Water Vapor Deposition Research Articles

Revealing the water vapor transport during the Henan “7.20” heavy rainstorm based on ERA5 and Real-Time GNSS

In July 2021, a heavy rainstorm was sweeping across Henan Province, causing geological disasters such as floods, mudslides, and landslides, which seriously threatened the safety of human life and property. Precipitable water vapor (PWV) is related to the occurrence and scale of rainfall. Here, based on Global Navigation Satellite System (GNSS) observations, in-situ meteorological files (GMET), ephemeris products, ERA5 data, and weather station data, the relationship between PWV and rainstorm from July 1st to 30th was studied. The results show that GMET and ERA5 in July 2021 have high consistency in some stations, with a root mean square error (RMSE) for temperature below 1.6 °C, for pressure below 0.5 hPa, and for relative humidity below 9 %. During the week before the heavy rainstorm, the temperature dropped remarkably and the temperature difference decreased, while the relative humidity increased and the relative humidity difference decreased. Compared with ERA5 PWV, the RMSE of GNSS PWV retrieved using real-time ephemeris is 3.238 mm. Different from the normal rainfall, we found that the PWV variation during the Henan rainstorm experienced a unique “accumulation” period. We also observed a clear correlation between PWV and the rainstorm, both temporally and spatially. In addition, the PWV in the severely damaged area was 20 mm higher than the average value of the past decade. Ten days after the rainstorm, the surface of this area had subsided by 1.5–3 mm. Finally, we found that the topography of Henan, the low vortex, the north-biased subtropical high, and the double typhoons all played a role in the successful transport and deposition of water vapor.

Atomic force microscopy observation of surface morphologies and measurements of local contact potential differences of amorphous solid water samples deposited at 15 and 100 K.

We use an ultra-high vacuum cryogenic atomic force microscope to investigate the surface morphology of amorphous solid water (ASW) prepared by oblique deposition of water vapor onto Si(111)7 × 7 substrates at temperatures of 15 and 100 K. Height-height correlation function analysis of topographic images suggests that ASW at 15 K has a columnar structure and that the typical diameter of the column is 5-10 nm. At 100 K, the typical diameter is 10-30 nm, although columnar features are less prominent. The surface roughness (i.e., deviation of the height) is greater at 15 K than at 100 K, indicating that the surface at 100 K exhibits a relatively flat morphology. This result implies that transient diffusion of deposited water molecules affects the surface morphology at 100 K. In addition, measurements of the local contact potential difference between the tip and the ASW surface suggest that the magnitude of the negative surface potential at the microscopic scale, which is attributed to spontaneous polarisation, cannot simply be scaled by the thickness of ASW as predicted in previous experiments with Kelvin probes.

Ice Supersaturation Variability in Cirrus Clouds: Role of Vertical Wind Speeds and Deposition Coefficients

AbstractAircraft measurements reveal ice supersaturation statistics in cirrus (ISSs) with broad maxima around ice saturation and pronounced variance. In this study, processes shaping ISSs in midlatitude and tropical upper tropospheric conditions are systematically investigated. Water vapor deposition and sublimation of size‐resolved ice crystal populations are simulated in an air parcel framework. Mesoscale temperature fluctuations (MTFs) due to gravity waves force the temporal evolution of supersaturation. Various levels of background wave forcing and cirrus thickness are distinguished in stochastic ensemble simulations. Kinetic limitations to ice mass growth are brought about by supersaturation‐dependent deposition coefficients that represent efficient and inefficient growth modes as a function of ice crystal size. The simulations identify a wide range of deposition coefficients in cirrus, but most values stay above 0.01 such that kinetic limitations to water uptake remain moderate. Supersaturation quenching times are long, typically 0.5–2 hr. The wave forcing thus causes a remarkably large variability in ISSs and cirrus microphysical properties except in the thickest cirrus, producing ensemble‐mean ISSs in line with in‐situ measurements. ISS variance is controlled by MTFs and increases with decreasing cirrus integral radii. In comparison, the impact of ice crystal growth rates on ISSs is small. These results contribute to efforts directed at identifying and solving issues associated with ice‐supersaturated areas and non‐equilibrium cirrus physics in global models.

Tracking cubic ice at molecular resolution.

