Water-ice Phase Transition Research Articles

Mapping “At Risk” Snow in the Pacific Northwest

Abstract One of the most visible and widely felt impacts of climate warming is the change (mostly loss) of low-elevation snow cover in the midlatitudes. Snow cover that accumulates at temperatures close to the ice-water phase transition is at greater risk to climate warming than cold climate snowpacks because it affects both precipitation phase and ablation rates. This study maps areas in the Pacific Northwest region of the United States that are potentially at risk of converting from a snow-dominated to a rain-dominated winter precipitation regime, under a climate-warming scenario. A data-driven, climatological approach of snow cover classification is used to reveal these “at risk” snow zones and also to examine the relative frequency of warm winters for the region. For a rain versus snow temperature threshold of 0°C the at-risk snow class covers an area of about 9200 km2 in the Pacific Northwest region and represents approximately 6.5 km3 of water. Many areas of the Pacific Northwest would see an increase in the number of warm winters, but the impacts would likely be concentrated in the Cascade and Olympic Ranges. A number of lower-elevation ski areas could experience negative impacts because of the shift from winter snows to winter rains. The results of this study point to the potential for using existing datasets to better understand the potential impacts of climate warming.

Electrical properties of porous oxides with adsorbed water

AbstractThe impedance of porous alumina (por‐Al2O3) and titanium oxide (por‐TiO2) with adsorbed water has been investigated in a wide frequency range and at temperatures near the water–ice phase transition. The equivalent circuit of the investigated structures has been determined. It has been shown that water adsorption in the pores of a solid‐state matrix has a great influence on its electrical properties. The characteristics of the electrical properties of experimental structures related to the water–ice phase transition have been revealed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electromagnetic Properties of Ice near the Water–Ice Phase Transition Temperature

Freshwater ice in a cavity was studied under heating to 0°C followed by cooling at a frequency of 6.3 GHz. Splitting of a resonant transmission line at 60–70 MHz was detected. This effect may be associated with the existence of two vibrational modes in ice, with the coupling between them increasing near 0°C. In such a medium, two waves with identical polarizations and similar wavenumbers can exist. This assumption was confirmed experimentally by measuring the 13-GHz radiation transmission through a natural freshwater ice cover. These measurements detected signal oscillations caused by the interference of two waves, with alternation of maxima and minima with a period of 4.6 m, which corresponds to a beat frequency of ∼37 MHz.

Calculation of temperature fields in the ground with water-ice phase transitions in the temperature spectrum

An algorithm of integration of the nonlinear heat-conduction equation for a semi-bounded medium with a uniform initial distribution of temperature and its constant value on the surface in the case of nonlinear dependence of thermophysical characteristics on temperature is described. This algorithm can be used to test numerical grid methods of calculation of temperature fields in freezing and thawing of grounds. The procedure of correction of a step-by-step mechanism of temperature variation in numerical calculation in the zone of intense phase transitions by a grid method was suggested and tested.

Low-temperature DSC study of the hydration of ss-DNA and ds-DNA and the role of hydrogen-bonded network to the duplex transition thermodynamics

The study of thermodynamic parameters of ice–water phase transition in aqueous solutions of ss-DNA, at different concentration of polynucleotide single chains is reported and the critical concentration for which the enthalpy of transition is zero has been determined. The thermodynamic parameters of ice–water phase transitions, obtained for native ds-DNA and for ss-DNA in the whole concentration region (0.2–2.0 g H 2O/g DNA) and the hydration values (bound water quantity) for native ( helix), denatured ( single strand coils) and unfolded ss-DNA are compared. The critical values of the hydration at which all the water in the DNA–H 2O system exists in the bound ( unfrozen) state are established, for these conformations, with great precision: N ds-DNA Σ=(0.55±0.01) g H 2O/g DNA, N ss-DNA Σ=(0.40±0.01) g H 2O/g DNA. According to this calorimetric data the transformation “ double stranded helix”→“single stranded chains” is accompanied by dehydration of ds-DNA: Δ N= N ds Σ− N ss Σ=(0.15±0.01) g H 2O/g DNA. We suggest that the formation of B-DNA duplex from mixing of their complementary single strands is mostly accompanied by the uptake of structural water molecules and so, the overall hydration of a duplex is mainly determined by its conformation and stability.

