forming nuclei in the high Arctic  

NASA Astrophysics Data System (ADS)

Concentrations of ice forming nuclei detected by the membrane filter technique were measured at temperatures of -12.5, -15 and -17.5°C during a voyage on the icebreaker Oden to the North Pole between 1 August and 6 October 1991. Geometric mean concentrations ranged from 13m-3 at -15°C during the first 17days of the expedition to 2.9m-3 on the last 17days of the voyage in good agreement with surface measurements made earlier north of latitude 70°N. On average, concentrations increased by a factor of 4.5 for a 5°C fall in temperature, less than is common in continental regions. Although air trajectory analysis showed that land sources occasionally influenced concentrations strongly, the time since the air had been over the open ocean was clearly the most important determining factor other than the seasonal decline. This implies an oceanic origin of the nuclei, the relationship being consistent with a halflife of 48.5 h (e-folding time of 70h), about 60% longer than that of condensation nuclei. An apparent decrease in ice nucleus concentrations with temperature was mainly due to the seasonal change in concentrations but partly to the air trajectories associated with low temperatures. Elapsed time since the air was above the planetary boundary layer or over land also influenced concentrations, suggesting that the upper troposphere was deficient in ice nuclei while land was a weak source. Changes in the mixed depth of the atmosphere appeared to affect ice nucleus concentrations in the same way as condensation nucleus concentrations although poor time resolution limited this to two good examples. North of latitude 80°N, a few ice crystals were present near the surface for a considerable proportion of the total time. Single stellar crystals constituted about 80% of the total, implying growth near -15°C in predominantly supercooled clouds. Their concentrations were usually but not always consistent with surface ice nucleus concentrations.

Bigg, E. K.

1996-04-01

338

Antarctica's Whillans Ice Plain ice flows are highly variable  

NASA Astrophysics Data System (ADS)

The Whillans Ice Plain (WIP) is a roughly 20,000-square-kilometer region of the West Antarctic Ice Sheet that acts as a massive conveyor, driving glacial ice into the Ross Ice Shelf. As the climate changes, knowing how large bodies of ice like the WIP behave will be important to assessing sea level rise.

Schultz, Colin

2014-05-01

339

The role of acids in electrical conduction through ice  

NASA Astrophysics Data System (ADS)

Electrical conduction through meteoric polar ice is controlled by soluble impurities that originate mostly from sea salt, biomass burning, and volcanic eruptions. The strongest conductivity response is to acids, yet the mechanism causing this response has been unclear. Here we elucidate conduction mechanisms in ice using broadband dielectric spectroscopy of meteoric polar ice cores. We find that conduction through polycrystalline polar ice is consistent with Jaccard theory for migration of charged protonic point defects through single ice crystals, except that bulk DC conduction is impeded by grain boundaries. Neither our observations nor modeling using Archie's Law support the hypothesis that grain-boundary networks of unfrozen acids cause significant electrolytic conduction. Common electrical logs of ice cores (by electrical conductivity measurement [ECM] or dielectric profiling [DEP]) and the attenuation of radio waves in ice sheets thus respond to protonic point defects only. This response implies that joint interpretation of electrical and chemical logs can determine impurity partitioning between the lattice and grain boundaries or inclusions. For example, in the Greenland Ice Core Project (GRIP) ice core from central Greenland, on average more than half of the available lattice-soluble impurities (H+, Cl-, NH4+) create defects. Understanding this partitioning could help further resolve the nature of past changes in atmospheric chemistry.

Stillman, David E.; MacGregor, Joseph A.; Grimm, Robert E.

2013-03-01

340

Sea Level: Ice Volume Changes  

NSDL National Science Digital Library

In this exercise, students observe simulations of melting sea ice and a melting continental ice sheet in order to investigate the relationship between the melting of the ice and the water level in the tank. The water tanks simulate the world oceans. In the first example, the ice is floating in water. This would be an example of icebergs or Arctic ice floating on the ocean. In the second example the ice lies on a wood structure. The structure simulates a continent. The block of ice on top of the structure simulates ice grounded on top of a continent. This would be an example of ice sheets in Greenland and Antarctica.

341

Determination of the Boltzmann constant with an acoustic quasi-spherical resonator filled with argon  

E-print Network

point of wa- ter, TTPW. M is the molar mass of the gas, 0 = Cp/Cv is the ratio of the specific heat capacities for dilute monatomic gases. The term lim P0 indicates that we estimate the terms independent

Paris-Sud XI, Université de

342

Satellite remote sensing over ice  

Microsoft Academic Search

Satellite remote sensing provides unique opportunities for observing ice- covered terrain. Passive microwave data give information on snow cover on land, sea ice extent and type, and zones of summer melting on the polar ice sheets, and they have the potential of estimating snow accumulation rates on these ice sheets. All-weather, high-resolution imagery of sea ice is obtained by using

Robert H. Thomas

1986-01-01

343

Ice-Nucleating Bacteria  

NASA Astrophysics Data System (ADS)

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.

Obata, Hitoshi

344

New insights into ice growth and melting modifications by antifreeze proteins  

PubMed Central

Antifreeze proteins (AFPs) evolved in many organisms, allowing them to survive in cold climates by controlling ice crystal growth. The specific interactions of AFPs with ice determine their potential applications in agriculture, food preservation and medicine. AFPs control the shapes of ice crystals in a manner characteristic of the particular AFP type. Moderately active AFPs cause the formation of elongated bipyramidal crystals, often with seemingly defined facets, while hyperactive AFPs produce more varied crystal shapes. These different morphologies are generally considered to be growth shapes. In a series of bright light and fluorescent microscopy observations of ice crystals in solutions containing different AFPs, we show that crystal shaping also occurs during melting. In particular, the characteristic ice shapes observed in solutions of most hyperactive AFPs are formed during melting. We relate these findings to the affinities of the hyperactive AFPs for the basal plane of ice. Our results demonstrate the relation between basal plane affinity and hyperactivity and show a clear difference in the ice-shaping mechanisms of most moderate and hyperactive AFPs. This study provides key aspects associated with the identification of hyperactive AFPs. PMID:22787007

Bar-Dolev, Maya; Celik, Yeliz; Wettlaufer, J. S.; Davies, Peter L.; Braslavsky, Ido

2012-01-01

345

Expression and Characterization of an Ice Binding Protein from a Bacterium Isolated at a Depth of 3,519 Meters in the Vostok Ice Core, Antarctica  

NASA Astrophysics Data System (ADS)

