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1

Triangular ice crystals  

NASA Astrophysics Data System (ADS)

We are all familiar with the hexagonal form of snow crystals and it is well established that this shape is derived from the arrangement of water molecules in the crystal lattice. However, crystals with a triangular form are often found in the Earth's atmosphere and the reason for this non-hexagonal shape has remained elusive. Recent laboratory work has shed light on why ice crystals should take on this triangular or three-fold scalene habit. Studies of the crystal structure of ice have shown that ice which initially crystallises can be made of up of hexagonal layers which are interlaced with cubic layers to produce a 'stacking disordered ice'. The degree of stacking disorder can vary from crystals which are dominantly hexagonal with a few cubic stacking faults, through to ice where the cubic and hexagonal sequences are fully randomised. The introduction of stacking disorder to ice crystals reduces the symmetry of the crystal from 6-fold (hexagonal) to 3-fold (triangular); this offers an explanation for the long standing problem of why some atmospheric ice crystals have a triangular habit. We discuss the implications of triangular crystals for halos, radiative properties, and also discuss the implications for our understanding of the nucleation and early stages of ice crystal growth for ice crystals in the atmosphere.

Murray, Benjamin; Salzmann, Christoph; Heymsfield, Andrew; Neely, Ryan

2014-05-01

2

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

3

Ice crystal terminal velocities.  

NASA Technical Reports Server (NTRS)

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 terminal velocity at any altitude, and almost any crystal type. Two sets of equations were derived. The 'general' equations provide a good estimate of terminal velocities at any altitude. The 'specific' equations are a set of equations for ice crystal terminal velocities at 1000 mb. The calculations are in good agreement with terminal velocity measurements. The results from the present study were also compared to prior calculations by others and seem to give more reasonable results, particularly at higher altitudes.

Heymsfield, A.

1972-01-01

4

Bacterial Ice Crystal Controlling Proteins  

PubMed Central

Across the world, many ice active bacteria utilize ice crystal controlling proteins for aid in freezing tolerance at subzero temperatures. Ice crystal controlling proteins include both antifreeze and ice nucleation proteins. Antifreeze proteins minimize freezing damage by inhibiting growth of large ice crystals, while ice nucleation proteins induce formation of embryonic ice crystals. Although both protein classes have differing functions, these proteins use the same ice binding mechanisms. Rather than direct binding, it is probable that these protein classes create an ice surface prior to ice crystal surface adsorption. Function is differentiated by molecular size of the protein. This paper reviews the similar and different aspects of bacterial antifreeze and ice nucleation proteins, the role of these proteins in freezing tolerance, prevalence of these proteins in psychrophiles, and current mechanisms of protein-ice interactions. PMID:24579057

Lorv, Janet S. H.; Rose, David R.; Glick, Bernard R.

2014-01-01

5

The effect of ice crystal shape on aircraft contrails  

NASA Astrophysics Data System (ADS)

Aircraft contrails are a common phenomenon observed in the sky. They are formed mainly of water, from the ambient atmosphere and as a by-product of the combustion process, in the form of ice crystals. They have been identified as a potential contributor to global warming. Some contrails can be long-lived and create man-made cloud cover, thus possibly altering the radiative balance of the earth. There has been a great deal of research on various aspects of contrail development, but to date, little has been done on the influence of ice crystal shapes on the contrail evolution. In-situ studies have reported that young contrails are mainly quasi-spherical crystals while older contrails can have a much more diverse spectrum of possible shapes. The most common shapes found in contrails are quasi-spherical, hexagonal columns, hexagonal plates, and bullet rosettes. Numerical simulations of contrails to date typically have assumed "spherical" as the default ice shape. This work simulated contrail development with a large eddy simulation (LES) model that implemented both spherical and non-spherical shapes to examine the effects. The included shape effect parameters, such as capacitance coefficient, ventilation factor, Kelvin effect, fall velocity and ice crystal surface area, help to establish the shape difference in the results. This study also investigated initial sensitivities to an additional ice parameter, the ice deposition coefficient. The literature shows conflicting values for this coefficient over a wide range. In the course of this investigation a comparison of various ice metrics was made for simulations with different assumed crystal shapes (spheres, hexagonal columns, hexagonal plates, bullet rosettes and combination of shapes). The simulations were performed at early and late contrail time, with a range of ice crystal sizes, and with/without coupled radiation. In young and older contrails and without coupled radiation, the difference from the shape effect in ice crystal number, N(t), is not significant compared with the level of uncertainty. In young contrails, the difference between spherical and non-spherical shapes in N(t) is less than 7% for relatively large ice particles and 23% for relatively small ice particles. The ice mass, M(t), is not significantly affected by the crystal shapes, with less than 8% difference. However, the ice surface area, S(t), is the ice metric more sensitive to crystal shape, with a maximum difference of 68%. It increases at late time, though it is mainly governed by geometrical rather than dynamical effects. The small sensitivity to shape effects in the ice contrail metrics when radiation is not included suggests that the spherical shape will provide a reasonable representation for all shapes found in the in-situ studies. The radiation is included at late time, when the lasting effects of contrails are more critical. The inclusion of coupled radiation increases the level of dispersion in the results and hence increases slightly the differences due to shape effects. The small difference is also observed in the infrared heating rates of contrails.

Meza Castillo, Omar E.

6

Biosynthesis of quasi-spherical Ag nanoparticle by Pseudomonas aeruginosa as a bioreducing agent  

NASA Astrophysics Data System (ADS)

Use of microorganism as a novel and eco-friendly strategy to production of nanomaterials is an important aspect of modern nanotechnology. Biosynthesis of quasi-spherical silver nanoparticles (Ag-NPs) has been investigated using Pseudomonas aeruginosa. We observe that silver (Ag+) ions when exposed to P. aeruginosa biomass are reduced in solution, thereby leading to the formation of Ag-NPs. Quasi-spherical shape and nearly well distribution and FCC crystal structure of Ag-NPs were confirmed by XRD pattern, STM and TEM micrographs. UV-Vis spectra show a surface plasmon resonance (SPR) band at ~ 435 nm.

Taheri Otaqsara, S. M.

2011-12-01

7

Quasi-spherical direct drive fusion.  

SciTech Connect

The authors present designs of quasi-spherical direction drive z-pinch loads for machines such as ZR at 28 MA load current with a 150 ns implosion time (QSDDI). A double shell system for ZR has produced a 2D simulated yield of 12 MJ, but the drive for this system on ZR has essentially no margin. A double shell system for a 56 MA driver at 150 ns implosion has produced a simulated yield of 130 MJ with considerable margin in attaining the necessary temperature and density-radius product for ignition. They also represent designs for a magnetically insulated current amplifier, (MICA), that modify the attainable ZR load current to 36 MA with a 28 ns rise time. The faster pulse provided by a MICA makes it possible to drive quasi-spherical single shell implosions (QSDD2). They present results from 1D LASNEX and 2D MACH2 simulations of promising low-adiabat cryogenic QSDD2 capsules and 1D LASNEX results of high-adiabat cryogenic QSDD2 capsules.

VanDevender, J. Pace; Abbott, Lucas M.; Langston, William L.; McDaniel, Dillon Heirman; Nash, Thomas J.; Roderick, Norman Frederick; Silva, M.

2007-01-01

8

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.

9

Role of Pressure in Quasi-Spherical Gravitational Collapse  

E-print Network

We study quasi-spherical Szekeres space-time (which possess no killing vectors) for perfect fluid, matter with tangential stress only and matter with anisotropic pressure respectively. In the first two cases cosmological solutions have been obtained and their asymptotic behaviour have been examined while for anisotropic pressure, gravitational collapse has been studied and the role of the pressure has been discussed.

Subenoy Chakraborty; Sanjukta Chakraborty; Ujjal Debnath

2005-06-08

10

Ice crystallization during the manufacture of ice cream  

Microsoft Academic Search

Control of ice crystallization during the manufacture of ice cream is important for the development of proper texture, product quality and storage stability. Improving our somewhat limited understanding of the mechanisms that control ice-crystal formation, as well as of the effects of formulation and process factors, may lead to improvements in processing techniques.

Richard W. Hartel

1996-01-01

11

Cluster self-organization of intermetallic systems: Quasi-spherical nanocluster precursors with internal Friauf polyhedra (A-172) and icosahedra (B-137) in the Li{sub 19}Na{sub 8}Ba{sub 15} (hP842) crystal structure  

SciTech Connect

A combinatorial and topological analysis of Li{sub 19}Na{sub 8}Ba{sub 15} (hP842, a = 20 A, c = 93 A, V = 33552 A{sup 3}, P3-bar) has been performed using computer methods (the TOPOS program package). Two types of crystal-forming quasi-spherical nanoclusters about 20 A in diameter with internal Friauf polyhedra (A-172) and icosahedra (B-137) have been established by the complete decomposition of the 3D factor graph of the structure into cluster substructures. Each type of nanoclusters forms close-packed 2D layers 3{sup 6}, which alternate along the c axis. The B-137 and A-172 nanoclusters are composed of three layers and have shell compositions (1 + 12 + 32 + 92) and (1 + 16 + 59 + 103) with local symmetries 3 and 3-bar, respectively; they were revealed for the first time in crystal structures as cluster precursors. The icosahedral B-137 nanocluster contains a 104-atom quasicrystal approximant (Samson cluster).

Ilyushin, G. D., E-mail: ilyushin@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Blatov, V. A. [Samara State University (Russian Federation)

2010-12-15

12

Evolution of crystal fabric: Ice-Age ice versus Holocene ice  

Microsoft Academic Search

Ice-Age ice has smaller crystals and higher concentrations of impurities than Holocene ice; these properties cause it to develop a more strongly-aligned crystal-orientation fabric. In many regions of the Antarctic and Greenland ice sheets, the Ice-Age ice is now at depth and its flow properties may dominate the ice flow patterns, particularly where sliding is minimal. We use a fabric

J. H. Kennedy; E. C. Pettit

2009-01-01

13

Viewing Ice Crystals Using Polarized Light.  

ERIC Educational Resources Information Center

Describes a method for identifying and examining single ice crystals by photographing a thin sheet of ice placed between two inexpensive polarizing filters. Suggests various natural and prepared sources for ice that promote students' insight into crystal structures, and yield colorful optical displays. Includes directions, precautions, and sample…

Kinsman, E. M.

1992-01-01

14

Relationships between ice cream mix viscoelasticity and ice crystal growth in ice cream  

Microsoft Academic Search

The relationship between ice cream mix viscoelasticity and ice crystal growth in ice cream as a function of stabilizer addition was studied by a simulation of freeze-concentration using a series of ice cream mixes containing reduced quantities of water. Ice cream mixes were formulated with guar gum concentrations ranging from 0 to 0.25% and a series of concentrated mixes from

S. Bolliger; H. Wildmoser; H. D. Goff; B. W. Tharp

2000-01-01

15

Evolution of crystal fabric: Ice-Age ice versus Holocene ice  

NASA Astrophysics Data System (ADS)

Ice-Age ice has smaller crystals and higher concentrations of impurities than Holocene ice; these properties cause it to develop a more strongly-aligned crystal-orientation fabric. In many regions of the Antarctic and Greenland ice sheets, the Ice-Age ice is now at depth and its flow properties may dominate the ice flow patterns, particularly where sliding is minimal. We use a fabric evolution model, based on that developed by Thorsteinsson (2002), to explore the evolution of Ice-Age ice fabric along particle paths for ice within Taylor Glacier, a cold-based outlet glacier of the East Antarctic Ice Sheet. The bulk of the ice within Taylor Glacier consists of Ice-Age and older ice because the Holocene ice has ablated away (there is no Holocene ice remaining within 25km of the terminus, Aciego, 2007). We initialize the evolving fabric based on fabric measurements from Taylor Dome where available (DiPrinzio, 2003) and other ice core records. We compare model results with thin-section data from shallow cores taken near the terminus. As expected, crystal alignment strengthens along the ice particle path. Due to lateral shearing along valley walls and the ice cliffs (terminal ice cliffs are cold in winter and present a resistance to flow), a tilted single maximum is common near the terminus. The highly-aligned fabric of Ice-Age ice is significantly softer than Holocene ice in simple shear parallel to the bed, this softness not only results in faster flow rates for glaciers and ice sheets such as Taylor, but creates a climate-flow-fabric feedback loop through concentrating ice-sheet flow within the Ice-Age ice. Thorsteinsson, T. (2002), Fabric development with nearest-neighbor interaction and dynamic recrystallization, J. Geophys. Res., 107(B1), 2014, doi:10.1029/2001JB000244. S.M. Aciego, K.M. Cuffey, J.L. Kavanaugh, D.L. Morse, J.P. Severinghaus, Pleistocene ice and paleo-strain rates at Taylor Glacier, Antarctica, Quaternary Research, Volume 68, Issue 3, November 2007, Pages 303-313, ISSN 0033-5894, DOI: 10.1016/j.yqres.2007.07.013. DiPrinzio, Eos Trans. AGU, 84(46), Fall Meet. Suppl., Abstract C11C-0834, 2003

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

2009-12-01

16

Ice crystals in high clouds and contrails  

NASA Astrophysics Data System (ADS)

In honor of Dr. Helmut K. Weickmann's lifetime achievements, some of his early discoveries on ice crystals in high clouds are resurrected and discussed. It is demonstrated that the shapes and sizes of cloud meteors convey information related to cloud type, cloud duration, cloud amount, cloud radiative forcing, and the environment in which the cloud forms. For example, persistence of a contrail behind an aircraft depends on ice crystal concentration and size distribution, which are governed by the ambient temperature, humidity, and the concentration of ice nuclei. It is suggested that increased air traffic, especially high-flying jets over the past three decades, may have modified global cirrus cloud amount, which in turn may affect surface temperature and global climate.

Parungo, F.

17

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

18

Disturbed basal ice seen in radio echo images coincide with zones of big interlocking ice crystals.  

NASA Astrophysics Data System (ADS)

Improvement of the depth sounding radio echo sounding (RES) over Antarctica and Greenland Ice Sheet has made it possible to map the near basal layers that have not been 'seen' earlier due to the very high demand of attenuation needed to reach through more than 3000m of ice. The RES internal reflectors show that the near basal ice at many locations has disturbed layering. At the locations where ice cores reach the bedrock both in Greenland and Antarctica studies of the ice crystal size and orientation show that the near basal ice has big and interlocking ice crystals which suggests the ice is not actively deforming. These observations challenge the often used constitutive equations like Glens flow law in ice sheet modelling. A discussion of the impact of the RES findings on ice sheet modeling and the quest to find the oldest ice in Antarctic based on the anisotropy of the basal ice will follow.

Dahl-Jensen, Dorthe; Gogineni, Sivaprasad; Panton, Christian

2014-05-01

19

An immune response to ice crystals in North Atlantic fishes.  

PubMed

In mammals, the presence of crystals composed of small organic molecules, including urate and related compounds, has been shown to trigger an inflammatory response and the subsequent production of specific immunoglobulins (Ig's). Many fishes that are exposed to ice crystals in cold temperate and polar oceans may harbour ice crystals internally. Here, we report evidence for a specific immune response to ice crystals in cold-ocean marine fishes. Using ice nucleation activity as an assay, anti-ice Ig's were detected in the sera of the cold-ocean marine fish species, ocean pout (Macrozoarces americanus) and Atlantic herring (Clupea harengus harengus), but not in the sera of species that are not exposed to ice. Purified Ig's isolated from ocean pout serum using two different protocols showed ice nucleation activity, thus demonstrating the presence of ice binding specificity among these Ig's. PMID:8944760

Verdier, J M; Ewart, K V; Griffith, M; Hew, C L

1996-11-01

20

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

21

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

22

Factors Affecting the Changes of Ice Crystal Form in Ice Cream  

NASA Astrophysics Data System (ADS)

In this study, the shape of ice crystals in ice cream was quantitatively evaluated by introducing fractal analysis. A small droplet of commercial ice cream mix was quickly cooled to about -30°C on the cold stage of microscope. Subsequently, it was heated to -5°C or -10°C and then held for various holding time. Based on the captured images at each holding time, the cross-sectional area and the length of circumference for each ice crystal were measured to calculate fractal dimension using image analysis software. The results showed that the ice crystals were categorized into two groups, e.g. simple-shape and complicated-shape, according to their fractal dimensions. The fractal dimension of ice crystals became lower with increasing holding time and holding temperature. It was also indicated that the growing rate of complicated-shape ice crystals was relatively higher because of aggregation.

Wang, Xin; Watanabe, Manabu; Suzuki, Toru

23

Light Scattering by Ice Crystals and Mineral Dust Aerosols in the Atmosphere  

E-print Network

regular faceted particles (such as hexagon columns, plates, etc.) and imperfect ice crystals. Modeling of the scattering by regular ice crystals is straightforward, as their morphologies can be easily de?ned. For imperfect ice crystals, the morphology...

Bi, Lei

2012-07-16

24

Ice crystal number concentration versus temperature for climate studies  

Microsoft Academic Search

ABSTRACT Ice crystal number concentration (Ni) is an important parameter, having a strong influence on the calculation of cloud ,optical and ,microphysical ,parameters. Cloud and ,precipitation parameterizations within climate and weather forecasting models, affecting the heat and moisture budget of the atmosphere, cannot be determined accurately if Ni is not estimated correctly. Previous studies of ice ,crystal number ,concentration versus

I. Gultepe; G. A. Isaac; S. G. Cober

2001-01-01

25

Quasi-spherical microwells on superhydrophobic substrates for long term culture of multicellular spheroids and high throughput assays.  

PubMed

Multicellular tumour spheroids closely recapitulate the physiological environment of tumour tissues. However, their implementation in drug screening assays remains limited due to the technological challenges of forming large numbers of high quality spheroids in platforms compatible with high throughput screening. A simple bench-top microfabrication strategy is demonstrated here based on the principle of ice lithography carried out on superhydrophobic substrates to fabricate quasi-spherical microwells (spheriwells). The microwells shapes and dimensions are directly controlled by the hydrophobicity of the substrate and the volume of the water droplets. The prepared concave microwells enable the formation of dense and homogeneous multicellular tumour spheroids. Spheroids formed within spheriwells are trapped within the microwells, which eliminate loss during media manipulation and facilitate long-term on-chip culture. Morphological and phenotypical changes associated with the growth of MCF-7 adenocarcinoma cells in spheriwells were characterised using imaging flow cytometry and revealed the appearance of heterogeneous populations with loss of E-Cadherin expression. The compatibility of the spheriwells with an on-chip MTT assay is demonstrated. The very unusual shape of the spheriwells, prepared using materials and methods routinely used in most research laboratories, provides a straightforward and scalable platform to prepare high quality multicellular tumour spheroids compatible with high throughput biological screening assays. PMID:24797879

Liu, Tianqing; Winter, Marnie; Thierry, Benjamin

2014-07-01

26

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

27

Scattering Properties of Oriented Hexagonal Ice Crystals  

E-print Network

. In this study, the dipole approximation (DDA) method is employed to the scattering of light on oriented hexagonal ice columns and plates with various tilting angles. It is found that the oriented hexagonal ice particles tend to have strong backscattering...

Zhang, Feng

2010-01-14

28

Mixing of the Immiscible: Hydrocarbons in Water-Ice near the Ice Crystallization Temperature.  

PubMed

Structural changes in hydrocarbon-doped water-ice during amorphous to crystalline phase conversion are investigated using polycyclic aromatic hydrocarbons (PAHs) as probes. We show that aggregation of impurity molecules occurs due to the amorphous-crystalline transition in ice, especially when they are hydrophobic molecules such as PAHs. Using ultraviolet-visible (UV-vis), Fourier-transform Infrared (FTIR), and laser-induced-fluorescence (LIF) spectroscopic techniques, we show that, although ice infrared absorption features change from a broad structureless band corresponding to amorphous ice to a sharp structured crystalline ice bands, simultaneously, sharper isolated PAH UV absorption features measured in the amorphous ice host turn broad upon ice crystallization. A simultaneous decrease in the monomer fluorescence and increase in the excimer emission band is observed, a clear indication for the formation of PAH molecular aggregates when amorphous ice is converted to crystalline ice at higher temperatures. Similar to the irreversible amorphous-crystalline phase transitions, the UV, fluorescence, and excimer emissions indicate that PAHs undergo irreversible aggregation. Our studies suggest that organic impurities exist as aggregates rather than monomers trapped in crystalline water-ice when cycled through temperatures that convert amorphous ice to crystalline ice, rendering a better insight into phenomena such as the formation of cometary crust. This aggregate formation also may significantly change the secondary reaction pathways and rates in impurity-doped ices in the lab, on Earth, in the solar system, and in the interstellar medium. PMID:25302532

Lignell, Antti; Gudipati, Murthy S

2014-10-27

29

Steady-state and stability analysis of a population balance based nonlinear ice cream crystallization model  

E-print Network

Steady-state and stability analysis of a population balance based nonlinear ice cream the key phenomenons of the crystallization process. In ice cream crystallization, it is well known that the quality of the product, that is the hardness and the texture of the ice cream, depends on the ice crystal

Boyer, Edmond

30

Mixed Crystals of Ice and Ammonium Fluoride  

Microsoft Academic Search

THE ``inability of forming solid solutions with any compound'' was attributed to water two years ago by Mironov and Bergman1, who refuted previous reports by Giguere and Maass2 and by Kubaschewski and Weber3 of the solubility of hydrogen peroxide in ice. Yet Kathleen Lonsdale4 directed attention to the fact that ice and ammonium fluoride are not only isomorphous but also

R. Brill; S. Zaromb

1954-01-01

31

Superheating of ice crystals in antifreeze protein solutions.  

PubMed

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 degrees 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

2010-03-23

32

Growth of ice discs from the vapor and the mechanism of habit change of ice crystals  

NASA Technical Reports Server (NTRS)

Ice crystals nucleated on a liquid nitrogen cooled glass fiber grow first as thin disks which subsequently transform to plates and columns as they thicken and extend to regions of higher supersaturation. Crystals are often found to be dislocation-free, which suggests that growth results from surface nucleation, the habit depending on preferential nucleation in an adsorbed multilayer on basal or prism face.

Keller, V. W.; Mcknight, C. V.; Hallett, J.

1980-01-01

33

On the correlation between ice water content and ice crystal size and its application to radiative transfer and general circulation models  

E-print Network

observations from aircraft, and attests to the fact that small and large ice crystals are related to coldOn the correlation between ice water content and ice crystal size and its application to radiative analysis involving ice water content (IWC) and mean effective ice crystal size (De) intended

Liou, K. N.

34

Variability in millimeter wave scattering properties of dendritic ice crystals  

NASA Astrophysics Data System (ADS)

A detailed electromagnetic scattering model for ice crystals is necessary for calculating radar reflectivity from cloud resolving model output in any radar simulator. The radar reflectivity depends on the backscattering cross sections and size distributions of particles in the radar resolution volume. The backscattering cross section depends on the size, mass and distribution of mass within the crystal. Most of the available electromagnetic scattering data for ice hydrometeors rely on simple ice crystal types and a single mass-dimensional relationship for a given type. However, a literature survey reveals that the mass-dimensional relationships for dendrites cover a relatively broad region in the mass-dimensional plane. This variability of mass and mass distribution of dendritic ice crystals cause significant variability in their backscattering cross sections, more than 10 dB for all sizes (0.5-5 mm maximum dimension) and exceeding 20 dB for the larger ones at X-, Ka-, and W-band frequencies. Realistic particle size distributions are used to calculate radar reflectivity and ice water content (IWC) for three mass-dimensional relationships. The uncertainty in the IWC for a given reflectivity spans an order of magnitude in value at all three frequencies because of variations in the unknown mass-dimensional relationship and particle size distribution. The sensitivity to the particle size distribution is reduced through the use of dual frequency reflectivity ratios, e.g., Ka- and W-band frequencies, together with the reflectivity at one of the frequencies for estimating IWC.

Botta, Giovanni; Aydin, Kültegin; Verlinde, Johannes

2013-12-01

35

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

36

Simulation of quasi spherical direct drive capsules for pulsed-power driven inertial fusion energy  

NASA Astrophysics Data System (ADS)

Magnetic pressure from 35-MA current in a 1-mm-radius liner is equivalent to the ablation pressure in the beryllium pusher of an inertial fusion capsule in a 300 eV hohlraum and can, in principle, drive a Quasi Spherical Direct Drive (QSDD) fusion capsule to yields of ˜600 MJ with a 45 MA, 40 ns pulsed power driver. Analytic theory and 1D and 2D simulations of QSDD capsules show insensitivity to magnetic Rayleigh-Taylor instability, internal pulse shaping, efficient compression of cryogenic fuel on a low (?=1.5) adiabat, hot spot heating, current diffusion into the hot spot with alpha trapping, and burn. However, practical QSDD capsules require a large rate of change of current dI/dt ˜1.5 MA/ns and are susceptible to a wall instability, which must be further mitigated.

Vandevender, J. P.; Slutz, S. A.; Vesey, R. A.; Herrmann, M. C.; Sinars, D. B.; Nash, T. J.; Roderick, N. F.; Sefkow, A. B.

2011-11-01

37

Quasi-spherical direct drive fusion simulations for the Z machine and future accelerators.  

SciTech Connect

We explored the potential of Quasi-Spherical Direct Drive (QSDD) to reduce the cost and risk of a future fusion driver for Inertial Confinement Fusion (ICF) and to produce megajoule thermonuclear yield on the renovated Z Machine with a pulse shortening Magnetically Insulated Current Amplifier (MICA). Analytic relationships for constant implosion velocity and constant pusher stability have been derived and show that the required current scales as the implosion time. Therefore, a MICA is necessary to drive QSDD capsules with hot-spot ignition on Z. We have optimized the LASNEX parameters for QSDD with realistic walls and mitigated many of the risks. Although the mix-degraded 1D yield is computed to be {approx}30 MJ on Z, unmitigated wall expansion under the > 100 gigabar pressure just before burn prevents ignition in the 2D simulations. A squeezer system of adjacent implosions may mitigate the wall expansion and permit the plasma to burn.

VanDevender, J. Pace; McDaniel, Dillon Heirman; Roderick, Norman Frederick; Nash, Thomas J.

2007-11-01

38

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.; Muñoz Caro, Guillermo M.; Cruz-Diaz, Gustavo A.; Rodríguez-Lazcano, Yamilet; Maté, Belén

2013-01-01

39

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

PubMed

Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by solution. We predict that micrometer-sized particles and nanoparticles have the same equilibrium internal structure. The variation of liquid-vapor surface tension with solute concentration is a key factor in determining whether a solution-embedded ice core or vapor-exposed ice cap is the equilibrium structure of the aerosols. In agreement with experiments, we predict that the structure of mixed-phase HNO3-water particles, representative of polar stratospheric clouds, consists of an ice core surrounded by freeze-concentrated solution. The results of this work are important to determine the phase state and internal structure of sea spray ultrafine aerosols and other mixed-phase particles under atmospherically relevant conditions. PMID:24820354

Hudait, Arpa; Molinero, Valeria

2014-06-01

40

The scavenging of high altitude aerosol by small ice crystals  

NASA Astrophysics Data System (ADS)

There have been several global models developed for the theoretical investigation of the removal of high altitude aerosol from the atmosphere, following concern about the injection of particulate material by nuclear explosions and volcanic events. These models lack a knowledge of the scavenging efficiencies of the small ice crystals associated with cirus clouds and storm ice anvils. These are the only hydrometers that could remove the injected particles. In the past there have been a number of practical studies into the scavenging efficiencies of large ice crystaks and snowflakes. A comparison of the extrapolated results of these findings and the theoretical models of Martin et al. (1980, Pure appl. Phys.188, 1109-1129, J. atmos. Sci.37, 1628-1638) for the small crystal situation has been made. It was found that in general the extrapolated results gave efficiencies that were significantly higher than the predicted value. This difference was found to be enhanced as the crystal diameter decreased. Experiments used small ice plates grown at ˜-18.5°C in a cloud chamber, which were then permitted to fall through a dense aerosol cloud, to provide the first direct measurements of the scavenging efficiencies of this small crystals under cloud conditions. Initial results are presented for mono-disperse NaCl aerosol particles of size 4-6 ?m.

Andrew Bell, D.; Saunders, Clive P. R.

41

Computation of the scattering properties of nonspherical ice crystals  

E-print Network

This thesis is made up of three parts on the computation of scattering properties of nonspherical particles in the atmosphere. In the first part, a new crystal type-droxtal-is introduced to make a better representation of the shape of small ice...

Zhang, Zhibo

2004-11-15

42

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

43

Dimensions and aspect ratios of natural ice crystals  

NASA Astrophysics Data System (ADS)

During the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) in the Tropics, the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) in the Arctic, and the 2010 Small PARTicles In CirrUS (SPARTICUS) campaign in mid-latitudes, high-resolution images of ice crystals were recorded by a Cloud Particle Imager at temperatures (T) between -87 and 0 °C. The projected maximum dimension (D'), length (L'), and width (W') of pristine columns, plates, and component bullets of bullet rosettes were measured using newly developed software, the Ice Crystal Ruler. The number of bullets in each bullet rosette was also measured. Column crystals were further distinguished as either horizontally oriented columns or columns with other orientations to eliminate any orientation effect on the measured dimensions. Dimensions and aspect ratios (AR, dimension of major axis divided by dimension of minor axis) of crystals were determined as functions of temperature, geophysical location, and type of cirrus. Dimensions of crystals generally increased as temperature increased. Columns and bullets had larger dimensions (i.e., W') of the minor axis (i.e., a axis) for a given dimension (i.e., D' or L') of the major axis (i.e., c axis), and thus smaller AR, as T increased, whereas this trend did not occur for plate crystals. The average number of branches in bullet rosettes was 5.50±1.35 during three campaigns and 6.32±1.34 (5.46±1.34; 4.95±1.01) during TWP-ICE (SPARTICUS; ISDAC). The AR of bullets increased with the number of branches in bullet rosettes. Most dimensions of crystals and ARs of columnar crystals measured during SPARTICUS were larger than those measured during TWP-ICE and ISDAC at -67 < T < -35 °C and at -40 < T < -15 °C, respectively. The relative occurrence of varying pristine habits depended strongly on cirrus type (i.e., anvil or non-anvil clouds), with plates especially occurring more frequently in anvils. The L-W relationships of columns derived using current data exhibited a strong dependence on temperature; similar relationship determined in previous studies were within the range of the current data.

Um, J.; McFarquhar, G. M.; Hong, Y. P.; Lee, S.-S.; Jung, C. H.; Lawson, R. P.; Mo, Q.

2014-12-01

44

Increase in the energy density of the pinch plasma in 3D implosion of quasi-spherical wire arrays  

NASA Astrophysics Data System (ADS)

Results are presented from experimental studies of the characteristics of the soft X-ray (SXR) source formed in the implosion of quasi-spherical arrays made of tungsten wires and metalized kapron fibers. The experiments were carried out at the Angara-5-1 facility at currents of up to 3 MA. Analysis of the spatial distribution of hard X-ray emission with photon energies above 20 keV in the pinch images taken during the implosion of quasi-spherical tungsten wire arrays (QTWAs) showed that a compact quasi-spherical plasma object symmetric with respect to the array axis formed in the central region of the array. Using a diffraction grazing incidence spectrograph, spectra of SXR emission with wavelengths of 20-400 Å from the central, axial, and peripheral regions of the emission source were measured with spatial resolutions along the array radius and height in the implosion of QTWAs. It is shown that the emission spectra of the SXR sources formed under the implosion of quasi-spherical and cylindrical tungsten wire arrays at currents of up to 3 MA have a maximum in the wavelength range of 50-150 Å. It is found that, during the implosion of a QTWA with a profiled linear mass, a redistribution of energy in the emission spectrum takes place, which indicates that, during 3D implosion, the energy of longitudinal motion of the array material additionally contributes to the radiation energy. It is also found that, at close masses of the arrays and close values of the current in the range of 2.4-3 MA, the average energy density in the emission source formed during the implosion of a quasi-spherical wire array is larger by a factor of 7 than in the source formed during the implosion of a cylindrical wire array. The experimental data were compared with results of 3D simulations of plasma dynamics and radiation generation during the implosion of quasi-spherical wire arrays with a profiled mass by using the MARPLE-3D radiative magnetohydrodynamic code, developed at the Keldysh Institute of Applied Mathematics, Russian Academy of Sciences.

Aleksandrov, V. V.; Gasilov, V. A.; Grabovski, E. V.; Gritsuk, A. N.; Laukhin, Ya. N.; Mitrofanov, K. N.; Oleinik, G. M.; Ol'khovskaya, O. G.; Sasorov, P. V.; Smirnov, V. P.; Frolov, I. N.; Shevel'ko, A. P.

2014-12-01

45

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

46

Steady-state and stability analysis of a population balance based nonlinear ice cream crystallization model  

E-print Network

Steady-state and stability analysis of a population balance based nonlinear ice cream that adequately describes the key phenomena of the crystallization process. In ice cream crystallization, it is well known that the quality of the product, that is the hardness and the texture of the ice cream

Boyer, Edmond

47

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

48

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

49

Ice-Crystallization Kinetics during Fuel-Cell Cold-Start  

NASA Astrophysics Data System (ADS)

Proton-exchange-membrane fuel cells (PEMFCs) show promise in automotive applications because of their high efficiency, high power density, and potentially low emissions. To be successful in automobiles, PEMFCs must permit rapid startup with minimal energy from subfreezing temperatures, known as cold-start. In a PEMFC, reduction of oxygen to water occurs in the cathode catalyst layer (CL). Under subfreezing conditions, water generated during startup solidifies and hinders access of gaseous oxygen to the catalytic sites in the cathode CL, severely inhibiting cell performance and potentially causing cell failure. Achieving cold-start is difficult in practice, due to potential flooding, sluggish reaction kinetics, durability loss, and rapid ice crystallization. Currently, however, few studies focus on the fundamentals of ice crystallization during cold-start. Elucidation of the mechanisms and kinetics of ice formation within PEMFC porous media is, therefore, critical to successful cell startup and high performance at low temperatures. First, an experimental method is presented for obtaining isothermal ice-crystallization kinetics in water-saturated gas-diffusion layers (GDLs). Ice formation is initially studied in the GDL because this layer retains a significant amount of product water during cold-start. Isothermal ice-crystallization and ice-nucleation rates are obtained in commercial Toray GDLs as functions of subcooling using differential scanning calorimetry (DSC). A nonlinear ice-crystallization 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. Predicted ice-crystallization rates are in excellent agreement with experiment. A validated rate expression is thus available for predicting ice-crystallization kinetics in GDLs. Ice-crystallization kinetics is also considered under experimental settings similar to real PEMFC operating conditions where ice invariably forms non-isothermally. Non-isothermal ice-crystallization rates and ice-crystallization temperatures are obtained in water-saturated GDLs as a function of cooling rate. Our previously developed ice-crystallization rate expression is extended to non-isothermal crystallization to predict ice-crystallization kinetics at various cooling rates. For non-isothermal ice formation, we find that cooling rate has a negligible effect on the crystallization rate when crystallization times are much faster than the time to decrease the sample temperature by the subcooling. Therefore, a pseudo-isothermal method is proposed for non-isothermal crystallization kinetics using isothermal crystallization kinetics evaluated at the non-isothermal crystallization temperature. Catalyst layers also retain a significant amount of product water during cold-start. Accordingly, ice nucleation and growth in PEMFC CLs are investigated using isothermal DSC and compared to isothermal galvanostatic membrane-electrode assembly (MEA) cold-starts. Measured ice-crystallization and ice-nucleation rates follow expected trends from classical nucleation theory. Following our previous approach, a quantitative nonlinear ice-crystallization rate expression is developed from the JMAK framework. To validate ice-crystallization kinetics within PEMFCs, we further measure and predict MEA cell-failure time during isothermal galvanostatic cold-start. Using a simplified PEMFC isothermal cold-start continuum model, MEA cell-failure times predicted using the newly obtained rate expression are compared to that predicted using a traditional thermodynamics-based approach. From this comparison, conditions are identified under which including ice-crystallization kinetics is critical and to elucidate the impact of freezing kinetics on low-temperature PEMFC operation. During cold-start, the time for recovering cell performance strongly depends on the rate of melting residual ice by reactive heat generation. Non-isothermal ice melting in water-saturated GDLs is investigated using DSC with various he

Dursch, Thomas James, Jr.

