Frost Surface Research Articles

The interaction of Io’s plumes and sublimation atmosphere

Io’s volcanic plumes are the ultimate source of its SO2 atmosphere, but past eruptions have covered the moon in surface frost which sublimates in sunlight. Today, Io’s atmosphere is a result of some combination of volcanism and sublimation, but it is unknown exactly how these processes work together to create the observed atmosphere. We use the direct simulation Monte Carlo (DSMC) method to model the interaction of giant plumes with a sublimation atmosphere. Axisymmetric plume/atmosphere simulations demonstrate that the total mass of SO2 above Io’s surface is only poorly approximated as the sum of independent volcanic and sublimated components. A simple analytic model is developed to show how variation in the mass of erupting gas above Io’s surface can counteract variation in the mass of its hydrostatic atmosphere as surface temperature changes over a Jupiter year. Three-dimensional, unsteady simulations of giant plumes over an Io day are also presented, showing how plume material becomes suspended in the sublimation atmosphere. We find that a plume which produces some total mass above Io’s surface at night will cause a net increase in the noon-time atmosphere of only a fraction of the night-time value. However, as much as seven times the night-side mass of the plume will become suspended in the sublimation atmosphere, altering its composition and displacing sublimated material.

Quantitative x-ray microanalysis of model biological samples in the SEM using remote standards and the XPP analytical model.

It is shown that accurate x-ray microanalysis of frozen-hydrated and dry organic compounds, such as model biological samples, is possible with a silicon drift detector in combination with XPP (exponential model of Pouchou and Pichoir matrix correction) software using 'remote standards'. This type of analysis is also referred to as 'standardless analysis'. Analyses from selected areas or elemental images (maps) were identical. Improvements in x-ray microanalytical hardware and software, together with developments in cryotechniques, have made the quantitative analysis of cryoplaned frozen-hydrated biological samples in the scanning electron microscope a much simpler procedure. The increased effectiveness of pulse pile-up rejection renders the analysis of Na, with ultrathin window detectors, in the presence of very high concentrations of O, from ice, more accurate. The accurate analysis of Ca (2 mmol kg-1 ) in the presence of high concentrations of K is possible. Careful sublimation of surface frost from frozen-hydrated samples resulted in a small increase in analysed elemental concentrations. A more prolonged sublimation from the same resurfaced sample and other similar samples resulted in higher element concentrations.

The Application and Evaluation of Simple Permafrost Distribution Models on the Qinghai-Tibet Plateau

The performance of simple permafrost distribution models widely used on the Qinghai–Tibet Plateau (QTP) has not been fully evaluated. In this study, two empirical models (the elevation model and mean annual ground temperature model) and three semi-physical models (the surface frost number model, the temperature at the top of permafrost model and the Kudryavtsev model) were investigated. The simulation results from the models were compared to each other and validated against existing permafrost maps of the entire QTP and in three representative areas investigated in the field. The models generally overestimated permafrost distribution in the investigated areas, but they captured the broad characteristics of permafrost distribution on the entire QTP, and performed best in areas with colder, continuous permafrost. Large variations in performance occurred at elevations of 3800–4500 m asl and in areas with thermally unstable permafrost. The two empirical models performed best in areas where permafrost is strongly controlled by elevation, such as eastern QTP. In contrast, the three semi-physical models were better in southern island permafrost areas with relatively flat terrain, where local factors considerably impact the distribution of permafrost. Model performance could be enhanced by explicitly considering the effects of elevation zones and regional conditions. Copyright © 2017 John Wiley & Sons, Ltd.