Ice is present everywhere on Earth and has an essential role in several areas, such as cloud physics, climate change and cryopreservation. The role of ice is determined by its formation behaviour and associated structure. However, these are not fully understood1. In particular, there is a long-standing debate about whether water can freeze to form cubic ice-a currently undescribed phase in the phase space of ordinary hexagonal ice2-6. The mainstream view inferred from a collection of laboratory data attributes this divergence to the inability to discern cubic ice from stacking-disordered ice-a mixture of cubic and hexagonal sequences7-11. Using cryogenic transmission electron microscopy combined with low-dose imaging, we show herethe preferential nucleation of cubic ice at low-temperature interfaces, resulting in two types of separate crystallization of cubic ice and hexagonal ice from water vapour deposition at 102 K. Moreover, we identifya series of cubic-ice defects, including two types of stacking disorder, revealing the structure evolution dynamics supported by molecular dynamics simulations. The realization of direct, real-space imaging of ice formation and its dynamic behaviour at the molecular level provides an opportunity for ice research at the molecular level using transmission electron microscopy, which may be extended to other hydrogen-bonding crystals.

Ammonia Adsorption on Crystalline Ice Surface: Adsorption Structure and Site Selectivity

The structural heterogeneity of an ice surface at the atomic level is an important characteristic that influences the interactions between adsorbate molecules and the ice surface. In this study, we investigated the adsorption of ammonia on the basal (0001) surface of crystalline ice (CI) films to examine the adsorption selectivity of ammonia molecules on atomistically different sites of the ice surface. The adsorption structure and site-selectivity of ammonia adsorption on ice surfaces were examined by conducting temperature-programmed desorption, low energy sputtering, reactive ion scattering, reflection–absorption infrared spectroscopy, and surface voltage measurements. Ammonia adsorbs on ice surfaces without undergoing protonation, dissociation, or penetration into the bulk ice. At low coverages, adsorption occurs exclusively at the dangling H atom sites of the surface via N···H–O bond formation. The average orientation of the adsorbed molecular dipoles leans substantially toward the surface. After saturation of the dangling H sites, further adsorption of ammonia leads to the formation of a multilayer with isotropic molecular orientation. Titration experiment for the surface population of dangling H sites with ammonia reveals that the surface density of free O–H groups is 0.29 ± 0.04 monolayers for the CI films prepared by water vapor deposition at 140 K and postannealing at 160 K, indicating that the basal ice surface is not significantly reconstructed under vacuum conditions.

Numerical analysis on burning and particle formation of a single ethanol-based droplet in flame spray pyrolysis

Ethanol is a common inexpensive solvent for industrial flame spray pyrolysis. This work presents a numerical study of a single ethanol-based droplet burning with different precursor concentrations under both dry and wet air conditions. The evaporation and decomposition of precursors, the deposition of water vapor and its diffusion and transport in the liquid phase are considered. The micro-explosion behavior and droplet burning constant were well predicted as compared to existing experimental data in literature. The results show that surface condensation, dissolution, and re-evaporation of water were controlled by the disparity of mass transfer and evaporation priorities of different components in the droplet at different temperatures. Water in the ethanol droplet increases first during the initial burning stage and then decreases with increasing temperature as water preferentially vaporized than the formed less-volatile viscous layer on the droplet surface during the droplet combustion. The ratio of particle synthesis through evaporation and thermal decomposition decreases with increasing precursor concentration. It is further identified that the presence of water from either combustion products or humid air suppresses evaporation of the precursors in ethanol droplets because water dissolved in droplets evaporates preferably than the precursor, thereby potentially inhibiting the gas-to-particle route and providing another potential option for the control of flame synthesis process.

Laboratory set-up for surface hoar layer growth over rounded grain snow

Growth of surface hoar (SH) crystals by deposition of water vapour onto the snow surface and their subsequent burial by snowfall leads to the formation of a persistent weak SH layer in mountain snowpack of Greater Himalayas. The mechanical properties and failure behaviour of SH layers are critical for avalanche hazard assessment as failure of buried SH layers is frequently the primary cause for the release of dry snow slab avalanches. However, extraction of snow samples containing sandwiched SH layer and their transportation to cold laboratory for experimentation is extremely difficult due to the fragile nature of SH layer. To overcome this limitation, we developed a setup that mimics the natural environmental conditions under which the SH crystals grow. The setup consists of a hot (Th = 1oC) and a cold (Tc = − 25oC) environmental chambers which are connected via an air-duct. The warm air from hot chamber is driven over a water bath through the air-duct towards the cold chamber. A sieved snow sample of desired dimension, which act as the base snow layer, is placed just below the air-duct outlet inside the cold chamber. Difference between the temperature and water vapour pressure of the air at duct outlet, and the surface of base snow layer, resulted in the deposition of water vapour and growth of SH crystals on the exposed snow surface. The growth of SH crystals was primarily observed in the direction normal to the snow surface while their typical shapes were predominantly plates, sector plates and dendrite. With the present setup, an SH layer of ∼10 mm thickness over a base snow layer of surface area 0.07 m2 could be grown within a time interval of ∼13 hr. The average growth rate of SH layer is found to be in the range of ∼0.5 − 0.9 mm hr−1 and the accommodation coefficient of water vapour derived from the analysis of growth measurements varied between α = 0.54 − 0.94 under different experimental conditions. Comparison of cumulative mass of deposited water vapour with measured SH layer thickness also yielded an apparent SH density of 42.5 kg m−3. The strength values (0.6 − 2.2 kPa) of snow samples with artificially grown sandwiched SH layer prepared in this study matches closely with weak layer strength reported in literature thereby indicating the usefulness of present experimental setup for investigating the multi-axial failure behaviour of surface hoar under controlled conditions.