50

Surface and bulk diffusion of HDO on ultrathin single-crystal ice multilayers on Ru(001)  

Microsoft Academic Search

The kinetics of HDO surface and bulk diffusion on ultrathin (25-192 BL; 90-700 Å) single-crystal H216O ice multilayers were studied using a combination of laser-induced thermal desorption (LITD) probing and isothermal desorption depth-profiling. The single-crystal hexagonal ice multilayers were grown epitaxially on a single-crystal Ru(001) metal substrate with the basal (001) facet of ice parallel to the Ru(001) surface. HDO

Frank E. Livingston; Galen C. Whipple; Steven M. George

1998-01-01

51

Surface and bulk diffusion of HDO on ultrathin single-crystal ice multilayers on Ru(001)  

Microsoft Academic Search

The kinetics of HDO surface and bulk diffusion on ultrathin (25–192 BL; 90–700 Å) single-crystal H216O ice multilayers were studied using a combination of laser-induced thermal desorption (LITD) probing and isothermal desorption depth-profiling. The single-crystal hexagonal ice multilayers were grown epitaxially on a single-crystal Ru(001) metal substrate with the basal (001) facet of ice parallel to the Ru(001) surface. HDO

Frank E. Livingston; Galen C. Whipple; Steven M. George

1998-01-01

52

Crystallization of Cubic Ice in Liquid Water and Aqueous Solutions  

Microsoft Academic Search

It is often assumed that the only natural phase of ice that forms on Earth is that of hexagonal ice (ice Ih). However, the rare observation of haloes around the sun at 28o and cloud particles of cubic habit indicates that the metastable crystalline form of ice, cubic ice (ice Ic), may form in Earth's atmosphere. The conditions used to

B. J. Murray; D. A. Knopf; A. K. Bertram

2004-01-01

53

Radar Sounding of Layering in Polar Ice Sheets: Possibilities and Limitations Considering the Dielectric Properties of Ice Crystals  

NASA Astrophysics Data System (ADS)

Radio frequency radar sounding is now an essential part of methodology to observe the ice sheets on polar continents. We can detect physical conditions within the several thousand meters thick ice sheets using proper platforms such as ground-based vehicles or airplanes. We can also extend information of ice-core data from a drilling point to wider regions of polar ice sheets. Ice sounding technique has its basis in the high-frequency dielectric properties of the target object, that is, ice and snow. In the past decade, new progress has appeared in understanding of the high-frequency electrical properties of water ice (Ih) through laboratory measurements. This progress consequently brought about significant progress in interpretation of the radar data from Antarctica. In particular, using multiple frequencies, we can distinguish reflections due to changes in dielectric permittivity and due to changes in electrical conductivity. Through this discrimination, we can deduce that what factor (density, impurity or crystal orientation fabrics) cause electromagnetic scattering. We introduce the physical principles of the ice-radar-data interpretation using actual data from a traverse line Dome F region to marginal area in Antarctica, and present knowledge of the dielectric properties of ice and its limitations. We mainly put stress on the knowledge of water ice and data from Antarctic ice sheet, considering application and extension of the knowledge to the Mars polar region.

Fujita, Shuji

2000-08-01

54

Long-term climatic changes indicated by crystal growth in polar ice  

Microsoft Academic Search

A new and independent way to obtain data on paleotemperatures from polar ice samples by using crystal size change profiles is proposed. From central Antarctica Dome C and Vostok ice cores data, it is suggested that crystal growth rate is mainly driven by a built-in 'memory' of the surface temperature conditions at the time of deposition. A semiempirical model of

J. R. Petit; P. Duval; C. Lorius

1987-01-01

55

Ice Crystal Concentration in Cumulus Clouds: Influence of the Drop Spectrum  

Microsoft Academic Search

Secondary ice crystals are thrown off when supercooled cloud drops are captured and freeze on a moving target in a cloud at -5 degrees C. The rate of production of these ice crystals is proportional to the rate of accretion of drops of diameter >= 24 micrometers.

S. C. Mossop; J. Hallett

1974-01-01

56

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

PubMed

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

2013-01-22

57

Modeling of Commercial Turbofan Engine With Ice Crystal Ingestion: Follow-On  

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 is 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. In a previous study, analysis of select PSL test data points helped to calibrate the engine icing computational tool to assess the risk of ice accretion. This current study is a continuation of that data analysis effort. The study focused on tracking the variations in wet bulb temperature and ice particle melt ratio through the engine core flow path. The results from this study have identified trends, while also identifying gaps in understanding as to how the local wet bulb temperature and melt ratio affects the risk of ice accretion and subsequent engine behavior.

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

2014-01-01

58

Demonstration of novel polarization lidar technique for identifying horizontally oriented ice crystals  

NASA Astrophysics Data System (ADS)

Ice crystals are known to horizontally orient in the atmosphere when drag forces overcome the randomizing effects of Brownian motion. Such ice crystals have been shown to have an impact on radiative transfer, reflecting a greater portion of incident sunlight than their randomly oriented counter parts. However, regular identification of oriented ice crystals in the atmosphere has proven challenging. Existing lidar techniques rely on detection of strong specular backscatter from oriented platelets. These measurements are not common to most lidar systems, and are in fact, frequently avoided because such strong specular signals generally overwhelm lidar detector systems designed for typical cloud and aerosol studies. When lidars are tilted to avoid these specular returns, the low polarization ratio observed in some clouds consisting of oriented ice crystals will cause researchers to incorrectly conclude they are composed of liquid water, thereby skewing cloud phase statistics and providing an incorrect estimate of the cloud's impact on radiative transfer. To address these problems, we apply a novel lidar configuration, which provides a unique polarization capability that detects oriented ice crystals. By tilting the lidar off zenith and performing three polarization measurements, diattenuation, a polarization attribute only exhibited by oriented ice crystals, can be measured. This allows us to disambiguate clouds consisting of oriented ice crystals and water. We present here some of the first measurements of diattenuation for detection of oriented ice crystals as performed by the CAPABL lidar system in Summit Camp, Greenland. This polarization technique avoids detecting the strong specular reflections commonly used to identify oriented ice crystals, allowing return signals from oriented crystals to remain in the same dynamic range as other clouds and aerosols. This feature makes it possible for CAPABL to perform accurate, high performance measurements of all clouds and aerosols, even when oriented crystals are present.

Hayman, M. M.; Thayer, J. P.; Neely, R. R.; O'Neill, M.; Stillwell, R.

2011-12-01

59

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

60

New metastable form of ice and its role in the homogeneous crystallization of water  

NASA Astrophysics Data System (ADS)

The homogeneous crystallization of water at low temperature is believed to occur through the direct nucleation of cubic (Ic) and hexagonal (Ih) ices. Here, we provide evidence from molecular simulations that the nucleation of ice proceeds through the formation of a new metastable phase, which we name Ice 0. We find that Ice 0 is structurally similar to the supercooled liquid, and that on growth it gradually converts into a stacking of Ice Ic and Ih. We suggest that this mechanism provides a thermodynamic explanation for the location and pressure dependence of the homogeneous nucleation temperature, and that Ice 0 controls the homogeneous nucleation of low-pressure ices, acting as a precursor to crystallization in accordance with Ostwald’s step rule of phases. Our findings show that metastable crystalline phases of water may play roles that have been largely overlooked.

Russo, John; Romano, Flavio; Tanaka, Hajime

2014-07-01

61

Effects of ice crystals on the FSSP measurements in mixed phase clouds  

NASA Astrophysics Data System (ADS)

In this paper, we show that in mixed phase clouds FSSP-100 measurements may be contaminated by ice crystals, inducing wrong interpretation of particle size and subsequent bulk parameters. This contamination is generally revealed by a bimodal feature of the particle size distribution; in other words, in mixed phase clouds bimodal features could be an indication of the presence of ice particles. The combined measurements of the FSSP-100 and the Polar Nephelometer give a coherent description of the effect of the ice crystals on the FSSP-100 response. The FSSP-100 particle size distributions are characterized by a bimodal shape with a second mode peaked between 25 and 35 ?m related to ice crystals. This feature is observed with the FSSP-100 at airspeed up to 200 m s-1 and with the FSSP-300 series. In order to assess the size calibration for clouds of ice crystals the response of the FSSP-100 probe has been numerically simulated using a light scattering model of randomly oriented hexagonal ice particles and assuming both smooth and rough crystal surfaces. The results suggest that the second mode measured between 25 ?m and 35 ?m, does not necessarily represent true size responses but likely corresponds to bigger aspherical ice particles. According to simulation results, the sizing understatement would be neglected in the rough case but would be major with the smooth case. Qualitatively, the Polar Nephelometer phase function suggests that the rough case is the more suitable to describe real crystals. Quantitatively, however, it is difficult to conclude. Previous cloud in situ measurements suggest that the FSSP-100 secondary mode, peaked in the range 25-35 ?m, is likely to be due to the shattering of large ice crystals on the probe tips. This finding is supported by the rather good relationship between the concentration of particles larger than 20 ?m (hypothesized to be ice shattered-fragments measured by the FSSP) and the concentration of (natural) ice particles larger than 100 ?m (CPI data). The shattering efficiency is defined as the ratio of the measured ice shattered-fragments to the number of natural ice particles (with d>100 ?m) impacting the probe leading edge. In the present study the shattering efficiency is evaluated to ~7%. It is found that about 400 ice fragments may result from the shattering of one equivalent irregular shaped ice crystal with a mean volume diameter of 310 ?m. Obviously, these values could be strongly dependent on the inlet design, the airspeed and the robustness of ice crystals via the impact kinetic energy to surface energy ratio providing the particle breakup.

Febvre, G.; Gayet, J.-F.; Shcherbakov, V.; Gourbeyre, C.; Jourdan, O.

2012-03-01

62

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

63

On the importance of small ice crystals in tropical anvil cirrus  

Microsoft Academic Search

In situ measurements of ice crystal concentrations and sizes made with aircraft instrumentation over the past two decades have often indicated the presence of numerous relatively small (< 50 mum diameter) crystals in cirrus clouds. Further, these measurements frequently indicate that small crystals account for a large fraction of the extinction in cirrus clouds. The fact that the instruments used

E. J. Jensen; P. Lawson; B. Baker; B. Pilson; Q. Mo; A. J. Heymsfield; A. Bansemer; T. P. Bui; M. McGill; D. Hlavka; G. Heymsfield; S. Platnick; G. T. Arnold; S. Tanelli

2009-01-01

64

Synthesis, characterization and photocatalytic activity of annealing dependent quasi spherical and capsule like ZnO nanostructures  

NASA Astrophysics Data System (ADS)

Quasi spherical and capsule like ZnO nanostructures have been successfully synthesized via a simple precipitation route without the assistance of external capping agents. The effect of annealing temperature on the properties of ZnO was investigated. In all cases, hexagonal wurtzite crystalline structure of phase pure ZnO was obtained. The crystallinity was found to be gradually increasing with annealing temperature. At low annealing temperatures, more or less spherical ZnO nanoparticles were clearly observed, whereas they tend to grow as nanocapsules with increasing the annealing temperature. The formation of single crystalline nanocapsules was observed at 600 °C. The photoluminescence spectra indicated the annealing dependent emission features, especially in the spectral intensity. The dye pollutant methylene blue was found to be completely degraded under UV light irradiation over the ZnO nano photocatalysts. The highest photoactivity was shown by nanocapsules obtained at 600 °C and was found to be highly reusable.

Pudukudy, Manoj; Hetieqa, Ain; Yaakob, Zahira

2014-11-01

65

Some effects of ice crystals on the FSSP measurements in mixed phase clouds  

NASA Astrophysics Data System (ADS)

In this paper, we show that in mixed phase clouds, the presence of ice crystals may induce wrong FSSP 100 measurements interpretation especially in terms of particle size and subsequent bulk parameters. The presence of ice crystals is generally revealed by a bimodal feature of the particle size distribution (PSD). The combined measurements of the FSSP-100 and the Polar Nephelometer give a coherent description of the effect of the ice crystals on the FSSP-100 response. The FSSP-100 particle size distributions are characterized by a bimodal shape with a second mode peaked between 25 and 35 ?m related to ice crystals. This feature is observed with the FSSP-100 at airspeed up to 200 m s-1 and with the FSSP-300 series. In order to assess the size calibration for clouds of ice crystals the response of the FSSP-100 probe has been numerically simulated using a light scattering model of randomly oriented hexagonal ice particles and assuming both smooth and rough crystal surfaces. The results suggest that the second mode, measured between 25 ?m and 35 ?m, does not necessarily represent true size responses but corresponds to bigger aspherical ice particles. According to simulation results, the sizing understatement would be neglected in the rough case but would be significant with the smooth case. Qualitatively, the Polar Nephelometer phase function suggests that the rough case is the more suitable to describe real crystals. Quantitatively, however, it is difficult to conclude. A review is made to explore different hypotheses explaining the occurrence of the second mode. However, previous cloud in situ measurements suggest that the FSSP-100 secondary mode, peaked in the range 25-35 ?m, is likely to be due to the shattering of large ice crystals on the probe inlet. This finding is supported by the rather good relationship between the concentration of particles larger than 20 ?m (hypothesized to be ice shattered-fragments measured by the FSSP) and the concentration of (natural) ice particles (CPI data). In mixed cloud, a simple estimation of the number of ice crystals impacting the FSSP inlet shows that the ice crystal shattering effect is the main factor in observed ice production.

Febvre, G.; Gayet, J.-F.; Shcherbakov, V.; Gourbeyre, C.; Jourdan, O.

2012-10-01

66

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

67

Preferred Ice Crystal Orientation Fabric Measurements within the Greenland Ice Sheet Using Multi-Polarization Radar Data  

NASA Astrophysics Data System (ADS)

Discharge of ice from the Greenland Ice Sheet to the ocean has increased significantly over the last 25 years due to the acceleration of important outlet glaciers. It was reported that the Greenland Ice Sheet contributed about 2.5 m out of about 6 m of sea-level rise during the Eemian interglacial period. The temperatures during Eemian were reported to be about 8o×4o C higher than the mean of the past millennium. Laboratory measurements have shown that glacial ice, characterized by preferred crystal orientation fabric (COF), is three times more deformable than ice with randomly oriented crystalline structures. Layers characterized by preferred ice COF can influence the flow behavior of a glacier or ice sheet. However, COF measurements are typically obtained from ice cores, and thus are very spatially limited and mostly constrained to areas with little ice flow. A more efficient technique to map the extent of ice fabric over larger regions of ice sheets is needed to better understand the effects on large scale ice flow processes. Radar measurements are capable of discriminating between reflections caused by changes in density, electrical permittivity and COF by exploiting the anisotropic and birefringent properties of ice crystals. For this investigation two radar datasets were collected during the survey of the Greenland Eemian Ice Drilling Site (77.45°N 51.06°W) in August 2008, using a ground-based and chirped-pulse Multi-Channel Radar Depth Sounder (MCRDS) developed by the Center for Remote Sensing of Ice Sheets (CReSIS). The radar used two transmit and eight receive antennas at the center frequency of 150 MHz with a bandwidth of 30 MHz. The first data set consisted of polarimatric measurements acquired in a circular pattern (radius: 35 m) with two co-polarized antenna orientations (one transmitter and four receivers oriented with 90° offsets in the directions of the incident H-Field and E-Field, respectively). Analysis of the circular data shows a periodic power variation with four distinct extinction patterns occurring at 90 degree intervals starting at approximately 700 m depth. Furthermore a 20 degree phase change is observed between the E- and H-field data. Both observations suggest that approximately 72% of the 2542m ice column exhibits birefringent anisotropy caused by preferred ice crystal orientation. The second dataset was acquired in a grid pattern consisting of twenty 10-Km 2D lines (NW to SE) spaced at 0.5-Km and three 10-Km lines (NE to SW) spaced at 2.5-Km. Both transmit and eight receive antenna were oriented parallel to the vehicle track, resulting in E-Field co-polarized data. We will determine the dominant COF relative to the ice divide for a 100 square Km region around the NEEM camp using the results from both datasets. The results of this investigation will be compared to the NEEM ice core observations to determine the accuracy of the analysis. In this investigation we will provide a brief overview of the system and experiments and present the results of data analysis.

Velez-Gonzalez, J. A.; JiLu, L.; Leuschen, C.; Gogineni, P.; Van der Veen, C. J.; Tsoflias, G. P.; Drews, R.; Harish, A. R.

2013-12-01

68

Average ice crystal size and bulk short-wave single-scattering properties of cirrus clouds  

Microsoft Academic Search

The bulk single-scattering properties of cirrus clouds required for driving the radiation scheme in large-scale climate models are computed with respect to various size distributions and ice crystal shapes. It is shown that the average ice crystal size, defined as the ratio of total volume to the total projected area, can well-characterize the effect of various size distributions in determining

Klaus Wyser; Ping Yang

1998-01-01

69

A Theoretical Determination of the Capture Efficiency of Small Columnar Ice Crystals by Large Cloud Drops  

Microsoft Academic Search

A theoretical model has been formulated to study by numerical techniques the efficiency E with which columnar ice crystals grown at temperatures between 3 and 8°C are captured in a cloud by relatively large, supercooled cloud drops. The ice crystals studied had lengths L of 15 L 240 m and diameters D of 1.5 D 240 m. and L\\/D values

Jeffrey K. Lew; Hans R. Pruppacher

1983-01-01

70

Trapping of trace gases in growing ice crystals  

Microsoft Academic Search

An analytical model describing the combined effect of mass accomodation and net adsorption of trace gases on the surfaces of growing ice particles (trapping) is developed. An approximate solution for the release of trapped trace gases from evaporating ice particles is also given. The model fully accounts for the fact that atmospheric ice particles frequently experience substantial subsaturations and supersaturations.

B. Kärcher; M. M. Basko

2004-01-01

71

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

72

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

73

The Ice Selective Inlet: a novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds  

NASA Astrophysics Data System (ADS)

Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol-cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs) via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of supercooled liquid droplets. The Ice Selective Inlet (ISI), presented in this paper, is a novel inlet designed to selectively sample pristine ice crystals in mixed-phase clouds and extract the ice residual particles contained within the crystals for physical and chemical characterisation. Using a modular setup composed of a cyclone impactor, droplet evaporation unit and pumped counterflow virtual impactor (PCVI), the ISI segregates particles based on their inertia and phase, exclusively extracting small ice particles between 5 and 20 ?m in diameter. The setup also includes optical particle spectrometers for analysis of the number size distribution and shape of the sampled hydrometeors. The novelty of the ISI is a droplet evaporation unit, which separates liquid droplets and ice crystals in the airborne state, thus avoiding physical impaction of the hydrometeors and limiting potential artifacts. The design and validation of the droplet evaporation unit is based on modelling studies of droplet evaporation rates and computational fluid dynamics simulations of gas and particle flows through the unit. Prior to deployment in the field, an inter-comparison of the WELAS optical particle size spectrometers and a characterisation of the transmission efficiency of the PCVI was conducted in the laboratory. The ISI was subsequently deployed during the Cloud and Aerosol Characterisation Experiment (CLACE) 2013 - an extensive international field campaign encompassing comprehensive measurements of cloud microphysics, as well as bulk aerosol, ice residual and ice nuclei properties. The campaign provided an important opportunity for a proof of concept of the inlet design. In this work we present the setup of the ISI, including the modelling and laboratory characterisation of its components, as well as a case study demonstrating the ISI performance in the field during CLACE 2013.

Kupiszewski, P.; Weingartner, E.; Vochezer, P.; Bigi, A.; Rosati, B.; Gysel, M.; Schnaiter, M.; Baltensperger, U.

2014-12-01

74

Technical Note: Formation of airborne ice crystals in a wall independent reactor (WIR) under atmospheric conditions  

NASA Astrophysics Data System (ADS)

Both, gas and particle scavenging contribute to the transport of organic compounds by ice crystals in the troposphere. To simulate these processes an experimental setup was developed to form airborne ice crystals under atmospheric conditions. Experiments were performed in a wall independent reactor (WIR) installed in a walk-in cold chamber maintained constantly at -20°C. Aerosol particles were added to the carrier gas of ambient air by an aerosol generator to allow heterogeneous ice formation. Temperature variations and hydrodynamic conditions of the WIR were investigated to determine the conditions for ice crystal formation and crystal growth by vapour deposition. In detail, the dependence of temperature variations from flow rate and temperature of the physical wall as well as temperature variations with an increasing reactor depth were studied. The conditions to provide a stable aerosol concentration in the carrier gas flow were also studied. The temperature distribution inside the reactor was strongly dependent on flow rate and physical wall temperature. At an inlet temperature of -20°C, a flow rate of 30 L•min-1 and a physical wall temperature of +5°C turned out to provide ideal conditions for ice formation. At these conditions a sharp and stable laminar down draft "jet stream" of cold air in the centre of the reactor was produced. Temperatures measured at the chamber outlet were kept well below the freezing point in the whole reactor depth of 1.0 m. Thus, melting did not affect ice formation and crystal growth. The maximum residence time for airborne ice crystals was calculated to at 40 s. Ice crystal growth rates increased also with increasing reactor depth. The maximum ice crystal growth rate was calculated at 2.82 mg• s-1. Further, the removal efficiency of the cleaning device for aerosol particles was 99.8% after 10 min. A reliable particle supply was attained after a preliminary lead time of 15 min. Thus, the minimum lead time was determined at 25 min. Several test runs revealed that the WIR is suitable to perform experiments with airborne ice crystals.

Fries, E.; Haunold, W.; Starokozhev, E.; Palitzsch, K.; Sitals, R.; Jaeschke, W.; Püttmann, W.

2008-07-01

75

An experimental study of the ice column habit transitions. [crystal growth in atmosphere  

NASA Technical Reports Server (NTRS)

The influence of supersaturation on column growth of ice crystals forming from atmospheric water vapor was investigated. A high density of crystals was generated on a glass fiber cooled by liquid N2 in a thermal diffusion chamber. Attention was focused on a neighbor-free hollow prism during a stepwise decrease in supersaturation while the crystal temperature was maintained constant. Another experiment involved epitaxial growth of ice crystals on CuS, where nonthickening crystals could only be grown below -7 C. A critical supersaturation was found to be necessary for growth of the basal plane. Beyound the critical value, surface kinetics do not control the growth rate, which is then dominated by the penetration of water molecules through the diffusion field surrounding the crystal.

Cho, N.; Hallett, J.

1982-01-01

76

Effects of impurities and their redistribution during recrystallization of ice crystals  

NASA Astrophysics Data System (ADS)

In order to examine the effects of solutes on recrystallization and subsequent grain growth in ice, both doped and undoped ice single crystals were extruded through a 120° equal-channel angular extrusion jig, in order to impart a large shear strain (˜1.15). Upon subsequent annealing at -3°C, the original single crystals recrystallized, in most cases to a new single crystal with a different orientation. Increasing the solute concentration (for H2SO4 to ˜200-300 ppb, and for NaCl, KCl and MgSO4 to >5 ppm) was found to significantly retard the growth and possibly, for H2SO4-doped ice, the nucleation of new grains in the strained ice single crystals. This is indicative of how soluble impurities can retard grain growth in ice cores. It was also found that the migrating grain boundaries surrounding the newly formed grains contained large concentrations of impurities, often observed as filaments. These could have formed by the grain boundaries sweeping up impurities from the lattice into the boundary or by their diffusion to the boundary - mechanisms whereby impurities could be concentrated into the grain boundaries in ice cores - although the latter mechanism seems unlikely since it would require very high diffusion rates.

Iliescu, D.; Baker, I.

77

The capacitance of pristine ice crystals and aggregate snowflakes  

E-print Network

A new method of accurately calculating the capacitance of realistic ice particles is described: such values are key to accurate estimates of sublimation rates in numerical weather models. We have directly simulated the trajectories of diffusing water molecules, using random `walkers'. By counting how many of these trajectories intersect the surface of the ice particle (which may be any shape) and how many escape outside a spherical boundary far from the particle, we have estimated the capacitance of a number of model ice particle habits including hexagonal columns and plates, `scalene' columns and plates, bullets, bullet-rosettes, dendrites, and realistic aggregate snowflakes. For ice particles with sharp edges and corners this method is an efficient and straightforward way of solving Laplace's equation for the capacitance. Provided that a large enough number of random walkers are used to sample the particle geometry ($\\sim10^4$) we expect the calculated capacitances to be accurate to within $\\sim1%$. The cap...

Westbrook, C D; Illingworth, A J

2006-01-01

78

Phase transition of the hydrogen-bonded crystals and ice  

Microsoft Academic Search

The order–disorder phase transition for KH2PO4 (KDP) and ice VIII is studied in terms of the dipole–hydrogen coupling model. The effective interactions between hydrogens are obtained by averaging out the dipole’s degrees of freedom. It is found that the bonding energy of ice VIII obtained in the present theory compares with the hydrogen bond energy determined by Whalley. The isotope

Katsuhiko Fujii

1995-01-01

79

The capacitance of pristine ice crystals and aggregate snowflakes  

Microsoft Academic Search

A new method of accurately calculating the capacitance of realistic ice\\u000aparticles is described: such values are key to accurate estimates of deposition\\u000aand evaporation rates in NWP models. The trajectories of diffusing water\\u000amolecules are directly sampled, using random `walkers'. By counting how many of\\u000athese trajectories intersect the surface of the ice particle (which may be any\\u000ashape)

Christopher David Westbrook; Robin J. Hogan; Anthony J. Illingworth

2006-01-01

80

Snow crystal imaging using scanning electron microscopy: III. Glacier ice, snow and biota  

USGS Publications Warehouse

Low-temperature scanning electron microscopy (SEM) was used to observe metamorphosed snow, glacial firn, and glacial ice obtained from South Cascade Glacier in Washington State, USA. Biotic samples consisting of algae (Chlamydomonas nivalis) and ice worms (a species of oligochaetes) were also collected and imaged. In the field, the snow and biological samples were mounted on copper plates, cooled in liquid nitrogen, and stored in dry shipping containers which maintain a temperature of -196??C. The firn and glacier ice samples were obtained by extracting horizontal ice cores, 8 mm in diameter, at different levels from larger standard glaciological (vertical) ice cores 7.5 cm in diameter. These samples were cooled in liquid nitrogen and placed in cryotubes, were stored in the same dry shipping container, and sent to the SEM facility. In the laboratory, the samples were sputter coated with platinum and imaged by a low-temperature SEM. To image the firn and glacier ice samples, the cores were fractured in liquid nitrogen, attached to a specimen holder, and then imaged. While light microscope images of snow and ice are difficult to interpret because of internal reflection and refraction, the SEM images provide a clear and unique view of the surface of the samples because they are generated from electrons emitted or reflected only from the surface of the sample. In addition, the SEM has a great depth of field with a wide range of magnifying capabilities. The resulting images clearly show the individual grains of the seasonal snowpack and the bonding between the snow grains. Images of firn show individual ice crystals, the bonding between the crystals, and connected air spaces. Images of glacier ice show a crystal structure on a scale of 1-2 mm which is considerably smaller than the expected crystal size. Microscopic air bubbles, less than 15 ??m in diameter, clearly marked the boundaries between these crystal-like features. The life forms associated with the glacier were easily imaged and studied. The low-temperature SEM sample collecting and handling methods proved to be operable in the field; the SEM analysis is applicable to glaciological studies and reveals details unattainable by conventional light microscopic methods.Low temperature scanning electron microscopy (SEM) was used to observe metamorphosed snow, glacial firn, and glacial ice obtained from South Cascade Glacier in Washington State, USA. Biotic samples consisting of algae and ice worms were also collected and imaged. The SEM images provide a clear and unique view of the surface of the samples because they are generated from electrons emitted or reflected only from the surface of the sample. The SEM has a great depth of field with a wide range of magnifying capabilities.

Rango, A.; Wergin, W.P.; Erbe, E.F.; Josberger, E.G.

2000-01-01

81

Dynamic pressure-induced dendritic and shock crystal growth of ice VI  

PubMed Central

Crystal growth mechanisms are crucial to understanding the complexity of crystal morphologies in nature and advanced technological materials, such as the faceting and dendrites found in snowflakes and the microstructure and associated strength properties of structural and icy planetary materials. In this article, we present observations of pressure-induced ice VI crystal growth, which have been predicted theoretically, but had never been observed experimentally to our knowledge. Under modulated pressure conditions in a dynamic-diamond anvil cell, rough single ice VI crystal initially grows into well defined octahedral crystal facets. However, as the compression rate increases, the crystal surface dramatically changes from rough to facet, and from convex to concave because of a surface instability, and thereby the growth rate suddenly increases by an order of magnitude. Depending on the compression rate, this discontinuous jump in crystal growth rate or “shock crystal growth” eventually produces 2D carpet-type fractal morphology, and moreover dendrites form under sinusoidal compression, whose crystal morphologies are remarkably similar to those predicted in theoretical simulations under a temperature gradient field. The observed strong dependence of the growth mechanism on compression rate, therefore, suggests a different approach to developing a comprehensive understanding of crystal growth dynamics. PMID:17296943

Lee, Geun Woo; Evans, William J.; Yoo, Choong-Shik

2007-01-01

82

Influence of snow and ice crystal formation and accumulation on mercury deposition to the Arctic.  

PubMed

Mercury is deposited to the Polar Regions during springtime atmospheric mercury depletion events (AMDEs) but the relationship between snow and ice crystal formation and mercury deposition is not well understood. The objective of this investigation was to determine if mercury concentrations were related to the type and formation of snow and ice crystals. On the basis of almost three hundred analyses of samples collected in the Alaskan Arctic, we suggestthat kinetic crystals growing from the vapor phase, including surface hoar, frost flowers, and diamond dust, yield mercury concentrations that are typically 2-10 times higher than that reported for snow deposited during AMDEs (approximately 80 ng/L). Our results show that the crystal type and formation affect the mercury concentration in any given snow sample far more than the AMDE activity prior to snow collection. We present a conceptual model of how snow grain processes including deposition, condensation, reemission, sublimation, and turbulent diffusive uptake influence mercury concentrations in snow and ice. These processes are time dependent and operate collectively to affect the retention and fate of mercury in the cryosphere. The model highlights the importance of the formation and postdeposition crystallographic history of snow or ice crystals in determining the fate and concentration of mercury in the cryosphere. PMID:18441801

Douglas, Thomas A; Sturm, Matthew; Simpson, William R; Blum, Joel D; Alvarez-Aviles, Laura; Keeler, Gerald J; Perovich, Donald K; Biswas, Abir; Johnson, Kelsey

2008-03-01

83

Crystal structure of an insect antifreeze protein and its implications for ice binding.  

PubMed

Antifreeze proteins (AFPs) help some organisms resist freezing by binding to ice crystals and inhibiting their growth. The molecular basis for how these proteins recognize and bind ice is not well understood. The longhorn beetle Rhagium inquisitor can supercool to below -25 °C, in part by synthesizing the most potent antifreeze protein studied thus far (RiAFP). We report the crystal structure of the 13-kDa RiAFP, determined at 1.21 ? resolution using direct methods. The structure, which contains 1,914 nonhydrogen protein atoms in the asymmetric unit, is the largest determined ab initio without heavy atoms. It reveals a compressed ?-solenoid fold in which the top and bottom sheets are held together by a silk-like interdigitation of short side chains. RiAFP is perhaps the most regular structure yet observed. It is a second independently evolved AFP type in beetles. The two beetle AFPs have in common an extremely flat ice-binding surface comprising regular outward-projecting parallel arrays of threonine residues. The more active, wider RiAFP has four (rather than two) of these arrays between which the crystal structure shows the presence of ice-like waters. Molecular dynamics simulations independently reproduce the locations of these ordered crystallographic waters and predict additional waters that together provide an extensive view of the AFP interaction with ice. By matching several planes of hexagonal ice, these waters may help freeze the AFP to the ice surface, thus providing the molecular basis of ice binding. PMID:23486477

Hakim, Aaron; Nguyen, Jennifer B; Basu, Koli; Zhu, Darren F; Thakral, Durga; Davies, Peter L; Isaacs, Farren J; Modis, Yorgo; Meng, Wuyi

2013-04-26

84

Crystal Structure of an Insect Antifreeze Protein and Its Implications for Ice Binding*  

PubMed Central

Antifreeze proteins (AFPs) help some organisms resist freezing by binding to ice crystals and inhibiting their growth. The molecular basis for how these proteins recognize and bind ice is not well understood. The longhorn beetle Rhagium inquisitor can supercool to below ?25 °C, in part by synthesizing the most potent antifreeze protein studied thus far (RiAFP). We report the crystal structure of the 13-kDa RiAFP, determined at 1.21 ? resolution using direct methods. The structure, which contains 1,914 nonhydrogen protein atoms in the asymmetric unit, is the largest determined ab initio without heavy atoms. It reveals a compressed ?-solenoid fold in which the top and bottom sheets are held together by a silk-like interdigitation of short side chains. RiAFP is perhaps the most regular structure yet observed. It is a second independently evolved AFP type in beetles. The two beetle AFPs have in common an extremely flat ice-binding surface comprising regular outward-projecting parallel arrays of threonine residues. The more active, wider RiAFP has four (rather than two) of these arrays between which the crystal structure shows the presence of ice-like waters. Molecular dynamics simulations independently reproduce the locations of these ordered crystallographic waters and predict additional waters that together provide an extensive view of the AFP interaction with ice. By matching several planes of hexagonal ice, these waters may help freeze the AFP to the ice surface, thus providing the molecular basis of ice binding. PMID:23486477

Hakim, Aaron; Nguyen, Jennifer B.; Basu, Koli; Zhu, Darren F.; Thakral, Durga; Davies, Peter L.; Isaacs, Farren J.; Modis, Yorgo; Meng, Wuyi

2013-01-01

85

Influence of air velocity on the habit of ice crystal growth from the vapor  

NASA Technical Reports Server (NTRS)

The effect of air velocity on the growth behavior of ice crystals growing from water vapor was investigated at temperatures between 0 and -35 C and at supersaturation levels ranging from 2 to 40 percent, using a laboratory chamber in which it was possible to make these variations. It was found that crystal growth was most sensitive to changes in the air velocity at temperatures near -4 C and -15 C where, near water saturation, the introduction of only a 5 cm/s air velocity induced skeletal transitions (columns to needles near -4 C and plates to dendrites near -15 C). The experiments provide conditions which simulate growth of ice crystals in the atmosphere, where crystal growth takes place at or somewhat below water saturation.

Keller, V. W.; Hallett, J.

1982-01-01

86

Best face forward: crystal-face competition at the ice-water interface.  