Magnesium Dry Mixes for Outer Wall Decoration

A promising mode of magnesia binder use in construction is dry building mixtures production. Depending on purpose they can be self-leveling, plastering, painting, primer, putty, etc. To produce those different binders, including magnesia one, can be used, depending on the desired aesthetic, environmental and anti-bacterial properties. It can be used in children's, medical, public institutions, and residential premises. The most preferable use for magnesia dry building mixes (MDBM) is as plaster for inner or outer buildings decoration. Plasters for external use have to be light, creating a ‘breathing’ coating that prevents thermal cold bridges formation, has high vapor permeability that can adjust to the equilibrium moisture content of magnesia design on the whole, has good adhesion to the coated surface and adequate frost resistance. Ordinary Portland cement and lime-silica binders are most often used for such products. Unlike materials based on these binders, magnesia products are characterized by rapid strength development under natural conditions. Therefore, the use of magnesia binders which allow obtaining high-strength, environmentally friendly and bioresistant materials for construction is particularly interesting.

Frost Formation: Optimizing solutions under a finite volume approach

A three-dimensional transient formulation of the frost formation process is developed by means of a finite volume approach. Emphasis is put on the frost surface boundary condition as well as the wide range of empirical correlations related to the thermophysical and transport properties of frost. A study of the numerical solution is made, establishing the parameters that ensure grid independence. Attention is given to the algorithm, the discretised equations and the code optimization through dynamic relaxation techniques. A critical analysis of four cases is carried out by comparing solutions of several empirical models against tested experiments. As a result, a discussion on the performance of such parameters is started and a proposal of the most suitable models is presented.

Defrosting on horizontal hydrophobic surfaces and the shrink angle

Defrosting of a frosted surface is a crucial part for system recovery in refrigeration and cryogenic engineering. The performances of defrosting on a horizontal surface can better reflect the defrosting and drainage characteristics of the surface itself, since the influence of gravity is almost eliminated. This work performed defrosting experiments on horizontal hydrophobic surfaces with the defrosting process divided into three stages including frost melting, meltwater breaking and meltwater shrinking. The meltwater on the hydrophobic surface finally shrinks into a droplet with a final contact angle which is called the shrink angle. A theoretical model was also developed to analyze the free energy change of the meltwater during defrosting with the shrink angle predicted and its influencing factors discussed. Based on the model, the shrink angle relates to the static contact angle, contact angle hysteresis and meltwater size. When the meltwater size is less than the capillary length, the shrink angle is only related to the surface wettability. With increasing static contact angle and reducing contact angle hysteresis, the shrink angle increases and approaches the static contact angle. The predicted shrink angles were consistent with the experimental results with a maximum difference of 7%.

CMIP5 permafrost degradation projection:A comparison among different regions

AbstractThe considerable impact of permafrost degradation on hydrology and water resources, ecosystems, human engineering facilities, and climate change requires us to carry out more in‐depth studies, at finer spatial scales, to investigate the issue. In this study, regional differences of the future permafrost changes are explored with respect to the regions (high altitude and high latitude, and in four countries) based on the surface frost index (SFI) model and multimodel and multiscenario data from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Results show the following: (1) Compared with seven other sets of driving data, Climatic Research Unit air temperature combined with Climate Forecast System Reanalysis snow data (CRU_CFSR) yield a permafrost extent with the least absolute area bias and was thus used in the simulation. The SFI model, driven by CRU_CFSR data climatology plus multimodel mean anomalies, produces a present‐day (1986–2005) permafrost area of 15.45 × 106 km2 decade−1, which compares reasonably with observations of 15.24 × 106 km2 decade−1. (2) The high‐altitude (Tibetan Plateau) permafrost area shows a larger decreasing percentage trend than the high‐latitude permafrost area. This indicates that, in terms of speed, high‐altitude permafrost thaw is faster than high‐latitude permafrost, mainly due to the larger percentage sensitivity to rising air temperature of the high‐altitude permafrost compared to the high‐latitude permafrost, which is likely related to their thermal conditions. (3) Permafrost in China shows the fastest thaw, which is reflected by the percentage trend in permafrost area, followed by the United States, Russia, and Canada. These discrepancies are mainly linked to different percentage sensitivities of permafrost areas in these four countries to air temperature change. (4) In terms of the ensemble mean, permafrost areas in all regions are projected to decrease by the period 2080–2099. Under representative concentration pathway (RCP)4.5, permafrost retreats toward the Arctic, and the thaw in every region mainly occurs at the southern edge of the permafrost area. Under RCP8.5, almost no permafrost is expected to remain in China, the United States, and the Tibetan Plateau. Permafrost in Russia will remain mainly in the western part of the east Siberian Mountains, and permafrost in Canada will retreat to the north of 65°N. Possible uncertainties in this study are primarily attributed to the climate model's coarse horizontal resolution. The results of the present study will be useful for understanding future permafrost degradation from the regional perspective.