The cryopreservation of microorganisms in ancient glacial ice is possible if lethal levels of macromolecular damage are not incurred and cellular integrity is not compromised via intracellular ice formation or recrystallization. There are numerous examples of cold-adapted species that prevent or limit ice crystal growth by producing ice-binding proteins (IBP). Previously, a bacterium (isolate 3519-10; Flavobacteriaceae family) recovered from a depth of 3,519 meters below the surface in the Vostok ice core was shown to produce and secrete an IBP that inhibits the recrystallization of ice. To explore the phenotypic advantage that IBPs confer to ice-entrapped cells, experiments were designed to examine the expression of 3519-10's IBP gene and protein at different temperatures, assess the effect of the IBP on bacterial viability in ice, and determine how the IBP influences the physical structure of the ice. Total RNA isolated from aerobic cultures grown at temperatures between 4C to 25C and analyzed by reverse transcription-PCR indicated constitutive expression of the IBP gene. Additionally, SDS-PAGE analysis of 3519-10's extracellular proteins revealed a polypeptide corresponding to the predicted size of the 54 kDa IBP at all temperatures tested. The total extracellular protein fraction was subsequently used in assays with Escherichia coli to examine the effect of the IBP on bacterial survival in warm ice (-5C) and after freeze-thaw cycling. In the presence of 100 ?g mL-1 of extracellular protein from 3519-10, the survival of E. coli was increased by greater than 100-fold; however, the survival of E. coli suspensions containing the same concentration of bovine serum albumin was not significantly different than controls (p<0.05). Microscopic analysis of ice formed in the presence of the IBP indicated that in a mm^2 field of view, there were 5 times as many crystals as in ice formed in the presence of washed 3519-10 cells and non-IBP producing bacteria, and 10 times as many crystals as in particle-free deionized water. Presumably, the effect that the IBP has on bacterial viability and ice crystal structure is due to its activity as an inhibitor of ice recrystallization. Although a myriad of molecular adaptations are likely to play a role in bacterial persistence under frozen conditions, the ability of 3519-10's IBP to control ice crystal structure may provide one explanation for its successful survival deep within the Antarctic ice sheet for thousands of years.

Christner, B. C.; Achberger, A.; Brox, T. I.; Skidmore, M. L.

2011-12-01

346

Ice in the Shadows  

NSDL National Science Digital Library

This is a lesson about detecting ice on the permanently shadowed craters of Mercury and the Moon. Learners will consider what might be in that ice and will examine why the polar regions of Earth, Mercury and the Moon are colder than elsewhere on the planets. Activities include small group miming, speaking, drawing, and/or writing. This is the lesson 12 of 12 in the unit, Exploring Ice in the Solar System.

347

The ice sheet model The polythermal ice sheet  

E-print Network

. The simulated HEs affect large areas of the Laurentide ice sheet. Up to 15 percentage of ice volume can (Fig- ure 4f). The Laurentide ice sheet changes between a single-dome and a multi- dome complex during

Calov, Reinhard

348

The Ice Age  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 9-12. It explains what ice ages are, what causes ice ages to occur, plants and animals that lived during the last Ice Age, and why some Ice Age animals went extinct. It includes objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order that complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

349

Ice age paleotopography  

SciTech Connect

A gravitationally self-consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the Last Glacial Maximum (LGM). The results show that LGM ice volume was approximately 35 percent lower than suggested by the CLIMAP reconstruction and the maximum heights of the main Laurentian and Fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level. Use of these Ice Age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the CLIMAP data set.

Peltier, W.R. (Univ. of Toronto, Ontario (Canada))

1994-07-08

350

Past Tense Ice  

NSDL National Science Digital Library

Some of the thickest and oldest ice in the Arctic Ocean is disappearing. This radio broadcast (2003) reports on new large cracks found in the Ward Hunt Ice Shelf, which had been intact for the last 3000 years. Scientists say these cracks are a sign of a warmer Arctic climate. As the ice shelf melts, it is changing the Arctic environment in profound ways, causing changes in the food chain based on the ice habitat. The clip is 4 minutes and 34 seconds in length.

351

Microwave ice prevention  

NASA Technical Reports Server (NTRS)

The concept of using microwave energy to provide aircraft ice protection, specifically an anti-icing system, and the feasibility of such a system are discussed. In a microwave anti-icing system impinging supercooled water droplets are heated to above freezing by the resonant absorption of microwave energy located upstream of the aircraft. This process is inherently more efficient than existing anti-icing devices due to the saving of the latent heat of fusion (a substantial 334 joules/gm (80 cal/gm)) and the fact that only the droplets are heated, thereby reducing convective losses to the air.

Hansman, R. J., Jr.; Hollister, W.

1982-01-01

352

An ice lithography instrument  

SciTech Connect

We describe the design of an instrument that can fully implement a new nanopatterning method called ice lithography, where ice is used as the resist. Water vapor is introduced into a scanning electron microscope (SEM) vacuum chamber above a sample cooled down to 110 K. The vapor condenses, covering the sample with an amorphous layer of ice. To form a lift-off mask, ice is removed by the SEM electron beam (e-beam) guided by an e-beam lithography system. Without breaking vacuum, the sample with the ice mask is then transferred into a metal deposition chamber where metals are deposited by sputtering. The cold sample is then unloaded from the vacuum system and immersed in isopropanol at room temperature. As the ice melts, metal deposited on the ice disperses while the metals deposited on the sample where the ice had been removed by the e-beam remains. The instrument combines a high beam-current thermal field emission SEM fitted with an e-beam lithography system, cryogenic systems, and a high vacuum metal deposition system in a design that optimizes ice lithography for high throughput nanodevice fabrication. The nanoscale capability of the instrument is demonstrated with the fabrication of nanoscale metal lines.

Han, Anpan [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Chervinsky, John [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Branton, Daniel [Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Golovchenko, J. A. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

2011-06-15

353

Near-Infrared Spectral Monitoring of Pluto's Ices II: Recent Decline of CO and N$_2$ Ice Absorptions  

E-print Network

IRTF/SpeX observations of Pluto's near-infrared reflectance spectrum during 2013 show vibrational absorption features of CO and N$_2$ ices at 1.58 and 2.15 {\\mu}m, respectively, that are weaker than had been observed during the preceding decade. To reconcile declining volatile ice absorptions with a lack of decline in Pluto's atmospheric pressure, we suggest these ices could be getting harder to see because of increasing scattering by small CH$_4$ crystals, rather than because they are disappearing from the observed hemisphere.

Grundy, W M; Young, L A; Holler, B J

2014-01-01

354

Treatment of TNT red water by layer melt crystallization.  