PubMed

The ice-water interface plays an important role in determining the outcome of both biological and environmental processes. Under ambient pressure, the most stable form of ice is hexagonal ice (Ih). Experimentally probing the surface free energy between each of the major faces of Ih ice and the liquid is both experimentally and theoretically challenging. The basis for the challenge is the near-equality of the surface free energy for the major faces along with the tendency of water to supercool. As a result, morphology from crystallization initiated below 0 °C is kinetically controlled. The reported work circumvents supercooling consequences by providing a polycrystalline seed, followed by isothermal, equilibrium growth. Natural selection among seeded faces results in a single crystal. A record of the growth front is preserved in the frozen boule. Crystal orientation at the front is revealed by examining the boule cross section with two techniques: (1) viewing between crossed polarizers to locate the optical axis and (2) etching to distinguish the primary-prism face from the secondary-prism face. Results suggest that the most stable ice-water interface at 0 °C is the secondary-prism face, followed by the primary-prism face. The basal face that imparts the characteristic hexagonal shape to snowflakes is a distant third. The results contrast with those from freezing the vapor where the basal and primary-prism faces have comparable free energy followed by the secondary-prism face. PMID:24784996

Shultz, Mary Jane; Bisson, Patrick J; Brumberg, Alexandra

2014-07-17

87

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

88

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

E-print Network

Radiative influences on ice crystal and droplet growth within mixed-phase stratus clouds Z. J. Lebo and droplet growth within mixed-phase stratus clouds, J. Geophys. Res., 113, D09203, doi:10.1029/2007JD009262-tropospheric levels in the sub-Arctic and Arctic (Arctic stratus and stratocumulus, [e.g., Curry et al., 1996

Johnson, Nat

89

An Investigation of Light Scattering by Irregular Ice Crystals via PSTD  

E-print Network

generated from different power functions.(a) P (k) = 1/k2 (b) P (k) = 1/k4 (c) Write noise: P (k) = 1 (d)Gaussian type power function: P (k) = e?(k/?k) 2 . . . . . . . . . . . . . . . . . 19 3.2 Hexagonal ice plate... Hexagonal Mono-crystal model iv TABLE OF CONTENTS Page ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii NOMENCLATURE...

Zhang, Jianing

2014-07-28

90

Kinetics of conversion of air bubbles to air hydrate crystals in antarctic ice.  

PubMed

The depth dependence of bubble concentration at pressures above the transition to the air hydrate phase and the optical scattering length due to bubbles in deep ice at the South Pole are modeled with diffusion-growth data from the laboratory, taking into account the dependence of age and temperature on depth in the ice. The model fits the available data on bubbles in cores from Vostok and Byrd and on scattering length in deep ice at the South Pole. It explains why bubbles and air hydrate crystals coexist in deep ice over a range of depths as great as 800 meters and predicts that at depths below approximately 1400 meters the AMANDA neutrino observatory at the South Pole will operate unimpaired by light scattering from bubbles. PMID:17775808

Price, P B

1995-03-24

91

Modeling variability in dendritic ice crystal backscattering cross sections at millimeter wavelengths using a modified Rayleigh-Gans theory  

NASA Astrophysics Data System (ADS)

Using the Generalized Multi-particle Mie-method (GMM), Botta et al. (in this issue) [7] created a database of backscattering cross sections for 412 different ice crystal dendrites at X-, Ka- and W-band wavelengths for different incident angles. The Rayleigh-Gans theory, which accounts for interference effects but ignores interactions between different parts of an ice crystal, explains much, but not all, of the variability in the database of backscattering cross sections. Differences between it and the GMM range from -3.5 dB to +2.5 dB and are highly dependent on the incident angle. To explain the residual variability a physically intuitive iterative method was developed to estimate the internal electric field within an ice crystal that accounts for interactions between the neighboring regions within it. After modifying the Rayleigh-Gans theory using this estimated internal electric field, the difference between the estimated backscattering cross sections and those from the GMM method decreased to within 0.5 dB for most of the ice crystals. The largest percentage differences occur when the form factor from the Rayleigh-Gans theory is close to zero. Both interference effects and neighbor interactions are sensitive to the morphology of ice crystals. Improvements in ice-microphysical models are necessary to predict or diagnose internal structures within ice crystals to aid in more accurate interpretation of radar returns. Observations of the morphology of ice crystals are, in turn, necessary to guide the development of such ice-microphysical models and to better understand the statistical properties of ice crystal morphologies in different environmental conditions.

Lu, Yinghui; Clothiaux, Eugene E.; Aydin, Kültegin; Botta, Giovanni; Verlinde, Johannes

2013-12-01

92

High-strain-rate deformation of armco iron induced by spherical and quasi-spherical converging shock waves and the mechanism of the ?-? transformation  

NASA Astrophysics Data System (ADS)

The structures of two balls made of plain commercial-purity iron and subjected to loading by spherical and quasi-spherical converging shock waves are studied by optical microscopy and transmission electron microscopy at various depths. The high-strain-rate plastic deformation of armco iron under the loading conditions is found to occur via slip, and, in medium and deep layers, it also occurs via the formation of localized deformation bands. An atomic-crystallographic mechanism for the lattice restructuring during the ?-? transformation is proposed.

Dobromyslov, A. V.; Kozlov, E. A.; Taluts, N. I.

2008-11-01

93

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

94

Formation of Large (Approximately 100 micrometers) Ice Crystals Near the Tropical Tropopause  

NASA Technical Reports Server (NTRS)

Recent high-altitude aircraft measurements with in situ imaging instruments indicated the presence of relatively large (approx.100 microns length), thin (aspect ratios of approx.6:1 or larger) hexagonal plate ice crystals near the tropical tropopause in very low concentrations (<0.01/L). These crystals were not produced by deep convection or aggregation. We use simple growth-sedimentation calculations as well as detailed cloud simulations to evaluate the conditions required to grow the large crystals. Uncertainties in crystal aspect ratio leave a range of possibilities, which could be constrained by knowledge of the water vapor concentration in the air where the crystal growth occurred. Unfortunately, water vapor measurements made in the cloud formation region near the tropopause with different instruments ranged from <2 ppmv to approx.3.5 ppmv. The higher water vapor concentrations correspond to very large ice supersaturations (relative humidities with respect to ice of about 200%). If the aspect ratios of the hexagonal plate crystals are as small as the image analysis suggests (6:1, see companion paper (Lawson et al., 2008)) then growth of the large crystals before they sediment out of the supersaturated layer would only be possible if the water vapor concentration were on the high end of the range indicated by the different measurements (>3 ppmv). On the other hand, if the crystal aspect ratios are quite a bit larger (approx.10:1), then H2O concentrations toward the low end of the measurement range (approx.2-2.5 ppmv) would suffice to grow the large crystals. Gravity-wave driven temperature and vertical wind perturbations only slightly modify the H2O concentrations needed to grow the crystals. We find that it would not be possible to grow the large crystals with water concentrations less than 2 ppmv, even with assumptions of a very high aspect ratio of 15 and steady upward motion of 2 cm/s to loft the crystals in the tropopause region. These calculations would seem to imply that the measurements indicating water vapor concentrations less than 2ppmv are implausible, but we cannot rule out the possibility that higher humidity prevailed upstream of the aircraft measurements and the air was dehydrated by the cloud formation. Simulations of the cloud formation with a detailed model indicate that homogeneous freezing should generate ice concentrations larger than the observed concentrations (20/L), and even concentrations as low as 20/L should have depleted the vapor in excess of saturation and prevented growth of large crystals. It seems likely that the large crystals resulted from ice nucleation on effective heterogeneous nuclei at low ice supersaturations. Improvements in our understanding of detailed cloud microphysical processes require resolution of the water vapor measurement discrepancies in these very cold, dry regions of the atmosphere.

Jensen, E. J.; Pfister, L.; Bui, T. V.; Lawson, P.; Baker, B.; Mo, Q.; Baumgardner, D.; Weinstock, E. M.; Smith, J. B.; Moyer, E. J.; Hanisco, T. F.; Sayres, D. S.; SaintClair, J. M.; Alexander, M.; Toon, O. B.; Smith, J. A.

2008-01-01

95

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

96

Size and location of ice crystals in pork frozen by high-pressure-assisted freezing as compared to classical methods  

Microsoft Academic Search

In high-pressure-assisted freezing, samples are cooled under pressure (200 MPa) to ? 20 °C without ice formation then pressure is released (0.1 MPa) and the high super-cooling reached (approx. 20 °C), promotes uniform and rapid ice nucleation. The size and location of ice crystals in large meat pieces (Longissimus dorsi pork muscle) as a result of high-pressure-assisted freezing were compared

M. N. Martino; L. Otero; P. D. Sanz; N. E. Zaritzky

1998-01-01

97

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

98

Charge Transfer Process During Collision of Riming Graupel Pellet with Small Ice Crystals within a Thundercloud  

NASA Technical Reports Server (NTRS)

A charge transfer process during the collision of a riming graupel pellet and an ice-crystal at low temperature is proposed. During riming, the surface structure of graupel deviates from perfect crystalline structure. A concept of quasi-solid layer (QSL) formation on the surface is introduced. This QSL contains defects formed during riming. In absence of impurities, positively charged X-defect abundance is considered in the outer layer. These defects are assumed to be the charge carriers during the charge transfer process. Some part of the QSL is stripped off by the colliding ice crystals, which thereby gain some positive charge, leaving the graupel pellet negatively charged. With the proposed model, fC to pC of charge transfer is observed per collision. A transition temperature between -10 C to -15 C is also noted beyond which the QSL concept does not hold. This transition temperature is dependent on the bulk liquid water content of the cloud.

Datta, Saswati; De, Utpal K.; Goswami, K.; Jones, Linwood

1999-01-01

99

Sea Ice  

NSDL National Science Digital Library

In this resource, students will discover that there are notable differences between sea ice and fresh-water ice, such as density. In on segment, students learn that the first sign of freezing on the sea is an oily appearance of the water caused by the formation of needle-like crystals. The site explains the relationship between growth and the rate at which heat flows from the water and that the ice pack can alter its shape and dimension due to the movement of winds, currents, thermal expansion, and contraction of the ice. Types of ice described here include new ice, nilas, young ice, first-year ice, and old ice while the forms of ice covered include pancake ice, brash ice, ice cake, floe, and fast ice. The site also explains the meteorological and oceanographic factors that control the amount and movement of ice.

100

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

101

Ice  

NSDL National Science Digital Library

When a chunk of ice "twice the size of Manhattan" broke away from the northernmost part of the Antarctic Peninsula in February, ice was at the forefront of scientific news. Now, with the spectacular discovery of bacteria in Antarctic ice and with new evidence of slush beneath the frozen surface of Jupiter's moon Europa, water in its frozen form is once again in the news. The discovery of living organisms in the Antarctic ecosystem, described in the June 26, 1998 issue of Science, is significant because it presents a model for "how life may have arisen and persisted on other worlds." Scientists speculate that if organisms can thrive in the hard ice of Antarctica, they may possibly have done so on Europa and Mars. Galileo's closest approach to Europa occurred on July 21, 1998, offering new images of ice in space. The nine sites listed offer insights and details of the recent findings and discoveries related to ice.

Harris, Kathryn L.

102

Evaluation of Morphological Change and Aggregation Process of Ice Crystals in Frozen Food by Using Fractal Analysis  

NASA Astrophysics Data System (ADS)

Size and shape of ice crystals in frozen food materials are very important because they affect not only quality of foods but also the viability of industrial processing such as freeze-drying of concentration. In this study, 30%wt sucrose solution is used as test samples. For examining the effect of stabilizerspectine and xantan gum is added to the sucrose solution. They are frozen on the cold stage of microscope to be observed their growing ice crystals under the circumstance of -10°C. Their size and shape are measured and quantitatively evaluated by applying fractal analysis. lce crystal of complicated shape has large fractal dimension, and vice versa. It successflly categorized the ice crystals into two groups; one is a group of large size and complicated shape, and the other is a group of small size and plain shape. The critical crystal size between the two groups is found to become larger with increasing holding time. It suggests a phenomenological model for metamorphoses process of ice crystals. Further, it is indicated that xantan gum is able to suppress the smoothing of ice crystals.

Koshiro, Yoko; Watanabe, Manabu; Takai, Rikuo; Hagiwara, Tomoaki; Suzuki, Toru

103

Communication: Anti-icing characteristics of superhydrophobic surfaces investigated by quartz crystal microresonators  

NASA Astrophysics Data System (ADS)

We investigated the anti-icing characteristics of superhydrophobic surfaces with various morphologies by using quartz crystal microresonators. Anodic aluminum oxide (AAO) or ZnO nanorods were synthesized directly on gold-coated quartz crystal substrates and their surfaces were rendered hydrophobic via chemical modifications with octyltrichlorosilane (OTS), octadecyltrichlorosilane (ODS), or octadecanethiol (ODT). Four different hydrophobic nanostructures were prepared on the quartz crystals: ODT-modified hydrophobic plain gold (C18-Au), an OTS-modified AAO nanostructure (C8-AAO), an ODS-modified AAO nanostructure (C18-AAO), and ODT-modified ZnO nanorods (C18-ZnO). The water contact angles on the C18-Au, C8-AAO, C18-AAO, and C18-ZnO surfaces were measured to be 91.4°, 147.2°, 156.3°, and 157.8°, respectively. A sessile water droplet was placed on each quartz crystal and its freezing temperature was determined by monitoring the drastic changes in the resonance frequency and Q-factor upon freezing. The freezing temperature of a water droplet was found to decrease with decreases in the water contact radius due to the decreases in the number of active sites available for ice nucleation.

Lee, Moonchan; Yim, Changyong; Jeon, Sangmin

2015-01-01

104

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

105

Variation of ice crystal size, shape, and asymmetry parameter in tops of tropical deep convective clouds  

NASA Astrophysics Data System (ADS)

The variation of ice crystal properties in the tops of deep convective clouds off the north coast of Australia is analyzed. Cloud optical thickness, ice effective radius, aspect ratio of ice crystal components, crystal distortion parameter and asymmetry parameter are simultaneously retrieved from combined measurements of the Moderate Resolution Imaging Spectroradiometer (MODIS) and Polarization and Directionality of the Earth's Reflectances (POLDER) satellite instruments. The data are divided into periods with alternating weak and strong convection. Mostly plate-like particle components with aspect ratios closer to unity and lower asymmetry parameters characterize strongly convective periods, while weakly convective periods generally show lower aspect ratios, relatively more column-like shapes and somewhat greater asymmetry parameters. Results for strongly convective periods show that, with increasing cloud top temperature, the distortion parameter generally decreases, while the asymmetry parameter and effective radius increase. For one of the strongly convective periods, the rate at which effective radii increase with cloud top temperature is more than double that of the other periods, while the temperature dependence of the other microphysical quantities for this period is substantially weaker. Atmospheric state analysis indicates that these differences are concurrent with differences in middle-to-upper tropospheric zonal wind shear. The observed variation of microphysical properties may have significant effects on the shortwave radiative fluxes and cloud absorption associated with deep convection. Additionally, MODIS collection 5 effective radii are estimated to be biased small with an artificially narrow range. Collection 6 products are expected to have less severe biases that depend on cloud top temperature and atmospheric conditions.

van Diedenhoven, Bastiaan; Fridlind, Ann M.; Cairns, Brian; Ackerman, Andrew S.

2014-10-01

106

A discussion of mechanisms proposed to explain habit changes of vapor-grown ice crystals  

NASA Astrophysics Data System (ADS)

In the present work, surface kinetics processes that can contribute to the growth behavior of ice crystals from the vapor phase are revised and proposed interpretations of crystal habit changes are discussed. Following the main initial papers on this subject by Hallet, Mason et al. and Kobayashi, relationships are considered between linear growth rate and step velocity. More recent results obtained by Sei and Gonda (SG2) for molecular steps naturally formed on basal and prism surfaces are shown to confirm Hallet's interpretation of previous curves obtained for the velocity of giant steps that were artificially formed on basal surfaces only. The different behavior of the condensation coefficient ?( T) characterizing growth in pure water vapor, observed by Lamb and Scott for surfaces intersecting a substrate and by Sei and Gonda for free surfaces, is discussed by considering that ? is the product of the adsorption and accommodation coefficients ? and ?, respectively. It is noted that, as in previous works, ?=1 was assumed, the variations of ? discussed to interpret crystal habit changes were made to coincide with variations of ?. However, Sei and Gonda's results show that in the temperature range where crystal habit changes are observed, values of ?( T)?1 are found. As these depend on surface orientation, they should play an important role in the phenomenon. The dependence of crystal habits on two-dimensional nucleation is also discussed on the basis of measurements carried out by Nelson and Knight of the critical supersaturation ?cr on the basal and prism surfaces. A possible relationship between the curves for ?cr( T) and those of ?( T) derived from Sei and Gonda's results is suggested. The mechanisms determining the large anisotropy exhibited by crystals grown in atmospheric conditions are discussed by taking into account that the growth rate curves R( T) on the basal and prism surfaces show a correlation between maximum and minimum values, which are not observed for crystals grown in pure vapor.

Levi, Laura; Nasello, Olga B.

107

Scattering of partially coherent electromagnetic beams by water droplets and ice crystals  

NASA Astrophysics Data System (ADS)

The conventional Lorenz-Mie theory is generalized for a case when the light source is partially spatially coherent. The influence of the degree of coherence of the incident field on the generalized Mueller matrix and the spectral degree of coherence of the scattered light is analytically studied by using the vector field instead of the scalar field to extend previous results on the angular intensity distribution. The results are compared with the Mueller matrix obtained from the Discrete Dipole Approximation (DDA) method, which is an average over an ensemble of stochastic incident beams. Special attention is paid to the Mueller matrix elements in the backward direction, and the results show some Mueller matrix elements, such as P22, depend monotonically on the coherence length of the incident beam. Therefore, detecting back scattering Mueller matrix elements may be a promising method to measure the degree of coherence. The new formalism is applied to cases of large spherical droplets in water clouds and hexagonal ice crystals in cirrus clouds. The corona and glory phenomena due to spheres and halos associated with hexagonal ice crystals are found to disappear if the incident light tends to be highly incoherent.

Liu, Jianping; Bi, Lei; Yang, Ping; Kattawar, George W.

2014-02-01

108

Radiative properties of visible and subvisible Cirrus: Scattering on hexagonal ice crystals  

NASA Technical Reports Server (NTRS)

One of the main objectives of the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) is to provide a better understanding of the physics of upper level clouds. The focus is on just one specific aspect of cirrus physics, namely on characterizing the radiative properties of single, nonspherical ice particles. The basis for further more extensive studies of the radiative transfer through upper level clouds is provided. Radiation provides a potential mechanism for strong feedback between the divergence of in-cloud radiative flux and the cloud microphysics and ultimately on the dynamics of the cloud. Some aspects of ice cloud microphysics that are relevant to the radiation calculations are described. Next, the Discrete Dipole Approximation (DDA) is introduced and some new results of scattering by irregular crystals are presented. The Anomalous Diffraction Theory (ADT) was adopted to investigate the scattering properties of even larger crystals. In this way the scattering properties of nonspherical particles were determined over a range of particle sizes.

Flatau, Piotr J.; Stephens, Graeme L.; Draine, Bruce T.

1990-01-01

109

Solar radiative transfer in cirrus clouds. I - Single-scattering and optical properties of hexagonal ice crystals. II - Theory and computations of multiple scattering in an anisotropic medium  

NASA Technical Reports Server (NTRS)

The light scattering and absorption programs of Cai and Liou (1982) and Takano and Jaweera (1985) are extended to include hexagonal ice crystals randomly and horizontally oriented in space. The scattering and polarization results for the ice crystals are calculated. The results are compared with measurement data. The single-scattering properties for horizontally oriented columns and plates are presented and used to explain halos and arcs observed in the atmopshere. In the second section, the theory and computations for multiple scattering in cirrus clouds containing oriented ice crystals are presented. The radiative transfer in clouds composed of horizontally oriented ice crystals is formulated. Also, reflected and transmitted intensities, planetary albedo, and polarization in multiple scattering by ice crystals are discussed.

Takano, Yoshihide; Liou, Kuo-Nan

1989-01-01

110

Importance of aggregation and small ice crystals in cirrus clouds, based on observations and an ice particle growth model  

NASA Technical Reports Server (NTRS)

The 1 November 1986 FIRE I case study was used to test an ice particle growth model which predicts bimodal size spectra in cirrus clouds. The model was developed from an analytically based model which predicts the height evolution of monomodal ice particle size spectra from the measured ice water content (IWC). Size spectra from the monomodal model are represented by a gamma distribution, N(D) = N(sub o)D(exp nu)exp(-lambda D), where D = ice particle maximum dimension. The slope parameter, lambda, and the parameter N(sub o) are predicted from the IWC through the growth processes of vapor diffusion and aggregation. The model formulation is analytical, computationally efficient, and well suited for incorporation into larger models. The monomodal model has been validated against two other cirrus cloud case studies. From the monomodal size spectra, the size distributions which determine concentrations of ice particles less than about 150 mu m are predicted.

Mitchell, David L.; Chai, Steven K.; Dong, Yayi; Arnott, W. Patrick; Hallett, John

1993-01-01

111

Finite-difference time domain method for light scattering by small ice crystals in three-dimensional space  

Microsoft Academic Search

The finite-difference time domain (FDTD) method for the solution of light scattering by nonspherical particles has been developed for small ice crystals of hexagonal shapes including solid and hollow columns, plates, and bullet rosettes commonly occurring in cirrus clouds. To account for absorption, we have introduced the effec- tive permittivity and conductivity to circumvent the required complex calculations in the

Ping Yang; K. N. Liou

1996-01-01

112

Final Report for "Improved Representations of Cloud Microphysics for Model and Remote Sensing Evaluation using Data Collected during ISDAC, TWP-ICE and RACORO  

SciTech Connect

We were funded by ASR to use data collected during ISDAC and TWP-ICE to evaluate models with a variety of temporal and spatial scales, to evaluate ground-based remote sensing retrievals and to develop cloud parameterizations with the end goal of improving the modeling of cloud processes and properties and their impact on atmospheric radiation. In particular, we proposed to: 1) Calculate distributions of microphysical properties observed in arctic stratus during ISDAC for initializing and evaluating LES and GCMs, and for developing parameterizations of effective particle sizes, mean fall velocities, and mean single-scattering properties for such models; 2) Improve representations of particle sizes, fall velocities and scattering properties for tropical and arctic cirrus using TWP-ICE, ISDAC and M-PACE data, and to determine the contributions that small ice crystals, with maximum dimensions D less than 50 ?m, make to mass and radiative properties; 3) Study fundamental interactions between clouds and radiation by improving representations of small quasi-spherical particles and their scattering properties. We were additionally funded 1-year by ASR to use RACORO data to develop an integrated product of cloud microphysical properties. We accomplished all of our goals.

McFarquhar, Greg M. [University of Illinois] University of Illinois

2003-06-11

113

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

114

Millimeter wave scattering from ice crystals and their aggregates: Comparing cloud model simulations with X- and Ka-band radar measurements  

NASA Astrophysics Data System (ADS)

Arctic clouds are often mixed-phase, such that the radiative properties of the clouds are a strong function of the relative amounts of cloud liquid and ice. Modeling studies have shown that the poorly understood ice phase processes are the regulators of the liquid water fraction. However, evaluating the fidelity of the model ice parameterizations has proven to be a difficult task. This study evaluates results of different ice microphysics representations in a cloud resolving model (CRM) using cloud radar measurements. An algorithm is presented to generate realistic ice crystals and their aggregates from which radar backscattering cross sections may be calculated using a generalized solution for a cluster of spheres. The aggregate is composed of a collection of ice crystals, each of which is constructed from a cluster of tiny ice spheres. Each aggregate satisfies the constraints set by the component crystal type and the mass-dimensional relationship used in the cloud resolving model, but is free to adjust its aspect ratio. This model for calculating radar backscattering is compared to two spherical and two spheroidal (bulk model) representations for ice hydrometeors. It was found that a refined model for representing the ice hydrometeors, both pristine crystals and their aggregates, is required in order to obtain good comparisons between the CRM calculations and the radar measurements. The addition of the radar-CRM comparisons to CRM-in situ measurements comparisons allowed conclusions about the appropriateness of different CRM ice microphysics parameterizations.

Botta, Giovanni; Aydin, Kultegin; Verlinde, Johannes; Avramov, Alexander E.; Ackerman, Andrew S.; Fridlind, Ann M.; McFarquhar, Greg M.; Wolde, Mengistu

2011-01-01

115

Convective Troposphere-Stratosphere Transport in the Tropics and Hydration by ice Crystals Geysers  

NASA Astrophysics Data System (ADS)

Twenty-five years ago the suggestion was made by Danielsen of direct fast convective penetration of tropospheric air in the stratosphere over land convective systems. Although the existence of the mechanism is accepted, it was thought to be rare and thus its contribution to Troposphere-Stratosphere Transport (TST) of chemical species and water vapour at global scale unimportant at global scale. In contrast to this assumption, observations of temperature, water vapour, ice particles, long-lived tropospheric species during HIBISCUS, TROCCINOX and SCOUT-O3 over Brazil, Australia and Africa and more recently CALIPSO aerosols observations suggest that it is a general feature of tropical land convective regions in the summer. Particularly relevant to stratospheric water vapour is the observation of geyser like ice crystals in the TTL over overshooting events which may result in the moistening of the stratosphere. Although such events successfully captured by small scale Cloud-Resolving Models may have a significant impact on stratospheric ozone chemistry and climate, they are currently totally ignored by NWPs, CTMs and CCMs. Several recent balloon and aircraft observations of overshoots and CRM simulations will be shown illustrating the mechanism, as well as observations from a variety of satellites suggesting a significant impact at global scale.

Pommereau, J.

2008-12-01

116

Isothermal ice crystallization kinetics in the gas-diffusion layer of a proton-exchange-membrane fuel cell.  

PubMed

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 ice-crystallization 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 ice-crystallization kinetics in GDLs. PMID:22133053

Dursch, T J; Ciontea, M A; Radke, C J; Weber, A Z

2012-01-17

117

Dependence on accelerating voltage of crystal structural changes in water ice thin film under electron beam irradiation  

NASA Astrophysics Data System (ADS)

The dependence on accelerating voltage of crystal structural changes in water ice thin film under electron beam irradiation was investigated by cryogenic transmission electron microscopy (cryo-TEM) at 95 K and accelerating voltages of 25, 50, 75, 100, or 125 kV. Ice thin film was prepared by depositing residual moisture in the TEM column onto both sides of a carbon membrane at 95 K. The major phase of the deposited film at 95 K was identified as ice Ic by transmission electron diffractometry. We found that the mass loss rate of the ice thin film decreased sharply as the accelerating voltage was increased. From this result, we conclude the mass loss mechanism was the ionization of water by inelastic scattering of incident electrons. Moreover, the phase transition from ice Ic to ice Ih was observed at accelerating voltages of 75 kV or greater. At 50 kV or lower, however, the phase transition was hardly observed by TEM. Because the phase transition can also be attributed to inelastic scattering of incident electrons, the results suggest that whether mass loss or a phase transition occurs depends primarily on the accelerating voltage.

Kobayashi, Keita; Yasuda, Hidehiro

2013-02-01

118

Formation of ridges on Europa above crystallizing water bodies inside the ice shell  

NASA Astrophysics Data System (ADS)

Jupiter’s second Galilean satellite, Europa, is a Moon-sized body with an icy shell and global ocean approximately 100 km thick surrounding a rocky interior. Its surface displays extensive tectonic activity in a geologically recent past. Europa’s most ubiquitous surface features, double ridges, have a central trough flanked by two raised edifices. Double ridges can extend hundreds of kilometers and appear genetically related to cracks formed in the Europan ice shell. The origin of the raised flanks has been the center of much debate and many models have been proposed. There are also ridges without a central trough, single ridges. These ridges are far less common than their double ridge counterparts. However, there are locations where along-strike changes in ridge type appear to occur. We explore an elastic model in which the ridges form in response to crystallization of a liquid water intrusion. In our model, liquid water fills tension cracks that open in the Europan crust in response to tidal stress or perhaps overpressure of a subsurface ocean. The crack would be long and essentially continuous, similar to dikes on Earth, explaining the remarkable continuity and lack of segmentation of Europan ridges. The freezing of the water would cause a volume expansion, compressing and buckling the adjacent crust. We find that the geometry of the intruding water body controls the shape of the resulting ridges, with single ridges forming above sill-like intrusions and double ridges above dike-like intrusions. In order to match the ridge heights observed for double ridges we would need approximately 1.5 km2 of water intruded at a shallow depth in the ice shell, potentially over the course of multiple events. Deeper intrusions result in a broader, lower amplitude ridge than shallow intrusions.

Johnston, Stephanie A.; Montési, Laurent G. J.

2014-07-01

119

Tightly integrated single- and multi-crystal data collection strategy calculation and parallelized data processing in JBluIce beamline control system  

PubMed Central

The calculation of single- and multi-crystal data collection strategies and a data processing pipeline have been tightly integrated into the macromolecular crystallographic data acquisition and beamline control software JBluIce. Both tasks employ wrapper scripts around existing crystallographic software. JBluIce executes scripts through a distributed resource management system to make efficient use of all available computing resources through parallel processing. The JBluIce single-crystal data collection strategy feature uses a choice of strategy programs to help users rank sample crystals and collect data. The strategy results can be conveniently exported to a data collection run. The JBluIce multi-crystal strategy feature calculates a collection strategy to optimize coverage of reciprocal space in cases where incomplete data are available from previous samples. The JBluIce data processing runs simultaneously with data collection using a choice of data reduction wrappers for integration and scaling of newly collected data, with an option for merging with pre-existing data. Data are processed separately if collected from multiple sites on a crystal or from multiple crystals, then scaled and merged. Results from all strategy and processing calculations are displayed in relevant tabs of JBluIce. PMID:25484844

Pothineni, Sudhir Babu; Venugopalan, Nagarajan; Ogata, Craig M.; Hilgart, Mark C.; Stepanov, Sergey; Sanishvili, Ruslan; Becker, Michael; Winter, Graeme; Sauter, Nicholas K.; Smith, Janet L.; Fischetti, Robert F.

2014-01-01

120

Tightly integrated single- and multi-crystal data collection strategy calculation and parallelized data processing in JBluIce beamline control system.  

PubMed

The calculation of single- and multi-crystal data collection strategies and a data processing pipeline have been tightly integrated into the macromolecular crystallographic data acquisition and beamline control software JBluIce. Both tasks employ wrapper scripts around existing crystallographic software. JBluIce executes scripts through a distributed resource management system to make efficient use of all available computing resources through parallel processing. The JBluIce single-crystal data collection strategy feature uses a choice of strategy programs to help users rank sample crystals and collect data. The strategy results can be conveniently exported to a data collection run. The JBluIce multi-crystal strategy feature calculates a collection strategy to optimize coverage of reciprocal space in cases where incomplete data are available from previous samples. The JBluIce data processing runs simultaneously with data collection using a choice of data reduction wrappers for integration and scaling of newly collected data, with an option for merging with pre-existing data. Data are processed separately if collected from multiple sites on a crystal or from multiple crystals, then scaled and merged. Results from all strategy and processing calculations are displayed in relevant tabs of JBluIce. PMID:25484844

Pothineni, Sudhir Babu; Venugopalan, Nagarajan; Ogata, Craig M; Hilgart, Mark C; Stepanov, Sergey; Sanishvili, Ruslan; Becker, Michael; Winter, Graeme; Sauter, Nicholas K; Smith, Janet L; Fischetti, Robert F

2014-12-01

121

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

122

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

E-print Network

Extinction and absorption eficiencies of hexagonal columns from the composite method based on the FDTD, Mie and IGOM (?=6.7 µm)…………… 8 2 Comparison of bidirectional reflectances from DISORT with true coeficients, ?-fit truncation and ?-M truncation... by cloud optical thicknes, efective particle size, cloud-top temperature and ice water path in general circulation models. Satelite-based cloud retrieval algorithms often require a function of cloud particle types in the forward radiative transfer models...

Xie, Yu

2007-09-17

123

Influence of freezing conditions on ice crystallisation in ice cream  

Microsoft Academic Search

Successful optimisation of the ice cream freezing process to deliver a product with small ice crystals, and therefore a smooth texture, requires an understanding of the mechanisms of ice crystallisation. The purpose of this work was to relate the processing variables available to the ice cream manufacturer to measured ice crystal size distributions, with a view to elucidating the dominant

A. B. Russell; P. E. Cheney; S. D. Wantling

1999-01-01

124

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

125

Effects of Ice-Crystal Structure on Halo Formation: Cirrus Cloud Experimental and Ray-Tracing Modeling Studies  

NASA Technical Reports Server (NTRS)

During the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22 deg halo-producing cirrus clouds were studied jointly from a ground-based polarization lidar and an instrumented aircraft. The lidar data show the vertical cloud structure and the relative position of the aircraft, which collected a total of 84 slides by impaction, preserving the ice crystals for later microscopic examination. Although many particles were too fragile to survive impaction intact, a large fraction of the identifiable crystals were columns and radial bullet rosettes, with both displaying internal cavitations and radial plate-column combinations. Particles that were solid or displayed only a slight amount of internal structure were relatively rare, which shows that the usual model postulated by halo theorists, i.e., the randomly oriented, solid hexagonal crystal, is inappropriate for typical cirrus clouds. With the aid of new ray-tracing simulations for hexagonal hollow-ended column and bullet-rosette models, we evaluate the effects of more realistic ice-crystal structures on halo formation and lidar depolarization and consider why the common halo is not more common in cirrus clouds.

Sassen, Kenneth; Knight, Nancy C.; Takano, Yoshihide; Heymsfield, Andrew J.

1994-01-01

126

Ice Cream  

NSDL National Science Digital Library

In this chemistry activity, learners use the lowered freezing point of water to chill another mixture (ice cream) to the solid state. Learners will record the temperature of the ice before and after mixing it with the ice cream ingredients and discover that adding a solute to a solvent lowers the freezing point of that solvent (also known as a colligative property). This activity can also be used to introduce learners to crystallization.

The Science House

2014-01-28

127

Lactose Crystallization in Ice Cream. IV. Factors Responsible for Reduced Incidence of Sandiness  

Microsoft Academic Search

SUMMARY An explanation was sought for the virtual disappearance of sandiness from commercial ice cream. Only five of 36 commercial samples became sandy when stored seven months at 12 F. Nuclei formation was accelerated by drawing ice cream from freezers at low temperatures and hardening it rapidly. Partial sub- stitution of corn syrup solids for sucrose neither delayed the development

T. A. Nickerson

1962-01-01

128

Discovery of Crystallized Water Ice in a Silhouette Disk in the M43 Region  

E-print Network

We present the 1.9--4.2um spectra of the five bright (Lsilhouette disks with moderate to high inclination angle of 39--80deg 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 3.1um 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 65deg and 75deg 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 6.38x10^(-18) g cm^(-3). The water ice absorp...

Terada, Hiroshi

2012-01-01

129

Part A: Cirrus ice crystal nucleation and growth. Part B: Automated analysis of aircraft ice particle data  

NASA Technical Reports Server (NTRS)

Specific measurement of cirrus crystals by aircraft and temperature modified CN are used to specify measurements necessary to provide a basis for a conceptual model of cirrus particle formation. Key to this is the ability to measure the complete spectrum of particles at cirrus levels. The most difficult regions for such measurement is from a few to 100 microns, and uses a replicator. The details of the system to automate replicator data analysis are given, together with an example case study of the system provided from a cirrus cloud in FIRE 2, with particles detectable by replicator and FSSP, but not 2DC.

Arnott, William P.; Hallett, John; Hudson, James G.

