Ice Density Research Articles

Observation and Analysis of Meteorological Conditions for Icing of Wires in Guizhou, China

Icing of wires is a product of rain, fog, and freezing rain, and is a common meteorological disaster in winter in Guizhou Province of China. It is extremely harmful to facilities such as power transmission and communication lines, and has caused huge economic loss up to 48.9566 billion dollars a year. Based on the meteorological records of Guizhou from 1967, we analyze the meteorological characteristics during the icing of wires, and obtain the temperature, wind speed and direction conditions of the ice accident. The icing of wires is carried out by supercooling raindrops, freezing of the clouds, freezing and spreading on the wires. Different types of supercooled raindrops and cloud freezing and freezing processes will form different types of ice accretion; wind direction and wind speed will affect the growth of ice accretion by changing the speed of sub-cooling raindrops and cloud falling. The weight of rain-type ice accretion is between 24 and 152 g, and the weight of smog-type ice is between 40 - 76 g. The average ice density of these two places can be calculated to be 0.2 - 0.5 g/cm3. The longer the icing of wires, the higher the ice disaster rate.

Retrievals of Riming and Snow Density From Vertically Pointing Doppler Radars

AbstractRetrievals of ice and snow are made from Ka‐ and W‐band zenith‐pointing Doppler radars at Hyytiälä, Finland, during the snow experiment component of the Biogenic Aerosols: Effects on Clouds and Climate (2014) field campaign. In a novel optimal estimation retrieval, mean Doppler velocity is exploited to retrieve a density factor parameter, which modulates the mass, shape, terminal velocity, and backscatter cross sections of ice particles. In a case study including aggregate snow and graupel we find that snow rate and ensemble mean ice density can be retrieved to within 50% of in situ measurements at the surface using dual‐frequency Doppler radar retrievals. While Doppler measurements are essential to the retrieval of particle density, the dual‐frequency ratio provides a strong constraint on particle size. The retrieved density factor is strongly correlated with liquid water path, indicating that riming is the primary process by which the density factor is modulated. Using liquid water path as a proxy for riming, profiles classified as unrimed snow, rimed snow, and graupel exhibit distinct features characteristic of aggregation and riming processes, suggesting the potential to make estimates of process rates from these retrievals. We discuss the potential application of the technique to future satellite missions.

The Nucleus of comet 67P/Churyumov–Gerasimenko – Part I: The global view – nucleus mass, mass-loss, porosity, and implications

The radio science experiment RSI on-board Rosetta determined the mass of the nucleus of comet 67P/Churyumov–Gerasimenko at the start of the prime mission from 2014 August to November (GM = 666.2 ± 0.2 m3 s−2 or 9982 ± 3 × 1012 kg) and shortly before the end of the mission from 2016 July to September (GM = 665.5 ± 0.1 m3 s−2 or 9971.5 ± 1.5 × 1012 kg). The mass-loss is ΔM = 10.5 ± 3.4·109 kg, about 0.1 per cent of the nucleus mass. Almost 50 per cent of the mass-loss occurred during the 32 d before and 62 d after perihelion. The nucleus mass combined with the new very precise nucleus volume of 18.56 ± 0.02 km3 yields a bulk density of 537.8 ± 0.6 kg m−3. This low bulk density suggests that the nucleus is highly porous. The porosity is constrained by the observed bulk density, the density of ices, mostly water ice, and the density of compacted nucleus dust material. For a range of compacted dust material density from 2000 to 3500 kg m−3, the porosity varies between 65–79 per cent when the dust-to-ice mass ratio Fnucleus for the nucleus body lies in the range 3 ≤ Fnucleus ≤ 7. The nucleus is thus a highly porous very dusty body with very little ice. The total mass-loss ΔM puts hard constraints on the models of interpretation of the observations from other instruments on Rosetta. The loss from gas, based on ROSINA and MIRO observations, suggests that Fcoma, the dust-to-gas mass ratio of cometary matter in the coma beyond the Hill sphere of the nucleus is of the order of Fcoma ≤ 0.5 and therefore at least six times, and perhaps as much as 14 times, smaller than Fnucleus. It seems that the lost gas mass was overestimated by the instruments. The lost gas mass shall be 5.25 × 109 kg for Fcoma = 1. For any other gas mass values > 5.25 × 109 kg Fcoma is < 1. Most of the lifted dust mass will not leave the cometary Hill sphere but falls back to the nucleus. For 3 ≤ Fnucleus ≤ 7 and Fcoma = 0.5, the fallback mass is between 1.8·ΔM and 4.3·ΔM.