PubMed

Treatment of the red water, which is wastewater of 2,4,6- trinitrotoluene (TNT) manufacturing process has been explored using ice crystallization. This study focuses on the formation of ice crystals from the red water in a layer crystallizer under various operating conditions. Among the parameters which affect layer crystallization, attention was given to cooling rate, cooling temperature, sweating rate and concentration of the red water. The study highlights the effect of subcooling and growth rate on purity of the ice crystalline layers produced. After sweating, the COD value of crystalline ice layer was significantly reduced from 10,000mg/L to below 20mg/L. Most organic contaminants were removed in sweating fractions of 0.5. Eventually, the red water was treated by layer crystallization combined with the sweating process. PMID:25151241

Jo, Jeong-Hyeon; Ernest, Takyi; Kim, Kwang-Joo

2014-09-15

355

A new optical ice particle counter at LACIS  

NASA Astrophysics Data System (ADS)

Clouds play an important role within the climate system, especially for the radiative energy budget of the earth. The radiative properties of a cloud depend strongly on the fractions of ice crystals and water droplets, their size distributions, and the ice crystal shapes within the particular cloud. One option to gain this kind of information is using optical particle counters. A new optical particle counter is developed for laboratory work and is based on the concept of the Thermostabilized Optical Particle Spectrometer for the Detection of Ice Particles (TOPS-Ice, Clauss et al., 2013). TOPS-Ice uses linearly polarized green laser light and the depolarization of the scattered light at a scattering angle of 42.5° to discriminate between liquid water droplets and ice crystals in the lower ?m range. However, the measurements are usually limited to ice fractions in the order of 1%. To improve the determination of the ice fraction, several modifications of the original setup are implemented including an additional detection system at another scattering angle. The new scattering angle is optimized for least interference between the droplet and ice signals. This is achieved by finding the angle with the maximum difference in scattered intensity of water droplets compared to ice crystals with the same volume equivalent diameter. The suitable scattering angle of 100° for linearly polarized light was chosen based on calculations using T-Matrix method, Lorenz-Mie theory, Müller matrices and distribution theory. The new optical setup is designed to run in combination with a laminar flow tube, the so-called Leipzig Aerosol Cloud Interaction Simulator (LACIS, Stratmann et al., 2004; Hartmann et al., 2011). Using LACIS and its precisely controlled thermodynamic conditions, we are able to form small water droplets and ice crystals which will then be detected, classified and sized by our new optical device. This setup is planned to be tested in ice measurements including Snomax® and several dusts (e.g. illite, kaolinite, ATD) as ice nuclei which all show different behaviors in ice formation. Furthermore, a detailed comparison of both instruments TOPS-Ice and the new setup is planned. This project is part of the Leipzig Graduate School on Clouds, Aerosols and Radiation and is partly supported by the German Research Foundation (DFG project WE 4722/1-1) within the DFG Research Unit FOR 1525 INUIT. Clauss, T., Kiselev, A., Hartmann, S., Augustin, S., Pfeifer, S., Niedermeier, D., Wex, H., and Stratmann, F, 2013, Application of linear polarized light for the discrimination of frozen and liquid droplets in ice nucleation experiments, Atmos. Meas. Tech., 6, 1041-1052. Hartmann, S., Niedermeier, D., Voigtländer, J., Clauss, T., Shaw, R. A., Kiselev, A., and Stratmann, F., 2011, Homogeneous and heterogeneous ice nucleation at LACIS: operating principle and theoretical studies, Atmos. Chem. Phys., 11, 1753-1767. Stratmann, F., Kiselev, A., Wurzler, S., Wendisch, M., Heintzenberg, J., Charlson, R. J., Diehl, K., Wex, H., and Schmidt, S., 2004, Laboratory Studies and Numerical Simulations of Cloud Droplet Formation under Realistic Supersaturation Conditions, J. Atmos. Oceanic. Technol., 21, 876-887.

Bieligk, Henner; Voelker, Georg Sebastian; Clauss, Tina; Grundmann, Marius; Stratmann, Frank

2014-05-01

356

Deposition Ice Nuclei Concentration at Different Temperatures and Supersaturations  

NASA Astrophysics Data System (ADS)

Ice formation is one of the main processes involved in the initiation of precipitation. Some aerosols serve to nucleate ice in clouds. They are called ice nuclei (IN) and they are generally solid particles, insoluble in water. At temperatures warmer than about -36°C the only means for initiation of the ice phase in the atmosphere involves IN, and temperature and supersaturation required to activate IN are considered as key information for the understanding of primary ice formation in clouds. The objective of this work is to quantify the IN concentration at ground level in Córdoba City, Argentina, under the deposition mode, that is to say that ice deposits on the IN directly from the vapor phase. It happens when the environment is supersaturated with respect to ice and subsaturated with respect to liquid water. Ice nuclei concentrations were measured in a cloud chamber placed in a cold room with temperature control down to -35°C. The operating temperature was varied between -15°C and -30°C. Ice supersaturation was ranged between 2 and 20 %. In order to quantify the number of ice particles produced in each experiment, a dish containing a supercooled solution of cane sugar, water and glycerol was placed on the floor of the cloud chamber. The activated IN grew at the expense of vapor until ice crystals were formed and these then fell down onto the sugar solution. Once there, these crystals could grow enough to be counted easily with a naked eye after a period of about three minutes, when they reach around 2 mm in diameter. In order to compare the present results with previously reported results, the data were grouped in three different ranges of supersaturation: the data with supersaturations between 2 and 8 %, the data with supersaturations between 8 and 14% and the data with supersaturations between 14 and 20 %. In the same way, in order to analize the behavior of IN concentration with supersaturation, the data were grouped for three different temperatures, the data with temperatures between -15°C and -20°C, the data with temperatures between -20°C and -25°C and the data with temperatures between -25°C and -30°C. The results confirm that for each temperature range, the concentration of IN increases at higher supersaturation, and show the tendency of the IN concentration to increase with increasing ice supersaturation. Based on previous parameterizations, a combination of IN concentration in relation with temperature and ice supersaturation is proposed in this work. As far as we know, this is among the first work to measure and parameterize the concentration of deposition ice nuclei in the Southern Hemisphere.

López, M. L.; Avila, E.