1995-01-01

130

Dielectric constant adjustments in computations of the scattering properties of solid ice crystals using the Generalized Multi-particle Mie method  

NASA Astrophysics Data System (ADS)

Ice crystal scattering properties at microwave radar wavelengths can be modeled with the Generalized Multi-particle Mie (GMM) method by decomposing an ice crystal into a cluster of tiny spheres composed of solid ice. In this decomposition the mass distribution of the tiny spheres in the cluster is no longer equivalent to that in the original ice crystal because of gaps between the tiny spheres. To compensate for the gaps in the cluster representation of an ice crystal in the GMM computation of crystal scattering properties, the Maxwell Garnett approximation is used to estimate what the dielectric function of the tiny spheres (i.e., the inclusions) in the cluster must be to make the cluster of tiny spheres with associated air gaps (i.e., the background matrix) dielectrically equivalent to the original solid ice crystal. Overall, compared with the T-matrix method for spheroids outside resonance regions this approach agrees to within mostly 0.3 dB (and often better) in the horizontal backscattering cross section ?hh and the ratio of horizontal and vertical backscattering cross sections ?hh/?vv, and 6% for the amplitude scattering matrix elements Re{S22-S11} and Im{S22} in the forward direction. For crystal sizes and wavelengths near resonances, where the scattering parameters are highly sensitive to the crystal shape, the differences are generally within 1.2 dB for ?hh and ?hh/?vv, 20% for Re{S22-S11} and 6% for Im{S22}. The Discrete Dipole Approximation (DDA) results for the same spheroids are generally closer than those of GMM to the T-matrix results. For hexagonal plates the differences between GMM and the DDA at a W-band wavelength (3.19 mm) are mostly within 0.6 dB for ?hh, 1 dB for ?hh/?vv, 11% for Re{S22-S11} and 12% for Im{S22}. For columns the differences are within 0.3 dB for ?hh and ?hh/?vv, 8% for Re{S22-S11} and 4% for Im{S22}. This method shows higher accuracy than an alternative method that artificially increases the thickness of ice plates to provide the same mass as the original ice crystal.

Lu, Yinghui; Aydin, Kültegin; Clothiaux, Eugene E.; Verlinde, Johannes

2014-03-01

131

Ice water content retrievals using an estimation theory approach: examples from the NASA CRYSTAL-FACE experiment  

NASA Astrophysics Data System (ADS)

This study introduces a new, robust and reliable method to estimate ice cloud microphysical properties from cloud radar reflectivities and visible optical depth. The retrieval is formulated in an estimation theory framework which permits the introduction of optimal combinations of different measurements and a complete characterization of retrieval errors. The sensitivity of the retrieval to the assumed error statistics is assessed performing experiments with variablea priori, optical depth and forward model uncertainties. Quantitative estimates of the uncertainties show that the average ice water content is retrieved with errors varying between 20--30%. The relative error on ice water path is of the same order of magnitude. The retrieval is applied to synthetic and real observations. Retrieved products are checked against other retrieval methods andin situ observations when available. The results compare well with results from other methods. The retrieval appears to be robust and can be applied successfully to a variety of cirrus clouds without suffering from the problems often encountered when using empirically--based methods. As part of ongoing research the method is being evaluated using data from the NASA CRYSTAL--FACE experiment and the Atmospheric Radiation Measurement - Unmanned Aerospace Vehicle (ARM-UAV) Fall 2002 experiment.

Benedetti, A.; Stephens, G.; Haynes, J.

2003-04-01

132

Meth (Crank, Ice) Facts  

MedlinePLUS

Listen to this page Meth (Crank, Ice) Facts Methamphetamine—meth for short—is a white, bitter powder. ... names for meth are: Crank Ice Crystal Glass Chalk En español "Heart disease runs in some families. ...

133

More accurate determination of the quantity of ice crystallized at low cooling rates in the glycerol and 1,2-propanediol aqueous solutions: comparison with equilibrium.  

PubMed

It is generally assumed that when cells are cooled at rates close to those corresponding to the maximum of survival, once supercooling has ceased, above the eutectic melting temperature the extracellular ice is in equilibrium with the residual solution. This did not seem evident to us due to the difficulty of ice crystallization in cryoprotective solutions. The maximum quantities of ice crystallized in glycerol and 1,2-propanediol solutions have been calculated from the area of the solidification and fusion peaks obtained with a Perkin-Elmer DSC-2 differential scanning calorimeter. The accuracy has been improved by several corrections: better defined baseline, thermal variation of the heat of fusion of the ice, heat of solution of the water from its melting with the residual solution. More ice crystallizes in the glycerol than in the 1,2-propanediol solutions, of which the amorphous residue contains about 40 to 55% 1,2-propanediol. The equilibrium values are unknown in the presence of 1,2-propanediol. With glycerol, in our experiments, the maximum is first lower than the equilibrium but approaches it as the concentration increases. It is not completely determined by the colligative properties of the solutes. PMID:6713947

Boutron, P

1984-04-01

134

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

135

Differential propagation constants on slant paths through snow and ice crystals as measured by 16.5 GHz polarization-diversity radar  

Microsoft Academic Search

Radar measurements of differential propagation constants at a wavelength of 1.82 cm on slant paths through heavy snow and ice crystals are described. The data from three snow storms show that the differential phase shift per kilometer through heavy snow may be considerably larger on slant paths with elevation angles of 10 to 30 deg than it is on terrestrial

A. Hendry; Y. M. M. Antar; G. C. McCormick

1981-01-01

136

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

137

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

138

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

SciTech Connect

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.

Araujo, C. I. L. de, E-mail: dearaujo@ufv.br; Silva, R. C.; Ribeiro, I. R. B.; Nascimento, F. S.; Felix, J. F.; Ferreira, S. O.; Moura-Melo, W. A.; Pereira, A. R. [Departamento de Física, Universidade Federal de Viçosa, Viçosa 36570-900, Minas Gerais (Brazil); Mól, L. A. S. [Departamento de Física, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Minas Gerais (Brazil)

2014-03-03

139

Recrystallization of ice during bulk storage of ice cream  

Microsoft Academic Search

Ice recrystallization was studied in 1.9 L containers of ice cream stored so that surface temperature of ice cream was controlled with fluctuations of ±1.0 °C. Core and surface samples were taken at regular intervals and analyzed for ice crystal size by cold-stage microscopy and image analysis. Mean ice crystal size plotted vs. time0.33 resulted in a straight line, with

Daniel P. Donhowe; Richard W. Hartel

1996-01-01

140

Chemical Characterization of Individual Particles and Residuals of Cloud Droplets and Ice Crystals Collected On Board Research Aircraft in the ISDAC 2008 Study  

SciTech Connect

Although it has been shown that size of atmospheric particles has a direct correlation with their ability to act as cloud droplet and ice nuclei, the influence of composition of freshly emitted and aged particles in nucleation processes is poorly understood. In this work we combine data from field measurements of ice nucleation with chemical imaging of the sampled particles to link aerosol composition with ice nucleation ability. Field measurements and sampling were conducted during the Indirect and Semidirect Aerosols Campaign (ISDAC) over Barrow, Alaska, in the springtime of 2008. In-situ ice nucleation measurements were conducted using a Continuous Flow Diffusion Chamber (CFDC). Measured number concentrations of ice nuclei (IN) varied from frequent values of 0.01 per liter to more than 10 per liter. Residuals of airborne droplets and ice crystals were collected through a counterflow virtual impactor (CVI). The compositions of individual atmospheric particles and the residuals were studied using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis (CCSEM/EDX) and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy (STXM/NEXAFS). Chemical analysis of cloud particle residuals collected during an episode of high ice nucleation suggests that both size and composition may influence aerosol's ability to act as IN. The STXM/NEXAFS chemical composition maps of individual residuals have characteristic structures of either inorganic or black carbon cores coated by organic materials. In a separate flight, particle samples from a biomass burning plume were collected. Although it has previously been suggested that episodes of biomass burning contribute to increased numbers of highly effective ice nuclei, in this episode we observed that only a small fraction were effective ice nuclei. Most of the particles from the biomass plume episode were smaller in size and were composed of homogeneous organic material without identifiable cores.

Hiranuma, Naruki; Brooks, Sarah D.; Moffet, Ryan C.; Glen, Andrew; Laskin, Alexander; Gilles, Marry K.; Liu, Peter; MacDonald, A. M.; Strapp, J. Walter; McFarquhar, Greg

2013-06-24

141

Impact of ice crystal habit on the parameterization of cloud microphysical properties when using 94ghz polarimetric scanning cloud radar during STORMVEX  

NASA Astrophysics Data System (ADS)

Through the analysis of scanning polarimetric W-band cloud radar data collected during STORMVEX, an algorithm has been developed to both identify and parameterize various ice crystal habits present within mixed-phase clouds. Armed with a unique dataset, the development of the algorithm took advantage of a slant 45° linear depolarization ratio (SLDR) measurement that was made as a function of the radar elevation angle when in range height indicator (RHI) scanning mode. This measurement technique proved to be invaluable in that it limited the influence of the particle's maximum dimension on the measured depolarization, which instead became more a function of the ice particle's shape. Validated through in situ measurements; pristine dendrites, lightly rimed dendrites, rimed stellar crystals, aggregates of dendrites, columns, and graupel particles were identified and matched with specific SLDR signatures. With a known ice particle habit and SLDR signature, the ice particle habit identification segment of the newly developed algorithm was then applied to the entire dataset consisting of 38,190 individual scans, in order to identify ice particle habits at a combined 849,745 range-heights and scanning angles. Through this analysis and the use of a chi-square test statistic, the predominant ice particle habit could be determined. Of primary interest in this study were the parameterizations of the ice particle mass and radar backscatter cross section. Through the modeling of the chosen ice particle habit as an oblate spheroid, these parameterizations were carried out in part by relying on previously published empirical studies as well as T-matrix scattering calculations of oblate spheroids composed of an ice/air mixture. Due to the computational expense of T-matrix calculations, however, a new T-matrix scaling factor was derived from the Clausius-Mossotti relation, which relates the refractive index of a material to its polarizability. With this scaling factor, new T-matrix results could be found, still functions of ice particle mass and shape. Using this new parameterization scheme, a radar-based cloud microphysical property retrieval algorithm was then executed for two cases and compared to generic parameterizations. Results show that the potential difference in the retrieved microphysical properties for the generic versus the ice particle habit-based parameterization could be as high as a factor of two.

Hammonds, Kevin Don

142

The Cloud Particle Spectrometer with Polarization Detection (CPSPD): A next generation open-path cloud probe for distinguishing liquid cloud droplets from ice crystals  

NASA Astrophysics Data System (ADS)

The differentiation of small water droplets and ice crystals by in situ measurements, in the size range < 50 ?m, remains a challenge and the lack of such measurements is an obstacle to progress in understanding ice formation in clouds. A new microphysical instrument, the Cloud Particle Spectrometer with Polarization Detection (CPSPD), has been developed that measures light intensity scattered (in forward and backward directions) by individual cloud particles that pass through a focused laser beam and derives their size and thermodynamic phase (liquid or ice) in the optical diameter range from 2 to 50 ?m. The optical equivalent diameter is derived from the light scattered in the forward direction. The change in polarization state of the incident light, caused by interaction with the cloud particle, is determined from the polarized components of the backscattered light. The CPSPD, along with several other cloud microphysical probes, has been flown on the University of North Dakota Citation aircraft in mixed phase clouds. It has also been deployed and operated at the Zugspitze research station studying mountain clouds. The preliminary results show that liquid cloud droplets can be distinguished from ice crystals and that the ice fraction can be estimated; an important parameter for better understanding of cloud processes, particularly that of glaciation.

Baumgardner, Darrel; Newton, Roy; Krämer, Martina; Meyer, Jessica; Beyer, Alexander; Wendisch, Manfred; Vochezer, Paul

2014-06-01

143

Hydrohalite in cold sea ice: Laboratory observations of single crystals, surface accumulations, and migration rates under a temperature gradient, with application to “Snowball Earth”  

NASA Astrophysics Data System (ADS)

When NaCl precipitates out of a saturated solution, it forms anhydrous crystals of halite at temperatures above +0.11°C, but at temperatures below this threshold it instead precipitates as the dihydrate "hydrohalite," NaCl · 2H2O. When sea ice is cooled, hydrohalite begins to precipitate within brine inclusions at about -23°C. In this work, hydrohalite crystals are examined in laboratory experiments: their formation, their shape, and their response to warming and desiccation. Sublimation of a sea ice surface at low temperature leaves a lag deposit of hydrohalite, which has the character of a fine powder. The precipitation of hydrohalite in brine inclusions raises the albedo of sea ice, and the subsequent formation of a surface accumulation further raises the albedo. Although these processes have limited climatic importance on the modern Earth, they would have been important in determining the surface types present in regions of net sublimation on the tropical ocean in the cold phase of a Snowball Earth event. However, brine inclusions in sea ice migrate downward to warmer ice, so whether salt can accumulate on the surface depends on the relative rates of sublimation and migration. The migration rates are measured in a laboratory experiment at temperatures from -2°C to -32°C; the migration appears to be too slow to prevent formation of a salt crust on Snowball Earth.

Light, Bonnie; Brandt, Richard E.; Warren, Stephen G.

2009-07-01

144

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

145

Crystal Distortion of Dy2Ti2O7 at the Spin Ice Transition Temperature  

SciTech Connect

Dy2Ti2O7 with the pyrochlore structure shows a spin ice transition at about 1 K. The Dy3+ ion in this compound has an effective spin Seff=1/2. The Dy ions reside on the vertices of corner-linked tetrahedra. Due to a strong single-ion anisotropy, the ground state of Dy3+ is well expressed by an Ising doublet with local <111> quantization axes. We measured the x-ray diffraction for a Dy2Ti2O7 powder sample between 0.15 K. and 20 K. The lattice spacing increases drastically between 1.5 K and about 1 K, with decreasing temperature. The lattice spacing of the (222) diffraction is considerably larger than the other directions.

Suzuki, H.; Hata, F.; Xue, Y.; Kaneko, H.; Hosomichi, A.; Abe, S. [Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa 920-1192 (Japan); Higashinaka, R.; Nakatsuji, S.; Maeno, Y. [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)

2006-09-07

146

Ice forming experiment  

NASA Technical Reports Server (NTRS)

A low gravity experiment to assess the effect of the presence of supercooled cloud droplets on the diffusional growth rate of ice crystals is described. The theoretical work and the feasibility studies are summarized. The nucleation of ice crystals in supercooled clouds is also discussed.

Vali, G.

1982-01-01

147

Ice Spikes  

NSDL National Science Digital Library

This webpage from SnowCrystals.com provides instructions for growing ice spikes in ordinary freezer. The page explains the physics of growing these spikes and concludes useful information on water purity and growing temperature. Related photos and drawings are provided.

Libbrecht, Kenneth

2012-02-28

148

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

149

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

150

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

E-print Network

the fractional volumes of ice, gas, brine, and precipitated salt. [3] Temperatures within sea ice exhibit a wide and desiccation. Sublimation of a sea ice surface at low temperature leaves a lag deposit of hydrohalite, which depend strongly on temperature, because of freezing-equilibrium relationships which dictate

Warren, Stephen

151

Differential propagation constants on slant paths through snow and ice crystals as measured by 16.5 GHz polarization-diversity radar  

Microsoft Academic Search

Radar determinations of differential propagation constants at a wavelength of 1.82 cm on slant paths through heavy snow and\\u000a ice crystals are reported. Also reported are measurements of differential propagation effects in the melting layer. The slant\\u000a path results indicate an increase of differential phase shift with height, to a value at 2000 m which may exceed 1.3 deg\\/\\u000a km,

Archibald Hendry; Glendon C. McCormick; Yahia M. M. Antar

1981-01-01

152

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

153

Crystallization and preliminary X-ray crystallographic studies of the ice-binding protein from the Arctic [correction of Aantarctic] yeast Leucosporidium sp. AY30.  

PubMed

Freezing is dangerous to cellular organisms because it causes an increase in the concentration of ions and other solutes in the plasma, denatures biomolecules and ruptures cell membranes. Some cold-adapted organisms can survive at subzero temperatures by producing proteins that bind to and inhibit the growth of ice crystals. To better understand the structure and function of these proteins, the ice-binding protein from Leucosporidium sp. AY30 (LeIBP) was overexpressed, purified and crystallized. The native crystal belonged to space group P4(3)2(1)2, with unit-cell parameters a=b=98.05, c=106.13?Å. Since LeIBP lacks any cysteine or methionine residues, two leucine residues (Leu69 and Leu155) were substituted by methionine residues in order to obtain selenomethionine-substituted LeIBP for use in multiple-wavelength anomalous diffraction (MAD) phasing. The selenomethionine-substituted mutant crystallized in the same space group as the native protein. PMID:21795798

Park, Ae Kyung; Park, Kyoung Sun; Kim, Hak Jun; Park, Hyun; Ahn, In Young; Chi, Young Min; Moon, Jin Ho

2011-07-01

154

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.

Chris Wilson

155

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

156

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

157

Examining Crystal Fabric Develoment in Ice: Cryo EBSD, Deformation Experiments and the Link to En-glacial Reflectivity  

NASA Astrophysics Data System (ADS)

Over the past few years, cryogenic electron back-scatter diffraction (Cryo-EBSD) has been increasingly used to examine micro-structures in both natural and experimentally deformed ice samples on a micron-scale. Experiments that investigate grain size-sensitive behavior require working on fine-grained ice. These samples present a number of experimental challenges. Issues that present particular difficulties include stable mounting of ice samples, transport of mounted samples and producing a planar, frost-free and damage-free surface. Recent work at the new Otago Ice Deformation Lab has led to the development of a number of experimental methods that help overcome these challenges and enable routine EBSD analysis of fine-grained ice. A brief outline of these experimental methods and some EBSD results from variably deformed ice samples will be presented. Shear deformation experiments on polycrystalline ice are being conducted in order to further explore the relationships between deformation, processes of recrystallization, and the development of anisotropic fabrics that lead to en-glacial seismic reflections. Self-contained, refrigerated deformation units fitted with digital controllers and hardware have been designed for unconfined deformation experiments on polycrystalline synthetic ice. Methods of analysis, from time-lapse photography to random-point tracking, are being employed for monitoring strain in real time. Various methods have been explored for monitoring the development of anisotropic fabrics in ice during progressive deformation. Ultra-sonic transducers can be used to monitor wave velocity changes in various orientations in materials under strain. These experiments have been designed with the objective of quantifying the relationship between deformation fabrics and en-glacial seismic reflectivity observed in thick grounded ice sheets.

Vaughan, Matthew; Prior, David; Seidemann, Meike; Gorman, Andrew; Lilly, Kat; Langhorne, Pat; Easingwood, Richard; Golding, Narayana; Durham, Bill

2014-05-01

158

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

159

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

160

Comparison of the ray-tracing and beam-tracing methods in the problem of light scattering by ice crystals of cirrus clouds  

NASA Astrophysics Data System (ADS)

Comparison of two approaches within the framework of geometric optics, called the ray-tracing and beam-tracing methods, is considered in application to the problem of light scattering by ice crystal particles of cirrus clouds. A good conformity between the numerical data obtained by these algorithms is demonstrated. The computer time spent for the calculations by these algorithms is analyzed depending on spatial orientations of the particles. It is shown that the beamtracing methods exceeds its counterpart at small number of reflection/refraction events (up to 5) while the situation becomes opposite if this number is larger than 5.

Kustova, Natalia V.; Konoshonkin, Alexander V.; Borovoi, Anatoli G.

2014-11-01

161

Recrystallization of ice in ice cream during controlled accelerated storage  

Microsoft Academic Search

Accelerated ice recrystallization in a thin film of vanilla ice cream was studied on a cold stage microscope, housed in a refrigerated glove box. Sample temperature was held constant (within ±0.01 °C) or sinusoidally oscillated for 5 days. Changes in ice crystal size distribution were monitored using an image analysis technique. Several recrystallization mechanisms were observed. Melt-refreeze recrystallization was important

Daniel P. Donhowe; Richard W. Hartel

1996-01-01

162

Relationship between Recrystallization Rate of Ice Crystals in Sugar Solutions and Water Mobility in Freeze-Concentrated Matrix  

Microsoft Academic Search

To better understand the relation between recrystallization rate and water mobility in freeze-concentrated matrix, isothermal ice recrystallization rates in several sugar aqueous solutions and self-diffusion coefficients of water component in corresponding freeze-concentrated matrix were measured. The sugars used were fructose, glucose, maltose, and sucrose. The sugar concentrations and temperature were varied so that ice contents for all samples were almost

Tomoaki Hagiwara; Richard W. Hartel; Shingo Matsukawa

2006-01-01

163

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

164

Stacking disorder in ice I.  

PubMed

Traditionally, ice I was considered to exist in two well-defined crystalline forms at ambient pressure: stable hexagonal ice (ice Ih) and metastable cubic ice (ice Ic). However, it is becoming increasingly evident that what has been called cubic ice in the past does not have a structure consistent with the cubic crystal system. Instead, it is a stacking-disordered material containing cubic sequences interlaced with hexagonal sequences, which is termed stacking-disordered ice (ice Isd). In this article, we summarise previous work on ice with stacking disorder including ice that was called cubic ice in the past. We also present new experimental data which shows that ice which crystallises after heterogeneous nucleation in water droplets containing solid inclusions also contains stacking disorder even at freezing temperatures of around -15 °C. This supports the results from molecular simulations, that the structure of ice that crystallises initially from supercooled water is always stacking-disordered and that this metastable ice can transform to the stable hexagonal phase subject to the kinetics of recrystallization. We also show that stacking disorder in ice which forms from water droplets is quantitatively distinct from ice made via other routes. The emerging picture of ice I is that of a very complex material which frequently contains stacking disorder and this stacking disorder can vary in complexity depending on the route of formation and thermal history. PMID:25380218

Malkin, Tamsin L; Murray, Benjamin J; Salzmann, Christoph G; Molinero, Valeria; Pickering, Steven J; Whale, Thomas F

2015-01-01

165

Crystals  

NSDL National Science Digital Library

In this earth science/math/art activity, learners use simple ingredients to grow crystals and examine the repeating geometric shapes and patterns. Learners compare the growth of crystals from four types of crystal-starters (table salt, Borax, sand, and Epsom salt) to see which starter grows the most crystals in 14 days. Learners report their results online and find out what other learners discovered. Afterward, learners can use the crystals they grew to create works of art.

Science, Lawrence H.

2009-01-01

166

Crystal-like low frequency phonons in the low-density amorphous and high-density amorphous ices.  

PubMed

The structure and vibrational properties of high- and low-density amorphous (HDA and LDA, respectively) ices have been determined using reverse Monte Carlo, molecular dynamics, and lattice dynamics simulations. This combined approach leads to a more accurate and detailed structural description of HDA and LDA ices when compared to experiment than was previously possible. The water molecules in these ices form well connected hydrogen-bond networks that exhibit modes of vibration that extend throughout the solid and can involve up to 70% of all molecules. However, the networks display significant differences in their dynamical behavior. In HDA, the extended low-frequency vibrational modes occur in dense parallel two dimensional layers of water that are approximately 10 nm thick. In contrast, the extended modes in LDA resemble a holey structure that encapsulates many small pockets of nonparticipating water molecules. PMID:19044969

Belosludov, R V; Subbotin, O S; Mizuseki, H; Rodger, P M; Kawazoe, Y; Belosludov, V R

2008-09-21

167

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

168

Three-dimensional rocking curve imaging to measure the effective distortion in the neighbourhood of a defect within a crystal: an ice example.  

PubMed

Rocking curve imaging (RCI) is a quantitative version of monochromatic beam diffraction topography that involves using a two-dimensional detector, each pixel of which records its own 'local' rocking curve. From these local rocking curves one can reconstruct maps of particularly relevant quantities (e.g. integrated intensity, angular position of the centre of gravity, FWHM). Up to now RCI images have been exploited in the reflection case, giving a quantitative picture of the features present in a several-micrometre-thick subsurface layer. Recently, a three-dimensional Bragg diffraction imaging technique, which combines RCI with 'pinhole' and 'section' diffraction topography in the transmission case, was implemented. It allows three-dimensional images of defects to be obtained and measurement of three-dimensional distortions within a 50?×?50?×?50?µm elementary volume inside the crystal with angular misorientations down to 10(-5)-10(-6)?rad. In the present paper, this three-dimensional-RCI (3D-RCI) technique is used to study one of the grains of a three-grained ice polycrystal. The inception of the deformation process is followed by reconstructing virtual slices in the crystal bulk. 3D-RCI capabilities allow the effective distortion in the bulk of the crystal to be investigated, and the predictions of diffraction theories to be checked, well beyond what has been possible up to now. PMID:24046486

Philip, Armelle; Meyssonnier, Jacques; Kluender, Rafael T; Baruchel, José

2013-08-01

169

Three-dimensional rocking curve imaging to measure the effective distortion in the neighbourhood of a defect within a crystal: an ice example  

PubMed Central

Rocking curve imaging (RCI) is a quantitative version of monochromatic beam diffraction topography that involves using a two-dimensional detector, each pixel of which records its own ‘local’ rocking curve. From these local rocking curves one can reconstruct maps of particularly relevant quantities (e.g. integrated intensity, angular position of the centre of gravity, FWHM). Up to now RCI images have been exploited in the reflection case, giving a quantitative picture of the features present in a several-micrometre-thick subsurface layer. Recently, a three-dimensional Bragg diffraction imaging technique, which combines RCI with ‘pinhole’ and ‘section’ diffraction topography in the transmission case, was implemented. It allows three-dimensional images of defects to be obtained and measurement of three-dimensional distortions within a 50?×?50?×?50?µm elementary volume inside the crystal with angular misorientations down to 10?5–10?6?rad. In the present paper, this three-dimensional-RCI (3D-RCI) technique is used to study one of the grains of a three-grained ice polycrystal. The inception of the deformation process is followed by reconstructing virtual slices in the crystal bulk. 3D-RCI capabilities allow the effective distortion in the bulk of the crystal to be investigated, and the predictions of diffraction theories to be checked, well beyond what has been possible up to now. PMID:24046486

Philip, Armelle; Meyssonnier, Jacques; Kluender, Rafael T.; Baruchel, José

2013-01-01

170

Ice Nucleation in Deep Convection  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

171

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

172

Numerical simulations of contrail-to-cirrus transition - Part 2: Impact of initial ice crystal number, radiation, stratification, secondary nucleation and layer depth  

NASA Astrophysics Data System (ADS)

Simulations of contrail-to-cirrus transition were performed with an LES model. In Part 1 the impact of relative humidity, temperature and vertical wind shear was explored in a detailed parametric study. Here, we study atmospheric parameters like stratification and depth of the supersaturated layer and processes which may affect the contrail evolution. We consider contrails in various radiation scenarios herein defined by the season, time of day and the presence of lower-level cloudiness which controls the radiance incident on the contrail layer. Under suitable conditions, controlled by the radiation scenario and stratification, radiative heating lifts the contrail-cirrus and prolongs its lifetime. The potential of contrail-driven secondary nucleation is investigated. We consider homogeneous nucleation and heterogeneous nucleation of preactivated soot cores released from sublimated contrail ice crystals. In our model the contrail dynamics triggered by radiative heating does not suffice to force homogeneous freezing of ambient liquid aerosol particles. Furthermore, our model results suggest that heterogeneous nucleation of preactivated soot cores is unimportant. Contrail evolution is not controlled by the depth of the supersaturated layer as long as it exceeds roughly 500 m. Deep fallstreaks however need thicker layers. A variation of the initial ice crystal number is effective during the whole evolution of a contrail. A cut of the soot particle emission by two orders of magnitude can reduce the contrail timescale by one hour and the optical thickness by a factor of 5. Hence future engines with lower soot particle emissions could potentially lead to a reduction of the climate impact of aviation.

Unterstrasser, S.; Gierens, K.

2010-02-01

173

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

174

The viscoplastic behaviour of ice in polar ice sheets: experimental results and modelling  

Microsoft Academic Search

The slow motion of polar ice sheets is governed by the viscous deformation of anisotropic ices. Physical mechanisms controlling the deformation of ice crystal and polycrystal are reviewed. For the low stress conditions prevailing in ice sheets, the stress exponent of the flow law is lower than 2 and the deformation is dominated by the glide of dislocations on the

Maurine Montagnat; Paul Duval

2004-01-01

175

MEAT, POULTRY, Still contains ice  

E-print Network

MEAT, POULTRY, SEAFOOD Still contains ice crystals and feels as cold, and ground meats Refreeze Discard Poultry and ground poultry Refreeze Discard Variety meats, entree, specialty items (pizza, sausage and biscuit, meat pie,convenience foods

Liskiewicz, Maciej

176

Ice analog halos.  

PubMed

Crystals of sodium fluorosilicate are used to produce easy to set up visual displays of atmospheric halos, including the 22 degrees halo, the Parry arc, and upper tangent arcs. Scattering phase functions for single ice-analog rosettes, including a rough one, and a column aggregate, measured in randomized orientation, are also given. The phase functions show prominent halo features, with the exception of the rough crystal. PMID:16201438

Ulanowski, Zbigniew

2005-09-20

177

Overview of Icing Research at NASA Glenn  

NASA Technical Reports Server (NTRS)

The aviation industry continues to deal with icing-related incidents and accidents on a regular basis. Air traffic continues to increase, placing more aircraft in adverse icing conditions more frequently and for longer periods. Icing conditions once considered rare or of little consequence, such as super-cooled large droplet icing or high altitude ice crystals, have emerged as major concerns for modern aviation. Because of this, there is a need to better understand the atmospheric environment, the fundamental mechanisms and characteristics of ice growth, and the aerodynamic effects due to icing, as well as how best to protect these aircraft. The icing branch at NASA Glenn continues to develop icing simulation methods and engineering tools to address current aviation safety issues in airframe, engine and rotorcraft icing.

Kreeger, Richard E.

2013-01-01

178

Layered Ice  

USGS Multimedia Gallery

An ice jam on the East Branch Wesserunsett Stream in Athens, Maine in January 2014 left 3-5 ft ice walls on the riverbanks. On a January 21, 2014 site visit Nick Stasulis and Charlie Culbertson chisled away some of the ice wall so a discharge measurement could be made. The ice walls showed the ...

179

Ice Sheets  

NSDL National Science Digital Library

This educational brief describes the nature and properties of the Greenland and Antarctica ice sheets. Topics include the thickness and aereal extent of the ice sheets, volume of water contained in them, mass balance, and the mechanisms by which ice is lost from or accumulated by the ice sheets.

180

crystals  

NASA Astrophysics Data System (ADS)

We present the crystal growth, optical spectroscopy, and room temperature continuous-wave (CW) laser operation of monoclinic Ho:KLu(WO4)2 crystals. Macro defect-free crystals of several dopant concentrations were grown by top-seeded solution growth slow-cooling method. The evolution of unit cell parameters with holmium doping level and temperature was studied using X-ray powder diffraction. The spectroscopic properties were characterized in terms of room- and low-temperature optical absorption and photoluminescence. From low-temperature optical absorption measurements, the energy of the Stark levels was determined. Calculation of the emission and gain cross sections is presented. CW laser action was realized for 3 and 5 at. % Ho-doped KLu(WO4)2 by in-band pumping using a Tm:KLu(WO4)2 pump laser. A maximum output power of 507 mW with a slope efficiency of ~38 % with respect to the incident power was achieved at 2,080 nm with the Ho:KLu(WO4)2 laser.

Jambunathan, V.; Mateos, X.; Pujol, M. C.; Carvajal, J. J.; Zaldo, C.; Griebner, U.; Petrov, V.; Aguiló, M.; Díaz, F.

2014-08-01

181

Colloidal aspects of ice cream—A review  

Microsoft Academic Search

Ice cream is a complex food colloid that consists of air bubbles, fat globules, ice crystals and an unfrozen serum phase. Ice crystals and air bubbles are usually in the range of 20–50 ?m. The air bubbles are usually partially coated with fat globules and the fat globules are coated with a protein\\/emulsifier layer. The serum phase consists of the

H. Douglas Goff

1997-01-01

182

Visible and near infrared reflectances measured from laboratory ice clouds  

E-print Network

based on the fact that the reflec- tion from ice clouds in the nonabsorbing VIS is pri- marily dependentVisible and near infrared reflectances measured from laboratory ice clouds Brian Barkey* and K. N typically used for inferring optical depth and ice crystal size from satellite radiometers, from ice clouds

Liou, K. N.

183

Method of forming calthrate 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 ultransonically so that small crystals are formed in the liquid. Thes 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, T.; Gorski, A.J.

1985-09-30

184

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

185

PSL Icing Facility Upgrade Overview  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center Propulsion Systems Lab (PSL) was recently upgraded to perform engine inlet ice crystal testing in an altitude environment. The system installed 10 spray bars in the inlet plenum for ice crystal generation using 222 spray nozzles. As an altitude test chamber, the PSL is capable of simulating icing events at altitude in a groundtest facility. The system was designed to operate at altitudes from 4,000 to 40,000 ft at Mach numbers up to 0.8M and inlet total temperatures from -60 to +15 degF. This paper and presentation will be part of a series of presentations on PSL Icing and will cover the development of the icing capability through design, developmental testing, installation, initial calibration, and validation engine testing. Information will be presented on the design criteria and process, spray bar developmental testing at Cox and Co., system capabilities, and initial calibration and engine validation test. The PSL icing system was designed to provide NASA and the icing community with a facility that could be used for research studies of engine icing by duplicating in-flight events in a controlled ground-test facility. With the system and the altitude chamber we can produce flight conditions and cloud environments to simulate those encountered in flight. The icing system can be controlled to set various cloud uniformities, droplet median volumetric diameter (MVD), and icing water content (IWC) through a wide variety of conditions. The PSL chamber can set altitudes, Mach numbers, and temperatures of interest to the icing community and also has the instrumentation capability of measuring engine performance during icing testing. PSL last year completed the calibration and initial engine validation of the facility utilizing a Honeywell ALF502-R5 engine and has duplicated in-flight roll back conditions experienced during flight testing. This paper will summarize the modifications and buildup of the facility to accomplish these tests.

Griffin, Thomas A.; Dicki, Dennis J.; Lizanich, Paul J.

2014-01-01

186

The Development of Measurement Techniques to Identify and Characterize Dusts and Ice Nuclei in the Atmosphere  

E-print Network

Mineral dusts and ice crystals directly influence the Earth's radiative budget through radiative scattering and absorption. The interaction of spherical particles on the radiative budget are well known, however mineral dusts and ice crystals...

Glen, Andrew

2014-01-15

187

Identification of Clathrate Hydrates, Hexagonal Ice, Cubic Ice, and Liquid Water in Simulations: the CHILL+ Algorithm.  

PubMed

Clathrate hydrates and ice I are the most abundant crystals of water. The study of their nucleation, growth, and decomposition using molecular simulations requires an accurate and efficient algorithm that distinguishes water molecules that belong to each of these crystals and the liquid phase. Existing algorithms identify ice or clathrates, but not both. This poses a challenge for cases in which ice and hydrate coexist, such as in the synthesis of clathrates from ice and the formation of ice from clathrates during self-preservation of methane hydrates. Here we present an efficient algorithm for the identification of clathrate hydrates, hexagonal ice, cubic ice, and liquid water in molecular simulations. CHILL+ uses the number of staggered and eclipsed water-water bonds to identify water molecules in cubic ice, hexagonal ice, and clathrate hydrate. CHILL+ is an extension of CHILL (Moore et al. Phys. Chem. Chem. Phys. 2010, 12, 4124-4134), which identifies hexagonal and cubic ice but not clathrates. In addition to the identification of hydrates, CHILL+ significantly improves the detection of hexagonal ice up to its melting point. We validate the use of CHILL+ for the identification of stacking faults in ice and the nucleation and growth of clathrate hydrates. To our knowledge, this is the first algorithm that allows for the simultaneous identification of ice and clathrate hydrates, and it does so in a way that is competitive with respect to existing methods used to identify any of these crystals. PMID:25389702

Nguyen, Andrew H; Molinero, Valeria

2014-11-25

188

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

189

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.