Interfacial Interactions of Sucrose during Cryopreservation Detected by Raman Spectroscopy.

There is considerable interest in the use of sugars to preserve cells. In this study, low temperature Raman spectroscopy was used to characterize the behaviors of sucrose during freezing. The hydrogen bond network between sucrose and water was investigated at -10 °C and -50 °C, and the Raman spectra showed strengthened sucrose-water and sucrose-sucrose hydrogen bonds in more concentrated sucrose solution at -50 °C. The concentration of sucrose at the ice interface increased as the ice density decreased, and it plateaued across a narrow channel of nonfrozen sucrose solution before it decreased toward the next ice interface. The biophysical environment at interfaces between the cell and nonfrozen sucrose solution and between the cell and extracellular ice was also studied. A thin layer of nonfrozen sucrose solution was observed at the interface between the cell and extracellular ice. The extracellular concentration of sucrose at this interface was generally lower than that of bulk nonfrozen sucrose solution. The variation of sucrose concentration outside different regions of the cell membrane suggests that the chemical environment around the cell during freezing may be more heterogeneous than previously thought. Raman spectra and images also showed colocalization of nonfrozen sucrose solution and the cell, which implied that direct interaction between sucrose and cell membrane might be responsible for protective properties of sucrose. Sucrose was predominantly distributed outside the cell, and the observation of strong partitioning of sucrose across the cell membrane is consistent with substantial cell dehydration detected by the Raman spectra. This work enhances our understanding of the behaviors of sucrose solution and its interactions with cells at low temperature and can improve cryopreservation protocols of cells frozen in a sucrose-based media.

Wind turbine blade ice accretion: A correlation with nacelle ice accretion

This paper focuses on the meteorological icing phase of typical icing events to determine the factors that affect the ice accretion rate on a wind turbine blade. The linear mass density of ice on the nacelle of a 2 MW horizontal-axis wind turbine is estimated with a camera and is compared to the linear mass density of ice on a blade evaluated by a commercial blade ice detector (e.g. a fos4X ice detector). An automated image analysis software measures the dimension of the ice on a cylindrical tube located on the nacelle and calculates the linear mass density of the ice. The fos4X ice detector estimates the total ice load on the blade by measuring variations in the vibration frequencies of the blade. The total load is then divided by the blade length to obtain the linear density. On-site results were compared to simulations for validation. The ISO 12494 method for theoretical ice accretion on a cylindrical tube was adapted to simulate ice accretion on a rotating wind turbine blade. The main results show that wind speed and turbine rotor RPM directly influence the blade ice accretion rate. A correlation is made between blade and nacelle icing, with on-site results matching the simulation. In summary, for an operating turbine, as wind speed decreases, the rate of ice accretion on the blade increases relative to the ice accretion rate on the nacelle.

X-ray streaked refraction enhanced radiography for inferring inflight density gradients in ICF capsule implosions.

In the quest for reaching ignition of deuterium-tritium (DT) fuel capsule implosions, experiments on the National Ignition Facility (NIF) have shown lower final fuel areal densities than simulated. Possible explanations for reduced compression are higher preheat that can increase the ablator-DT ice density jump and induce mix at that interface or reverberating shocks. We are hence developing x-ray Refraction Enhanced Radiography (RER) to infer the inflight density profiles in layered fuel capsule implosions. We use a 5 μm slit backlit by a Ni 7.8 keV He-α NIF laser driven x-ray source positioned at 20 mm from the capsule to cast refracted images of the inflight capsule onto a streak camera in a high magnification (M ∼ 60×) setup. Our first experiments have validated our setup that recorded a streaked x-ray fringe pattern from an undriven high density carbon (HDC) capsule consistent with ray tracing calculations at the required ∼6 μm and 25 ps resolution. Streaked RER was then applied to inflight layered HDC capsule implosions using a hydrogen-tritium fuel mix rather than DT to reduce neutron yields and associated backgrounds. The first RER of an imploding capsule revealed strong features associated with the ablation front and ice-ablator interface that are not visible in standard absorption radiographs.