2013-05-01

357

Cloud structure and crystal growth in nimbostratus clouds. Mengistu Wolde*  

E-print Network

1 Cloud structure and crystal growth in nimbostratus clouds. Mengistu Wolde* , Gabor Vali-mail: mengistu.wolde@nrc.ca. #12;2 Abstract Cloud structure and crystal growth in two nimbostratus were examined made available by large scale lifting was taken up by depositional growth of the ice crystals

Vali, Gabor

358

Hartree–Fock and DFT calculations of quadrupole coupling constants in water clusters and ice  

Microsoft Academic Search

Periodic ab initio calculations of the 17O and 2H quadrupole coupling constants (QCC) and their shifts have been performed for ice VIII and ice IX. Cluster calculations were done for smaller water clusters and chains. The ice VIII crystal structure was optimized at the Hartree–Fock and BLYP (DFT) levels with a 6-311g** basis. Out of the methods tested here the

Maria Alfredsson; Kersti Hermansson

1999-01-01

359

Mountain of Ice: If the Ice Melts  

NSDL National Science Digital Library

This interactive resource portrays what might happen to world coastlines if entire sections of the Antarctic Ice Sheet were to melt. Viewers can see how much land area might be flooded by a relatively modest 17-foot rise in sea level (represented by the collapse of the Western Antarctic Ice Sheet), or a more severe 170-foot rise, represented by the collapse of the Eastern Antarctic Ice Sheet. By comparing present-day coastline positions with those from the peak glacial advance 20,000 years ago, it is possible to appreciate how much water is contained in glaciers, the importance of monitoring their condition, and the impact accelerated global warming could one day have on sea level. A background essay and list of discussion questions are also provided.

360

Spectroscopic signature for ferroelectric ice  

NASA Astrophysics Data System (ADS)

Various forms of ice exist within our galaxy. Particularly intriguing type of ice - ‘ferroelectric ice' was discovered experimentally and is stable in temperatures below 72 K. This form of ice can generate enormous electric fields and can play an important role in planetary formation. In this letter we present Car-Parrinello simulation of infrared spectra of ferroelectric ice and compare them with spectra of hexagonal ice. Librational region of the spectra can be treated as spectroscopic signature of ice XI and can be of help to identify ferroelectric ice in the Universe.

Wójcik, Marek J.; G?ug, Maciej; Boczar, Marek; Boda, ?ukasz

2014-09-01

361

Ice core drilling at Vostok  

NSF Publications Database

... Subject: Initial Environmental Evaluation (Deep Ice Core Drilling at Vostok Station, Antarctica ... for the National Science Foundation's Deep Ice Core Drilling project at Vostok Station, prepare an ...

362

Ice hockey injuries  

Microsoft Academic Search

Ice hockey is a team sport that has recently grown in popularity not only in the United States but also in Canada and Europe. With this increase in popularity has come a growing concern about the number and severity of injuries. The world literature on the biome chanics and physiology of ice hockey was reviewed in an attempt to evaluate

Franklin H. Sim; William T. Simonet; L. Joseph Melton; Tracy A. Lehn

1987-01-01

363

Making an Ice Core.  

ERIC Educational Resources Information Center

Explains an activity in which students construct a simulated ice core. Materials required include only a freezer, food coloring, a bottle, and water. This hands-on exercise demonstrates how a glacier is formed, how ice cores are studied, and the nature of precision and accuracy in measurement. Suitable for grades three through eight. (Author/PVD)

Kopaska-Merkel, David C.

1995-01-01

364

Dr. Carnelley's Hot Ice  

Microsoft Academic Search

THE remarkable observation made by Dr. Carnelley that ice in a vacuum is very permanent, even though surrounded by and apparently in contact with very hot bodies, has caused him to suppose and maintain that the ice itself is at a high temperature; a supposition which has been apparently confirmed by preliminary calorimetric determinations. This proposition has naturally met with

Oliver J. Lodge

1881-01-01

365

Ice Formation in Worcestershire  

Microsoft Academic Search

ON January 27, when the great snowstorm was developing, the Evesham district experienced a relatively light fall and this changed at night to `supercooled' rain. Sunday, January 28, found us awaking to a strange `creaking' of trees in the wind due, I found, to an armour of thick ice. Most of the ice was on top-my aerial had ¾ in.

A. A. Newbold

1940-01-01

366

Global Ice Viewer  

NSDL National Science Digital Library

With this simulation from the NASA Climate website, learners explore different examples of how ice is melting due to climate change in four places where large quantities of ice are found. The photo comparisons, graphs, animations, and especially the time lapse video clips of glaciers receding are astonishing and dramatic.

Tenenbaum, Laura; Jackson, Randal; Nasa

367

Whither Arctic Sea Ice?  

NSDL National Science Digital Library

In this activity students work with real datasets to investigate a real situation regarding disappearing Arctic sea ice. The case study has students working side-by-side with a scientist from the National Snow and Ice Data Center and an Inuit community in Manitoba.

Youngman, Betsy; Chapter, Earth E.

368

A Changing Ice Sheet  

NSDL National Science Digital Library

This animation shows the retreat of glacial ice, changes in the shoreline, and the disappearance of the land bridge across the Bering Sea which occurred at the end of the last ice age, beginning just over 21,000 years ago.

369

Ice Core Investigations  

ERIC Educational Resources Information Center

What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

Krim, Jessica; Brody, Michael

2008-01-01

370

Laboratory and field observations related to ice particle and aircraft charging in convective storms  

NASA Technical Reports Server (NTRS)

Graupel particle charging in simulated cloud conditions which show the need for the presence of ice crystals and cloud water simultaneously except under conditions where secondary ice crystal production occurs when charging initially occurs in the absence of ice crystals was examined. The magnitude of the charging increases with size of ice crystals, and impact velocity; it is also sensitive to impurities. The magnitude of the charge is also sensitive to temperature and the sign changes between -10 and -20 C, depending on cloud liquid water content. Aircraft studies were carried out in Montana convective clouds to test the validity of the extrapolation of the laboratory data to the atmosphere from the viewpoint of generation of charge, electric field, and aircraft charging during cloud penetration.

Christian, H.; Lillie, L.; Saunders, C. P. R.; Hallett, J.

1983-01-01

371

A study on the primary and secondary nucleation of ice by power ultrasound.  

PubMed

Several different investigations have been carried out to study the primary and secondary nucleation of ice by sonocrystallisation. Firstly, the primary nucleation of discrete ice crystals in a supercooled sucrose solution has been observed. For increasing concentrations of sucrose solutions from 0 to 45 wt%, the nucleation temperature consistently occurs at a higher nucleation temperature in the presence of ultrasound. The nucleation temperature also increases as the power output and duty cycle of a commercial ultrasonic horn are increased. Snap shot images of the bubble clouds obtained from the ultrasonic horn also show that the number of bubbles appears to increase as the ultrasonic output is increased. This suggests that the nucleation of ice is related to the power output and number of cavitation bubbles. The effect of a single bubble on the sonocrystallisation of ice is discussed. High-speed movies (1120 fps) have shown that the crystallisation appears to occur in the immediate vicinity of the single bubble. In most cases, many crystals are observed and it is not known whether a single ice crystal is being fragmented by the bubble or whether many crystals are being initiated. The bubble appears to undergo a dancing regime, frequently splitting and rejoining and also emitting some small microbubbles. A study on the secondary nucleation of ice in sucrose solutions has been carried out using a unique ultrasonic cold stage device. Images taken using a microscope system show that the pre-existing ice dendrite crystals can be broken up into smaller fragments by an ultrasonic field. Cavitation bubbles appear to be important during the fragmentation process, possibly melting any ice crystals in their path. Flow patterns around cavitation bubbles have also been observed, and these may be responsible for the fragmentation of ice crystals. PMID:15567197