Features of the charge transfer in nanoporous silicon nd silicon oxide with adsorbed water

The experimental plots of electric conductivity versus temperature for a porous silicon and a silicon oxide with adsorbed water exhibit features at temperatures significantly below 0°C, which are related to an ice-water phase transition in nanopores of the solid matrix.

Chemical and physical aging of comets

AbstractAging effects for comet nuclei encompass both chemical and physical changes to the nucleus which may be manifested as a change in the level of and type of activity that the nucleus experiences. Recent observations have shown the importance of the amorphous to crystalline water ice phase transition in comet nuclei for controlling activity at large distances, and for altering the porosity and volatile distribution in the interior of comets. Evidence for secular changes in activity levels or differences between dynamical classes of comets which have spent different amounts of time in the inner solar system must be decoupled from expected primordial differences between comets. Long-term observational programs by several groups have demonstrated that the effects of aging are detectable. This paper will discuss the expected primordial comet differences, the expected physical and chemical effects of aging, the techniques for observing differences in activity levels, and will present summaries of results of several observing programs.

Complementary studies on the unexpected activity of comet Schwassmann-Wachmann 1

The orbit of comet P/Schwassmann-Wachmann 1 (P/SW 1) is confined to a range of heliocentric distances between 5.7 and 6.4 AU. Despite the large distance from the sun, this comet presents an unexpected and irregular activity. Its brightness can change up to six orders of magnitude during “outbursts”. Up to now, no generally accepted theory exists which explains this behaviour. In a previous paper (Cabot et al., 1996), it was shown that collisions of this comet with interplanetary objects were unlikely events and thus, were unable to account for the frequent outbursts. A data analysis of total magnitudes was performed and did not show any periodicity in the signal. Nevertheless an increase of the average level of activity was found after the recent orbit change, which was caused by a secular perturbation of Jupiter. The present work tries to shed light on these unexpected phenomena. The light curve analysis of P/SW 1 is completed with data recorded after 1986. This study tends to confirm earlier results. Although there are much more data during recent years, no characteristic frequency in the signal is detected. The peak of activity after perihelion is confirmed. The delay between the two events seems to increase through the last three revolutions. In order to explain this tendency, the propagation time of a heat wave in a cometary nucleus is estimated. The result is in good agreement with the observed lag. The erratic activity of P/SW 1 can be explained by the amorphous-crystalline water ice phase transition, which is triggered by the propagation of a heat wave into the nucleus.

Some processes defining the rheological behavior of frozen soils under load

In developing long-term-strength and deformability criteria for plastically frozen soils, it is expedient to account for the effect of basic physical processes that take place in them on the local level. The proposed mathematical model of a frozen soil makes it possible to predict its deformations under load, which are associated with the local ice-water phase transition in the vicinity of a mineral particle and with the release of accumulated moisture onto the free surface (it is proven that primary consolidation is also possible in frozen soils).

A numerical and experimental study of the artificial freezing of sand

A study is presented of the transfer of heat within a saturated sand with reference to the analysis of artificial freezing of the ground. First, the main characteristics of the adopted finite element approach and of the technique that introduces the latent-heat effects during the water–ice phase transition are illustrated. Subsequently, the results of some laboratory freezing tests are presented on the basis of which the computer program and the procedure for working out the thermal constants of the soil were calibrated. Finally, a parametric study is discussed that concerns the effects of pipe diameter, distance between pipes, and coolant temperature on the progress of the 0 °C isotherm. Key words : artificial freezing, finite elements, heat transfer, laboratory test, Stefan problem.