Densities, infrared band strengths, and optical constants of solid methanol

Contact. The increasing capabilities of space missions like the James Webb Space Telescope or ground-based observatories like the European Extremely Large Telescope demand high quality laboratory data of species in astrophysical conditions for the interpretation of their findings. Aims. We provide new physical and spectroscopic data of solid methanol that will help to identify this species in astronomical environments. Methods. Ices were grown by vapour deposition in high vacuum chambers. Densities were measured via a cryogenic quartz crystal microbalance and laser interferometry. Absorbance infrared spectra of methanol ices of different thickness were recorded to obtain optical constants using an iterative minimization procedure. Infrared band strengths were determined from infrared spectra and ice densities. Results. Solid methanol densities measured at eight temperatures vary between 0.64 g cm−3 at 20 K and 0.84 g cm−3 at 130 K. The visible refractive index at 633 nm grows from 1.26 to 1.35 in that temperature range. New infrared optical constants and band strengths are given from 650 to 5000 cm−1 (15.4–2.0 μm) at the same eight temperatures. The study was made on ices directly grown at the indicated temperatures, and amorphous and crystalline phases have been recognized. Our optical constants differ from those previously reported in the literature for an ice grown at 10 K and subsequently warmed. The disagreement is due to different ice morphologies. The new infrared band strengths agree with previous literature data when the correct densities are considered.

Impacts of Ice Particle Shape and Density Evolution on the Distribution of Orographic Precipitation

Abstract An IMPROVE-2 orographic precipitation case is simulated using the Ice-Spheroids Habit Model with Aspect-Ratio Evolution (ISHMAEL) microphysics. In ISHMAEL, the evolution of ice particle properties such as mass, shape, size, density, and fall speed are predicted. These ice particle properties along with the ice size distributions from ISHMAEL and model-derived spatial distribution of accumulated precipitation are compared to observations. ISHMAEL predicts planar and columnar particles at spatial locations that agree with observations. Sensitivity simulations are used to explore the impact of predicting ice particle shape evolution on orographic cloud properties and precipitation compared to the traditional approach of representing snow and graupel using separate categories with conversion from snow to graupel during riming. High biases in both IWCs aloft and surface precipitation accumulation occur in the Umpqua River valley using separate snow and graupel categories because snow that does not convert to graupel is advected over the Coast Range and precipitates out in the valley. Improvements in IWCs aloft and surface precipitation using ISHMAEL occur from both predicting various vapor-grown habits and predicting the impact of partial riming on ice particle properties. Compared to traditional microphysics schemes, ISHMAEL also produces less spatial variability in accumulated precipitation.

Cassini-VIMS observations of Saturn’s main rings: II. A spectrophotometric study by means of Monte Carlo ray-tracing and Hapke’s theory

This work is the second in a series of manuscripts devoted to the investigation of the spectrophotometric properties of Saturn’s rings from Cassini-VIMS (Visible and Infrared Mapping Spectrometer) observations. The dataset used for this analysis is represented by ten radial spectrograms of the rings which have been derived in Filacchione et al. (2014) by radial mosaics produced by VIMS. Spectrograms report the measured radiance factor I/F of the main rings of Saturn as a function of both radial distance (from 73500 to 141375 km) and wavelength (0.35–5.1 µm) for different observation geometries (phase angle ranging in the 2°–132° interval). We take advantage of a Monte Carlo ray-tracing routine (Ciarniello et al., 2014) to characterize the photometric behavior of the rings at each wavelength and derive the spectral Bond albedo of ring particles. This quantity is used to infer the composition of the regolith covering ring particles by applying Hapke’s theory. Four different regions, characterized by different optical depths, and respectively located in the C ring, inner B ring, mid B ring and A ring, have been investigated. Results from photometric modeling indicate that, in the VIS-NIR spectral range, B ring particles are intrinsically brighter than A and C ring particles, with the latter having the lowest albedo, while the single particle phase function of the ring’s particles is compatible with an Europa-like or Callisto-like formulation, depending on the investigated region. Spectral modeling of the inferred Bond albedo indicates that ring spectrum can be reproduced by water ice grains with inclusion of organic materials (tholin) as a UV absorber intimately mixed with variable amounts of other compounds in pure form (carbon, silicates) or embedded in water ice grains (nanophase hydrated iron oxides, carbon, silicates, crystalline hematite, metallic iron, troilite). The abundance of tholin decreases with radial distance from C ring (0.2–0.6%) to A ring (0.06%) for the selected regions. Its distribution is compatible with an intrinsic origin and is possibly related to the different plasma environment of the different ring regions. The identification of the other absorber(s) and its absolute volumetric abundance is uncertain, depending on the adopted grain size and mixing modality (intraparticle or intimate). However, assuming a common composition of the other absorber in the ring plane, we find that its abundance anti-correlates with the optical depth of the investigated regions, being maximum in the thinnest C ring and minimum in the thickest mid B ring. In the case of the C ring, an additional population of low-albedo grains is required to match the positive spectral slope of the continuum in the 0.55–2.2 µm interval, represented by an intraparticle mixture of water ice and a spectrum similar to troilite or metallic iron. The distribution of the darkening compounds is interpreted as the result of a contamination by exogenous material, which is more effective in the less dense regions of the rings because of their lower surface mass density of pure water ice.