Diagnostic and model dependent uncertainty of simulated Tibetan permafrost area

Abstract. We perform a land-surface model intercomparison to investigate how the simulation of permafrost area on the Tibetan Plateau (TP) varies among six modern stand-alone land-surface models (CLM4.5, CoLM, ISBA, JULES, LPJ-GUESS, UVic). We also examine the variability in simulated permafrost area and distribution introduced by five different methods of diagnosing permafrost (from modeled monthly ground temperature, mean annual ground and air temperatures, air and surface frost indexes). There is good agreement (99 to 135 × 104 km2) between the two diagnostic methods based on air temperature which are also consistent with the observation-based estimate of actual permafrost area (101 × 104 km2). However the uncertainty (1 to 128 × 104 km2) using the three methods that require simulation of ground temperature is much greater. Moreover simulated permafrost distribution on the TP is generally only fair to poor for these three methods (diagnosis of permafrost from monthly, and mean annual ground temperature, and surface frost index), while permafrost distribution using air-temperature-based methods is generally good. Model evaluation at field sites highlights specific problems in process simulations likely related to soil texture specification, vegetation types and snow cover. Models are particularly poor at simulating permafrost distribution using the definition that soil temperature remains at or below 0 °C for 24 consecutive months, which requires reliable simulation of both mean annual ground temperatures and seasonal cycle, and hence is relatively demanding. Although models can produce better permafrost maps using mean annual ground temperature and surface frost index, analysis of simulated soil temperature profiles reveals substantial biases. The current generation of land-surface models need to reduce biases in simulated soil temperature profiles before reliable contemporary permafrost maps and predictions of changes in future permafrost distribution can be made for the Tibetan Plateau.

Phase change mass transfer model for frost growth and densification

A frosting mechanism was used to develop a phase change mass transfer model to predict the frost layer growth and densification. The model with a criterion can describe the mass transfer of water vapor from the humid air to increase the frost thickness and the frost density. Frost formation on a cold surface with local cooling was simulated by using the model as a source term in FLUENT to predict the frost morphology, temperature distribution and frost weight which are all in good agreement with the experimental results. The results show that the frost first forms around the cooling block and then extends gradually to other directions, with the frost above the cooling block having the greatest density. The average frost thickness increases gradually with time with the growth rate slowing down, while the average frost density increases with the increases rate getting faster. The temperature distribution in the computational domain is related to the frost layer morphology and the frost surface temperature is usually lower than the freezing point temperature. As the frost layer grows, the average air velocity increases with the maximum local velocity located above the thickest part of the frost layer.

Likely frost events at Gale crater: Analysis from MSL/REMS measurements

We provide indirect evidence for the formation of frost at the surface of Gale crater by analyzing the highest confidence data from simultaneous measurements of relative humidity and ground temperature during the first 1000sols of the Mars Science Laboratory (MSL) mission. We find that except for sol 44, frost events could have occurred only between sols 400 and 710, corresponding to the most humid and coldest time of the year (from early fall to late winter). In particular, measurements at Dingo Gap during sols 529–535, at an unnamed place during sols 554–560, at Kimberley during sols 609–617 and at an unnamed place during sols 673–676 showed the largest likelihood of the occurrence of frost events. At these four locations, the terrain is composed of fine-grained and loosely packed material with thermal inertia values of ∼200 SI units, much lower than the 365±50 SI units value found at the landing ellipse. This is important because terrains with exceptionally low thermal inertia favor the formation of frost by lowering minimum daily ground temperatures. An order-of-magnitude calculation to determine the thickness of the frost layer at these four locations results in values of tenths of µm, while the precipitable water content is a few pr-µm. Therefore, surface frost events can have important implications for the local water cycle at Gale crater. In addition, frost is the most likely type of water that can be temporarily found in bulk amounts on the surface of Mars at low latitudes and therefore can cause weathering, influencing the geology of Gale crater.