Chow, R; Blindt, R; Chivers, R; Povey, M

2005-02-01

372

Minimalist model of ice microphysics in mixed-phase stratiform clouds  

NASA Astrophysics Data System (ADS)

The question of whether persistent ice crystal precipitation from supercooled layer clouds can be explained by time-dependent, stochastic ice nucleation is explored using an approximate, analytical model and a large-eddy simulation (LES) cloud model. The updraft velocity in the cloud defines an accumulation zone, where small ice particles cannot fall out until they are large enough, which will increase the residence time of ice particles in the cloud. Ice particles reach a quasi-steady state between growth by vapor deposition and fall speed at cloud base. The analytical model predicts that ice water content (wi) has a 2.5 power-law relationship with ice number concentration (ni). wi and ni from a LES cloud model with stochastic ice nucleation confirm the 2.5 power-law relationship, and initial indications of the scaling law are observed in data from the Indirect and Semi-Direct Aerosol Campaign. The prefactor of the power law is proportional to the ice nucleation rate and therefore provides a quantitative link to observations of ice microphysical properties. Ice water content (wi) and ice number concentration (ni) relationship from LES. a and c: Accumulation zone region; b and d: Selective accumulation zone region. Black lines in c and d are best fitted 2.5 slope lines. Colors in Figures a and b represent updraft velocity, while colors in c and d represent altitude. The cloud base and top are at about 600 m and 800 m, respectively. Ice water content (wi) and ice number concentration (ni) relationship for two ice nucleation rates. Blue points are from LES with low ice nucleation rate and red points with high ice nucleation rate. Solid and dashed lines are best fitted 2.5 slope lines.

Yang, F.; Ovchinnikov, M.; Shaw, R. A.

2013-12-01

373

Experiments on planetary ices at UCL  

NASA Astrophysics Data System (ADS)

Using a suite of techniques and equipment, we conduct several different types of experiments on planetary ices at UCL. Samples are prepared in the Ice Physics Laboratory, which consists of a 5 chamber complex of inter-connected cold rooms, controllable from +30 to -30 deg C. Within this laboratory we have a functioning triaxial deformation cell operating at low temperature (down to -90 deg C) and high pressures (300 MPa), an Automatic Ice Fabric Analyser (AIFA) and a low-temperature microscope with CCD output. Polycrystalline samples, 40mm diameter by 100mm long, are compressed in the triaxial rig with a confining pressure; single crystal specimens are compressed in a separate uniaxial creep rig which operates at zero confining pressure for surface studies. A cold stage is also available for study of ice microstructural studies on our new Jeol JSM-6480LV SEM, which also allows tensile, compression and/or bending tests, with load ranges from less than 2N to 5000N. Finally, we also use a cold stage on a new PANalytical, X'pert PRO MPD, high resolution powder diffractometer to study the structure and phase behaviour of icy materials. Recent highlights of our work include: (1) derivation of a manufacturing process for methane clathrate at low temperatures, analysed in the X-Ray Diffraction Laboratory, for future rheological experiments, (2) analysed the growth behaviour of MS11, (3) refurbished and commenced calibration tests on the triaxial deformation cell using ice Ih, and (4) performed creep tests on gypsum and epsomite using the single crystal deformation cell. Further experiments will build on these preliminary results.

Grindrod, P. M.; Fortes, A. D.; Wood, I. G.; Dobson, D.; Sammonds, P. R.; Stone-Drake, L.; Vocadlo, L.

2007-08-01

374

Thermal desorption of circumstellar and cometary ice analogs  

NASA Astrophysics Data System (ADS)

Context. Thermal annealing of interstellar ices takes place in several stages of star formation. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. Aims: For the first time we present the results of temperature programmed desorption (TPD) experiments with pre-cometary ice analogs composed of up to five molecular components: H2O, CO, CO2, CH3OH, and NH3. Methods: The experiments were performed with an ultra-high vacuum chamber. A gas line with a novel design allows the controlled preparation of mixtures with up to five molecular components. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. Results: The TPD curves of water ice containing CO, CO2, CH3OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and co-desorption peaks with water. Desorption peaks of CH3OH and NH3 at temperatures similar to the pure ices takes place when their abundance relative to water is above ~3% in the ice matrix. We found that CO, CO2, and NH3 also present co-desorption peaks with CH3OH, which cannot be reproduced in experiments with binary water-rich ice mixtures. These are extensively used in the study of thermal desorption of interstellar ices. Conclusions: These results reproduce the heating of circumstellar ices in hot cores and can be also applied to the late thermal evolution of comets. In particular, TPD curves represent a benchmark for the analysis of the measurements that mass spectrometers on board the ESA-Rosetta cometary mission will perform on the coma of comet 67P/Churyumov-Gerasimenko, which will be active before the arrival of Rosetta according to our predictions.

Martín-Doménech, R.; Muñoz Caro, G. M.; Bueno, J.; Goesmann, F.

2014-04-01

375

Reionization on ice  

E-print Network

The case for substantial far infrared ice emission in local ultraluminous infrared galaxies, expected based on the presence of mid-infrared ice absorption in their spectra and the known far infrared optical properties of ice, is still largely unsupported by direct observation owing to insufficient far infrared spectral coverage. Some marginal supportive evidence is presented here. A clear consequence of far infrared ice emission is the need to extend the range of redshifts considered for submillimeter sources. This is demonstrated via the example of HDF 850.1. The solid phase of the ISM during reionization may be dominated by ice, and this could lead to the presence of reionization sources in submillimeter source catalogs. Submillimeter sources not detected at 24 micron in the GOODS-N field are examined. Two candidate reionization sources are identified at 3.6 micron through possible Gunn-Peterson saturation in the Z band.