Activity of Supercooled Water on the Ice Curve and Other Thermodynamic Properties of Liquid Water up to the Boiling Point at Standard Pressure.

A simple model for thermodynamic properties of water from subzero temperatures up to 373 K was derived at ambient pressure. The heat capacity of supercooled water was assessed as lambda transition. The obtained properties for supercooled water such as heat capacity, vapor pressure, density and thermal expansion are in excellent agreement with literature data. Activity of water on ice curve, independent of used electrolyte and Debye−Hückel constant applied in modeling, is also calculated. Thus, the ice curve activity of supercooled water can be used as a universal basis for thermodynamic modeling of aqueous solutions, precipitating hydrated and anhydrous solids. A simple model for heat capacity, density and thermal expansion of ice are also derived from 170 K up to melting point.

QTL Analysis for Grain Iron and Zinc Concentrations in Two O. nivara Derived Backcross Populations

Identification of quantitative trait loci (QTLs) for grain mineral elements can assist in faster and more precise development of micronutrient dense rice varieties through marker-assisted breeding. In the present study, QTLs were mapped for Fe and Zn concentrations in two BC2F3 mapping populations derived from the crosses of O. sativa cv Swarna with two different accessions of O. nivara. In all, 10 and 8 QTLs were identified for grain Fe and Zn concentrations in population 1, and 7 and 5 QTLs were identified in population 2, respectively. Eighty percent of the QTLs detected in both populations were derived from O. nivara. Five QTLs for Fe and three QTLs for Zn explained more than 15% phenotypic variance either in interval or composite interval mapping. The locations of O. nivara derived QTLs such as qFe2.1, qFe3.1, qFe8.2 and qZn12.1 were consistently identified in both the populations. Epistatic interaction was observed only between RM106 and RM6 on chromosome 2 and between RM22 and RM7 on chromosome 3 for Fe concentration in population 1. Sixteen candidate genes for metal homeostasis were found to co-locate with 10 QTLs for Fe and Zn concentrations in both the populations. Most of the Fe and Zn QTLs were found to co-locate with QTLs for grain yield and grain quality traits. Some of the major effect QTLs identified can be used to improve rice grain Fe and Zn concentrations.

Proton dynamics and the phase diagram of dense water ice.

All the different phases of water ice between 2 GPa and several megabars are based on a single body-centered cubic sub-lattice of oxygen atoms. They differ only by the behavior of the hydrogen atoms. In this study, we investigate the dynamics of the H atoms at high pressures and temperatures in water ice from first-principles molecular dynamics simulations. We provide a detailed analysis of the O-H⋯O bonding dynamics over the entire stability domain of the body-centered cubic (bcc) water ices and compute transport properties and vibrational density-of-states. We report the first ab initio evidence for a plastic phase of water and we propose a coherent phase diagram for bcc water ices compatible with the two groups of melting curves and with the multiple anomalies reported in ice VII around 15 GPa.