A study in contrasts for inhibiting surface frost

Combining water-attracting and water-repelling regions can discourage water droplets from freezing.

A study in contrasts for inhibiting surface frost

A study in contrasts for inhibiting surface frost

Modeling the effects of martian surface frost on ice table depth

Ground ice has been observed in small fresh craters in the vicinity of the Viking 2 lander site (48°N, 134°E). To explain these observations, current models for ground ice invoke levels of atmospheric water of 20 precipitable micrometers – higher than observations. However, surface frost has been observed at the Viking 2 site and surface water frost and snow have been shown to have a stabilizing effect on Antarctic subsurface ice. A snow or frost cover provides a source of humidity that should reduce the water vapor gradient and hence retard the sublimation loss from subsurface ice. We have modeled this effect for the Viking 2 landing site with combined ground ice and surface frost models. Our model is driven by atmospheric output fields from the NASA Ames Mars General Circulation Model (MGCM). Our modeling results show that the inclusion of a thin seasonal frost layer, present for a duration similar to that observed by the Viking Lander 2, produces ice table depths that are significantly shallower than a model that omits surface frost. When a maximum frost albedo of 0.35 was permitted, seasonal frost is present in our model from Ls=182° to Ls=16°, resulting in an ice table depth of 64cm – which is 24cm shallower than the frost-free scenario. The computed ice table depth is only slightly sensitive to the assumed maximum frost albedo or thickness in the model.

Remote Sensing of the Mean Annual Surface Temperature and Surface Frost Number for Mapping Permafrost in China

The use of satellite-infrared sensors to map permafrost distribution is a new research topic. Two important permafrost indices, the mean annual surface temperature (MAST) and the surface frost number (SFN), are estimated using MODIS Aqua/Terra LST products based on a pragmatic scheme proposed in this study. The advantage of this approach is that it allows the full use of every value at any time and at any pixel of MODIS LST products. This scheme is simple, easy to implement, and independent of other observations. The accuracy of the method depends only on the accuracy of the MODIS LST products. Eight years of data sets from 2003 to 2010 were generated using this scheme to reflect the spatial distribution of permafrost and the surface thermal state. A comparison between the southern/lower limit of permafrost and results from the 8-year average MAST and SFN show that the 0 °C MAST isotherm and 0.5 contour of SFN agree well with the identified southern/lower limits of permafrost in China.

The Intelligent Winter Road Maintenance Management in Slovak Conditions

The paper describes a multi-level solution for intelligent winter road maintenance management. The system is based on monitoring and forecasting of weather conditions and the road surface conditions at selected road locations. Automatic data collection and transmission is ensured by road weather stations, which provide early warnings about dangerous situations on the road (such as frost, ice, mist, wet or snow-covered surface). Data from these weather stations, together with weather forecasting models and date from weather radars and satellites are processed, presented and used for prediction of the pavement surface state and temperature. The result is information support for right maintenance decision and for effective and timely treatment of roads in the winter. Further part of the system is the winter maintenance dynamic dispatching which provides on-line fleet monitoring and management to ensure optimization and timely intervention. In addition, variable message signs are in the system for ensuring of information for drivers or even for traffic control on a dangerous road sections with the aim to improve traffic safety.

Non-detection of post-eclipse changes in Io’s Jupiter-facing atmosphere: Evidence for volcanic support?