Thermocrystallization flow of nonfreezing water films on the surface of capillaries

The rates of mass transfer under the influence of a temperature gradient between the menisci of ice in a thin quartz capillary are measured. The mass transfer rate is determined by the diffusion of vapor and by the flow of a nonfrozen polymolecular adsorption film over the capillary surface. It is shown that the flow of the film is attributable neither to the thermoosmotic nor to the thermocapillary flow. The flow rate of a nonfrozen film is well described by a thermocrystallization transfer equation derived earlier, the thermocrystallization transfer being controlled by the water-ice phase transition heat.

Submillimeter-wave scattering indicatrices for oversized water drops and ice particles in a cloud

Angular distribution functions for the intensity scattered by oversized water drops and ice particles in the raining clouds are considered in the paper for five wavelength values in the submillimeter (SubMM) wave band. It is shown that the obtained scattering indicatrices may be used to explain the effect of abnormal SubMM backscatter originating in the water-ice phase transition of oversized drops, as well as the effect of small-angle scattering on abnormal backscatter emission.

Extinction, scattering, and absorption of anomalous radar-reflected emission in a cloud and atmosphere

For the anomalous radar reflection from the oversized water drops originating in water-ice phase transition observable in the submillimeter band transparency “window” of ice [1] we consider the process of extinction, scattering, and absorption in a cloud and atmosphere. Our calculations, which are based on experimental results, show that in the situation when the convective cloud is illuminated from nadir by a narrow-beam submillimeter radar (carried on board an airplane or a satellite), the total extinction and absorption in the cloud and atmosphere is nearby 20dB in the long-wave transparency “window” of atmosphere. In the central part of submillimeter band these losses may be as high as 40dB.However,the level of losses has no effect on a difference between the radar reflection coefficients for overcooled water and ice existing due to phase transition, and this difference may be over 20dB in the 0.3 to 0.8mm ice transparency “window”.

Linear problem of water-ice phase transitions in unsaturated soils

The approach proposed by Menot is developed. The problem of the freezing of an unsaturated soil is formulated for a compressible gas and equal component pressures. An analytic solution is obtained in the linear approximation. The results indicate the strong dependence of the ice saturation on the permeability of the soil and the applied pressure gradient.

Raman scattering spectra recorded in the course of the water–ice phase transition and laser diagnostics of heterophase water systems

The method of laser Raman spectroscopy was used to study heterophase water systems. The apparatus included an argon laser, an optical multichannel analyzer, and a microcomputer. The temperature dependences of the profiles of the valence (stretching) band in the Raman spectrum of liquid water between + 50 °C and – 7 °C and of polycrystalline ice Ih (from 0 to – 62 °C) were determined, as well as the spectral polarization characteristics of the Raman valence band. A method was developed for the determination of the partial concentrations of the H2O molecules in liquid and solid phases present as a mixture. An analysis was made of the errors of the method and the sources of these errors. Applications of the method to multiparameter problems in more complex water systems (for example, solutions of potassium iodide in water) were considered. Other potential practical applications of the method were discussed.

Thermocrystallization flow of nonfreezing water films on the surface of capillaries

The rates of mass transfer under the influence of a temperature gradient between the menisci of ice in a thin quartz capillary are measured. The mass transfer rate is determined by the diffusion of vapor and by the flow of a nonfrozen polymolecular adsorption film over the capillary surface. It is shown that the flow of the film is attributable neither to the thermoosmotic nor to the thermocapillary flow. The flow rate of a nonfrozen film is well described by a thermocrystallization transfer equation derived earlier, the thermocrystallization transfer being controlled by the water-ice phase transition heat.

Reply to “Comments on the Existence of Measured Discontinuity in the Thermal-Neutron Diffusion Coefficient Across the Ice-Water Phase Transition”

"Reply to “Comments on the Existence of Measured Discontinuity in the Thermal-Neutron Diffusion Coefficient Across the Ice-Water Phase Transition”." Nuclear Science and Engineering, 48(2), p. 232