Shear strength of frozen sand with dissociating pore methane hydrate: An experimental study

This paper presents experimental results for peak shear strength of frozen sand containing methane hydrates within the pore space under dissociation at atmospheric pressure. During the experiments, the samples retained metastable pore methane hydrate due to the self-preservation effect. The tested samples were subjected to short-term uniaxial compression at temperatures from −1.8 to −6.5 °C. The gas hydrate component turned out to considerably affect the strength of the host frozen soil: the shear strength of frozen sediments decreased as saturation with metastable gas hydrate became lower. There is some critical hydrate saturation value (~30%) below, which no further strength reduction occurs. Cyclic thawing-freezing increases considerably the strength of frozen samples that contain relict hydrates, primarily because denser ice, with fewer structural defects, forms by freeze back instead of molten porous hydrate-bearing ice. The obtained results indicate that geomechanical properties of frozen sediments correlate with the contents of relict gas hydrate and can be used for detection of hydrate-bearing permafrost layers.

Experimental investigation of generic ice block trajectories under freestream conditions

An experimental database of trajectories featuring idealized, simplified artificial ice blocks under freestream conditions has been created. It includes a variation of key parameters such as the ice block geometry, density, freestream velocity and release angle of attack. The ice block’s position and attitude were optically tracked using a system of two high-speed cameras and a dedicated post-processing routine. The work performed in the scope of the EU co-funded research project STORM aims at the validation and further development of current simulation tools for ice release and ice block trajectories in terms of their ability to cope with the high complexity and randomness of this phenomenon. These tools of different level of fidelity are currently used during the aircraft certification process to estimate the threat of large ice pieces released from the aircraft’s surface impacting into downstream components. The major experimental findings are discussed in this article alongside first promising results from numerical trajectory simulations.

Wind Stress Mediated Variability of the Filchner Trough Overflow, Weddell Sea

AbstractThe Filchner Trough (FT) is a key site for exchange of water masses between the Weddell Sea continental shelf and the deep ocean. Cold and dense Ice Shelf Water (ISW), a precursor for Antarctic Bottom Water, flows north along the FT and overflows the Filchner Sill. Although access of warm water to the Weddell Sea continental shelf is limited due to the presence of the Antarctic Slope Front, southward transport of warm water is facilitated through the FT. We use moored current meters from the Filchner Sill region to show that the monthly scale variability of the ISW overflow is connected to the variability of the alongslope wind stress upstream. Periods with significant correlation between the wind and ISW overflow are characterized by (I) wind directed along the continental slope, (II) high ISW overflow speed, and (III) high variability in the 16–64 day period band for wind and current. We propose that a recirculation of the slope current, associated with the Antarctic Slope Front, may occur in the FT during periods of strong wind forcing, and that such recirculation could explain the correlation between the wind stress and the ISW overflow. We further show that an increased wind stress along the continental slope leads to increased current speed within the slope current and the Antarctic Coastal Current, with possible implications for the on‐shore heat transport.

Experimental study of the polyamorphism of water. I. The isobaric transitions from amorphous ices to LDA at 4 MPa.

The existence of more than one solid amorphous state of water is an extraordinary feature. Since polyamorphism might be connected to the liquid-liquid critical point hypothesis, it is particularly important to study the relations amongst the different amorphous ices. Here we study the polyamorphic transformations of several high pressure amorphous ices to low-density amorphous ice (LDA) at 4 MPa by isobaric heating utilising in situ volumetry and ex situ X-ray diffraction. We find that very-high density amorphous ice (VHDA) and unannealed high density amorphous ice (HDA) show significant relaxation before transforming to LDA, whereby VHDA is seen to relax toward HDA. By contrast, expanded HDA shows almost no relaxation prior to the transformation. The transition to LDA itself obeys criteria for a first-order-like transition in all cases. In the case of VHDA, even macroscopic phase separation is observed. These findings suggest that HDA and LDA are two clearly distinct polyamorphs. We further present evidence that HDA reaches the metastable equilibrium at 140 K and 0.1 GPa but only comes close to that at 140 K and 0.2 GPa. The most important is the path independence of the amorphous phase reached at 140 K and 0.1 GPa.