190

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.

2012-07-19

191

Effect of Sweetener, Stabilizer, and Storage Temperature on Ice Recrystallization in Ice Cream  

Microsoft Academic Search

ABSTRACT In ice cream manufacturing, control of ice crystal growth,through,proper formulation,and storage tem- perature is important,for stability during storage. The objective of this study was,to investigate the influence of sweetener (sucrose, 20 dextrose equivalent corn syrup, 42 dextrose equivalent corn syrup, and 42 high fructose corn syrup), with and without stabilizer, on ice recrystallization in ice cream,at three storage temperatures.

Tadashi Hagiwara; Richard W. Hartelt

1996-01-01

192

Cometary Ices  

NASA Astrophysics Data System (ADS)

The purpose of this chapter is to survey the empirical situation of cometary ices, as they are known today - their location in the solar system, the discernable nature of the ices from remote sensing measurements, and the important physico-chemical properties of the ice known from previous laboratory studies. We then attempt to synthesize this phenomenological data into a framework for recognizing the most important unresolved issues in understanding the behavior of low temperature, porous, mixed amorphous/crystalline and radiation damaged ices together with their ability to trap gases and release them upon warming - with the hope of launching new, important laboratory studies of cometary ice analogues.

Lisse, Carey; Bar-Nun, Akiva; Laufer, Diana; Belton, Michael; Harris, Walter; Hsieh, Henry; Jewitt, David

193

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.

194

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

195

Frost flower formation on sea ice and lake ice  

NASA Astrophysics Data System (ADS)

Frost flowers are clusters of ice crystals found on freshly formed sea ice and occasionally on frozen lakes. They belong to a class of vapour-related phenomena that includes freezing fog, hoar frost and dew. It has hitherto been supposed that they form by condensation from a supersaturated atmosphere or from water wicked up through porous sea ice. Here we show that they can form on solid, pure ice sublimating into an unsaturated atmosphere. We derive a general regime diagram showing the atmospheric conditions under which the different vapour-related phenomena occur and confirm our predictions of frost-flower formation with a series of laboratory experiments. Our results can be used in climate models to predict occurrence of frost flowers, which significantly enhance albedo and provide the substrate for chemical production of ozone-depleting bromine monoxide, and in paleo-climate reconstructions by relating observations of sea-salt aerosols in ice cores to atmospheric conditions.

Style, Robert W.; Worster, M. Grae

2009-06-01

196

Ice Nuclei Production in Volcanic Clouds  

NASA Astrophysics Data System (ADS)

The paper [Durant et al., 2008] includes a review of research on ice nucleation in explosive volcanic clouds in addition to reporting their own research on laboratory measurements focused on single-particle ice nucleation. Their research as well as the research they reviewed were concerned with the freezing of supercooled water drops (250 to 260 K) by volcanic ash particles acting as ice freezing nuclei. Among their conclusions are: Fine volcanic ash particles are very efficient ice freezing nuclei. Volcanic clouds likely contain fine ash concentrations 104 to 105 times greater than found in meteorological clouds. This overabundance of ice nuclei will produce a cloud with many small ice crystals that will not grow larger as they do in meteorological clouds because the cloud water content is widely distributed among the numerous small ice crystals. The small ice crystals have a small fall velocity, thus volcanic clouds are very stable. The small ice crystals are easily lofted into the stratosphere transporting water and adsorbed trace gasses. In this paper we examine the mechanism for the production of the small ice nuclei and develop a simple model for calculating the size of the ice nuclei based upon the distribution of magma around imbedded bubbles. We also have acquired a volcanic bomb that exhibits bubble remnants on its entire surface. The naturally occurring fragments from the volcanic bomb reveal a size distribution consistent with that predicted by the simple model. Durant, A. J., R. A. Shaw, W. I. Rose, Y. Mi, and G. G. J. Ernst (2008), Ice nucleation and overseeding of ice in volcanic clouds, J. Geophys. Res., 113, D09206, doi:10.1029/2007JD009064.

Few, A. A.

2012-12-01

197

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

198

Physical states of astronomical ices  

NASA Astrophysics Data System (ADS)

The physical state of water ice at low temperatures is a subject of continuing research and debate. Particularly in astrophysics, the phases of water ice are an important indicator of the state, history and evolution of the icy astrophysical surfaces such as those found in the outer solar system (e.g., icy satellites and planetary surfaces, rings, trans-Neptunian objects), comets, or in the interstellar clouds. When deposited from the vapor phase, and depending on the substrate temperature, water ice can be found crystalline (hexagonal or cubic) or amorphous. In this work, we address the question of how the deposition rate (several orders of magnitude different between laboratory conditions and real astrophysical surfaces), the presence of contaminants (a likely scenario for astrophysical bodies) and the constantly exposure to radiation environments can affect the final state for the water ice phases.We also present a detailed study of the isothermal crystallization of thick ASW ice films grown at 100 K. These films are thick enough to ensure that the crystallization rate remains independent of substrate and influenced/initiated by surface nucleation. The phase transformation is studied as a function of annealing temperature and is monitored via infrared spectroscopy over a range of temperatures (130 - 140 K). Determination of the extent of crystalline during annealing is determined via the de-convolution of the partially crystallized infrared spectrum into amorphous and crystalline components. The present measurements aim to resolve some anomalies in the literature regarding the crystallization mechanism of ASW.

Fama, Marcelo A.; Burke, D.; Baragiola, R. A.

2009-09-01

199

Oily Ice  

NSDL National Science Digital Library

In this activity, learners experiment with the density of ice, water, and oil. Learners will discover that the density of a liquid determines whether it will float above or sink below another liquid. Learners will be surprised to find that ice floats and water sinks in oil, even though ice and water are made of the same thing. Learners will also examine the hydrophilic properties of water and the hydrophobic nature of oil.

Workshop, Mission S.

2013-01-01

200

Sea Ice  

NASA Technical Reports Server (NTRS)

During 2013, Arctic sea ice extent remained well below normal, but the September 2013 minimum extent was substantially higher than the record-breaking minimum in 2012. Nonetheless, the minimum was still much lower than normal and the long-term trend Arctic September extent is -13.7 per decade relative to the 1981-2010 average. The less extreme conditions this year compared to 2012 were due to cooler temperatures and wind patterns that favored retention of ice through the summer. Sea ice thickness and volume remained near record-low levels, though indications are of slightly thicker ice compared to the record low of 2012.

Perovich, D.; Gerland, S.; Hendricks, S.; Meier, Walter N.; Nicolaus, M.; Richter-Menge, J.; Tschudi, M.

2013-01-01

201

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

202

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

203

Effect of Salts on the Properties of Aqueous Sugar Systems, in Relation to Biomaterial Stabilization. 1. Water Sorption Behavior and Ice Crystallization\\/Melting  

Microsoft Academic Search

Trehalose and sucrose, two sugars that are involved in the protection of living organisms under extreme conditions, and their mixtures with salts were employed to prepare supercooled or freeze-dried glassy systems. The objective of the present work was to explore the effects of different salts on water sorption, glass transition temperature (Tg), and formation and melting of ice in aqueous

M. F. Mazzobre; M. P. Longinotti; H. R. Corti; M. P. Buera

2001-01-01

204

The time-dependence of the defective nature of ice Ic (cubic ice) and its implications for atmospheric science  

Microsoft Academic Search

The possible atmospheric implication of ice Ic (cubic ice) has already been suggested some time ago in the context of snow crystal formation [1]. New findings from air-borne measurements in cirrus clouds and contrails have put ice Ic into the focus of interest to understand the so-called \\

Christian Sippel; Michael M. Koza; Thomas C. Hansen; Werner F. Kuhs

2010-01-01

205

Ice cream structural elements that affect melting rate and hardness.  

PubMed

Statistical models were developed to reveal which structural elements of ice cream affect melting rate and hardness. Ice creams were frozen in a batch freezer with three types of sweetener, three levels of the emulsifier polysorbate 80, and two different draw temperatures to produce ice creams with a range of microstructures. Ice cream mixes were analyzed for viscosity, and finished ice creams were analyzed for air cell and ice crystal size, overrun, and fat destabilization. The ice phase volume of each ice cream were calculated based on the freezing point of the mix. Melting rate and hardness of each hardened ice cream was measured and correlated with the structural attributes by using analysis of variance and multiple linear regression. Fat destabilization, ice crystal size, and the consistency coefficient of the mix were found to affect the melting rate of ice cream, whereas hardness was influenced by ice phase volume, ice crystal size, overrun, fat destabilization, and the rheological properties of the mix. PMID:14765804

Muse, M R; Hartel, R W

2004-01-01

206

Retrieval of Ice Cloud Properties Using Variable Phase Functions  

NASA Astrophysics Data System (ADS)

An enhancement to NASA Langley's Visible Infrared Solar-infrared Split-window Technique (VISST) is developed to identify and account for situations when errors are induced by using smooth ice crystals. The retrieval scheme incorporates new ice cloud phase functions that utilize hexagonal crystals with roughened surfaces. In some situations, cloud optical depths are reduced, hence, cloud height is increased. Cloud effective particle size also changes with the roughened ice crystal models which results in varied effects on the calculation of ice water path. Once validated and expanded, the new approach will be integrated in the CERES MODIS algorithm and real-time retrievals at Langley.

Heck, Patrick W.; Minnis, Patrick; Yang, Ping; Chang, Fu-Lung; Palikonda, Rabindra; Arduini, Robert F.; Sun-Mack, Sunny

2009-03-01

207

The DC-8 Submillimeter-Wave Cloud Ice Radiometer  

NASA Technical Reports Server (NTRS)

Submillimeter-wave cloud ice radiometry is an innovative technique for determining the amount of ice present in cirrus clouds, measuring median crystal size, and constraining crystal shape. The radiometer described in this poster is being developed to acquire data to validate radiometric retrievals of cloud ice at submillimeter wavelengths. The goal of this effort is to develop a technique to enable spaceborne characterization of cirrus, meeting key climate modeling and NASA measurement needs.

Walter, Steven; Batelaan, Paul; Siegel, Peter; Evans, K. Franklin; Evans, Aaron; Balachandra, Balu; Gannon, Jade; Guldalian, John; Raz, Guy; Shea, James; Smith, Christopher; Thomassen, John

2000-01-01

208

Flammable Ice  

NSDL National Science Digital Library

What's cooler than being cool? Setting ice on fire! In this demonstration, educators can amaze learners by setting ice on fire. Through this activity, learners can explore the properties of everyday materials and observe how these materials can change states to produce gas. Safety note: this activity is not suitable for learners to do themselves and should only be conducted by an experienced educator in a well ventilated lab area. Before doing this demonstration, educators should read the "Practicalities" section.

Museum, Science

2012-04-12

209

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

SciTech Connect

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

Jensen, E.J.; Toon, O.B. [NASA, Ames Research Center, Moffett Field, CA (United States)] [NASA, Ames Research Center, Moffett Field, CA (United States)

1994-09-01

210

Seismic anisotropy in ice: numerical modelling, ice core measurements and in-situ observations  

NASA Astrophysics Data System (ADS)

The stress distribution and style of flow in ice produces elastic and rheological anisotropy, which informs ice flow modelling as to how ice masses respond to external changes such as global warming. Here observations of shear wave splitting from three-component icequake seismograms are used to characterise ice anisotropy in the Rutford ice stream, West Antarctica. Over 110 high quality measurements are made on 41 events recorded at five stations temporarily deployed near the ice stream grounding line. The magnitude of the splitting ranges from 2ms to 80ms and suggest a maximum of 6% shear wave splitting. The fast shear wave polarisation direction is roughly perpendicular to the ice flow direction. Motivated by these observations, we consider mechanisms for seismic anisotropy in ice using numerical modelling of the development of crystal preferred orientation of ice and measurement of crystal alignment in an ice core using electron back-scattered diffraction (EBSD). These results suggest transitions in the style of anisotropy both with depth and laterally within an ice stream. Seismic anisotropy is developed with increasing hydrostatic pressure producing a VTI fabric with a vertical alignment of c-axes (so-called cluster fabric). However, convergence in the ice flow and along-flow extension leads to girdles of c-axes (and an HTI fabric). Based on the Rutford shear-wave splitting observations we can rule out a cluster fabric as the sole cause of anisotropy - an HTI component is needed, which may be due extension in the direction of flow forming a girdle fabric or the alignment of cracks or ice-films in the plane perpendicular to the flow direction. Cumulatively, our observations suggest a combination of anisotropy mechanisms are at play in deforming ice sheets. We discuss seismic measurements that can be made to better discriminate between plausible mechanisms for our shear-wave splitting observations and how these different mechanisms may in turn alter ice flow and glacial response to external changes.

Kendall, J. M.; Baird, A. F.; Walker, A.; Wookey, J. M.; Lloyd, G. E.; Stuart, G. W.; Harland, S.; Obbard, R. W.; Smith, A.; Brisbourne, A.

2013-12-01

211

Terrestrial Sea Ice Morphology: Considerations for Europa  

NASA Astrophysics Data System (ADS)

The Galileo mission has returned the first high-resolution (21 m/pixel) images of the surface of Europa. These images reveal structures with morphologies reminiscent of those seen on terrestrial sea ice. Although it is premature to make one-to-one analogies between sea ice and Europa's surface, a review of the types of surface features commonly formed on Earth and of various sea-ice processes can provide insight into the complex geology of Europa. For example, deformation of terrestrial sea ice results from winds, tides, and currents and from thermally induced stresses; the resulting features include fractures ranging in width from millimeters to kilometers, pressure ridges, shear ridges, and rafted ice. Potential agents of deformation on Europa are more likely to be limited to tidal flexing and possibly convection, but could produce similar features and perhaps account for the ridges and fractures seen in many areas. Subtle differences in albedo and color in terrestrial sea ice result from differences in ice thickness and grain size, attributed to factors such as the rate of ice-crystal growth, water turbulence, age of the ice, and deformation. Similar factors could account for differences observed in the bright icy plains of Europa. Moreover, salts in both the solid form and as brine vary in concentration and composition as a function of space and time on Earth, leading to differences in density and the strength of ice sheets. Salts are also suspected in the europan ice and could lead to similar differences, enhancing the creation of topographic relief from density contrasts and the formation of fractures from brittle failure of the ice. Differences in the environments between Europa and terrestrial sea ice in terms of parameters such as temperature, gravity, time, and ice compositions suggest caution in drawing direct analogies. Future work by the planetary and sea-ice communities must include understanding the terrestrial processes sufficiently for extrapolation to Europa.

Greeley, Ronald; Sullivan, Robert; Coon, Max D.; Geissler, Paul E.; Tufts, B. Randall; Head, James W.; Pappalardo, Robert T.; Moore, Jeffrey M.

1998-09-01

212

Influence of a phase transition of ice on the heat and mass balance of comets  

Microsoft Academic Search

The effects of the presence of amorphous ice, crystallized at temperatures below 100 K, in comet nuclei on the heat and mass balance of comets are examined. The heat conduction coefficient of amorphous ice is estimated to be at least ten times lower than that of hexagonal ice above 20 K, with the amorphous ice coefficient increasing with temperature up

J. Klinger

1980-01-01

213

Forecasting Aviation Icing: Icing Type and Severity  

NSDL National Science Digital Library

This module discusses the current theories of atmospheric conditions associated with aircraft icing and applies the theories to the icing diagnosis and forecast process. The contribution of liquid water content, temperature, and droplet size parameters to icing are examined. Identification of icing type, icing severity, and the hazards associated with icing features are presented. Tools to help diagnose atmospheric processes that may be contributing to icing and the special case of supercooled large drop (SLD) icing are examined and applied in short exercises. The use of graphics, animations, and interactive exercises in Forecasting Aviation Icing: Icing Type and Severity helps the forecaster to gain an understanding of icing processes, to identify icing hazards, and to apply diagnosis and forecast tools as aids to evaluate and anticipate potential aircraft icing threats. The subject matter expert for this module is Dr. Marcia Politovich of NCAR/Research Applications Program. This module is also available in French.

2014-09-14

214

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

215

laser ultrasonic characterization of ice cores  

NASA Astrophysics Data System (ADS)

We present preliminary measurements on ice cores of elastic wave forms at ultrasonic frequencies. The aim of the project is to map out internal properties of the ice to improve our understanding of the processes responsible for the ice structure. Annual layering is one of the targets, but the alignment of ice crystals is another.We use a system based on laser sources and receivers for a number of reasons. First, the lasers allow us to probe the ice in a non-destructive and non-contacting matter through optical windows into our cold room. Second, the lasers/core system is controlled via computerized stages, which allow us to have unprecedented data density, repeatable data acquisition, and high fidelity in each waveform. We calibrated layering properties with man-made ice structures, and we will present ongoing tests on Antarctic cores from various depths and locations.

van Wijk, K.; Otheim, L. T.; Marshall, H.; Kurbatov, A.; Spaulding, N. E.

2013-12-01

216

SURVIVAL OF AMORPHOUS WATER ICE ON CENTAURS  

SciTech Connect

Centaurs are believed to be Kuiper Belt objects in transition between Jupiter and Neptune before possibly becoming Jupiter family comets. Some indirect observational evidence is consistent with the presence of amorphous water ice in Centaurs. Some of them also display a cometary activity, probably triggered by the crystallization of the amorphous water ice, as suggested by Jewitt and this work. Indeed, we investigate the survival of amorphous water ice against crystallization, using a fully three-dimensional thermal evolution model. Simulations are performed for varying heliocentric distances and obliquities. They suggest that crystallization can be triggered as far as 16 AU, though amorphous ice can survive beyond 10 AU. The phase transition is an efficient source of outgassing up to 10-12 AU, which is broadly consistent with the observations of the active Centaurs. The most extreme case is 167P/CINEOS, which barely crystallizes in our simulations. However, amorphous ice can be preserved inside Centaurs in many heliocentric distance-obliquity combinations, below a {approx}5-10 m crystallized crust. We also find that outgassing due to crystallization cannot be sustained for a time longer than 10{sup 4}-10{sup 4} years, leading to the hypothesis that active Centaurs might have recently suffered from orbital changes. This could be supported by both observations (although limited) and dynamical studies.

Guilbert-Lepoutre, Aurelie, E-mail: aguilbert@ucla.edu [Department of Earth and Space Sciences, UCLA, Los Angeles, CA 90095 (United States)

2012-10-01

217

Investigating the « ice mélange » in an ice-shelf coastal rift along the Princess Ragnhild Coast (Antarctica)  

NASA Astrophysics Data System (ADS)

This paper presents the first results of a glaciological investigation conducted in the vicinity of the new Belgian Antarctic research station "Princess Elisabeth" during the 2008-2009 Antarctic field season. The study is part of the BELISSIMA project which aim is to investigate the dynamics of transition zones at the grounding line and the interaction of the ice sheet and the ice-shelf with the ocean, with respect to the stability of the ice sheet. The studied site is a conspicuous rift zone developed in a short floating ice shelf, a few kilometres downstream from the grounding line associated with the presence of a coastal ice dome. The rift, very close to the location of the old Belgian Station "Base Roi Baudouin", is about 10 km long and between 0.5 and 4 km wide. A natural ramp on the eastern apex of the rift allowed access to the rift base, from where a series of five, 10-38 m-long cores were recovered. Visual observation of these cores indicates that they consist of heterogeneous ice types, which is typical of what is often referred to as the "ice mélange". Wind-blown snow, firn and ice dominate outside the rift and within the rift's apex ramp. However, within the base of the rift proper, where episodic tensional stresses dominate, the ice is correspondingly more heavily crevassed and shows clear surface albedo contrasts, suggesting material heterogeneity. Ice cores from these areas show an abrupt transition within a few metres of the surface from surface-derived firn and ice to a sharply contrasting ice type that is translucent, greenish, and bubble-free -interpreted as marine ice. Such ice results from the consolidation of frazil ice crystals which are known to be forming in Ice Shelf Water through ice-ocean interactions in other regions of Antarctica (e.g. Filchner-Ronne Ice Shelf, Amery ice Shelf, Nansen Ice Shelf). One of our drill sites was located in a surface outcrop of marine ice, yielding 13 m of solid translucent ice, overlying ~0.5 m of fragile and loosely consolidated ice before the sub-shelf interface was reached. Borehole images from below this interface reveal an additional thickness of at least 5 m of loose platelet ice crystals located below the shelf, suggesting an active thermohaline convection in the region. The paper presents textural, structural, bulk salinity, bulk density and stable isotopes (DeltaD, Delta18O) results from the five ice cores and discusses origin and transformation of the various ice types forming the "ice mélange" and their potential impact on the welding efficiency of the rift.

Depoorter, Mathieu; Samyn, Denis; Hubbard, Bryn; Pattyn, Frank; Matsuoka, Kenny; Dierckx, Marie; Tison, Jean-Louis

2010-05-01

218

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

219

Comparing ice chart parameters against ice observations  

Microsoft Academic Search

Operational ice centres produce daily ice charts for offshore operators to help them operate safely and efficiently in ice-infested waters. The charts describe only the level ice component of the ice thickness, and not the deformed component. Using a helicopter-borne electromagnetic (EM)-laser system and downward-looking video camera, ice thickness distributions and video mosaics were obtained along long flight tracks, and

Simon Prinsenberg; Ingrid Peterson

220

Food Crystallization and Egg Products  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sugar, salt, lactose, tartaric acid and ice are examples of constituents than can crystallize in foods. Crystallization in a food product can be either beneficial or detrimental and is of particular importance in candy and frozen desserts. The most common crystal in foods is sugar which affects th...

221

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

222

High pressure ices  

PubMed Central

H2O will be more resistant to metallization than previously thought. From computational evolutionary structure searches, we find a sequence of new stable and meta-stable structures for the ground state of ice in the 1–5 TPa (10 to 50 Mbar) regime, in the static approximation. The previously proposed Pbcm structure is superseded by a Pmc21 phase at p = 930 GPa, followed by a predicted transition to a P21 crystal structure at p = 1.3 TPa. This phase, featuring higher coordination at O and H, is stable over a wide pressure range, reaching 4.8 TPa. We analyze carefully the geometrical changes in the calculated structures, especially the buckling at the H in O-H-O motifs. All structures are insulating—chemistry burns a deep and (with pressure increase) lasting hole in the density of states near the highest occupied electronic levels of what might be component metallic lattices. Metallization of ice in our calculations occurs only near 4.8 TPa, where the metallic C2/m phase becomes most stable. In this regime, zero-point energies much larger than typical enthalpy differences suggest possible melting of the H sublattice, or even the entire crystal. PMID:22207625

Hermann, Andreas; Ashcroft, N. W.; Hoffmann, Roald

2012-01-01

223

Smart Icing Systems for Aircraft Icing Safety  

Microsoft Academic Search

Ice accretion affects the performance and control of an aircraft and in extreme situations can lead to incidents and accidents. However, changes in performance and control are difficult to sense. As a result, the icing sensors currently in use sense primarily ice accretion, not the effect of the ice. No processed aircraft performance degradation information is available to the pilot.

Michael B. Bragg; Tamer Basar; William R. Perkins; Michael S. Selig

2002-01-01

224

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

225

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

226

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

227

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

228

Ice-surface adsorption enhanced colligative effect of antifreeze proteins in ice growth inhibition.  

PubMed

This Communication describes a mechanism to explain antifreeze protein's function to inhibit the growth of ice crystals. We propose that the adsorption of antifreeze protein (AFP) molecules on an ice surface induces a dense AFP-water layer, which can significantly decrease the mole fraction of the interfacial water and, thus, lower the temperature for a seed ice crystal to grow in a super-cooled AFP solution. This mechanism can also explain the nearly unchanged melting point for the ice crystal due to the AFP's ice-surface adsorption. A mathematical model combining the Langmuir theory of adsorption and the colligative effect of thermodynamics has been proposed to find the equilibrium constants of the ice-surface adsorptions, and the interfacial concentrations of AFPs through fitting the theoretical curves to the experimental thermal hysteresis data. This model has been demonstrated by using the experimental data of serial size-mutated beetle Tenebrio molitor (Tm) AFPs. It was found that the AFP's ice-surface adsorptions could increase the interfacial AFP's concentrations by 3 to 4 orders compared with those in the bulk AFP solutions. PMID:16965064

Mao, Yougang; Ba, Yong

2006-09-01

229

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

230

Ice-surface adsorption enhanced colligative effect of antifreeze proteins in ice growth inhibition  

NASA Astrophysics Data System (ADS)

This Communication describes a mechanism to explain antifreeze protein's function to inhibit the growth of ice crystals. We propose that the adsorption of antifreeze protein (AFP) molecules on an ice surface induces a dense AFP-water layer, which can significantly decrease the mole fraction of the interfacial water and, thus, lower the temperature for a seed ice crystal to grow in a super-cooled AFP solution. This mechanism can also explain the nearly unchanged melting point for the ice crystal due to the AFP's ice-surface adsorption. A mathematical model combining the Langmuir theory of adsorption and the colligative effect of thermodynamics has been proposed to find the equilibrium constants of the ice-surface adsorptions, and the interfacial concentrations of AFPs through fitting the theoretical curves to the experimental thermal hysteresis data. This model has been demonstrated by using the experimental data of serial size-mutated beetle Tenebrio molitor (Tm) AFPs. It was found that the AFP's ice-surface adsorptions could increase the interfacial AFP's concentrations by 3 to 4 orders compared with those in the bulk AFP solutions.

Mao, Yougang; Ba, Yong

2006-09-01

231

Civil Helicopter icing problems  

NASA Technical Reports Server (NTRS)

The ice capabilities of rotary wing aircraft are examined. Recommendations are given to improve the inadequacies of the weather forecasts pertaining to ice, and to adopt a low maintenance anti-ice system.

Sweenkey, P. B.

1979-01-01

232

Phase Transformation and Intense 2.7??m Emission from Er3+ Doped YF3/YOF Submicron-crystals  

PubMed Central

Yttrium fluoride YF3:Er3+ and yttrium oxyfluoride YOF:Er3+ submicron-crystals with mid-infrared fluorescent emissions were synthesized for the first time. The rhombohedral phase YOF submicron-crystals were synthesized by the crystalline phase transformation from pure orthorhombic YF3 submicron-crystals, which were prepared by co-precipitation method. The composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM), which showed that submicron-crystals were quasi-spherical with the particle size of ~400?nm. A novel formation mechanism of YOF submicron-crystals was proposed. Photoluminescence (PL) spectra indicated the 2.7??m emission of Er3+ has remarkably enhanced with the increase of Er3+ doping concentration, and a novel dynamic circulatory energy transfer mechanism was proposed. Fourier transform infrared spectra (FTIR) were used to demonstrate the change of hydroxyl content. These oxyfluoride submicron-crystals provide a new material for nano/submicron-crystals-glass composites, and open a brand new field for the realization of mid-infrared micro/nano-lasers. PMID:23604234

Chai, Guanqi; Dong, Guoping; Qiu, Jianrong; Zhang, Qinyuan; Yang, Zhongmin

2013-01-01

233

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

234

Aeronomy of Ice in the Mesosphere Frequently Asked Questions  

E-print Network

AIM Aeronomy of Ice in the Mesosphere Frequently Asked Questions What is the purpose of the AIM) above the surface of the Earth. They are composed of water ice crystals that are less than about 100 the AIM mission, visit: http://lasp.colorado.edu/home/missions-projects/quick-facts-aim. Quick Facts

Mojzsis, Stephen J.

235

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

236

The sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea ice  

NASA Astrophysics Data System (ADS)

This is an investigation to quantify the influence of the sub-ice platelet layer on satellite measurements of total freeboard and their conversion to thickness of Antarctic sea ice. The sub-ice platelet layer forms as a result of the seaward advection of supercooled ice shelf water from beneath ice shelves. This ice shelf water provides an oceanic heat sink promoting the formation of platelet crystals which accumulate at the sea ice-ocean interface. The build-up of this porous layer increases sea ice freeboard, and if not accounted for, leads to overestimates of sea ice thickness from surface elevation measurements. In order to quantify this buoyant effect, the solid fraction of the sub-ice platelet layer must be estimated. An extensive in situ data set measured in 2011 in McMurdo Sound in the south-western Ross Sea is used to achieve this. We use drill-hole measurements and the hydrostatic equilibrium assumption to estimate a mean value for the solid fraction of this sub-ice platelet layer of 0.16. This is highly dependent upon the uncertainty in sea ice density. We test this value with independent Global Navigation Satellite System (GNSS) surface elevation data to estimate sea ice thickness. We find that sea ice thickness can be overestimated by up to 19%, with a mean deviation of 12% as a result of the influence of the sub-ice platelet layer. It is concluded that in close proximity to ice shelves this influence should be considered universally when undertaking sea ice thickness investigations using remote sensing surface elevation measurements.

Price, D.; Rack, W.; Langhorne, P. J.; Haas, C.; Leonard, G.; Barnsdale, K.

2014-02-01

237

The sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea ice  

NASA Astrophysics Data System (ADS)

This is an investigation to quantify the influence of the sub-ice platelet layer on satellite measurements of total freeboard and their conversion to thickness of Antarctic sea ice. The sub-ice platelet layer forms as a result of the seaward advection of supercooled ice shelf water from beneath ice shelves. This ice shelf water provides an oceanic heat sink promoting the formation of platelet crystals which accumulate at the sea ice-ocean interface. The build-up of this porous layer increases sea ice freeboard, and if not accounted for, leads to overestimates of sea ice thickness from surface elevation measurements. In order to quantify this buoyant effect, the solid fraction of the sub-ice platelet layer must be estimated. An extensive in situ data set measured in 2011 in McMurdo Sound in the southwestern Ross Sea is used to achieve this. We use drill-hole measurements and the hydrostatic equilibrium assumption to estimate a mean value for the solid fraction of this sub-ice platelet layer of 0.16. This is highly dependent upon the uncertainty in sea ice density. We test this value with independent Global Navigation Satellite System (GNSS) surface elevation data to estimate sea ice thickness. We find that sea ice thickness can be overestimated by up to 19%, with a mean deviation of 12% as a result of the influence of the sub-ice platelet layer. It is concluded that within 100 km of an ice shelf this influence might need to be considered when undertaking sea ice thickness investigations using remote sensing surface elevation measurements.

Price, D.; Rack, W.; Langhorne, P. J.; Haas, C.; Leonard, G.; Barnsdale, K.

2014-06-01

238

Cryosalts: suppression of ice formation in macromolecular crystallography.  

PubMed

Quality data collection for macromolecular cryocrystallography requires suppressing the formation of crystalline or microcrystalline ice that may result from flash-freezing crystals. Described here is the use of lithium formate, lithium chloride and other highly soluble salts for forming ice-ring-free aqueous glasses upon cooling from ambient temperature to 100 K. These cryosalts are a new class of cryoprotectants that are shown to be effective with a variety of commonly used crystallization solutions and with proteins crystallized under different conditions. The influence of cryosalts on crystal mosaicity and diffraction resolution is comparable with or superior to traditional organic cryoprotectants. PMID:10944336

Rubinson, K A; Ladner, J E; Tordova, M; Gilliland, G L

2000-08-01

239

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

240

Use of Doppler radar to assess ice cloud particle fall velocity-size relations for remote sensing and climate studies  

Microsoft Academic Search

Abstract. Knowledge of ice crystal terminal velocities, both for individual crystals and for size distributions, is important for an adequate representation of ice particle sedimentation in climate models. While the terminal velocities (vt) of individual crystals of simple shapes have been measured, theoretical relations of the form vt 5 AD , (where D is the maximum particle dimension), obtained using

Sergey Y. Matrosov; Andrew J. Heymsfield

2000-01-01

241

Evidence of liquid dependent ice nucleation in highlatitude stratiform clouds from surface remote sensors  

E-print Network

November 2010; accepted 5 December 2010; published 6 January 2011. [1] Groundbased lidar, radar and contact freezing. In deposition freezing, ice supersaturated conditions result in deposition of water vapor onto ice forming nuclei (IN), forming ice crystals. Condensation freezing is similar, except

Shupe, Matthew

242

Sensitivity of radiative properties of persistent contrails to the ice water path  

Microsoft Academic Search

The dependence of the radiative properties of persistent linear contrails on the variability of their ice water path is assessed in a two-stream radiative transfer model. It is assumed that the ice water content and the effective size of ice crystals in aged contrails do not differ from those observed in natural cirrus; the parameterization of these two variables, based

R. Rodríguez de León; M. Krämer; D. S. Lee; J. C. Thelen

2011-01-01

243

The defective nature of ice Ic and its implications for atmospheric science  

Microsoft Academic Search

The possible atmospheric implication of ice Ic (cubic ice) has already been suggested some time ago in the context of snow crystal formation [1]. New findings from air-borne measurements in cirrus clouds and contrails have put ice Ic into the focus of interest to understand the so-called \\

W. F. Kuhs; T. C. Hansen

2009-01-01

244

The Influence of Polysaccharides on the Glass Transition in Frozen Sucrose Solutions and Ice Cream  

Microsoft Academic Search

The objective of this study was to describe further the mechanism by which polysaccharide stabilizers contribute to stability of frozen dairy desserts. The influence of stabilizers on the thermal properties and viscosity of carbohydrate solutions at subzero temperatures, on the thermal properties of ice cream mix, and on ice crystallization and growth in ice cream were investigated. Polysaccharide stabilizers did

H. D. Goff; K. B. Caldwell; D. W. Stanley; T. J. Maurice

1993-01-01

245

Waves in frazil and pancake ice and their detection in Seasat synthetic aperture radar imagery  

Microsoft Academic Search

A theoretical model of waves propagating into an ice cover composed of frazil and pancake ice is developed and compared with measurements of wavelength and direction derived from synthetic aperture radar (SAR) imagery obtained from Seasat in October 1978. The theoretical model is based on the concept that ice of these types, which consists of small crystals or cakes, has

Peter Wadhams; Benjamin Holt

1991-01-01

246

Detections of Trans-Neptunian Ice in Protoplanetary Disks  

NASA Astrophysics Data System (ADS)

We present Herschel Space Observatory PACS spectra of T Tauri stars, in which we detect amorphous and crystalline water ice features. Using irradiated accretion disk models, we determine the disk structure and ice abundance in each of the systems. Combining a model-independent comparison of the ice feature strength and disk size with a detailed analysis of the model ice location, we estimate that the ice emitting region is at disk radii >30 AU, consistent with a proto-Kuiper belt. Vertically, the ice emits most below the photodesorption zone, consistent with Herschel observations of cold water vapor. The presence of crystallized water ice at a disk location (1) colder than its crystallization temperature and (2) where it should have been re-amorphized in ~1 Myr suggests that localized generation is occurring; the most likely cause appears to be micrometeorite impact or planetesimal collisions. Based on simple tests with UV models and different ice distributions, we suggest that the SED shape from 20 to 50 ?m may probe the location of the water ice snowline in the disk upper layers. This project represents one of the first extra-solar probes of the spatial structure of the cometary ice reservoir thought to deliver water to terrestrial planets.

McClure, M. K.; Espaillat, C.; Calvet, N.; Bergin, E.; D'Alessio, P.; Watson, D. M.; Manoj, P.; Sargent, B.; Cleeves, L. I.

2015-02-01

247

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

248

Minimalist Model of Ice Microphysics in Mixed-phase Stratiform Clouds  

SciTech Connect

The question of whether persistent ice crystal precipitation from super cooled 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 also confirm the 2.5 power law relationship. 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.

Yang, F.; Ovchinnikov, Mikhail; Shaw, Raymond A.