A method of measuring transmittance of radiation from the film of ice 0 in the IR wave band deposited on a dielectric plate

A method of measuring transmittance of radiation from the film of ice 0 in the infrared wave band is described. Ice 0 is formed from supercooled water at the temperature below –23°C. This ice is ferroelectric and forms a highly conductive layer of the nanometric order of thickness at the boundary with dielectric. The complexity of the experiment consisted in the necessity of using low intensities of the probing signal and considering radiation of the cooled parts of the installation. In order to obtain a thin film of ice, the method of depositing water vapor on a substrate cooled in nitrogen was used. The method rules out formation of condensate in cooling. Deposition of water vapor is possible only in heating, when delivery of cold nitrogen vapor into the chamber with the sample is excluded. To ensure exposure of the film to IR radiation, two sources of infrared radiation were considered: a halogen lamp with a broad radiation spectrum (on the surface of heated glass) and a CO2 laser with the radiation wavelength of 10.6 µm. In the first case, spectral measurements are possible when filters are used. In the installation based on a CO2 laser, an intense signal is emitted, requiring consideration of sample heating. Components of the installation have been elaborated and investigated, on which transmittance of radiation from the film of ice 0 is planned to be measured.

Properties of Cirrus Clouds over the European Arctic (Ny-Ålesund, Svalbard)

Cirrus is the only cloud type capable of inducing daytime cooling or heating at the top of the atmosphere (TOA) and the sign of its radiative effect highly depends on its optical depth. However, the investigation of its geometrical and optical properties over the Arctic is limited. In this work the long-term properties of cirrus clouds are explored for the first time over an Arctic site (Ny-Ålesund, Svalbard) using lidar and radiosonde measurements from 2011 to 2020. The optical properties were quality assured, taking into account the effects of specular reflections and multiple-scattering. Cirrus clouds were generally associated with colder and calmer wind conditions compared to the 2011–2020 climatology. However, the dependence of cirrus properties on temperature and wind speed was not strong. Even though the seasonal cycle was not pronounced, the winter-time cirrus appeared under lower temperatures and stronger wind conditions. Moreover, in winter, geometrically- and optically-thicker cirrus were found and their ice particles tended to be more spherical. The majority of cirrus was associated with westerly flow and westerly cirrus tended to be geometrically-thicker. Overall, optically-thinner layers tended to comprise smaller and less spherical ice crystals, most likely due to reduced water vapor deposition on the particle surface. Compared to lower latitudes, the cirrus layers over Ny-Ålesund were more absorbing in the visible spectral region and they consisted of more spherical ice particles.

Vertical structure and microphysical observations of winter precipitation in an inner valley during the Cerdanya-2017 field campaign

Precipitation processes at windward and leeward sides of the mountains have been object of study for many decades. Instead, inner mountain valleys, where usually most mountain population lives, have received considerably less attention. This article examines precipitation processes during a winter field campaign in an inner valley of the Pyrenees (NE Spain) using, among other instruments, a K-band vertically pointing Doppler radar (Micro Rain Radar) and a laser-based optical disdrometer (Parsivel). A decoupling is found between the stalled air of the valley and the air of the free atmosphere above the mountain crest level, evidenced by an increase of turbulence and spectral width of precipitation particles. Wind shear layer may promote riming and aggregation of the ice and snow particles. Two main rainfall regimes are found during the campaign: (1) stratiform rainfall mostly produced by water vapour deposition processes, although sometimes riming and aggregation become important, and (2) weak convection with slight dominance of collision-coalescence processes. Precipitation characteristics at the bottom of the valley show typical continental features such as low Liquid Water Content, despite the valley is only about 100 km from the sea. This study demonstrates that inner valley may present distinct precipitation features with respect to windward and leeward precipitation.