C. C. Dudley; M. Imanishi; P. R. Maloney

2006-02-15

376

Determination of Thunderstorm Anvil Ice Contents and Other Cloud Properties from Satellite Observations of Lightning  

NASA Technical Reports Server (NTRS)

The lightning frequency model developed by Baker, Christian and Latham (1995) has been refined and extended, in an effort to provide a more realistic framework from which to examine computationally the relationships that might exist between lightning frequency f (which is now being routinely measured from satellites, using NASA/MSFC devices) and a variety of cloud physical parameters, including precipitation rate, updraught speed and non-precipitating ice content. The charging mechanism incorporated into the model is the non-inductive ice-ice mechanism - involving rebounding collisions between ice crystals and growing graupel pellets - which has achieved significant field, laboratory and modelling support in recent years. Model results indicate the existence of a simple relationship between lightning frequency f and the upward flux of ice crystals into the thunderstorm anvil. It follows that, for a particular situation, one can assign a specific mass of non-precipitating ice to an individual lightning stroke. Therefore it is possible - using satellite measurements of global lightning - to estimate the atmospheric loading of ice crystals in thunderstorm anvils: a parameter of climatological importance. One can also estimate the ice crystal loading associated with more localized storm systems. Early results from this work will be presented, together with further work on the relationships between f and other thundercloud parameters.

Blyth, Alan M.; Christian, Hugh J., Jr.; Latham, John

1999-01-01

377

The record may be in the fabric: Preservation of climate history in polar ice sheets  

NASA Astrophysics Data System (ADS)

Climate perturbations induce subtle changes in near-surface ice texture and fabric. These changes can persist and be enhanced deep in an ice divide -- even as the ice deforms and recrystallizes throughout the depth of the ice divide. In this way, texture and fabric may act as a record of past climate. Modeling the evolution of preferred crystal orientation fabric requires consideration of both micro-scale (e.g. recrystallization) and macro-scale ice processes (e.g. ice flow). Topological models have been used to model fabric evolution because they include both processes; micro-scale processes are parameterized and macro-scale processes are computed by averaging single crystal properties. The bulk deformation of ice is then the average deformation of the individual ice crystals. We use a topological flow model to simulate the evolution of a subtle fabric variation near the surface of a polar ice divide as it moves through the depth of the ice sheet. We examine the effects of polygonization, migration recrystallization, and temperature on the fabric variation using a variety of applied compressive and shear stresses. We show that a subtle change in the near-surface texture and fabric will persist deep in the ice sheet under a wide range of temperature and stress regimes. In certain cases, both migration recrystallization and polygonization can help maintain the fabric variation by increasing the time for the fabrics to equilibrate with the local stress state. Therefore, it is likely that information about past climate can be extracted directly from ice fabric because a climate-induced variation can be preserved throughout the depth of an ice sheet in a large variety of conditions.

Kennedy, J. H.; Pettit, E. C.

2013-12-01

378

Paleo-ice stream types  

NASA Astrophysics Data System (ADS)

During mapping of the Laurentide and Fennoscandian ice sheet beds we have observed and mapped a large number of paleo-ice streams, including apparently anomalous ice streams ocurring on high shear-stress bed materials, and with little or no topographic guidance. In addition, we have found evidence that in several places in the Canadian Arctic there developed a special category of small ephemeral ice streams during the deglaciation. They indicate flow patterns that are very different from older semi-stable ice streams in the respective areas. These observations of several types of "anomalous" ice streams lead us to think that scientific understanding of ice-stream behaviour has been hampered by an over-simplified terminology that presupposes that ice streams are one phenomenon, largely governed by one set of controls. Instead we hold the view that an understanding of ice-stream behaviour must start with a subdivision of the term "ice stream" into genetically distinct categories, with research focused at clarifying the controls for each category. A tentative classification scheme for paleo-ice streams should comprise at least five different types of ice streams, i/ Classical ice streams which occur on an excessively lubricated bed, i.e. preferably over fine-grained substrate with low permeability. Most of these ice streams terminated in lacustrine or marine water bodies. The numerous Baltic Ice Streams and the Cochrane surges into glacial lakes Agassis/Ojibway are examples of this type, ii/ Semi-stable ice streams which exist in locations where overall ice-sheet geometry favors the occurrence of long-lasting convergent flow, i.e. downstream of saddles in the ice-sheet surface. The Åre - Trondheim area in Scandinavia was likely a site for such an ice stream, iii/ Transient rigid-bed ice streams, which form without obvious topographical or substratum control when thawed spots start to develop under a largely cold-based ice sheet, which then finds itself with a steeper profile than the reduced bed traction can sustain. The unnamed Finnish ice streams that terminate in the Salpausselkä lobes are prime examples, and the Dubawnt ice stream in Keewatin may also be of this type, iiii/ Topographic ice streams, which are constrained by topography and fixed in space but variable in time. The Hudson Strait, Laurentian Channel, and Norwegian Channel ice streams are prime candidates for this type, and iiiii/ Re-equilibration ice streams, which probably develop as a response to rapid calving and breakup of ice in adjacent marine areas. Good examples are the east-trending ice stream on Prince of Wales Island, the small Cap Krusenstern ice stream and numerous ice streams on Baffin Island.

Kleman, J.; de Angelis, H.; Greenwood, S.

2010-12-01

379

Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements  

NASA Astrophysics Data System (ADS)

The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed phase and cirrus clouds. The patterns are analyzed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light scattering properties and also similar causes. Overall, the in situ data is consistent with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic airmasses than in a continental, polluted one. Overall, the roughness and complexity is expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.

Ulanowski, Z.; Kaye, P. H.; Hirst, E.; Greenaway, R. S.; Cotton, R. J.; Hesse, E.; Collier, C. T.

2013-09-01

380

Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements  

NASA Astrophysics Data System (ADS)

The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the context of radiative properties of ice and mixed-phase clouds. Limitations of current cloud probes to measure these properties can be circumvented by acquiring two-dimensional light-scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed-phase and cirrus clouds. The patterns are analysed using several measures of pattern texture, selected to reveal the magnitude of particle roughness or complexity. The retrieved roughness is compared to values obtained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corresponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have similar manifestations in terms of light-scattering properties and also similar causes. Overall, the in situ data are consistent, with ice particles with highly irregular or rough surfaces being dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cirrus forming in clean oceanic air masses than in a continental, polluted one. Overall, the roughness and complexity are expected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question suggestions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.

Ulanowski, Z.; Kaye, P. H.; Hirst, E.; Greenaway, R. S.; Cotton, R. J.; Hesse, E.; Collier, C. T.

2014-02-01

381

Ice Cream with a Heart Create a new Clemson Ice  

E-print Network

Ice Cream with a Heart Contest! Create a new Clemson Ice Cream flavor! Raise money for your favorite charity! Win a free Clemson Ice Cream party for your organization! Enter at www organizations. The contest is called Ice Cream with a Heart and its purpose is to help student organizations

Duchowski, Andrew T.