2013-07-28

249

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

250

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

251

West Antarctic Ice Streams  

Microsoft Academic Search

Solar heat is the acknowledged driving force for climatic change. However, ice sheets are also capable of causing climatic change. This property of ice sheets derives from the facts that ice and rock are crystalline whereas the oceans and atmosphere are fluids and that ice sheets are massive enough to depress the earth's crust well below sea level. These features

Terence J. Hughes

1977-01-01

252

West Antarctic ice streams  

Microsoft Academic Search

Solar heat is the acknowledged driving force for climatic change. However, ice sheets are also capable of causing climatic change. This property of ice sheets derives from the facts that ice and rock are crystalline whereas the oceans and atmosphere are fluids and that ice sheets are massive enough to depress the earth's crust well below sea level. These features

T. Hughes

1977-01-01

253

Make Ice Cream  

NSDL National Science Digital Library

Learners add salt to ice to chill it lower than its freezing point. This chilled ice can then be used to freeze milk and sugar into ice cream. Learners can experiment by adding different flavors such as fruit juices and candy to the ice cream mix.

2014-02-03

254

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

255

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

E-print Network

of light by randomly oriented large hexagonal ice crystals containing spherical or spheroidal air bubbles. The effect of the air bubbles within ice crystals is to smooth the phase functions, diminish the 22° and 46° halo peaks, and reduce the backscatter...

Xie, Yu

2011-02-22

256

Contact ice nucleation by submicron atmospheric aerosols  

NASA Technical Reports Server (NTRS)

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

Deshler, T.

1982-01-01

257

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

258

Analytical treatment of ice sublimation and test of sublimation parameterisations in two-moment ice microphysics models  

NASA Astrophysics Data System (ADS)

We derive an analytic solution to the spectral growth/sublimation equation for ice crystals and apply it to idealised cases. The results are used to test parameterisations of the ice sublimation process in two-moment bulk microphysics models. Although it turns out that the relation between number loss fraction and mass loss fraction is not a function since it is not unique, it seems that a functional parameterisation is the best that one can do in a bulk model. Testing a more realistic case with humidity oscillations shows that artificial crystal loss can occur in simulations of mature cirrus clouds with relative humidity fluctuating about ice saturation.

Gierens, K.; Bretl, S.

2009-04-01

259

Analytical treatment of ice sublimation and test of sublimation parameterisations in two-moment ice microphysics models  

NASA Astrophysics Data System (ADS)

We derive an analytic solution to the spectral growth/sublimation equation for ice crystals and apply it to idealised cases. The results are used to test parameterisations of the ice sublimation process in two-moment bulk microphysics models. Although it turns out that the relation between number loss fraction and mass loss fraction is not a function since it is not unique, it seems that a functional parameterisation is the best that one can do in a bulk model. Testing a more realistic case with humidity oscillations shows that artificial crystal loss can occur in simulations of mature cirrus clouds with relative humidity fluctuating about ice saturation.

Gierens, K.; Bretl, S.

2009-10-01

260

Department of Computer Science University of North Carolina at Chapel Hill March 2005 The visual complexity of ice is familiar to anyone who has  

E-print Network

The visual complexity of ice is familiar to anyone who has ever studied a snowflake or seen the crystal snowflake-like patterns. The Challenge The visual appeal of patterns in ice has not been lost on the visual interactive rates that allow for real-time aesthetic design of ice crystals. A snowflake grown with our

Whitton, Mary C.

261

Food Crystals: the Role of Eggs  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sugar, salt, lactose, tartaric acid and ice are examples of constituents than can crystallize in foods. Crystallization in a food product can be beneficial or detrimental and is of particular importance in candy and frozen desserts. The most common crystal in foods is sugar which affects the quali...

262

Polarimetric Signatures of Sea Ice. Part 1; Theoretical Model  

NASA Technical Reports Server (NTRS)

Physical, structural, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarimetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies for interpretation of sea ice polarimetric signatures.

Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

1995-01-01

263

Polarimetric signatures of sea ice. 1: Theoretical model  

NASA Technical Reports Server (NTRS)

Physical, structral, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarmetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies to interpretation of sea ice polarimetric signatures.

Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

1995-01-01

264

Ice Particle 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; Bailey, Matthew; Hallett, John

2010-01-01

265

Ice Particle Growth Under Conditions of the Upper Troposphere  

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 microns, 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

266

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

267

Study on Propagation Phenomenon of Ice on Solid Surface  

NASA Astrophysics Data System (ADS)

This study is on propagation process of ice on solid surface. A single ice crystal was used and propagation was started by letting the tip of the ice to touch the surface in supercooled water due to free growth of the crystal. Parameters, such as degree of supercooling, surface roughness by different degree of polishing, surface property by existence or non-existence of oxidation, direction of c-axis of as ingle ice crystal and thermal properties of solid material, were selected, and the effect on the velocity of propagation was investigated, experimentally. It was found that propagation is faster on the direction perpendicular to the c-axis of the crystal. It was also found that in a case of copper surface, dislocation of ice occurs quickly and correlation between the direction of the crystal and the speed of propagation on the surface disappears. In a case of linearly polished copper surface, if the amplitude of roughness is big enough, having an equivalent order of the thickness of the tip of ice, it was found that the propagation is faster in the direction parallel to the line of polishing than the direction normal to the line. Finally, using copper, stainless steel and polycarbonate as a material for the surface, it was also found that speed of propagation depends on the material.

Saito, Akio; Okawa, Seiji; Takiguchi, Hiroshi; Kumano, Hiroyuki; Hozumi, Tsutomu

268

Intercellular ice propagation: experimental evidence for ice growth through membrane pores.  

PubMed Central

Propagation of intracellular ice between cells significantly increases the prevalence of intracellular ice in confluent monolayers and tissues. It has been proposed that gap junctions facilitate ice propagation between cells. This study develops an equation for capillary freezing-point depression to determine the effect of temperature on the equilibrium radius of an ice crystal sufficiently small to grow through gap junctions. Convection cryomicroscopy and video image analysis were used to examine the incidence and pattern of intracellular ice formation (IIF) in the confluent monolayers of cell lines that do (MDCK) and do not (V-79W) form gap junctions. The effect of gap junctions on intracellular ice propagation was strongly temperature-dependent. For cells with gap junctions, IIF occurred in a directed wave-like pattern in 100% of the cells below -3 degrees C. At temperatures above -3 degrees C, there was a marked drop in the incidence of IIF, with isolated individual cells initially freezing randomly throughout the sample. This random pattern of IIF was also observed in the V-79W monolayers and in MDCK monolayers treated to prevent gap junction formation. The significant change in the low temperature behavior of confluent MDCK monolayers at -3 degrees C is likely the result of the inhibition of gap junction-facilitated ice propagation, and supports the theory that gap junctions facilitate ice nucleation between cells. PMID:11509353

Acker, J P; Elliott, J A; McGann, L E

2001-01-01

269

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

270

Cirrus cloud model parameterizations: Incorporating realistic ice particle generation  

NASA Technical Reports Server (NTRS)

Recent cirrus cloud modeling studies have involved the application of a time-dependent, two dimensional Eulerian model, with generalized cloud microphysical parameterizations drawn from experimental findings. For computing the ice versus vapor phase changes, the ice mass content is linked to the maintenance of a relative humidity with respect to ice (RHI) of 105 percent; ice growth occurs both with regard to the introduction of new particles and the growth of existing particles. In a simplified cloud model designed to investigate the basic role of various physical processes in the growth and maintenance of cirrus clouds, these parametric relations are justifiable. In comparison, the one dimensional cloud microphysical model recently applied to evaluating the nucleation and growth of ice crystals in cirrus clouds explicitly treated populations of haze and cloud droplets, and ice crystals. Although these two modeling approaches are clearly incompatible, the goal of the present numerical study is to develop a parametric treatment of new ice particle generation, on the basis of detailed microphysical model findings, for incorporation into improved cirrus growth models. For example, the relation between temperature and the relative humidity required to generate ice crystals from ammonium sulfate haze droplets, whose probability of freezing through the homogeneous nucleation mode are a combined function of time and droplet molality, volume, and temperature. As an example of this approach, the results of cloud microphysical simulations are presented showing the rather narrow domain in the temperature/humidity field where new ice crystals can be generated. The microphysical simulations point out the need for detailed CCN studies at cirrus altitudes and haze droplet measurements within cirrus clouds, but also suggest that a relatively simple treatment of ice particle generation, which includes cloud chemistry, can be incorporated into cirrus cloud growth.

Sassen, Kenneth; Dodd, G. C.; Starr, David OC.

1990-01-01

271

Sea Ice Ecosystems  

NASA Astrophysics Data System (ADS)

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.

Arrigo, Kevin R.

2014-01-01

272

Extension of an Ice Shelf Water plume model beneath sea ice with application in McMurdo Sound, Antarctica  

NASA Astrophysics Data System (ADS)

one-dimensional, frazil-laden plume model predicts the properties of Ice Shelf Water (ISW) as it evolves beneath sea ice beyond the ice shelf edge. An idealized background ocean circulation, which moves parallel to the plume, imitates forcings other than the plume's own buoyancy. The size distribution and concentration of the plume's suspended frazil ice crystals are affected by the background circulation velocity, the root-mean square tidal velocity, the drag coefficient, and the efficiency of secondary nucleation. Consequently, these variables are the key physical controls on the survival of supercooled water with distance from the ice shelf, which is predicted using several realistic parameter choices. Starting at 65 m thick, the in situ supercooled layer thins to 11 ± 5 and 4 ± 3 m at distances of 50 and 100 km, respectively. We apply the extended model in McMurdo Sound, Antarctica, along the expected path of the coldest water. Three late-winter oceanographic stations along this path, in conjunction with historical data, provide initial conditions and evaluation of the simulations. Near the ice shelf in the western Sound, the water column consisted entirely of ISW, and the subice platelet layer thickness exceeded 5 m with platelet crystals dominating the sea ice structure suggesting that ISW persisted throughout winter. Presuming a constant ISW flux, the model predicts that the plume increases thermodynamic growth of sea ice by approximately 0.1 m yr-1 (˜5% of the average growth rate) even as far as 100 km beyond the ice shelf edge.

Hughes, K. G.; Langhorne, P. J.; Leonard, G. H.; Stevens, C. L.

2014-12-01

273

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

274

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

275

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

276

NOAA Great Lakes Ice Atlas  

NSDL National Science Digital Library

This website presents the results of the analysis of Great Lakes ice charts dating back to 1960. After learning about the methods used to produce this online atlas, users can view the original ice charts. Researchers can find data on first ice, last ice, ice duration, and other ice related statistics. Students and educators can learn about variations in ice cover through the animations of ice cover time series. The website offers downloads of a few of the references and technical issues.

277

Diatom assemblages promote ice formation in large lakes.  

PubMed

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 (T(c)) 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; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

2013-08-01

278

A theoretical spongy spray icing model with surficial structure  

NASA Astrophysics Data System (ADS)

In an attempt to improve the predictive capability of atmospheric icing models, we have developed a theoretical model of spongy ice formation, including the surficial morphology under a falling supercooled liquid film. A steady-state model of freshwater spongy spray icing for a stationary vertical cylinder is presented. A falling film submodel accounts for the flow of excess liquid on the icing surface. Traditional heat and mass balance equations at the outer surface of the falling film are formulated, along with heat and mass balances for the falling film and for the dendritic freezing zone. The rate of advance of the icing interface is calculated by analogy with the rate of advance of freely-growing ice crystals in bulk supercooled liquid. This allows, for the first time, the prediction of ice accretion flux and accretion sponginess, for a specific icing configuration and environmental conditions. An analysis of the model's sensitivity to spray temperature reveals that spray supercooling enhances both the rate of accretion and its sponginess. A comparison of the model's performance with experiments shows rather good agreement, and suggests that further research into the nature of the icing surface and its effect on the accreted ice is warranted.

Blackmore, R. Z.; Lozowski, E. P.

279

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; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

2013-01-01

280

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

NASA Astrophysics Data System (ADS)

The influence of initial heterogeneous nucleation on subsequent homogeneous nucleation events in cirrus clouds is investigated using a box model which includes the explicit impact of aerosols on the nucleation of ice crystals and a new sedimentation scheme. Different effects are discussed, namely the impact of external versus internal mixtures of heterogeneous ice nuclei and the influence of size-dependent freezing thresholds. Several idealized experiments are carried out, which show that the treatment of external mixtures of ice nuclei can strongly change subsequent homogeneous nucleation events (i.e., the ice crystal number densities) over a large variety of environmental conditions relevant for the upper troposphere. In most cases a strong reduction in ice crystal number concentrations formed in subsequent homogeneous freezing events is observed. The use of size-dependent freezing thresholds can change cloud properties when compared to more simple parameterizations and is most important at largest ice nuclei concentrations.

Spichtinger, P.; Cziczo, D. J.

2010-07-01

281

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

282

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

283

Piscataquis River Ice Measurement  

USGS Multimedia Gallery

In this photo Terrence Talbot, a student with the Maine Office, drills holes with an ice auger in preparation for a discharge measurement through the ice at the USGS station on the Piscataquis River near Dover-Foxcroft, Maine.  After drilling 20-30 holes through the ice at known intervals we a...

284

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

285

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

286

Vote for Ice Cream  

NSDL National Science Digital Library

This lesson will pique your students' interest by reading about Curious George and his ice cream adventure. Students will move from George's adventure to a class chart of favorite ice cream flavors to organizing and completing their own ice cream chart.

chris worley

2012-04-20

287

Ice Versus Rock  

ERIC Educational Resources Information Center

During a snow bank exploration, students noticed "ice caves," or pockets, in some of the larger snow banks, usually below darker layers. Most of these caves had many icicles hanging inside. Students offered reasonable explanations of ice cave formation--squirrels, kids, snow blowers--and a few students came close to the true ice cave-formation…

Rule, Audrey C.; Olson, Eric A.; Dehm, Janet

2005-01-01

288

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.

David Williams

2003-01-22

289

Experiments in Ice Physics.  

ERIC Educational Resources Information Center

Describes experiments in ice physics that demonstrate the behavior and properties of ice. Show that ice behaves as an ionic conductor in which charge is transferred by the movement of protons, its electrical conductivity is highly temperature-dependent, and its dielectric properties show dramatic variation in the kilohertz range. (Author/GA)

Martin, P. F.; And Others

1978-01-01

290

Ice Formation on Wings  

NASA Technical Reports Server (NTRS)

This report makes use of the results obtained in the Gottingen ice tunnel in which the atmospheric conditions are simulated and the process of ice formation photographed. The effect of ice formation is threefold: 1) added weight to the airplane; 2) a change in the lift and drag forces; 3) a change in the stability characteristics.

Ritz, L

1939-01-01

291

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

292

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

293

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

294

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

295

Sublimation Coefficient of Water Ice  

NASA Astrophysics Data System (ADS)

In simulations of evolution of cometary nuclei it is commonly assumed that the coefficients of sublimation and condensation of the volatiles are both equal to one. However, the laboratory investigation of water ice samples under cometary-like conditions (Kossacki et al., 1997) suggests, that the sublimation flux calculated with the Hertz-Knudsen formula and the above assumption is nearly an order of magnitude too high. A similar conclusion can be drawn from the results of various experiments on growth from vapour phase and sublimation of ice crystals (Lamb and Scott, 1972; Beckmann and Lacmann, 1982; Sei and Gonda, 1989). These results imply that the sublimation coefficient can be as low as 0.1. The above coefficients depend on various parameters such as temperature, concentration of surface impurities as well as deviation of the vapour pressure from that of the phase equilibrium. In this work we discuss the temperature dependence of both of these coefficients. We also propose an empirical formula to fit the temperature dependence. This new formulation is also used to analyse the implications for the thermal conductivity of a porous cometary-like ice.

Kossacki, K. J.; Markiewicz, W. J.; Skorov, Y.; Koemle, N. I.

1999-09-01

296

Anchored Clathrate Waters Bind Antifreeze Proteins to Ice  

SciTech Connect

The mechanism by which antifreeze proteins (AFPs) irreversibly bind to ice has not yet been resolved. The ice-binding site of an AFP is relatively hydrophobic, but also contains many potential hydrogen bond donors/acceptors. The extent to which hydrogen bonding and the hydrophobic effect contribute to ice binding has been debated for over 30 years. Here we have elucidated the ice-binding mechanism through solving the first crystal structure of an Antarctic bacterial AFP. This 34-kDa domain, the largest AFP structure determined to date, folds as a Ca{sup 2+}-bound parallel beta-helix with an extensive array of ice-like surface waters that are anchored via hydrogen bonds directly to the polypeptide backbone and adjacent side chains. These bound waters make an excellent three-dimensional match to both the primary prism and basal planes of ice and in effect provide an extensive X-ray crystallographic picture of the AFP{vert_ellipsis}ice interaction. This unobstructed view, free from crystal-packing artefacts, shows the contributions of both the hydrophobic effect and hydrogen bonding during AFP adsorption to ice. We term this mode of binding the 'anchored clathrate' mechanism of AFP action.

C Garnham; R Campbell; P Davies

2011-12-31

297

Ice Concentration Retrieval in Stratiform Mixed-phase Clouds Using Cloud Radar Reflectivity Measurements and 1D Ice Growth Model Simulations  

SciTech Connect

Measurement of ice number concentration in clouds is important but still challenging. Stratiform mixed-phase clouds (SMCs) provide a simple scenario for retrieving ice number concentration from remote sensing measurements. The simple ice generation and growth pattern in SMCs offers opportunities to use cloud radar reflectivity (Ze) measurements and other cloud properties to infer ice number concentration quantitatively. To understand the strong temperature dependency of ice habit and growth rate quantitatively, we develop a 1-D ice growth model to calculate the ice diffusional growth along its falling trajectory in SMCs. The radar reflectivity and fall velocity profiles of ice crystals calculated from the 1-D ice growth model are evaluated with the Atmospheric Radiation Measurements (ARM) Climate Research Facility (ACRF) ground-based high vertical resolution radar measurements. Combining Ze measurements and 1-D ice growth model simulations, we develop a method to retrieve the ice number concentrations in SMCs at given cloud top temperature (CTT) and liquid water path (LWP). The retrieved ice concentrations in SMCs are evaluated with in situ measurements and with a three-dimensional cloud-resolving model simulation with a bin microphysical scheme. These comparisons show that the retrieved ice number concentrations are within an uncertainty of a factor of 2, statistically.

Zhang, Damao; Wang, Zhien; Heymsfield, Andrew J.; Fan, Jiwen; Luo, Tao

2014-10-01

298

Layers of Ice  

NSDL National Science Digital Library

This is a lesson about the formation of glaciers, ice layering and stratigraphy, and the cryosphere and cryobotics. Learners will collect evidence of layering, explore the science story that layering tells, study snow and ice for insights into climate change, and learn about the tools used to explore ice layers on Earth and in the solar system. Connections between rings of a tree and rings in an ice core will be made. Activities include small group miming, speaking, drawing, and/or writing. This is lesson 7 of 12 in the unit, Exploring Ice in the Solar System.

299

Greenland's Receeding Ice  

NSDL National Science Digital Library

After Antarctica, Greenland's ice cap contains the second largest mass of frozen fresh water in the world. Based on new research using NASA's airborne laser altimeter, scientists have identified pronounced thinning of Greenland's ice cap. This new research indicates enough ice loss to cause a measurable rise in sea levels. This site, produced by NASA's Scientific Visualization Studio, features text, photographs, satellite imagery, and animations to describe the loss of ice and the use of lidar (laser altimetry) to make the precise measurements necessary to reveal the loss of ice.

300

Alaska marine ice atlas  

SciTech Connect

A comprehensive Atlas of Alaska marine ice is presented. It includes information on pack and landfast sea ice and calving tidewater glacier ice. It also gives information on ice and related environmental conditions collected over several years time and indicates the normal and extreme conditions that might be expected in Alaska coastal waters. Much of the information on ice conditions in Alaska coastal waters has emanated from research activities in outer continental shelf regions under assessment for oil and gas exploration and development potential. (DMC)

LaBelle, J.C.; Wise, J.L.; Voelker, R.P.; Schulze, R.H.; Wohl, G.M.

1982-01-01

301

Numerical simulation of water transport and intracellular ice formation for freezing of endothelial cells.  

PubMed

Endothelial cell detachment may cause failure of blood vessel and corneal cryopreservation, and thus successful cryopreservation of endothelial cells is regarded to be the first step to optimize cryopreservation of endothelial cells containing tissues. In this study, the pre-determined biophysical parameters were incorporated into the model for intracellular ice formation (IIF) and the growth of intracellular ice crystals (ICG) to calculate cell water loss, supercooling of intracellular solution, intracellular ice formation and the growth of intracellular ice crystals. The optimal protocols were determined according to the combination effect of both solution injury and IIF injury. PMID:23435709

Zhao, G; Xu, Y; Ding, W P; Hu, M B

2013-01-01

302

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

303

Deformation in the Rutford ice stream, West Antarctica: measuring shear-wave anisotropy from icequakes  

NASA Astrophysics Data System (ADS)

Ice streams provide major drainage pathways for the Antarctic ice sheet. The stress distribution and style of flow in such ice streams produces elastic and rheological anisotropy, which informs ice flow modelling as to how ice masses respond to external changes such as global warming. Here we analyse elastic anisotropy in the Rutford ice stream, West Antarctica, using observations of shear wave splitting from three-component icequake seismograms to characterise ice deformation via crystal preferred orientation. Over 110 high quality measurements are made on 41 events recorded at five stations temporarily deployed near the ice stream grounding line. To the best of our knowledge this is the first well-documented observation of shear wave splitting from Antarctic icequakes. The magnitude of the splitting ranges from 2ms to 80ms and suggest a maximum of 6% shear wave splitting. The fast shear wave polarisation direction is roughly perpendicular to ice flow direction. We consider three mechanisms for ice anisotropy: a cluster model (VTI model); a girdle model (and HTI model); and crack-induced anisotropy (an HTI model). Based on the data we can rule out a VTI mechanism as the sole cause of anisotropy - an HTI component is needed, which may be due to ice crystal a-axis alignment in the direction of flow or the alignment of cracks or ice-films in the plane perpendicular to the flow direction. The results may suggest a combination of mechanisms are at play, which represent vertical variations in the symmetry of ice-crystal anisotropy in an ice stream, as predicted by ice fabric models.

Kendall, Michael; Harland, Sophie; Stuart, Graham; Baird, Alan; Lloyd, Geoff; Smith, Andy; Pritchard, Hamish; Brisbourne, Alex

2013-04-01

304

Antifreeze Protein Binds Irreversibly to Ice  

NASA Astrophysics Data System (ADS)

Many organisms are protected from freezing by antifreeze proteins (AFPs), which bind to ice and prevent its growth by a mechanism not completely understood. Although it has been postulated that AFPs would have to bind irreversibly to arrest the growth of an ice crystal bathed in excess liquid water, the binding forces seem insufficient to support such a tight interaction. By putting a fluorescent tag on a fish AFP, we were able to visualize AFP binding to ice and demonstrate, by lack of recovery after photo-bleaching, that it is indeed irreversible. Because even the most avid protein/ligand interactions exhibit reversibility, this finding is key to understanding the mechanism of antifreeze proteins, which are becoming increasingly valuable in cryopreservation and improving the frost tolerance of crops.

Braslavsky, I.; Pertaya, N.; di Prinzio, C. L.; Wilen, L.; Thomson, E.; Wettlaufer, J. S.; Marshall, C. B.; Davies, P. L.

2006-03-01

305

Sampling the composition of cirrus ice residuals  

NASA Astrophysics Data System (ADS)

Cirrus are high altitude clouds composed of ice crystals. They are the first tropospheric clouds that can scatter incoming solar radiation and the last which can trap outgoing terrestrial heat. Considering their extensive global coverage, estimated at between 25 and 33% of the Earth's surface, cirrus exert a measurable climate forcing. The global radiative influence depends on a number of properties including their altitude, ice crystal size and number density, and vertical extent. These properties in turn depend on the ability of upper tropospheric aerosol particles to initiate ice formation. Because aerosol populations, and therefore cirrus formation mechanisms, may change due to human activities, the sign of cirrus forcing (a net warming or cooling) due to anthropogenic effects is not universally agreed upon although most modeling studies suggest a positive effect. Cirrus also play a major role in the water cycle in the tropopause region, affecting not only redistribution in the troposphere but also the abundance of vapor entering the stratosphere. Both the current lack of understanding of cirrus properties and the need to improve our ability to project changes due to human activities in the future highlight the critical need to determine the aerosol particles on which cirrus form. This review addresses what is currently known about the abundance, size and composition of cirrus-forming particles. We review aircraft-based field studies which have either collected cirrus ice residuals for off-line analysis or determined their size, composition and other properties in situ by capturing ice crystals and sublimating/removing the condensed phase water. This review is predominantly restricted to cirrus clouds. Limited comparisons are made to other ice-containing (e.g., mixed-phase) cloud types. The findings of recent reviews on laboratory measurements that mimic upper tropospheric cirrus formation are briefly summarized. The limitations of the current state of the art in cirrus ice residual studies are outlined. Important ancillary measurements and how they are integrated with ice residual data are also presented. Concluding statements focus on the need for specific instrumentation and future studies.

Cziczo, Daniel J.; Froyd, Karl D.

2014-06-01

306

Bench Scale Test of Absorption Slurry-ice Maker  

NASA Astrophysics Data System (ADS)

Slurry ice system is desirable as cold heat source for air conditioning, because it requires less conveyance power or less pipe size. On the other hand, recently absorption refrigerator is reevaluated because it can utilize various types of waste heat and it does not use fluorocarbon refrigerant. But it had been regarded to be difficult to make ice by absorption refrigerator because the refrigerant is water. However making slurry ice is possible, of cource, if the slurry ice generated by partial freezing of water is continuously taken away from the evaporator. This method was certified experimentally with a bench scale model. For ice making continuously, ice had not to be frozen stiff at water surface or inside wall of the evaporator. Then refrigerant water in the evaporator was raised swirl flow. And inside wall of the evaporator was finished by water repellent coating, and heated from outside wall. This slurry ice was adaptable to hydraulic transportation, because ice was needle crystal with about 5 mm length and ice temperature was 0°C.

Sasao, Hiroyuki; Yoshida, Takashi

307

Anomalous Proton Dynamics in Ice at Low Temperatures  

SciTech Connect

We present incoherent quasielastic neutron scattering measurements on ice Ih (ordinary ice) and Ic (cubic ice) which show the existence of nonharmonic motion of hydrogen at low temperatures, down to 5 K. We show that this dynamics is localized, nonvibrational, and related to the hydrogen disorder since it is absent in ordered ice VIII. A main jump distance of 0.75 A is identified, hence close to the distance between the two possible proton sites along the oxygen-oxygen bond. The dynamics is non-Arrhenius, has a large time rate of 2.7x10{sup 11} s{sup -1}, and affects only a few percent of the total number of hydrogen atoms in the crystal. These results give evidence for the existence of concerted proton tunneling in these ice phases.

Bove, L. E.; Klotz, S. [IMPMC, CNRS-UMR 7590, Universite P and M Curie, F-75252 Paris (France); Paciaroni, A.; Sacchetti, F. [CNR-INFM CRS-Soft, c/o Dipartimento di Fisica, Universita di Perugia, I-06123 Perugia (Italy)

2009-10-16

308

Consider an Ice Stream.  

NASA Astrophysics Data System (ADS)

Forty years ago, John Nye was one of the leaders who introduced the rigors of classical physics to glaciology. His elegant treatments frequently took advantage of the then recent discovery that ice could be approximated as a plastic material. With this viewpoint, Nye was able to explain the shape of ice sheets and glaciers, to predict the expected pattern of stress and velocity within a glacier, and to derive the advance and retreat of a glacier from the record of accumulation and ablation. These advances have given generations of glaciologists tools to interpret the excellent observational record of glacier behavior and variation. In the 1980s, glaciologist, weaned on these works of Nye and of other similarly adept colleagues, carried their lessons to West Antarctica to study ice streams, the vast conveyor belts of ice that discharged nearly as much Antarctic ice as the much larger East Antarctic ice sheet. Ice streams were a glaciological conundrum. Despite the gently sloping surface, these broad features roared along, moving fastest when the gravitational impetus was least. After two decades of research, ice streams still have not given up all their secrets, yet much is now known. Internal deformation is negligible. Basal friction is frequently nil leaving the shattered margins as the primary means to avoid rapid wastage of the ice sheet. Within the margins, the resistive force results from a delicate balance of heat and evolving ice fabrics. Nevertheless, the bed beneath an ice stream cannot be ignored. It is ultimately the state of the underlying marine sediment that determines whether the ice stream can slide at all. There too, the heat balance is critical with an influx of water required to keep the bed wet enough to let the streams glide along. Ice stream research has been the portal through which glaciologists have seen and identified the complexities of West Antarctic ice sheet dynamics. Remarkably, nearly all time scales seem important. Ice stream positions in past millennia conform to radically different flow patterns while on the scale of hours an ice stream's motion is halted completely, then released to move at surge-like speeds, in tempo with the tides. Explaining these complexities constantly reminds us that the rigorous physics applied to ice so effectively by Nye still work.

Bindschadler, R.

2002-12-01

309

Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

Of all the recent observed changes in the Arctic environment, the reduction of sea ice cover stands out most prominantly. Several independent analysis have established a trend in Arctic ice extent of -3% per decade from the late 1970s to the late 1990s, with a more pronounced trend in summer. The overall downward trend in ice cover is characterized by strong interannual variability, with a low September ice extent in one year typically followed by recovery the next September. Having two extreme minimum years, such as what was observed in 2002 and 2003 is unusual. 2004 marks the third year in a row of substantially below normal sea ice cover in the Arctic. Early summer 2004 appeared unusual in terms of ice extent, with May a record low for the satellite period (1979-present) and June also exhibiting below normal ice extent. August 2004 extent is below that of 2003 and large reductions in ice cover are observed once again off the coasts of Siberia and Alaska and the Greenland Sea. Neither the 2002 or 2003 anomaly appeared to be strongly linked to the positive phase of the Arctic Oscillation (AO) during the preceding winter. Similarly, the AO was negative during winter 2003/2004. In the previous AO framework of Rigor et al (2002), a positive winter AO implied preconditioning of the ice cover to extensive summer decay. In this hypothesis, the AO does not explain all aspects of the recent decline in Arctic ice cover, such as the extreme minima of 2002, 2003 and 2004. New analysis by Rigor and Wallace (2004) suggest that the very positive AO state from 1989-1995 can explain the recent sea ice minima in terms of changes in the Arctic surface wind field associated with the previous high AO state. However, it is also reasonable to expect that a general decrease in ice thickness accompanying warming would manifest itself as greater sensitivity of the ice pack to wind forcings and albedo feedbacks. The decrease in multiyear ice and attendant changes in ice thickness distribution could in turn precondition the Arctic ice cover to further reductions in the subsequent summer(s) regardless if the summer temperatures were anomalously warm. The NSIDC Sea Ice Index (http://nsidc.org/data/seaice_index/) can be used to view trends and anomalies from 1979 on.

Stroeve, J. C.; Fetterer, F.; Knowles, K.; Meier, W.; Serreze, M.; Arbetter, T.

2004-12-01

310

Temporal dynamics of ikaite in experimental sea ice  

NASA Astrophysics Data System (ADS)

Ikaite (CaCO3 · 6H2O) is a metastable phase of calcium carbonate that normally forms in a cold environment and/or under high pressure. Recently, ikaite crystals have been found in sea ice, and it has been suggested that their precipitation may play an important role in air-sea CO2 exchange in ice-covered seas. Little is known, however, of the spatial and temporal dynamics of ikaite in sea ice. Here we present evidence for highly dynamic ikaite precipitation and dissolution in sea ice grown at an outdoor pool of the Sea-ice Environmental Research Facility (SERF) in Manitoba, Canada. During the experiment, ikaite precipitated in sea ice when temperatures were below -4 °C, creating three distinct zones of ikaite concentrations: (1) a millimeter-to-centimeter-thin surface layer containing frost flowers and brine skim with bulk ikaite concentrations of >2000 ?mol kg-1, (2) an internal layer with ikaite concentrations of 200-400 ?mol kg-1, and (3) a bottom layer with ikaite concentrations of <100 ?mol kg-1. Snowfall events caused the sea ice to warm and ikaite crystals to dissolve. Manual removal of the snow cover allowed the sea ice to cool and brine salinities to increase, resulting in rapid ikaite precipitation. The observed ikaite concentrations were on the same order of magnitude as modeled by FREZCHEM, which further supports the notion that ikaite concentration in sea ice increases with decreasing temperature. Thus, varying snow conditions may play a key role in ikaite precipitation and dissolution in sea ice. This could have a major implication for CO2 exchange with the atmosphere and ocean that has not been accounted for previously.

Rysgaard, S.; Wang, F.; Galley, R. J.; Grimm, R.; Notz, D.; Lemes, M.; Geilfus, N.-X.; Chaulk, A.; Hare, A. A.; Crabeck, O.; Else, B. G. T.; Campbell, K.; Sørensen, L. L.; Sievers, J.; Papakyriakou, T.

2014-08-01

311

Prospecting for Martian Ice  

NASA Technical Reports Server (NTRS)

During high Martian obliquity, ice is stable to lower latitudes than predicted by models of present conditions and observed by the Gamma Ray Spectrometer (approx. 60 deg N). An ice-rich layer deposited at mid-latitudes could persist to the present day; ablation of the top 1 m of ice leaving a thin insulating cover could account for lack of its detection by GRS. The presence of an ice-layer in the mid-latitudes is suggested by a network of polygons, interpreted as ice-wedge cracks. This study focuses on an exceptional concentration of polygons in Western Utopia (section of Casius quadrangle, roughly 40 deg - 50 deg N, 255 deg - 300 deg W). We attempt to determine the thickness and age of this ice layer through crater-polygons relations.

McBride, S. A.; Allen, C. C.; Bell, M. S.

2005-01-01

312

Relative importance of acid coating on ice nuclei in the deposition and contact modes for wintertime Arctic clouds and radiation  

NASA Astrophysics Data System (ADS)

Aerosols emitted from volcanic activities and polluted mid-latitudes regions are efficiently transported over the Arctic during winter by the large-scale atmospheric circulation. These aerosols are highly acidic. The acid coating on ice nuclei, which are present among these aerosols, alters their ability to nucleate ice crystals. In this research, the effect of acid coating on deposition and contact ice nuclei on the Arctic cloud and radiation is evaluated for January 2007 using a regional climate model. Results show that the suppression of contact freezing by acid coating on ice nuclei leads to small changes of the cloud microstructure and has no significant effect on the cloud radiative forcing (CRF) at the top of the atmosphere when compared with the effect of the alteration of deposition ice nucleation by acid coating on deposition ice nuclei. There is a negative feedback by which the suppression of contact freezing leads to an increase of the ice crystal nucleation rate by deposition ice nucleation. As a result, the suppression of contact freezing leads to an increase of the cloud ice crystal concentration. Changes in the cloud liquid and ice water contents remain small and the CRF is not significantly modified. The alteration of deposition ice nucleation by acid coating on ice nuclei is dominant over the alteration of contact freezing.

Girard, Eric; Sokhandan Asl, Niloofar

2014-01-01

313

Partitioning of fish and insect antifreeze proteins into ice suggests they bind with comparable affinity.  