We present observations of Io’s tenuous lower atmosphere on the Jupiter-facing hemisphere at ultraviolet wavelengths, from 2100 to 2250Å, using the Hubble Space Telescope’s Cosmic Origins Spectrometer, during the period immediately after Io emerges from Jupiter eclipse. The density of an atmosphere dominantly controlled by frost sublimation is highly dependent on the thermal properties of the surface frost and frost temperature, and the changing solar illumination conditions as Io enters and exits eclipses allow us to study the atmospheric response due to frost sublimation and its relative role compared to volcanic output. These new eclipse emergence observations were obtained to better understand the relative roles that frost sublimation and volcanoes play in supporting the overall atmosphere on Io. The observations were obtained on two separate dates, and in both cases, we observe Io post Jupiter eclipse, from approximately 2min after egress to approximately 2h post-egress. On both of these occasions, the atmospheric density was observed to be constant with time to within 15%, implying that the atmosphere did not collapse while in Jupiter eclipse. We use a thermal model to explore combinations of volcanic support and sublimation support with a variety of SO2 frost thermal inertias and bond albedos, which are consistent with these new observations. We find that a pure sublimation-supported atmosphere with a single surface component (100% frost coverage) is difficult to reconcile with the observed lack of post-eclipse atmospheric changes, unless the SO2 frost thermal inertia is very high (⩾500MKS) accompanied with moderate bond albedos (∼0.55). However, atmospheric support by high thermal inertia frost is difficult to reconcile with the dramatic cooling of much of Io’s surface in eclipse, which should lead to condensation of the atmosphere on the cold surface components. Alternatively, a Jupiter-facing atmosphere entirely dominated by volcanic emissions in which frost sublimation plays only a minor role fits the data well. The results are surprising given the previous observations of reduced FUV auroral emissions in eclipse that suggest that the atmosphere does collapse in eclipse. Future improvements to incorporate non-frost components into the thermal model will help improve our interpretations.

The Frost Resistance of LYTAG Concrete

This article studies the frost resistance of LYTAG concrete and ordinary concrete respectively used the RILEM recommended test method (CIF) about frost resistance of concrete. The results indicate that the single surface's frost resistance of Lytag concrete with mineral admixture is much better than normal density concrete's. And the rank of the single surface's frost resistance at 56 cycles of Lytag concrete with different mineral admixture is: silica fume and slag> silica fume and fly ash>slag and fly ash>silica fume>fly ash>slag. The important reasons why LYTAG concrete has good frost resistance is that the scope of blending interfacial transition zone of LYTAG concrete between aggregate ceramsite and cement stone was significantly smaller than ordinary concrete.