382

Southern Ocean CO2 sink: The contribution of the sea ice  

NASA Astrophysics Data System (ADS)

report first direct measurements of the partial pressure of CO2 (pCO2) within Antarctic pack sea ice brines and related CO2 fluxes across the air-ice interface. From late winter to summer, brines encased in the ice change from a CO2 large oversaturation, relative to the atmosphere, to a marked undersaturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate crystals, and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea ice cover using the NEMO-LIM3 large-scale sea ice-ocean and provide first estimates of spring and summer CO2 uptake from the atmosphere by Antarctic sea ice. Over the spring-summer period, the Antarctic sea ice cover is a net sink of atmospheric CO2 of 0.029 Pg C, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO2 of the Southern Ocean.

Delille, Bruno; Vancoppenolle, Martin; Geilfus, Nicolas-Xavier; Tilbrook, Bronte; Lannuzel, Delphine; Schoemann, Véronique; Becquevort, Sylvie; Carnat, Gauthier; Delille, Daniel; Lancelot, Christiane; Chou, Lei; Dieckmann, Gerhard S.; Tison, Jean-Louis

2014-09-01

383

Modelling biogeochemical tracer transport in sea ice due to gravity drainage  

NASA Astrophysics Data System (ADS)

Sea ice is a porous material, formed of an evolving array of solid ice crystals bathed in liquid brine. The liquid-filled pore space provides a habitat for life within the ice, and, when the ice is permeable, provides a pathway for exchange of gases and other chemicals between the ice, ocean, and atmosphere. This coupling between the physical, chemical, and biological evolution of sea ice has poorly constrained implications for biogeochemical processes, such as the impact of sea ice on the carbon cycle. During winter ice growth, so-called gravity drainage drives a convective exchange of brine between the ocean and the porous interior of sea ice. Here, we use two-dimensional mushy-layer simulations of convective flow to provide insight into the resulting transport of passive biogeochemical tracers through the ice. We quantify the chemical concentration in the liquid during periods of quasi-steady growth rate, and determine a scaling law for the total chemical tracer fluxes through the region of active convection inside the ice. Chemical concentrations show spatial heterogeneity, and our results predict enhanced chemical concentrations in the pore space near to brine channels. These results may provide useful insight for interpreting studies of sea-ice biogeochemistry, and offer a framework to develop models of physical, chemical, and biological interactions.

Hitchen, Joseph; Wells, Andrew

2014-05-01

384

Even at the margins of glaciers, streams have some algae growing in them. Translucent rocks have algae growing in and under them. Lakes with thick ice  

E-print Network

rocks have algae growing in and under them. Lakes with thick ice but a little light filtering through have simple ecosystems. Life is very tough and "extremophiles" grow in hot springs, deep in the earth, in the bottom of ice shelves where liquid water exists among ice crystals, and other extreme environments

Richerson, Peter J.

385

The microbubble mediated surface probe and the ice-antifreeze glycoprotein solution system  

NASA Astrophysics Data System (ADS)

Microbubble growth and its apparent "shrinkage" during the transient approach to steady-state crystal growth have been monitored by dynamic light scattering in the region immediately ahead of ice crystals growing into aqueous solutions containing dilute concentrations of macromolecules. This interfacial bubble growth occurs in the presence of a solution of globular macromolecules, and is independent of the crystal growth direction. In contrast, bubble growth becomes crystal-facet dependent when the solution contains a biological antifreeze molecule, the antifreeze glycoprotein (AFGP-4). This solution elicited an immediate, 100 x increase in bubble size above the prismatic surface of ice, followed by a gradual decrease in the averaged bubble size concomitant with a large increase in the size polydispersity. Furthermore, when the steady-state crystal growth condition is reached (in approximately one hour), the average bubble size was still ˜ 80x the size of those found in the pure ice-water system. However, when the same solution is above the basal facet, after the steady-state growth condition is attained, the microbubble diameter is unchanged from that found in the pure ice-water system. The difference in microbubble growth in the vicinity of the dynamic ice-solution interface between solutions of AFGP-4 samples and that of other molecules suggests facet-specific affinity of AFGP by ice, a condition necessary for facet-specific crystal growth inhibition.

Vesenka, J. P.; Feeney, R. E.; Yeh, Y.

1993-05-01

386

Applied Sea Ice Research  

NASA Astrophysics Data System (ADS)

In the late 1960s oil and gas development became an issue in the northern coastal areas of Alaska and Canada. More lately this has also become an issue in the Euroasian Arctic with the Barents and Kara Seas as example on where offshore hydrocarbon production now is being planned. In such waters the key questions prior to a development are related to water depths at the site and in case of ice, how frequent and what type of ice features will be met. Especially the ice conditions and knowledge about them are very decisive for the field development solutions to be chosen. The paper will highlight examples on development solutions where the ice conditions have played a paramount role in the field development plans. An example is the consequences of iceberg threaten in an area and the effect sudden changes in ice drift directions may have on the exploration and drilling solutions chosen. The paper will also discuss how to derive design ice actions values for such waters including scaling from nature to model ice basins.

Løset, S.

2009-04-01

387

High Speed Ice Friction  

NASA Astrophysics Data System (ADS)

Many different tribological experiments have been run to determine the frictional behaviour of ice at high speeds, ostensibly with the intention of applying results to everyday fields such as winter tyres and sports. However, experiments have only been conducted up to linear speeds of several metres a second, with few additional subject specific studies reaching speeds comparable to these applications. Experiments were conducted in the cold rooms of the Rock and Ice Physics Laboratory, UCL, on a custom built rotational tribometer based on previous literature designs. Preliminary results from experiments run at 2m/s for ice temperatures of 271 and 263K indicate that colder ice has a higher coefficient of friction, in accordance with the literature. These results will be presented, along with data from further experiments conducted at temperatures between 259-273K (in order to cover a wide range of the temperature dependent behaviour of ice) and speeds of 2-15m/s to produce a temperature-velocity-friction map for ice. The effect of temperature, speed and slider geometry on the deformation of ice will also be investigated. These speeds are approaching those exhibited by sports such as the luge (where athletes slide downhill on an icy track), placing the tribological work in context.