PubMed

Antifreeze proteins (AFPs) inhibit the growth of ice by binding to the surface of ice crystals, preventing the addition of water molecules to cause a local depression of the freezing point. AFPs from insects are much more effective at depressing the freezing point than fish AFPs. Here, we have investigated the possibility that insect AFPs bind more avidly to ice than fish AFPs. Because it is not possible to directly measure the affinity of an AFP for ice, we have assessed binding indirectly by examining the partitioning of proteins into a slowly growing ice hemisphere. AFP molecules adsorbed to the surface and became incorporated into the ice as they were overgrown. Solutes, including non-AFPs, were very efficiently excluded from ice, whereas AFPs became incorporated into ice at a concentration roughly equal to that of the original solution, and this was independent of the AFP concentration in the range (submillimolar) tested. Despite their >10-fold difference in antifreeze activity, fish and insect AFPs partitioned into ice to a similar degree, suggesting that insect AFPs do not bind to ice with appreciably higher affinity. Additionally, we have demonstrated that steric mutations on the ice binding surface that decrease the antifreeze activity of an AFP also reduce its inclusion into ice, supporting the validity of using partitioning measurements to assess a protein's affinity for ice. PMID:14705940

Marshall, Christopher B; Tomczak, Melanie M; Gauthier, Sherry Y; Kuiper, Michael J; Lankin, Christopher; Walker, Virginia K; Davies, Peter L

2004-01-13

314

Incorporation of crude and fuel oil into salt-and freshwater ice  

SciTech Connect

North Slope Crude, no. 2 fuel oil, and vegetable oil were each released under columnar freshwater and saltwater ice grown in a laboratory coldroom. Because the thermal conductivity of all the oils is lower than that of water or ice, thinner ice grew under the oil and resulted in a concave ice/water interface. Both the fresh and saline ice encapsulated the oils, but the saline ice did so more slowly. Thin sections of the ice blocks containing the crude and fuel oils show how the columnar ice crystals bend around and under the oil patches. The movement of the vegetable oil during melting was photographed, and spectral reflectance measurements of the ice surface were made to determine if the oil could be detected remotely. Although we could detect the presence of oil under 10 cm of ice, under field conditions the optical detectability of oil will depend upon the depth of the oil within the ice, the type of ice, and the contrast between the under-ice oil and the background against which it is being viewed.

Taylor, S.; Perron, N.

1995-02-01

315

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

316

An ice lithography instrument  

PubMed Central

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. PMID:21721733

Han, Anpan; Chervinsky, John; Branton, Daniel; Golovchenko, J. A.

2011-01-01

317

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

318

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.

319

Ice age paleotopography.  

PubMed

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. PMID:17750657

Peltier, W R

1994-07-01

320

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

321

Ice barrier construction  

SciTech Connect

A method is provided for constructing spray ice barriers to protect offshore structures in a frigid body of water from mobile ice, waves and currents. Water is withdrawn from the body of water and is sprayed through ambient air which is below the freezing temperature of the water so that a substantial amount of the water freezes as it passes through the air. The sprayed water is directed to build up a mass of ice having a size and shape adapted to protect the offshore structure. Spray ice barriers can also be constructed for the containment of pollutant spills.

Finucane, R. G.; Jahns, H. O.

1985-06-18

322

Tertiary flow relations for compression and shear components in combined stress tests on ice  

Microsoft Academic Search

The attainment of tertiary flow in ice involves the nonlinear response to the combination of applied stresses and the alteration\\u000a of both the ice crystals and the polycrystalline aggregate. Tertiary flow rates for individual component strain rates from\\u000a a series of ice deformation experiments under combined shear and compression stresses are presented, and the departure from\\u000a the predictions of isotropic

Roland C. Warner; T. Jacka; Li Jun; W. Budd

323

[Tail Plane Icing  

NASA Technical Reports Server (NTRS)

The Aviation Safety Program initiated by NASA in 1997 has put greater emphasis in safety related research activities. Ice-contaminated-tailplane stall (ICTS) has been identified by the NASA Lewis Icing Technology Branch as an important activity for aircraft safety related research. The ICTS phenomenon is characterized as a sudden, often uncontrollable aircraft nose- down pitching moment, which occurs due to increased angle-of-attack of the horizontal tailplane resulting in tailplane stall. Typically, this phenomenon occurs when lowering the flaps during final approach while operating in or recently departing from icing conditions. Ice formation on the tailplane leading edge can reduce tailplane angle-of-attack range and cause flow separation resulting in a significant reduction or complete loss of aircraft pitch control. In 1993, the Federal Aviation Authority (FAA) and NASA embarked upon a four-year research program to address the problem of tailplane stall and to quantify the effect of tailplane ice accretion on aircraft performance and handling characteristics. The goals of this program, which was completed in March 1998, were to collect aerodynamic data for an aircraft tail with and without ice contamination and to develop analytical methods for predicting the effects of tailplane ice contamination. Extensive dry air and icing tunnel tests which resulted in a database of the aerodynamic effects associated with tailplane ice contamination. Although the FAA/NASA tailplane icing program generated some answers regarding ice-contaminated-tailplane stall (ICTS) phenomena, NASA researchers have found many open questions that warrant further investigation into ICTS. In addition, several aircraft manufacturers have expressed interest in a second research program to expand the database to other tail configurations and to develop experimental and computational methodologies for evaluating the ICTS phenomenon. In 1998, the icing branch at NASA Lewis initiated a second multi-phase research program for tailplane icing (TIP II) to develop test methodologies and tailplane performance and handling qualities evaluation tools. The main objectives of this new NASA/Industry/Academia collaborative research programs were: (1) define and evaluate a sub-scale wind tunnel test methodology for determining tailplane performance degradation due to icing. (2) develop an experimental database of tailplane aerodynamic performance with and without ice contamination for a range of tailplane configurations. Wind tunnel tests were planned with representative general aviation aircraft, i.e., the Learjet 45, and a twin engine low speed aircraft. This report summarizes the research performed during the first year of the study, and outlines the work tasks for the second year.

1997-01-01

324

Commercial aviation icing research requirements  

NASA Technical Reports Server (NTRS)

A short range and long range icing research program was proposed. A survey was made to various industry and goverment agencies to obtain their views of needs for commercial aviation ice protection. Through these responsed, other additional data, and Douglas Aircraft icing expertise; an assessment of the state-of-the-art of aircraft icing data and ice protection systems was made. The information was then used to formulate the icing research programs.

Koegeboehn, L. P.

1981-01-01

325

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 10,000 mg/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

326

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

327

Designing for effective stationkeeping in ice  

E-print Network

, etc. · Ice geometry, ice age, density, salinity, etc. · Sea ice tracking (drift speed and directionDesigning for effective stationkeeping in ice CeSOS Highlights and AMOS Visions Conference DP Ice loads Ice #12;Effective stationkeeping in ice 1. Effective ship design. 2. An effective Ice

Nørvåg, Kjetil

328

A Molecular Mechanism of Ice Nucleation on Model AgI Surfaces.  

PubMed

Heterogeneous ice nucleation at solid surfaces is important in many physical systems including the Earth's atmosphere. AgI is one of the best ice nucleating agents known; however, why AgI is such an effective ice nucleus is unclear. Using molecular dynamics simulations, we show that a good lattice match between ice and a AgI surface is insufficient to predict the ice nucleation ability of the surface. Seven faces modeled to represent surfaces of both ?-AgI and ?-AgI, each having a good lattice match with hexagonal and/or cubic ice, are considered, but ice nucleation is observed for only three. Our model simulations clearly show that the detailed atomistic structure of the surface is of crucial importance for ice nucleation. For example, when AgI is cleaved along certain crystal planes two faces result, one with silver ions and the other with iodide ions exposed as the outermost layer. Both faces have identical lattice matches with ice, but in our simulations ice nucleation occurred only at silver exposed surfaces. Moreover, although hexagonal ice is often the only polymorph of ice considered in discussions of heterogeneous ice nucleation, cubic ice was frequently observed in our simulations. We demonstrate that one possible mechanism of ice nucleation by AgI consists of particular AgI surfaces imposing a structure in the adjacent water layer that closely resembles a layer that exists in bulk ice (hexagonal or cubic). Ice nucleates at these surfaces and grows almost layer-by-layer into the bulk. PMID:25255062

Zielke, Stephen A; Bertram, Allan K; Patey, Grenfell N

2014-10-01

329

Proton ordering in tetragonal and monoclinic H2O ice  

E-print Network

H2O ice remains one of the most enigmatic materials as its phase diagram reveals up to sixteen solid phases. While the crystal structure of these phases has been determined, the phase boundaries and mechanisms of formation of the proton-ordered phases remain unclear. From high precision measurements of the complex dielectric constant, we probe directly the degree of ordering of the protons in H2O tetragonal ice III and monoclinic ice V down to 80 K. A broadened first-order phase transition is found to occur near 202 K we attribute to a quenched disorder of the protons which causes a continuous disordering of the protons during cooling and metastable behavior. At 126 K the protons in ice III become fully ordered, and for the case of ice V becoming fully ordered at 113 K forming ice XIII. Two triple points are proposed to exist: one at 0.35 GPa and 126 K where ices III, IX and V coexist; and another at 0.35 GPa and 113 K where ices V, IX and XIII coexist. Our findings unravel the underlying mechanism driving th...

Yen, Fei; Berlie, Adam; Liu, Xiaodi; Goncharov, Alexander F

2015-01-01

330

Optically thin ice clouds in Arctic : Formation processes  

NASA Astrophysics Data System (ADS)

Arctic ice cloud formation during winter is poorly understood mainly due to lack of observations and the remoteness of this region. Their influence on Northern Hemisphere weather and climate is of paramount importance, and the modification of their properties, linked to aerosol-cloud interaction processes, needs to be better understood. Large concentration of aerosols in the Arctic during winter is associated to long-range transport of anthropogenic aerosols from the mid-latitudes to the Arctic. Observations show that sulphuric acid coats most of these aerosols. Laboratory and in-situ measurements show that at cold temperature (<-30°C), acidic coating lowers the freezing point and deactivates ice nuclei (IN). Therefore, the IN concentration is reduced in these regions and there is less competition for the same available moisture. As a result, large ice crystals form in relatively small concentrations. It is hypothesized that the observed low concentration of large ice crystals in thin ice clouds is linked to the acidification of aerosols. Extensive measurements from ground-based sites and satellite remote sensing (CloudSat and CALIPSO) reveal the existence of two types of extended optically thin ice clouds (TICs) in the Arctic during the polar night and early spring. The first type (TIC-1) is seen only by the lidar, but not the radar, and is found in pristine environment whereas the second type (TIC-2) is detected by both sensors, and is associated with high concentration of aerosols, possibly anthropogenic. TIC-2 is characterized by a low concentration of ice crystals that are large enough to precipitate. To further investigate the interactions between TICs clouds and aerosols, in-situ, airborne and satellite measurements of specific cases observed during the POLARCAT and ISDAC field experiments are analyzed. These two field campaigns took place respectively over the North Slope of Alaska and Northern part of Sweden in April 2008. Analysis of cloud type can be done from these observations, and a first classification has been performed. Results are then compared to satellite data analysis. The new retrieval scheme of Delanoë and Hogan, which combines CloudSat radar and CALIPSO lidar measurements, is used to recover profiles of the properties of ice clouds such as the visible extinction coefficient, the ice water content and the effective radius of ice crystals. Comparisons with in situ airborne measurements allow to validate this retrieval method, and thus the clouds and aerosols properties, for selected cases whereflights are coordinated with the satellite overpasses. A comparison of combined CloudSat/CALIPSO microphysical properties retrievals with airborne ice clouds measurements will be presented. The Lagrangian Particle Dispersion Model FLEXPART is use to study the origin of observed air masses, to be linked with pollution sources.

Jouan, C.; Girard, E.; Pelon, J.; Blanchet, J.; Wobrock, W.; Gultepe, I.; Gayet, J.; Delanoë, J.; Mioche, G.; Adam de Villiers, R.

2010-12-01

331

Characterization of Arctic ice cloud properties observed during ISDAC  

NASA Astrophysics Data System (ADS)

Extensive measurements from ground-based sites and satellite remote sensing (CloudSat and CALIPSO) reveal the existence of two types of ice clouds (TICs) in the Arctic during the polar night and early spring. The first type (TIC-2A), being topped by a cover of nonprecipitating very small (radar unseen) ice crystals (TIC-1), is found more frequently in pristine environment, whereas the second type (TIC-2B), detected by both sensors, is associated preferentially with a high concentration of aerosols. To further investigate the microphysical properties of TIC-1/2A and TIC-2B, airborne in situ and satellite measurements of specific cases observed during Indirect and Semi-Direct Aerosol Campaign (ISDAC) have been analyzed. For the first time, Arctic TIC-1/2A and TIC-2B microstructures are compared using in situ cloud observations. Results show that the differences between them are confined in the upper part of the clouds where ice nucleation occurs. TIC-2B clouds are characterized by fewer (by more than 1 order of magnitude) and larger (by a factor of 2 to 3) ice crystals and a larger ice supersaturation (of 15-20%) compared to TIC-1/2A. Ice crystal growth in TIC-2B clouds seems explosive, whereas it seems more gradual in TIC-1/2A. It is hypothesized that these differences are linked to the number concentration and the chemical composition of aerosols. The ice crystal growth rate in very cold conditions impinges on the precipitation efficiency, dehydration and radiation balance. These results represent an essential and important first step to relate previous modeling, remote sensing and laboratory studies with TICs cloud in situ observations.

Jouan, Caroline; Girard, Eric; Pelon, Jacques; Gultepe, Ismail; Delanoë, Julien; Blanchet, Jean-Pierre

2012-12-01

332

A STUDY OF ICE BREAK AND ICE FLOW DURING RIVER ICE BREAKUP  

NASA Astrophysics Data System (ADS)

It is important to clarify the formation, break and flow of river ice on frozen rivers. The aim of this study is to clarify ice break and flow phenomena during river ice breakup, as these phenomena are the initial stages of ice jam. With regard to the break of river ice, we developed a method of judging ice break by comparing the stress caused by the flowing water and flowing ice, and the allowable bending stress of the river ice. The ice flow is expressed using the continuity equation that considers the change in amount of ice, and the equation of motion that considers the effect of the flowing water. This one-dimensional mathematical model showed that although there is a problem with the reproducibility of ice jam, it is possible to reproduce ice break and flow phenomena by comparing the freezing conditions from the results of the calculations, with those of aerial images of the actual river.

Yoshikawa, Yasuhiro; Watanabe, Yasuharu; Hayakawa, Hiroshi; Hirai, Yasuyuki

333

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

334

On the Retrieval of Ice Cloud Particle Shapes from POLDER Measurements  

NASA Technical Reports Server (NTRS)

Shapes of ice crystals can significantly affect the radiative transfer in ice clouds. The angular distribution of the polarized reflectance over ice clouds strongly depends on ice crystal shapes. Although the angular-distribution features of the total or polarized reflectance over ice clouds implies a possibility of retrieving ice cloud particle shapes by use of remote sensing data, the accuracy of the retrieval must be evaluated. In this study, a technique, which applies single ice crystal habit and multidirectional polarized radiance to retrieve ice cloud particle shapes, is assessed. Our sensitivity studies show that the retrieved particle shapes &om this algorithm can be considered good approximations to those in actual clouds in calculation of the phase matrix elements. Although a fractal poly-crystal shape or an inhomogeneous hexagonal column may also produce this type of phase functions, more representative single-scattering properties from combinations of natural particle shapes and size distributions may still be necessary in accurate retrieval of other cloud properties such as optical thickness and particle size.

Sun, W.; Loeb, N. G.; Yang, P.

2004-01-01

335

The Structural Properties of Vapor Deposited Water Ice and Astrophysical Implications  

NASA Technical Reports Server (NTRS)

Films of vapor deposited water ice at low temperature (T<30 K) show a number of interesting structural changes during a gradual warmup. We would like to talk about the structure of the low temperature high density amorphous form of water ice, the process of crystallization, and some recent work on the morphological changes of water ice films at high temperature. The studies of the high density amorphous form are from in-situ electron microscopy as well as numerical simulations of molecular dynamics and have lead to new insights into the physical distinction between this high density amorphous form and the low density amorphous form. For the process of crystallization, we propose a model that describes the crystallization of water ice from the amorphous phase to cubic ice in terms of the nucleation of small domains in the ice. This model agrees well with the behavior of water ice in our electron microscopy studies and finds that pure water above the glass transition is a strong liquid. In more recent work, we have concentrated on temperatures above the crystallization temperature and we find interesting morphological changes related to the decrease in viscosity of the amorphous component in the cubic crystalline regime. Given enough time, we would like to put these results in an astrophysical context and discuss some observed features of the frost on interstellar grains and the bulk ice in comets.

Jenniskens, P.; Blake, D. F.; Chang, Sherwood (Technical Monitor)

1996-01-01

336

Anisotropic elastocreep in glacial ice: A mechanism for intergranular melt and recrystallization  

Microsoft Academic Search

Bonded ice crystals under pressure are in a heterogeneous stress state because of the mechanical anisotropy of constituent grains. This condition plays a role in intergranular melt and recrystallization, which in turn influence properties such as permeability and biologic habitability. To examine this, we develop an anisotropic elastocreep model simulating subgrain-scale stresses in polycrystalline ice, choosing in particular the thermal

Steven M. Jepsen; Edward E. Adams

2008-01-01

337

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.

338

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

339

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

340

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.

341

Investigating Ice Worlds  

NSDL National Science Digital Library

In this activity about the solar system, learners use various light sources to examine ice with different components to understand how NASA studies planets and moons from space. This detailed lesson guide includes background information about distant ice worlds in the outer solar system, literature connections, instructions for a pre-activity demonstration, modified activities by age, tips, discussion questions, and resources.

Education, Carnegie I.

2011-01-01

342

Prismatic Structure in Ice  

Microsoft Academic Search

``In one of the March numbers of NATURE I see a letter over your signature on the prismatic structure of ice, and as our climate gives us favourable opportunities of observing this and other curious facts respecting ice, I am induced to address a few words to you on the subject.

John Langters

1870-01-01

343

Larsen B Ice Shelf  

... within the disintegrating ice shelf appears vibrant blue. Water has an intrinsic blue color due to the selective absorption of longer wavelengths such as red and infrared, and the translucent properties of ice within the collapsing shelf enables this absorption to be ...

2013-04-16

344

Snow and Ice.  

ERIC Educational Resources Information Center

This experimental edition provides a number of activities useful for investigating snow and ice with elementary school children. Commencing with games with ice cubes, the activities lead through studies of snowflakes, snowdrifts, effects of wind and obstacles on the shape and formation of drifts, to a study of animals living under snow. The…

Minneapolis Independent School District 275, Minn.

345

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

346

Amery Ice Shelf  

... (bottom), and illustrate changes that took place over the year elapsed between the two views. Two longitudinal rifts, oriented ... of ice flow and measuring about 25 and 15 kilometers in length, are apparent near the seaward edge of the ice shelf. Between them, a ...

2013-04-16

347

Ross Ice Shelf  

... to hatch their young this year due to a combination of huge icebergs grounded near Ross Island and an unprecedented amount of sea ice in the Ross Sea. The grounded icebergs and sea ice have increased the distance between the penguins' feeding ...

2013-04-16

348

Helicopter icing research  

NASA Technical Reports Server (NTRS)

A representative of the U.S. Army Research and Technology Laboratories was called upon to brief the workshop on results of flight test experiments with ice-phobic coatings applied to helicopter rotor blades. An overview of the Applied Technology Laboratory helicopter icing R and D program is presented.

Adams, R. I.

1978-01-01

349

Coating Reduces Ice Adhesion  

NASA Technical Reports Server (NTRS)

The Shuttle Ice Liberation Coating (SILC) has been developed to reduce the adhesion of ice to surfaces on the space shuttle. SILC, when coated on a surface (foam, metal, epoxy primer, polymer surfaces), will reduce the adhesion of ice by as much as 90 percent as compared to the corresponding uncoated surface. This innovation is a durable coating that can withstand several cycles of ice growth and removal without loss of anti-adhesion properties. SILC is made of a binder composed of varying weight percents of siloxane(s), ethyl alcohol, ethyl sulfate, isopropyl alcohol, and of fine-particle polytetrafluoroethylene (PTFE). The combination of these components produces a coating with significantly improved weathering characteristics over the siloxane system alone. In some cases, the coating will delay ice formation and can reduce the amount of ice formed. SILC is not an ice prevention coating, but the very high water contact angle (greater than 140 ) causes water to readily run off the surface. This coating was designed for use at temperatures near -170 F (-112 C). Ice adhesion tests performed at temperatures from -170 to 20 F (-112 to -7 C) show that SILC is a very effective ice release coating. SILC can be left as applied (opaque) or buffed off until the surface appears clear. Energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) data show that the coating is still present after buffing to transparency. This means SILC can be used to prevent ice adhesion even when coating windows or other objects, or items that require transmission of optical light. Car windshields are kept cleaner and SILC effectively mitigates rain and snow under driving conditions.

Smith, Trent; Prince, Michael; DwWeese, Charles; Curtis, Leslie

2008-01-01

350

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

351

Water Ice and Life's Roots in Space  

NASA Technical Reports Server (NTRS)

Nearly three decades ago as Voyager 2 spacecraft raced out of the Solar System. NASA engineers turned its camera arm around (at the request of the American astronomer Carl Sagan) to take a parting snapshot of Earth. Earth's image was a single pale blue pixel, its color caused by the Rayleigh scattering of sunlight in the water of our oceans. Earth is a water planet, and this is the color of life. No matter how far we travel on our planet, no matter how high or deep, if we find liquid water, we find some form of life that manages to survive there. And yet there is a cruel irony. Water in its solid crystalline form is hostile to life. Organisms can roost in geysers, wallow in brine and gulp down acid, but they cowered from ice. The rigid ordering of water molecules in ice crystals expels impurities and tears organic tissue beyond repair. In fact, about the only good thing you can say about ice is that it gets out of the way: Its low density ensures that it floats and leaves the water dwelling creatures in peace. Recent discoveries have caused us to rethink this basic premise. New lines of evidence both observational and experimental - suggest that prebiotic organic compounds are not only comfortable in, but in fact had their origin in a peculiar form of solid water ice that is ubiquitous in interstellar space, but completely absent from Earth. Only recently have we been able to create even submicroscopic quantities of this ice in terrestrial laboratories, yet it constitutes the most abundant form of water in the universe. Interstellar ice is a far cry from the ice we are so familiar with on Earth. This interstellar ice has no crystalline structure, and despite the fact that its temperature is a scant few degrees above absolute zero (where all molecular motion ceases), it is highly reactive and can flow like water when exposed to radiation. It is in fact this ice's similarity to liquid water that allows it to participate in the creation of the very first organic compounds.

Blake, David; Jenniskens, Peter; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

352

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

353

Milankovitch solar radiation variations and ice age ice sheet sizes  

Microsoft Academic Search

The fluctuations in the size of ice age ice sheets are calculated using glacier mechanics and the Milankovitch solar radiation variations. The calculations are greatly simplified by considering only two-dimensional ice sheets with profiles that would be appropriate if ice obeyed the flow law of a perfectly plastic solid. The solar radiation variations seem to be large enough to account

Johannes Weertman

1976-01-01

354

Instant Ice Cream with a Dry Ice Bath  

NSDL National Science Digital Library

In this chemistry meets cooking activity, learners make carbonated, vanilla ice cream using dry ice and denatured ethanol, which are both inexpensive and accessible. This process to make ice cream is faster than using rock salt and water ice as the refrigerant. Use this activity to introduce learners to the process of sublimation and phase change and to provide a fun treat.

Ragan, Sean M.

2011-01-01

355

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.

356

Microphysical consequences of the spatial distribution of ice nucleation in mixed-phase stratiform clouds  

NASA Astrophysics Data System (ADS)

Mixed-phase stratiform clouds can persist even with steady ice precipitation fluxes, and the origin and microphysical properties of the ice crystals are of interest. Vapor deposition growth and sedimentation of ice particles along with a uniform volume source of ice nucleation lead to a power law relation between ice water content wi and ice number concentration ni with exponent 2.5. The result is independent of assumptions about the vertical velocity structure of the cloud and is therefore more general than the related expression of Yang et al. (2013). The sensitivity of the wi-ni relationship to the spatial distribution of ice nucleation is confirmed by Lagrangian tracking and ice growth with cloud volume, cloud top, and cloud base sources of ice particles through a time-dependent cloud field. Based on observed wi and ni from Indirect and Semi-Direct Aerosol Campaign, a lower bound of 0.006 m-3 s-1 is obtained for the ice crystal formation rate.

Yang, Fan; Ovchinnikov, Mikhail; Shaw, Raymond A.

2014-07-01

357

Icing Cloud Calibration of the NASA Glenn Icing Research Tunnel  

NASA Technical Reports Server (NTRS)

The icing research tunnel at the NASA Glenn Research Center underwent a major rehabilitation in 1999, necessitating recalibration of the icing clouds. This report describes the methods used in the recalibration, including the procedure used to establish a uniform icing cloud and the use of a standard icing blade technique for measurement of liquid water content. The instruments and methods used to perform the droplet size calibration are also described. The liquid water content/droplet size operating envelopes of the icing tunnel are shown for a range of airspeeds and compared to the FAA icing certification criteria. The capabilities of the IRT to produce large droplet icing clouds is also detailed.

Ide, Robert F.; Oldenburg, John R.

2001-01-01

358

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

PubMed Central

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. Previously, a bacterium (isolate 3519-10) recovered from a depth of 3,519?m below the surface in the Vostok ice core was shown to secrete an ice-binding protein (IBP) that inhibits the recrystallization of ice. To explore the 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 cultures grown between 4 and 25°C and analyzed by reverse transcription-PCR indicated constitutive expression of the IBP gene. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of 3519-10’s extracellular proteins revealed a polypeptide of the predicted size of the 54-kDa IBP at all temperatures tested. In the presence of 100??g?mL?1 of extracellular protein from 3519-10, the survival of Escherichia coli was increased by greater than 100-fold after 5 freeze-thaw cycles. Microscopic analysis of ice formed in the presence of the IBP indicated that per square millimeter 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 filtered 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. A myriad of molecular adaptations are likely to play a role in bacterial persistence under frozen conditions, but the ability of 3519-10’s IBP to control ice crystal structure, and thus the liquid vein network within the ice, may provide one explanation for its successful survival deep within the Antarctic ice sheet for thousands of years. PMID:22207866

Achberger, Amanda Marie; Brox, Timothy Ian; Skidmore, Mark Leslie; Christner, Brent Craig

2011-01-01

359

Skylab floating ice experiment  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Coupling of the aircraft data with the ground truth observations proved to be highly successful with interesting results being obtained with IR and SLAR passive microwave techniques, and standard photography. Of particular interest were the results of the PMIS system which operated at 10.69 GHz with both vertical and horizontal polarizations. This was the first time that dual polarized images were obtained from floating ice. In both sea and lake ice, it was possible to distinguish a wide variety of thin ice types because of their large differences in brightness temperatures. It was found that the higher brightness temperature was invariably obtained in the vertically polarized mode, and as the age of the ice increases the brightness temperature increases in both polarizations. Associated with this change in age, the difference in temperature was observed as the different polarizations decreased. It appears that the horizontally polarized data is the most sensitive to variations in ice type for both fresh water and sea ice. The study also showed the great amount of information on ice surface roughness and deformation patterns that can be obtained from X-band SLAR observations.

Campbell, W. J. (principal investigator); Ramseier, R. O.; Weaver, R. J.; Weeks, W. F.

1975-01-01

360

Ice sheets and nitrogen  

PubMed Central

Snow and ice play their most important role in the nitrogen cycle as a barrier to land–atmosphere and ocean–atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2–3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas. PMID:23713125

Wolff, Eric W.

2013-01-01

361

The time-dependence of the defective nature of ice Ic (cubic ice) and its implications for atmospheric science  

NASA Astrophysics Data System (ADS)

The possible atmospheric implication of ice Ic (cubic ice) has already been suggested some time ago in the context of snow crystal formation [1]. New findings from air-borne measurements in cirrus clouds and contrails have put ice Ic into the focus of interest to understand the so-called "supersaturation puzzle" [2,3,4]. Our recent microstructural work on ice Ic [5,6] appears to be highly relevant in this context. We have found that ice Ic is characterized by a complex stacking fault pattern, which changes as a function of temperature as well as time. Indeed, from our own [7] and other group's work [8] one knows that (in contrast to earlier believe) ice Ic can form up to temperatures at least as high as 240K - thus in the relevant range for cirrus clouds. We have good preliminary evidence that the "cubicity" (which can be related to stacking fault probabilities) as well as the particle size of ice Ic are the relevant parameters for this correlation. The "cubicity" of stacking faulty ice Ic (established by diffraction) correlates nicely with the increased supersaturation at decreasing temperatures observed in cirrus clouds and contrails, a fact, which may be considered as further evidence for the presence of ice Ic. Recently, we have studied the time-dependency of the changes in both "cubicity" and particle size at various temperatures of relevance for cirrus clouds and contrails by in-situ neutron powder diffraction. The timescales over which changes occur (several to many hours) are similar to the life-time of cirrus clouds and contrails and suggest that the supersaturation situation may change within this time span in the natural environment too. Some accompanying results obtained by cryo-SEM (scanning electron microscopy) work will also be presented and suggest that stacking-faulty ice Ic has kinky surfaces providing many more active centres for heterogeneous reactions on the surface than in the usually assumed stable hexagonal form of ice Ih with its rather flat low-indexed crystal faces. [1] T Kobayashi & T Kuroda (1987) Snow Crystals. In: Morphology of Crystals (ed. I Sunagawa), Terra Scientific Publishing, Tokyo, pp.649-743. [2] RS Gao & 19 other authors (2004) Evidence that nitric acid increases relative humidity in low-temperature cirrus clouds. Science 303, 516-520. [3] T Peter, C Marcolli, P Spichtinger, T Corti, MC Baker & T Koop (2006) When dry air is too humid. Science 314, 1399-1402. [4] JE Shilling, MA Tolbert, OB Toon, EJ Jensen, BJ Murray & AK Bertram (2006) Measurements of the vapor pressure of cubic ice and their implications for atmospheric ice clouds. Geophys.Res.Lett. 33, 026671. [5] TC Hansen, MM Koza & WF Kuhs (2008) Formation and annealing of cubic ice: I Modelling of stacking faults. J.Phys.Cond.Matt. 20, 285104. [6] TC Hansen, MM Koza, P Lindner & WF Kuhs (2008) Formation and annealing of cubic ice: II. Kinetic study. J.Phys.Cond.Matt. 20, 285105. [7] WF Kuhs, G Genov, DK Staykova & AN Salamatin, T Hansen (2004) Ice perfection and the onset of anomalous preservation of gas hydrates. Phys.Chem.Chem.Phys. 6, 4917-4920. [8] BJ Murray, DA Knopf & AK Bertram (2005) The formation of cubic ice under conditions relevant to Earth's atmosphere. Nature 434, 292-205.

Sippel, Christian; Koza, Michael M.; Hansen, Thomas C.; Kuhs, Werner F.

2010-05-01

362

Evaluating and Constraining Ice Cloud Parameterizations in CAM5 using Aircraft Measurements from the SPARTICUS Campaign  

SciTech Connect

This study uses aircraft measurements of relative humidity and ice crystal size distribution collected in synoptic cirrus during the SPARTICUS (Small PARTicles In CirrUS) field campaign to evaluate and constrain ice cloud parameterizations in the Community Atmosphere Model version 5. The probability density function (PDF) of ice crystal number concentration (Ni) derived from high frequency (1 Hz) measurements features a strong dependence on ambient temperature. As temperature decreases from -35°C to -62°C, the peak in the PDF shifts from 10-20 L-1 to 200-1000 L-1, while the ice crystal number concentration shows a factor of 6-7 increase. Model simulations are performed with two different insitu ice nucleation schemes. One of the schemes can reproduce a clear increase of Ni with decreasing temperature, by using either an observation based ice nuclei spectrum or a classical theory based spectrum with a relatively low (5%-10%) maximum freezing ratio for dust aerosols. The simulation with the other scheme, which assumes a high maximum freezing ratio (100%), shows much weaker temperature dependence of Ni. Simulations are also performed to test empirical parameters related to water vapor deposition and the auto-conversion of ice crystals to snow. Results show that a value between 0.05 and 0.1 for the water vapor deposition coefficient and 250 um for the critical ice crystal size can produce good agreements between model simulation and the SPARTICUS measurements in terms of ice crystal number concentration and effective radius. The climate impact of perturbing these parameters is also discussed.

Zhang, Kai; Liu, Xiaohong; Wang, Minghuai; Comstock, Jennifer M.; Mitchell, David; Mishra, Subhashree; Mace, Gerald G.

2013-05-14

363

Advances in ice mechanics - 1987  

SciTech Connect

This book presents the papers given at a symposium on the interaction of icebergs with offshore platforms. Topics considered at the symposium included advances in ice mechanics in the United Kingdom, ice mechanics in Finland, recent advances in ice mechanics in Canada, advances in sea ice mechanics in the USA, foundations, monitoring, hazards, risk assessment, and deformation.

Chung, J.S.; Hallam, S.D.; Maatanen, M.; Sinha, N.K.; Sodhi, D.S.

1987-01-01

364

THE WORLD OF UNDERGROUND ICE  

Microsoft Academic Search

Underground ice is restricted to permafrost areas where its distribution is sporadic and often unpredictable. A knowledge of the distribution and abundance of underground ice is essential to northern development, because a variety of man induced disturbances can cause underground ice to thaw, often with serious consequences. The criteria for a classification of the principal types of underground ice are

J. ROSS MACKAY

1972-01-01

365

Ice nucleation terminology  

NASA Astrophysics Data System (ADS)

Progress in the understanding of ice nucleation is being hampered by the lack of uniformity in how some terms are used in the literature. This even extends to some ambiguity of meanings attached to some terms. Suggestions are put forward here for common use of terms. Some are already well established and clear of ambiguities. Others are less engrained and will need a conscious effort in adoption. Evolution in the range of systems where ice nucleation is being studied enhances the need for a clear nomenclature. The ultimate limit in the clarity of definitions is, of course, the limited degree to which ice nucleation processes are understood.

Vali, G.; DeMott, P.; Möhler, O.; Whale, T. F.

2014-08-01

366

An ice shelf breakup  

SciTech Connect

Glaciers and ice sheets are controlled by the climate and must change if the conditions that led to their current configurations are changing. These ice masses exist at the interface between the atmosphere, which provides sustaining snowfall and thermal regulation, and the land, which provides a stable base and in many cases the elevation required to reach suitably cold conditions. Ice sheets and glaciers are distributed around the globe and can serve as potential indicators of past climate variability and current climatic trends. 9 refs.

Fahnestock, M. [Univ. of Maryland, College Park, MD (United States)

1996-02-09

367

Quantum Hall ice  

NASA Astrophysics Data System (ADS)

We show that the chiral kagome ice manifold exhibits an anomalous integer quantum Hall effect (IQHE) when coupled to itinerant electrons. Although electron-mediated interactions select a magnetically ordered ground state, the full ice manifold can coexist with the IQHE over a range of finite temperatures. The degenerate ice states provide a natural realization of power-law correlated flux disorder, for which the spectral gap of the system remains robust. The quantized (up to exponentially small finite-temperature corrections) Hall conductance persists over a wide range of electron densities due to the disorder-induced localization of electronic states.

Chern, Gia-Wei; Rahmani, Armin; Martin, Ivar; Batista, Cristian D.

2014-12-01

368

The Great Ice Age  

NSDL National Science Digital Library

The Great Ice Age, a recent chapter in the Earth's history, was a period of recurring widespread glaciations. Mountain glaciers formed on all continents, the ice caps of Antarctica and Greenland were more extensive and thicker than today, and vast glaciers, in places as much as several thousand feet thick, spread across North America and Eurasia. This ice age, the most recent in the history of the Earth, took place from 20 million years to 6 thousand years ago (Quaternary Period). The development of our understanding and the evidence for this worldwide event are covered in this United States Geological Survey (USGS) publication.