Seasonal variations in Pluto’s atmospheric tides

Pluto’s tenuous atmosphere exhibits remarkable seasonal change as a result of the planet’s substantial obliquity and highly eccentric orbit. Over the past two decades, occultations have revealed that the atmospheric pressure on Pluto has increased substantially, perhaps by a factor as large as 2 to 4, as the planet has moved from equinox towards solstice conditions. These data have also shown variations in the strength of the dynamical activity in the atmosphere, as revealed by the varying abundance and amplitude of spikes in the occultation light curves resulting from refractive focussing by atmospheric waves. Toigo et al. (Toigo et al. [2010]. Icarus, 208, 402–411) explored the possibility that these waves are caused by solar-induced sublimation and diurnal deposition from N2 frost patches, driven by weak vertical winds resulting from the rising and sinking gas as it is released from or deposited onto the surface. Here, we extend this model to account explicitly for seasonal variations in average insolation and for the significant damping of vertical wave propagation by kinematic viscosity and thermal diffusivity (Hubbard et al. [2009]. Icarus, 204, 284–289). Damping is extremely effective in suppressing vertical propagation of waves with vertical wavelengths of a few kilometers or less, and the dominant surviving tidal modes have characteristic vertical wavelengths λ∼10–13km. We estimate the expected strength and regional characteristics of atmospheric tides over the course of Pluto’s orbit for a variety of assumed spatial distributions of surface frost and atmospheric surface pressure. We compute the predicted strength of tide-induced wave activity based on the actual frost distribution observed on Pluto from Hubble Space Telescope (HST) observations (Stern et al. [1997]. Astron. J., 113, 827; Buie et al. [2010]. Astron. J., 139, 1128–1143), and compare the results to calculations for volatile transport models of Young (Young [2013]. Astrophys. J., 766, L22) and Hansen et al. (Hansen et al. [2015]. Icarus, 246, 183–191). We develop simple scaling rules to estimate the variation of the strength of tidal activity with surface pressure PS and solar declination δ⊙, and show that the maximum expected temperature perturbation at an atmospheric pressure of P=0.1Pa scales as dTmax∝cosδ⊙/PS. Wave activity is strongest in the near-equatorial region (latitude|ϕ|≲30°), being only weakly dependent on the detailed frost distribution. Using a 3-D time-dependent geometric optics ray-tracing code, we compute model light curves for the geometric circumstances of three high-SNR occultations (2002 August 21, 2006 June 12, and 2012 July 18), taking into account the detailed three-dimensional characteristics of the tides as different regions of the atmosphere are probed over the course of each occultation chord. We compare the strength and abundance of the scintillations in the models with those seen in the data, using both the HST frost maps and the volatile transport model predictions. The striking asymmetries in the strengths of spikes between ingress and egress seen in some events are reproduced in the tidal model simulations, due primarily to the latitudes probed during the occultation: occultations at high northern or southern latitudes uniformly have much weaker wave activity than more equatorial events. A surface pressure range of PS=1–2Pa provides the best match between models and observations. With the impending arrival of the New Horizons spacecraft at Pluto in 2015, we predict that wave activity in the upper atmosphere will be strongest at equatorial regions, and controlled in amplitude primarily by the surface pressure and damping effects, rather than by the detailed frost distribution. If Pluto’s atmosphere begins to collapse in the coming decades, we expect that future stellar occultations will provide evidence for greatly enhanced atmospheric wave activity.

Combining Time-Lapse Photography and Multisensor Monitoring to Understand Frost Creep Dynamics in the Japanese Alps

Automated monitoring that combines time-lapse photography and sensor-based data logging can elucidate the environmental conditions, processes and rates of soil movement on remote periglacial hillslopes. This study presents the results from 5 years of time-lapse photography of soil movements, supported by time series data on frost heave, soil temperature, soil moisture and surface weather, on an alpine stone-banked lobe subject to frequent diurnal freeze-thaw cycles and deep seasonal frost on Mt Ainodake in the Japanese Alps. The lobe is dominated by biannual shallow soil movements, mostly originating from diurnal frost heave by needle ice or shallow ice lens formation and approximated by potential frost creep. The surface velocity shows a small interannual variation mainly reflecting snow conditions that control the spatio-temporal variability of freeze-thaw action, while it is independent of mean annual air temperature that influences the intensity of seasonal freezing. Occasional rill erosion occurs when the topmost frozen soil is rapidly thawed and super-saturated by intensive rainfall during seasonal thawing periods. Copyright © 2014 John Wiley & Sons, Ltd.

Images of intravitreal objects projected onto posterior surface of model eye

To try to recreate the images reported by patients during vitreous surgery in a model eye. A fluid-filled model eye with a posterior frosted translucent surface which corresponded to the retina was used. Three holes were made in the model eye through which an endoillumination pipe and intraocular forceps could be inserted. A thin plastic sheet simulating an epiretinal membrane and an intraocular lens (IOL) simulating a dislocated IOL were placed on the retina. The images falling on the posterior surface were photographed from the rear. The images seen through the surgical microscope were also recorded. The images from the rear were mirror images of those seen through the surgical microscope. Intraocular instruments were seen as black shafts from the rear. When the plastic sheet was picked up, the tip of the forceps was seen more sharply on the posterior surface. The images of the dislocated IOL from the posterior were similar to that seen through the surgical microscope, including the yellow optics and blue haptics. Intravitreal objects can form images on the surface of a model eye. Objects located closer to the surface are seen more sharply, and the colour of the objects can be identified.