Seymour-Pierce, Alexandra; Sammonds, Peter; Lishman, Ben

2014-05-01

388

Coulombic charge ice  

NASA Astrophysics Data System (ADS)

We consider a classical model of charges ±q on a pyrochlore lattice in the presence of long-range Coulomb interactions. This model first appeared in the early literature on charge order in magnetite [P. W. Anderson, Phys. Rev. 102, 1008 (1956), 10.1103/PhysRev.102.1008]. In the limit where the interactions become short ranged, the model has a ground state with an extensive entropy and dipolar charge-charge correlations. When long-range interactions are introduced, the exact degeneracy is broken. We study the thermodynamics of the model and show the presence of a correlated charge liquid within a temperature window in which the physics is well described as a liquid of screened charged defects. The structure factor in this phase, which has smeared pinch points at the reciprocal lattice points, may be used to detect charge ice experimentally. In addition, the model exhibits fractionally charged excitations ±q/2 which are shown to interact via a 1/r potential. At lower temperatures, the model exhibits a transition to a long-range ordered phase. We are able to treat the Coulombic charge ice model and the dipolar spin ice model on an equal footing by mapping both to a constrained charge model on the diamond lattice. We find that states of the two ice models are related by a staggering field which is reflected in the energetics of these two models. From this perspective, we can understand the origin of the spin ice and charge ice ground states as coming from a dipolar model on a diamond lattice. We study the properties of charge ice in an external electric field, finding that the correlated liquid is robust to the presence of a field in contrast to the case of spin ice in a magnetic field. Finally, we comment on the transport properties of Coulombic charge ice in the correlated liquid phase.

McClarty, P. A.; O'Brien, A.; Pollmann, F.

2014-05-01

389

Buried glacier ice in permafrost, a window to the past: examples from Bylot Island, Canadian Arctic  

NASA Astrophysics Data System (ADS)

Bylot Island is located north of Baffin Island (73°N, 80°W) and is extensively covered by an ice cap and its outlet glaciers flowing towards the arctic lowland of the Lancaster formation. During summers of 2009 and 2011 several active-layer detachment slides exposed large massive ice bodies and other types of debris-rich ice that were interpreted as buried glacier ice. The upper part of the massive ice and debris-rich ice were usually in contact with various types of ice-contact or glacio-fluvial sediments and in some cases they were covered by mass wasting/colluvial deposits. This suggests that their preservation was likely related to burial of the ice and refreezing of the overlying sediments following permafrost aggradation. A preliminary analysis of the ice facies and ice crystals revealed the presence of four distinct types of ice: 1) clear-ice bodies with very few sediment and no organic inclusions. The ice crystals were large (cm), randomly oriented and air bubbles were observed at the junction of crystals. These characteristics could potentially indicate an englacial (snow-neve metamorphism) origin for these clear ice bodies; 2) large, meter thick, clear ice layers with no sediment, nor organics. The ice crystals were large (cm), several cm long, oriented in the same direction, and vertically aligned. These characteristics could potentially point to water that refroze in a tunnel incised in englacial ice; 3) Successive, mm to cm thick, ice layers, separated by undulating sand and gravel bands also containing cobles to boulder size rock fragments. These characteristics could potentially represent regelation ice formed at the base of glaciers and incorporated to the glacier sole; 4) mm to cm suspended aggregate of fine-grained sediments in clear ice. These micro-suspended and suspended cryostructures were sometimes deformed and aligned in the form of thin (mm) undulating layers. These micro-structures were very similar to basal ice facies, presumably related to glacio-hydrologic supercooling, that we observed at the Matanuska Glacier in Alaska. Interestingly, the various types of ice contained in buried glacier ice permafrost date back to the englacial ice formation and its subsequent deformation by glacier flow and glacio-hydrological dynamics. It is thus older by several centuries to millennia than the permafrost aggradation itself (burial and active layer development) and we used the term antegenetic, in opposition to epigenetic or syngenetic, to characterize this type of permafrost. Buried glacier ice is a window to the past and a unique tool to reconstruct the paleogeography and paleoclimatology of Arctic regions. In a warming climate, as glaciers are receding, the burial of ice in the proglacial environment will offer opportunities to characterize antegenetic permafrost aggradation and its related cryofacies. In warming permafrost environments, as active layers on slope deepen and detachment slides are triggered, more buried Pleistocene glacier ice will likely be exposed.

Fortier, D.; Coulombe, S.; Kanevskiy, M. Z.; Paquette, M.; Shur, Y.; Stephani, E.

2011-12-01

390

Climate Data Records (CDRs) for Ice Motion and Ice Age  

NASA Astrophysics Data System (ADS)

Climate Data Records (CDRs) for remotely-sensed Arctic sea ice motion and sea ice age are under development by our group at the University of Colorado, Boulder. The ice motion product, archived at NSIDC, has a considerable history of use, while sea ice age is a relatively new product. Our technique to estimate sea ice motion utilizes images from SSM/I, as well as SMMR and the series of AVHRR sensors to estimate the daily motion of ice parcels. This method is augmented by incorporating ice motion observations from the network of drifting buoys deployed as part of the International Arctic Buoy Program. Our technique to calculate ice age relies on following the actual age of the ice for each ice parcel, categorizing the parcel as first-year ice, second-year, ice, etc. based on how many summer melt seasons the ice parcel survives. Both of these research-grade products have been interpolated onto 25x25 km grid points spanning the entire Arctic Ocean using the Equal-Area Scalable Earth (EASE) grid. Datasets generated from this program have shown that the Arctic ice cover has experienced a significant (> 70%) decline in multiyear ice over the last 20 years, leaving a younger ice cover in 2011. By comparing ice age derived by the Lagrangian tracking method to ice thickness estimated by Ice, Cloud and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) data, it is observed that ice age is linearly related to ice thickness, up to an age of 10 years. Therefore, the shift in dominance of multiyear ice to first-year ice relates to a significant thinning of the ice. This thinning is estimated to correspond to a 40% reduction in ice volume in the last 20 years. An ancillary dataset (APP-X) produced by the University of Wisconsin, Madison has been combined with the ice motion product to monitor the properties of the sea ice parcels tracked by the ice motion product. This dataset includes ice surface and 2-meter air temperature, albedo, downwelling shortwave and longwave radiation, first year, multiyear, and total ice concentration, and passive microwave brightness temperatures. The combination of sea ice motion and sea ice surface properties can therefore be utilized to observe the evolution of these properties as the ice ages. Using this dataset, we observe that the evolution of albedo through the summer months varies between first year and mutliyear ice types, resulting in a greater amount of shortwave radiation absorbed per unit area over first-year ice through the melt season vs. multiyear ice. Given that a larger portion of the ice cover is now first-year ice, the total shortwave energy absorbed by the pack through the melt season has increased from two decades ago, a feedback associated with the change in predominant ice type.

Tschudi, M. A.; Fowler, C.; Maslanik, J. A.; Stroeve, J. C.

2011-12-01

391

Sea ice microbial communities (SIMCO)  

Microsoft Academic Search

Sea ice microbial communities (SIMCO) grow luxuriantly within several microhabitats of sea ice, indicating that the microorganisms comprising these communities are well adapted to the physicochemical gradients which characterize sea ice. We used SIMCO obtained from the bottom of congelation ice in McMurdo Sound, An