Ray, Louis

369

Global Ice Core Research  

NSDL National Science Digital Library

This informative site from the US Geological Survey (USGS) covers the latest ice-core research projects from around the world, including sites in Nepal, Norway, and Kyrghyzstan. Authored by researchers at the Global Ice core Research Office, the site contains an overview of the mid-latitude and polar glaciers, isotopic methods in glacial research, and applications to paleoclimatology. Links to maps, figures, and in some cases, full-text articles (HTML) about specific glaciers are available, and the site is peppered with color photos of glacial environments. Links to biographies of the scientists involved in the project, contacts, and other snow and ice sites are also listed.

370

Ice interaction with offshore structures  

SciTech Connect

Oil platforms and other offshore structures being built in the arctic regions must be able to withstand icebergs, ice islands, and pack ice. This reference explain the effect ice has on offshore structures and demonstrates design and construction methods that allow such structures to survive in harsh, ice-ridden environments. It analyzes the characteristics of sea ice as well as dynamic ice forces on structures. Techniques for ice modeling and field testing facilitate the design and construction of sturdy, offshore constructions. Computer programs included.

Cammaert, A.B.; Muggeridge, D.B.

1988-01-01

371

Molecular dynamics studies of molecular diffusion in ice Ih  

Microsoft Academic Search

We performed molecular dynamics simulations of the diffusion of interstitial He and H2O in ice Ih and found diffusion hops for these interstitial molecules from a stable site to an adjacent site. By observing the jumps of these diffusing species, we determined the jump frequencies, the crystal orientation dependence of the diffusion coefficients, and the diffusion activation energies. Most jumps

Tomoko Ikeda-Fukazawa; Shinichiro Horikawa; Takeo Hondoh; Katsuyuki Kawamura

2002-01-01

372

15/Oct/2010 1Univ. Minnesota Seminar Interstellar Ices  

E-print Network

Herschel/HIFI Observations of Hot Cores/Corinos Conclusions #12;15/Oct/2010 3Univ. Minnesota Seminar phase chemistry. ·"Grain surfaces are the watering holes of astrochemistry where species come to meet after H2O crystallization. CO2 ice heating heating observed toward YSOs #12;15/Oct/2010 10Univ

Boogert, Adwin

373

Interface limited growth of heterogeneously nucleated ice in supercooled water  

E-print Network

Heterogeneous ice growth exhibits a maximum in freezing rate arising from the competition between kinetics and the thermodynamic driving force between the solid and liquid states. Here, we use molecular dynamics simulations to elucidate the atomistic details of this competition, focusing on water properties in the interfacial region along the secondary prismatic direction. The crystal growth velocity is maximized when the efficiency of converting interfacial water molecules to ice, collectively known as the attachment kinetics, is greatest. We find water molecules that contact the intermediate ice layer in concave regions along the atomistically roughened surface are more likely to freeze directly. The increased roughening of the solid surface at large undercoolings consequently plays an important limiting role on the rate of ice growth, as water molecules are unable to integrate into increasingly deeper surface pockets. These results provide insights into the molecular mechanisms for self-assembly of solid phases that are important in many biological and atmospheric processes.

Razvan A. Nistor; Thomas E. Markland; B. J. Berne

2013-08-29

374

A new ice nuclei counter SPIN: characterization and first results  

NASA Astrophysics Data System (ADS)

Ice nuclei (IN) play an important role in a number of processes related to cloud formation and cloud properties. Despite significant progress within ice nucleation research in the past decades - a lot of questions remain to be answered. In situ measurements with portable IN counters are an important way to gain knowledge in this field. Spectrometer for Ice Nuclei (SPIN, Droplet Measurement Technologies, Inc.) is a new commercially available portable IN counter. SPIN is a continuous flow diffusion chamber with parallel plate geometry following the design of the portable IN counter PINC (Chou et al., Atmospheric Chemistry and Physics, 11:4725-4738, 2011). The aerosol sample flows through a chamber, where a supersaturation of water vapor with respect to ice is obtained by applying a temperature gradient between two ice covered plates. The aerosol sample is exposed to an evaporation section for evaporation of liquid droplets before detection of particles with an optical particle counter (OPC). Thus the formed ice crystals can be distinguished from other particles by size. With SPIN, it is possible to quantify ice nucleation in both, deposition nucleation and condensation/immersion freezing modes. In the laboratory, with SPIN, the involved groups studied various aerosol particle types, including ammonium sulfate, mineral dusts and biological particles. Results of these studies will be presented and discussed.

Stratmann, F.; Abbatt, J.; Cziczo, D. J.; Gallagher, M. W.; Lachlan-Cope, T.; Garemilla, S.; Ignatius, K.; Kristensen, T. B.; Moreno, L. A.

2013-12-01

375

Hydrographer on the Ice  

USGS Multimedia Gallery

Scott Bendtson, a hydrologic technician with the Maine Office of the New England Water Science Center, is seen here making a discharge measurement through the ice on the St. John River at Ninemile Bridge, USGS station number 01010000....

376

ION COMPOSITION ELUCIDATION (ICE)  

EPA Science Inventory

Ion Composition Elucidation (ICE) utilizes selected ion recording with a double focusing mass spectrometer to simultaneously determine exact masses and relative isotopic abundances from mass peak profiles. These can be determined more accurately and at higher sensitivity ...

377

Ice Cream Stick Math.  

ERIC Educational Resources Information Center

Described is a teaching technique which uses the collection of ice cream sticks as a means of increasing awareness of quantity in a self-contained elementary special class for students with learning disabilities and mild mental retardation. (DB)

Paddock, Cynthia

1992-01-01

378

Record Sea Ice Minimum  

NASA Technical Reports Server (NTRS)

Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 and substantially below the long-term average. This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA's Aqua satellite on September 16, 2007. In this image, blue indicates open water, white indicates high sea ice concentration, and turquoise indicates loosely packed sea ice. The black circle at the North Pole results from an absence of data as the satellite does not make observations that far north. Three contour lines appear on this image. The red line is the 2007 minimum, as of September 15, about the same time the record low was reached, and it almost exactly fits the sea ice observed by AMSR-E. The green line indicates the 2005 minimum, the previous record low. The yellow line indicates the median minimum from 1979 to 2000.

2007-01-01

379

Ices in planetary rings  

NASA Technical Reports Server (NTRS)

Understanding the structure and behavior of Saturnian rings in terms of properties of ices is basic for evolutionary planetology. The available information indicates the presence of quite pure, probably amorphous water ice in the form of medium-grained frost in a fairy castle structure with a low thermal inertia. Tidal forces and interparticle collisions lead to continuous break-up and re-formation of loose aggregates of smaller particles. Micrometeoroid bombardment and proton irradiation are important for explaining the mechanical and optical properties of the surfaces of ring particles. The transfer of angular momentum and mass among the rings should homogenize the chemical and structural characteristics of the ring ices. Uranian rings may be made of carbon-covered methane ice particles.

Smoluchowski, R.

1985-01-01

380

Global ice sheet modeling  

SciTech Connect

The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed.

Hughes, T.J.; Fastook, J.L. [Univ. of Maine, Orono, ME (United States). Institute for Quaternary Studies

1994-05-01

381

Sea Ice Index  

NSDL National Science Digital Library

This site presents average ice conditions estimated using satellite passive microwave data for the most recent month available, as well as snapshots of trends and anomalies that compare these recent conditions with the mean for the month.

Fetterer, Florence

382

Modeling ice sheets from the bottom up  

Microsoft Academic Search

Three facts should guide ice-sheet modeling. (1) Ice height above the bed is controlled by the strength of ice-bed coupling, reducing ice thickness by some 90 percent when coupling vanishes. (2) Ice-bed coupling vanishes along ice streams that end as floating ice shelves and drain up to 90 percent of an ice sheet. (3) Because of (1) and (2), ice

T. Hughes

2009-01-01

383

Hexagonal ice stability and growth in the presence of glyoxal and secondary organic aerosols.  

PubMed

The presence of ice dominates the microphysics of formation of high altitude cirrus and polar stratospheric clouds, as well as the maturity of thunderstorms. We report on the hexagonal (1h) ice stability and growth in binary as well as multi-compound aerosols in atmospherically relevant conformations. The ubiquitous atmospheric trace gas glyoxal along with secondary organic aerosol (SOA) also in the presence of CO2 interacts with large ice 1h crystals of 1300-2000 water molecules. The crystals are subjected to phase transitions under superheating and supercooling conditions by Molecular Dynamics (MD) simulations. Density Functional Theory (DFT) based geometry optimization and vibrational frequency analysis are also employed for a smaller ice 1h cell of 12 water molecules. The interaction of the latter with each organic molecule reveals the extent of the mechanical stress exerted on the ordered ice structure. Full hydration of glyoxal promotes ice 1h stability and growth in wet aerosols, while partial hydration or full oxidation exerts a destabilizing effect on the ice 1h lattice. This behavior is associated with the ability of each organic phase to match the order of the ice 1h crystal. We propose that aqueous chemistry in wet aerosols may also have a strong effect on the microphysics of cloud formation. PMID:25033409

Daskalakis, Vangelis; Hadjicharalambous, Marios

2014-09-01

384

ICE Biological Inventories Databases  

NSDL National Science Digital Library

The Information Center for the Environment (ICE) is a cooperative effort between scientists at University of California -- Davis and collaborators from over thirty organizations involved in environmental protection." The ICE Biological Inventory Databases contain "documented, taxonomically standardized species inventories of plants and animals reported from the world's protected areas." New to the Scout Report, these online databases have been updated recently to include botanical inventories from protected areas in Costa Rica and South Africa.

385

All About Sea Ice  

NSDL National Science Digital Library

This comprehensive site is an introduction to sea ice: what it is, how it forms, how it is studied, how it affected historical expedition in the polar regions, and what role it plays in the global climate. The site contains a glossary of sea ice terms and references to additional information, which all serve as an excellent introduction. Data are also available from various collection methods for student interpretation.

386

Ice On Venus  

NSDL National Science Digital Library

This resource is part of the Science Education Gateway (SEGway) project, funded by NASA, which is a national consortium of scientists, museums, and educators working together to bring the latest science to students, teachers, and the general public. Is there ice on Venus? If so, what kind of ice is it? In this activity, students find the answers to these questions by using internet resources. The teacher's page contains teaching strategies, vocabulary, homework ideas, and assessment possibilities.

387

Effect of okra cell wall and polysaccharide on physical properties and stability of ice cream.  

PubMed

Stabilizers are used in ice cream to increase mix viscosity, promote smooth texture, and improve frozen stability. In this study, the effects of varying concentrations (0.00%, 0.15%, 0.30%, and 0.45%) of okra cell wall (OKW) and its corresponding water-soluble polysaccharide (OKP) on the physical characteristics of ice cream were determined. Ice cream mix viscosity was measured as well as overrun, meltdown, and consumer acceptability. Ice recrystallization was determined after ice cream was subjected to temperature cycling in the range of -10 to -20 °C for 10 cycles. Mix viscosity increased significantly as the concentrations of OKW and OKP increased. The addition of either OKW or OKP at 0.15% to 0.45% significantly improved the melting resistance of ice cream. OKW and OKP at 0.15% did not affect sensory perception score for flavor, texture, and overall liking of the ice cream. OKW and OKP (0.15%) reduced ice crystal growth to 107% and 87%, respectively, as compared to 132% for the control (0.00%). Thus, our results suggested the potential use of OKW and OKP at 0.15% as a stabilizer to control ice cream quality and retard ice recrystallization. OKP, however, at 0.15% exhibited greater effect on viscosity increase and on ice recrystallization inhibition than OKW. PMID:25040189

Yuennan, Pilapa; Sajjaanantakul, Tanaboon; Goff, H Douglas

2014-08-01

388

Middle Pleistocene (?) buried glacial ice on Bylot Island, Canadian Arctic Archipleago  

NASA Astrophysics Data System (ADS)

Bylot Island is located north of Baffin Island (73°N, 80°W). More than the half of the island is covered by an ice cap and its outlet glaciers flowing towards the arctic lowland of the Lancaster formation. The study site comprises four main stratigraphic units. Overlying the shales (Tertiary) of the Lancaster Formation (500 m a.s.l.), a diamicton (unit 1) is covered by a “fossil forest-tundra” sequence (unit 2) containing abundant remains of trees and plants (Allard et al., submitted). Paleontological correlation of extinct species and reverse to normal palomagnetism polarities suggest a Late Pliocene to Early Pleistocene age for this unit. A sequence (unit 3) of ice-contact proximal to distal glacio-fluvial sediments overlies the organic beds. Paleomagnetic analysis showed that the upper glacio-fluvial sediments were likely deposited during the Brunhes polarity chron (younger than 0.73 Ma). The uppermost unit (unit 4) consists in a lodgement till containing clasts of Paleozoic limestone erratics. Based on amino acid ratios of shells fragments in the drift, Klassen (1993) suggested that this “foreign drift” was probably deposited during an "old" Quaternary glaciation named “Baffin glaciation” During July 2009 several active-layer detachment slides at the head of large gullies exposed large massive ice bodies located at the junction between units 3 and 4. A preliminary analysis of the ice facies and ice crystals revealed the presence of two distinct types of massive ice: 1) clear-ice bodies with very few sediments and no organic inclusions. The ice crystals were large (cm) and air bubbles were observed at the junction of crystals. These characteristics could potentially indicate an englacial origin for these clear ice bodies. In some places, the ice was stratified with undulating layers of sands and gravels. These micro-structures are very similar to basal ice facies we observed at the Matanuska Glacier in Alaska. The exposed massive ice sections were a few tens of meter wide and about 2 to 4 m deep but the real width and thickness of these ice masses are unknown. The upper part of the clear ice and stratified massive ice bodies were always in contact with various types of glacio-fluvial sediments which suggest that their preservation were likely related to rapid burial of the ice and refreezing of the overlying sediments following permafrost aggradation. 2) large, white to milky, epigenetic ice wedges with a typical sub-vertical foliated structure. The ice wedges were formed in unit 4 and, in some places, penetrated into the clear massive ice bodies described above which created a sharp visual contrast between the two types of ice. This also indicates that ice wedge development post-date the massive ice burial. Based on the chrono-stratigraphic context and on the similarities between 1) the clear ice masses and the contemporary englacial ice facies (e.g. on Bylot Island); and 2) the cryostructures of the stratified massive ice at the study site and the contemporary basal ice cryostructures observed at the Matanuska glaciers, we propose that the massive ice bodies exposed on Bylot Island are related to a Middle Pleistocene glaciation.

Fortier, D.; Godin, E.; Kanevskiy, M. Z.; Allard, M.

2009-12-01

389

Enhanced Sea Ice Concentration and Ice Temperature Algorithms for AMSR  

NASA Technical Reports Server (NTRS)

Accurate quantification of sea ice concentration and ice temperature from satellite passive microwave data is important because they provide the only long term, spatially detailed and consistent data set needed to study the climatology of the polar regions. Sea ice concentration data are used to derive large-scale daily ice extents that are utilized in trend analysis of the global sea ice cover. They are also used to quantify the amount of open water and thin ice in polynya and divergence regions which together with ice temperatures are in turn needed to estimate vertical heat and salinity fluxes in these regions. Sea ice concentrations have been derived from the NASA Team and Bootstrap algorithms while a separate technique for deriving ice temperature has been reported. An integrated technique that will utilizes most of the channels of AMSR (Advanced Microwave Scanning Radiometer) has been developed. The technique uses data from the 6 GHz and 37 GHz channels at vertical polarization obtain an initial estimate of sea ice concentration and ice temperature. The derived ice temperature is then utilized to estimate the emissivities for the corresponding observations at all the other channels. A procedure for calculating the ice concentration similar to the Bootstrap technique is then used but with variables being emissivities instead of brightness temperatures to minimizes errors associated with spatial changes in ice temperatures within the ice pack. Comparative studies of ice concentration results with those from other algorithms, including the original Bootstrap algorithm and those from high resolution satellite visible and infrared data will be presented. Also, results from a simulation study that demonstrates the effectiveness of the technique in correcting for spatial variations in ice temperatures will be shown. The ice temperature results are likewise compared with satellite infrared and buoy data with the latter adjusted to account for the effects of the snow cover.

Comiso, Josefino C.; Manning, Will; Gersten, Robert

1998-01-01

390

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

E-print Network

in the bubbles is about the same age as the ice, so scientists use bubbles to learn about the ancient atmosphereUsing 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

391

Increasing the protein content of ice cream.  

PubMed

Vanilla ice cream was made with a mix composition of 10.5% milk fat, 10.5% milk SNF, 12% beet sugar, and 4% corn syrup solids. None of the batches made contained stabilizer or emulsifier. The control (treatment 1) contained 3.78% protein. Treatments 2 and 5 contained 30% more protein, treatments 3 and 6 contained 60% more protein, and treatments 4 and 7 contained 90% more protein compared with treatment 1 by addition of whey protein concentrate or milk protein concentrate powders, respectively. In all treatments, levels of milk fat, milk SNF, beet sugar, and corn syrup solids were kept constant at 37% total solids. Mix protein content for treatment 1 was 3.78%, treatment 2 was 4.90%, treatment 5 was 4.91%, treatments 3 and 6 were 6.05%, and treatments 4 and 7 were 7.18%. This represented a 29.89, 60.05, 89.95, 29.63, 60.05, and 89.95% increase in protein for treatment 2 through treatment 7 compared with treatment 1, respectively. Milk protein level influenced ice crystal size; with increased protein, the ice crystal size was favorably reduced in treatments 2, 4, and 5 and was similar in treatments 3, 6, and 7 compared with treatment 1. At 1 wk postmanufacture, overall texture acceptance for all treatments was more desirable compared with treatment 1. When evaluating all parameters, treatment 2 with added whey protein concentrate and treatments 5 and 6 with added milk protein concentrate were similar or improved compared with treatment 1. It is possible to produce acceptable ice cream with higher levels of protein. PMID:16606711

Patel, M R; Baer, R J; Acharya, M R

2006-05-01

392

An Optical Study of Ice Grain Boundaries  

NASA Astrophysics Data System (ADS)

The equilibrium phase geometry and evolution of polycrystals underlies the nature of materials. In particular, grain boundaries dominate the total interfacial area within polycrystalline materials. Our experimental studies are motivated by the importance of the structure, evolution, and thermodynamic behavior of grain boundaries near bulk melting temperatures. Ice is singled out as a material of interest due to its geophysical importance and its advantageous optical properties. An experimental apparatus and light reflection technique is designed to measure grain boundary melting in ice bicrystals, in thermodynamic equilibrium The technique allows continuous monitoring of reflected light intensity from the grain boundary as the temperature and solutal composition are systematically varied. For each sample the individual crystal orientations are also measured. The type and concentration of impurity in the liquid is controlled and the temperature is continuously recorded and controlled over a range near the melting point. An optical model of the interface is developed in order to convert experimental reflection data into a physical measurement of the liquidity of the grain boundary. Solutions are found for reflection and transmission amplitude coefficients for waves propagating from an arbitrarily oriented uniaxial anisotropic material into an isotropic material. This general model is used to determine solutions for three layer, ice/water/ice, systems with crystals of arbitrary orientation, and is broadly applicable to layered materials. Experimental results show thicker grain boundary liquid layers than expected from classical colligative effects. A physically realistic model of intermolecular interactions succeeds in bounding the measurements. These measurements may have important implications for understanding a wide range of effects in polycrystalline materials. Likewise, the experimental techniques and optical theory may be applied to other systems of broad scientific significance.

Thomson, Erik S.

393

Origin of massive ice at Cape Marre-Sale, Yamal Peninsula, Siberia, Russia: contrasting views  

NASA Astrophysics Data System (ADS)

The origin of permafrost and ground ice of the Cape Marre-Sale polar station area, Western Yamal Peninsula, Russia, has been debated for decades. This can be explained by the extremely complex morphology of sedimentary strata and cryofacies exposed along the costal bluffs. Here, we report massive ice observations realized during summer 2012 as well as numerous laboratory and field analysis previously conducted on the massive ice bodies and reported in the literature. Our objective is to present contrasting views currently being proposed to explain the origin of massive ice at Cape Marre-Sale. Several types of massive ice bodies can be observed along the exposures. One striking cryofacies observed shows alternating cm-thick ice lenses and cm-to-dm thick bands of sediment-rich ice, which are commonly folded with an amplitude of several meters. This very ice-rich cryofacies is interpreted either as buried basal ice of the Eurasian ice-sheet or alternatively as massive segregated ice formed during epigenetic permafrost aggradation. This cryofacies comprised meters large clasts of stratified sand with organics, with some of these stratifications being folded and faulted and showing boudinage structure. The location of these large sand clasts within the foliated ice-rich massive ice could be explained either by glacio-tectonic activity (glacio-dislocation during ice flow) or alternatively by regional tectonic activity. Large m-thick and meters-long pure ice bodies were also observed within the foliated massive ice. The first type is withish and contains a very large amount of air bubbles without any clear orientation. The second type is made of blueish to clear ice and contains a few air bubbles and rare, randomly distributed, fine-grained sediment inclusions suspended in the ice. Ice crystallography revealed the presence of large (cm) ice crystals in both types of ice. These pure ice bodies cross-cut the massive foliated ice. They could be interpreted as refrozen water trapped in intra-glacial tunnels formed within the basal ice (oxygen-rich water and suspension freezing of fine-grained sediments) of the ice-sheet or alternatively as groundwater injection (and subsequent refreezing) during freezing of taliks following lake drainage. Finally, wedge-shaped massive ice can also be observed near the top of the exposures. The first type is yellowish, vertically foliated, extends downward for several meters in the massive foliated ice and contains a significant amount of fine-grained sediment. This is either interpreted as Pleistocene ice wedge (frost-cracking) or alternatively as hydrolaccolith formed by the upward intrusion/expulsion of water within the foliated massive ice, likely due to the joint action of groundwater, permafrost aggradation and tectonic processes. The second type of wedge ice is withish in color and foliated and has been interpreted unanimously as Holocene ice wedges (frost-cracking). The contrasting views presented here represent new and reasonable working hypothesis to explain the genesis of massive ice at Cape Marre-Sale. These hypotheses have considerable implications for the reconstruction of paleoclimates and paleoenvironments of Western Siberia.

Fortier, D.; Kurchatova, A. N.; Jorgenson, M. T.; Godin, E.; M-Lepage, J.; Stephani, E.; Kanevskiy, M. Z.; Shur, Y.

2012-12-01

394

Understanding Ice Supersaturation, Particle Growth, and Number Concentration in Cirrus Clouds  

SciTech Connect

Many factors control the ice supersaturation and microphysical properties in cirrus clouds. We explore the effects of dynamic forcing, ice nucleation mechanisms, and ice crystal growth rate on the evolution and distribution of water vapor and cloud properties in cirrus clouds using a detailed microphysical model and remote sensing measurements obtained at the Department of Energy’s Atmospheric Radiation Measurement (ARM) Climate Research Facility located near Lamont, OK. To help understand dynamic scales important in cirrus formation, we force the model using both large-scale forcing derived using ARM variational analysis, and mean mesoscale velocity derived from radar Doppler velocity measurements. Both heterogeneous and homogeneous nucleation processes are explored, where we have implemented a rigorous classical theory heterogeneous nucleation scheme to compare with empirical representations. We evaluate model simulations by examining both bulk cloud properties and distributions of measured radar reflectivity, lidar extinction, and water vapor profiles, as well as retrieved cloud microphysical properties. This approach allows for independent verification of both the large and small particle modes of the particle size distribution. Our results suggest that mesoscale variability is the primary mechanism needed to reproduce observed quantities, while nucleation mechanism is secondary. Slow ice crystal growth tends to overestimate the number of small ice crystals, but does not seem to influence bulk properties such as ice water path and cloud thickness. The most realistic simulations as compared with observations are forced using mesoscale waves, include fast ice crystal growth, and initiate ice by either homogeneous or heterogeneous nucleation. Ice crystal number concentrations on the order of 10-100 L-1 produce results consistent with both lidar and radar observations during a cirrus event observed on 7 December 1999, which has an optical depth range typical of midlatitude cirrus.

Comstock, Jennifer M.; Lin, Ruei-Fong; Starr, David O.; Yang, P.

2008-12-10

395

Arctic Summer Ice Processes  

NASA Technical Reports Server (NTRS)

The primary objective of this study is to estimate the flux of heat and freshwater resulting from sea ice melt in the polar seas. The approach taken is to examine the decay of sea ice in the summer months primarily through the use of spaceborne Synthetic Aperture Radar (SAR) imagery. The improved understanding of the dynamics of the melt process can be usefully combined with ice thermodynamic and upper ocean models to form more complete models of ice melt. Models indicate that more heat is absorbed in the upper ocean when the ice cover is composed of smaller rather than larger floes and when there is more open water. Over the course of the summer, floes disintegrate by physical forcing and heating, melting into smaller and smaller sizes. By measuring the change in distribution of floes together with open water over a summer period, we can make estimates of the amount of heating by region and time. In a climatic sense, these studies are intended to improve the understanding of the Arctic heat budget which can then be eventually incorporated into improved global climate models. This work has two focus areas. The first is examining the detailed effect of storms on floe size and open water. A strong Arctic low pressure storm has been shown to loosen up the pack ice, increase the open water concentration well into the pack ice, and change the distribution of floes toward fewer and smaller floes. This suggests episodic melting and the increased importance of horizontal (lateral) melt during storms. The second focus area is related to an extensive ship-based experiment that recently took place in the Arctic called Surface Heat Budget of the Arctic (SHEBA). An icebreaker was placed purposely into the older pack ice north of Alaska in September 1997. The ship served as the base for experimenters who deployed extensive instrumentation to measure the atmosphere, ocean, and ice during a one-year period. My experiment will be to derive similar measurements (floe size, open water, temporal change) using spaceborne SAR data obtained during the summer of 1998, and compare these results with an ocean and ice model of summer melt. Additional information is contained in the original.

Holt, Benjamin

1999-01-01

396

A Field Study of First Ice Formation in Maritime Cumulus Clouds  

NASA Astrophysics Data System (ADS)

Knowledge of when, where and by what mechanisms ice first forms in convective clouds is far from complete. Of particular interest are the conditions needed and processes required to form the first ice particles in maritime cumulus clouds. Past in situ measurements have suggested that ice nuclei concentrations fall well below those of the ice crystals measured in these clouds. Many mechanisms for the observed discrepancy have been proposed but none have been substantiated, as it is difficult to detect small, initial ice particles in low concentrations and the formation of ice can occur quickly, blurring the distinction between primary and secondary mechanisms. The Ice in Clouds Experiment - Tropical (ICE-T) field campaign, held in July 2011 in the central Caribbean, has attempted to answer these questions by taking in situ and remote-sensing measurements of maritime cumuli as they developed first ice. The goal of this study is to identify the appearance of first ice through the comparison of instrument responses onboard the NSF/NCAR C-130 research aircraft. First ice is defined here by the warmest temperature cloud pass during which ice particles are observed in a rising convective cloud mass that has not experienced colder temperatures and is not influenced by ice generated in other clouds. Key instruments for the detection of first ice include the FSSP-100, CDP, 2D-C, 3V-CPI (a combination of 2D-S and CPI) and SID-2H. Particle concentrations, images and specific instrument detected particle attributes, such as asymmetry, will be evaluated. The sensitivity of these instruments to discriminate water droplets from small ice particles (<~50 ?m) is a central focus. The aircraft was also equipped with up-and-downward looking Wyoming cloud radar (WCR) and cloud lidar (WCL, polarized). These instruments will be used to provide information about the environment in which first ice was detected and the overall structure of the convective cloud. Additionally, the ability of the WCR and WCL to detect initial ice formations is largely unknown. Through comparisons with in situ measurements and data from subsequent cloud passes a sensitivity for the amount of ice that can be detected will be estimated. Preliminary results will be presented for a selected case study to illustrate the formation of "first ice," along with an evaluation of the sensitivity of the in situ and remote-sensing instruments to ice formation, an overview of the evolution of ice within the case study and possible implications of these findings.

Johnson, A. V.; Lasher-Trapp, S.; Rogers, D. C.; Heymsfield, A.; Leon, D.; Wang, Z.; Sheffield, A.; Storer, R. L.

2011-12-01

397

Inflight characterization of aircraft icing  

NASA Astrophysics Data System (ADS)

This thesis advances the development of the Ice Management System (IMS), which has been previously proposed as an additional layer of safety against aircraft icing accidents, by presenting and validating a conceptual design for the icing characterization function of the IMS. This icing characterization function seeks to provide a near real-time estimate of the degradation of the aircraft flight dynamics due to icing. The icing characterization is extracted from various information sources comprising Hinfinity parameter identification of the flight dynamics, steady-state characterization of the aircraft trim, aerodynamic hinge moment sensing, and an estimate of the flight-dynamics excitation. Two aspects of the icing characterization are novel: (i) real-time Hinfinity parameter identification of the flight dynamics, and (ii) preprocessing and assimilation of the various measurements that individually provide partial information on the icing degradation into a single comprehensive icing characterization, the so-called sensor fusion function. These two aspects of the icing characterization are validated by applying them in computer simulation to a rich set of flight scenarios. Moreover, the Hinfinity parameter identification is applied successfully to flight-test data generated by the NASA Twin Otter icing research aircraft, and validated against an existing flight-dynamics identification technique. Finally, consideration of an independent icing degradation estimate from atmospheric and photographic measurements demonstrates that the H infinity parameter estimate provides an indication of icing degradation for a natural-icing flight test.

Melody, James William

398

Cubic ice and large humidity with respect to ice in cold cirrus clouds  

NASA Astrophysics Data System (ADS)

Recently several studies have reported about the possible formation of cubic ice in upper-tropospheric cirrus ice clouds and its role in the observed elevated relative humidity with respect to hexagonal ice, RHi, within the clouds. Since cubic ice is metastable with respect to stable hexagonal ice, its vapour pressure is higher. A key issue in determining the ratio of vapour pressures of cubic ice Pc and hexagonal ice Ph is the enthalpy of transformation from cubic to hexagonal ice Hcâ??h. By dividing the two integrated forms of the Clausius-Clapeyron equation for cubic ice and hexagonal ice, one obtains the relationship (1): ln Pc-- ln P*c-=--(Hcâ??h--) Ph P*h R 1T-- 1T* (1) from which the importance of Hcâ??h is evident. In many literature studies the approximation (2) is used: ln Pc-= Hc-â??h. Ph RT (2) Using this approximated form one can predict the ratio of vapour pressures by measuring Hcâ??h. Unfortunately, the measurement of Hcâ??h is difficult. First, the enthalpy difference is very small, and the transition takes place over a broad temperature range, e.g., between 230 K and 260 K in some of our calorimetry experiments. Second, cubic ice (by contrast to hexagonal ice) can not be produced as a pure crystal. It always contains hexagonal stacking faults, which are evidenced by the (111)-hexagonal Bragg peak in the powder diffractogram. If the number of hexagonal stacking faults in cubic ice is high, then one could even consider this material as hexagonal ice with cubic stacking faults. Using the largest literature value of the change of enthalpy of transformation from cubic to hexagonal ice, Hcâ??h ? 160 J/mol, Murphy and Koop (2005) calculated that Pc would be ~10% higher than that of hexagonal ice Phat 180 K - 190 K, which agrees with the measurements obtained later by Shilling et al. (2006). Based on this result Shilling et al. concluded that "the formation of cubic ice at T < 202 K may significantly contribute to the persistent in-cloud water supersaturations" in the upper-tropospheric cold cirrus clouds. Using instead the value of Hcâ??h ? 50 J/mol (Handa et al., 1986; Mayer and Hallbrucker, 1987) the calculation gives that Pc is only ~3% larger than that of Ph. Recently it has been reported that emulsified water droplets freeze to cubic ice when being cooled at a rate of 10 K/min (Murray and Bertram, 2006,). We prepared emulsified droplets using the same emulsification technique and studied them with a differential scanning calorimeter (DSC) between 278 and 180 K using a scanning rate of 10 K/min. During the warming of the samples we observed a very broad, tiny exothermal peak approximately between 230 and 260 K. Kohl et al. (2000) observed exothermal peak at ~230 K during the warming at 30 K/min of several samples of hyperquenched glassy water (HGW) prepared at temperature between 130 and 190 K. They attributed this peak to the cubic-to-hexagonal ice transition and estimated Hcâ??h to be between ~33 and 75 J/mol. Johari (2005) used the value of Hcâ??h ? 37 J/mol. Assuming that in our case the broad peak between 230 and 260 K is also due to the cubic-to-hexagonal ice transition we obtained approximately between 10 and 25 J/mol for Hcâ??h. This low enthalpy of transformation suggests that cubic ice in the atmosphere contains many hexagonal stacking faults. Using these values of Hcâ??h for cubic ice as produced at atmospheric cooling rates, the above mentioned formula gives that Pc is larger than that of Ph only by ~1%. We, therefore, suggest that the difference in the water vapor pressures between ice Ic and ice Ih is small and does not play a significant role in the elevation of RHi in cold cirrus clouds. Murphy, D. M., and T. Koop (2005), Q. J. R. Meteorol. Soc. 131, 1539-1565. Shilling, J. E. et al. (2006). Geophys. Res. Lett. 33, L17801, doi:1029/2006GL026671. Handa, P. Y., D. D. Klug, and E. Whalley (1986). J. Chem. Phys. 84, 7009-7010. Mayer, E., and A. Hallbr

Bogdan, A.; Loerting, T.

2009-04-01

399

Quantification of Ice Accretions for Icing Scaling Evaluations  

NASA Technical Reports Server (NTRS)

The comparison of ice accretion characteristics is an integral part of aircraft icing research. It is often necessary to compare an ice accretion obtained from a flight test or numerical simulation to one produced in an icing wind tunnel or for validation of an icing scaling method. Traditionally, this has been accomplished by overlaying two-dimensional tracings of ice accretion shapes. This paper addresses the basic question of how to compare ice accretions using more quantitative methods. For simplicity, geometric characteristics of the ice accretions are used for the comparison. One method evaluated is a direct comparison of the percent differences of the geometric measurements. The second method inputs these measurements into a fuzzy inference system to obtain a single measure of the goodness of the comparison. The procedures are demonstrated by comparing ice shapes obtained in the Icing Research Tunnel at NASA Glenn Research Center during recent icing scaling tests. The results demonstrate that this type of analysis is useful in quantifying the similarity of ice accretion shapes and that the procedures should be further developed by expanding the analysis to additional icing data sets.

Ruff, Gary A.; Anderson, David N.

2003-01-01

400

Optimising ice flow law parameters using borehole deformation measurements and numerical modelling  

NASA Astrophysics Data System (ADS)

Internal ice strain rates have been measured along two boreholes drilled through Glacier de Tsanfleuron, Switzerland. Differences between these measurements and the output from a 3D numerical model of glacier motion have been minimized by a scheme that optimizes three rheological parameters in the constitutive equation for ice creep: the stress exponent n, the rate factor A, and a Lower Zone (basal ice) enhancement factor E LZ . Results suggest that a linear rheology dominated by diffusion creep (n = 1) is more appropriate for modelling ice flow in this relatively thin (generally <80 m thick) glacier than the conventional n = 3, and that E LZ is ~2. For n = 1, the predicted ice crystal size and value of E LZ are both consistent with measurements made on ice cores recovered from the glacier, providing independent support for the optimization technique and the linear creep model.

Chandler, David; Hubbard, Bryn; Hubbard, Alun; Murray, Tavi; Rippin, David

2008-06-01