Meltwater storage in low-density near-surface bare ice in the Greenland ice sheet ablation zone

Abstract. We document the density and hydrologic properties of bare, ablating ice in a mid-elevation (1215 m a.s.l.) supraglacial internally drained catchment in the Kangerlussuaq sector of the western Greenland ice sheet. We find low-density (0.43–0.91 g cm−3, μ = 0.69 g cm−3) ice to at least 1.1 m depth below the ice sheet surface. This near-surface, low-density ice consists of alternating layers of water-saturated, porous ice and clear solid ice lenses, overlain by a thin (&lt; 0.5 m), even lower density (0.33–0.56 g cm−3, μ = 0.45 g cm−3) unsaturated weathering crust. Ice density data from 10 shallow (0.9–1.1 m) ice cores along an 800 m transect suggest an average 14–18 cm of specific meltwater storage within this low-density ice. Water saturation of this ice is confirmed through measurable water levels (1–29 cm above hole bottoms, μ = 10 cm) in 84 % of cryoconite holes and rapid refilling of 83 % of 1 m drilled holes sampled along the transect. These findings are consistent with descriptions of shallow, depth-limited aquifers on the weathered surface of glaciers worldwide and confirm the potential for substantial transient meltwater storage within porous low-density ice on the Greenland ice sheet ablation zone surface. A conservative estimate for the ∼ 63 km2 supraglacial catchment yields 0.009–0.012 km3 of liquid meltwater storage in near-surface, porous ice. Further work is required to determine if these findings are representative of broader areas of the Greenland ice sheet ablation zone, and to assess the implications for sub-seasonal mass balance processes, surface lowering observations from airborne and satellite altimetry, and supraglacial runoff processes.

The Presence of Dust and Ice Scattering in X-Ray Emissions from Comets

Abstract X-ray emissions from cometary atmospheres were modeled from first principles using the charge-exchange interaction with solar wind ions as well as coherent scattering of solar X-rays from dust and ice grains. Scattering cross-sections were interpolated over the 1 nm–1 cm grain radius range using approximations based on the optically thin or thick nature of grains with different sizes. The theoretical emission model was compared to Chandra observations of Comets ISON and Ikeya–Zhang due to their high signal-to-noise ratios and clearly defined spectral features. Comparing the observed intensities to the model showed that the charge-exchange mechanism accurately reproduced the emission spectra below 1 keV, while dust and ice scattering was negligible. Examining the 1–2 keV range found dust and ice scattering emissions to agree well with observations, while charge-exchange contributions were insignificant. Spectral features between the scattering model and observations also trended similarly over the 1–2 keV range. The dust and ice density within the cometary atmosphere n was varied with respect to grain size a as the function , with Ikeya–Zhang requiring and ISON requiring to best fit the observed spectral intensities. These grain size dependencies agreed with independent observations and simulations of such systems. The overall findings demonstrate evidence of significant scattering emissions present above 1 keV in the analyzed cometary emission spectra and that the dust/ice density dependence on grain radius a may vary significantly between comets.

Study on Bohai sea ice based on MODIS data

Based on MODIS L1B data, we identify information of sea ice area, peripheral line and density, and also use Landsat data with higher resolution to verify the results obtained from MODIS data. Using pseudo color processing technology is more intuitive and more clear to show the various information of the Bohai sea. The whole process of sea ice information extraction is described in detail from MODIS data downloads to image processing and analysis. The selected data basically cover the entire process from the initial ice age, the peak ice age to the final ice age. The ideal results are obtained, and it also shows that the MODIS satellite data is feasible to monitor sea ice, which provides a reference for the establishment of monitoring sea ice model.

Energy dense rice biscuit formulation to improve malnutrition status of urban street children in Bangladesh.

Rice is the main source of dietary energy for approximately 166 Million of Bangladeshi population. Rice based processed food items have potential scope in malnutrition mitigation approach. In this study we have formulated energy dense nutraceutically enriched rice-based bakery food formulation specially biscuits having energy density ranges from ED 4.5-5.5 per 100 g serving. Rice based balanced and nutritious food intake might reduce rice consumption from current rate of 367 g/capita/day to 300 g/capita/day or lesser for Bangladeshi population. Since floating urban street children classified as the most vulnerable group in Bangladeshi population so, nutraceutically enriched rice-based bakery food products might possibly play a role in shifting malnutrition status in this regard. In addition, in quest to attain required daily dietary allowance in scale of average 2000 kcal, rice-based energy dense food might assist as supplementary diet and it will be helpful to attain SDG goal for hunger free and sustain food security in Bangladesh in a way to properly and effectively utilizing the rice grain.