Synthesis of octadecyltrichlorosilane self-assembled monolayer films by vapor deposition on plasma activated silicon substrates

Molecular films of octadecyltrichlorosilane (OTS) silanized on silicon substrates were obtained by a succession of fabrication steps consisting in plasma hydroxylation of silicon surface, formation of a water layer adsorbed on hydroxylated surface by substrate exposure to water vapor and OTS vapor deposition. All fabrication steps were realized in the same vacuum chamber to avoid surface contamination and to control the amount of water adsorbed on the hydroxylated surface. It is proved that the amount of water on the substrate surface plays a key role in fabrication of smooth OTS molecular films, large amounts of water on substrates resulting in formation of 3D OTS aggregates. The atomic force microscopy (AFM) investigations of the film surface revealed formation of liquid-expanded and liquid-condensed domains in OTS molecular films. Annealing of the OTS films promotes film dehydration, increases the film hydrophobicity and reduces nanoscopic adhesion and friction forces between silicon AFM tips and film surface.

Impact of water vapor diffusion and latent heat on the effective thermal conductivity of snow

Abstract. Heat transport in snowpacks is understood to occur through the two processes of heat conduction and latent heat transport carried by water vapor, which are generally treated as decoupled from one another. This paper investigates the coupling between both these processes in snow, with an emphasis on the impacts of the kinetics of the sublimation and deposition of water vapor onto ice. In the case when kinetics is fast, latent heat exchanges at ice surfaces modify their temperature and therefore the thermal gradient within ice crystals and the heat conduction through the entire microstructure. Furthermore, in this case, the effective thermal conductivity of snow can be expressed by a purely conductive term complemented by a term directly proportional to the effective diffusion coefficient of water vapor in snow, which illustrates the inextricable coupling between heat conduction and water vapor transport. Numerical simulations on measured three-dimensional snow microstructures reveal that the effective thermal conductivity of snow can be significantly larger, by up to about 50 % for low-density snow, than if water vapor transport is neglected. A comparison of our numerical simulations with literature data suggests that the fast kinetics hypothesis could be a reasonable assumption for modeling heat and mass transport in snow. Lastly, we demonstrate that under the fast kinetics hypothesis the effective diffusion coefficient of water vapor is related to the effective thermal conductivity by a simple linear relationship. Under such a condition, the effective diffusion coefficient of water vapor is expected to lie in the narrow 100 % to about 80 % range of the value of the diffusion coefficient of water vapor in air for most seasonal snows. This may greatly facilitate the parameterization of water vapor diffusion of snow in models.

Macroscopic water vapor diffusion is not enhanced in snow

Abstract. Water vapor transport in dry snowpacks plays a significant role for snow metamorphism and the mass and energy balance of snowpacks. The molecular diffusion of water vapor in the interstitial pores is usually considered to be the main or only transport mechanism, and current detailed snow physics models therefore rely on the knowledge of the effective diffusion coefficient of water vapor in snow. Numerous previous studies have concluded that water vapor diffusion in snow is enhanced relative to that in air. Various field observations also indicate that for vapor transport in snow to be explained by diffusion alone, the effective diffusion coefficient should be larger than that in air. Here we show using theory and numerical simulations of idealized and measured snow microstructures that, although sublimation and deposition of water vapor onto snow crystal surfaces do enhance microscopic diffusion in the pore space, this effect is more than countered by the restriction of diffusion space due to ice. The interaction of water vapor with the ice results in water vapor diffusing more than inert molecules in snow but still less than in free air, regardless of the value of the sticking coefficient of water molecules on ice. Our results imply that processes other than diffusion play a predominant role in water vapor transport in dry snowpacks.

Control of amorphous solid water target morphology induced by deposition on a charged surface

Abstract Microstructured targets demonstrate an enhanced coupling of high-intensity laser pulse to a target and play an important role in laser-induced ion acceleration. Here we demonstrate an approach that enables us to control the morphology of amorphous solid water (ASW) microstructured targets, by deposition of water vapor on a charged substrate, cooled down to 100 K. The morphology of the deposited ASW structures is controlled by varying the surface charge on the substrate and the pressure of water vapor. The obtained target is structured as multiple, dense spikes, confined by the charged area on the substrate, with increased aspect ratio of up to 5:1 and having a diameter comparable with the typical spot size of the laser focused onto the target.

Tropical cyclones impact on tropopause and the lower stratosphere vapour based on satellite data

AbstractAs one of the deep convection systems, tropical cyclones (TCs) could significantly affect the thermodynamic structure and cloud microphysical processes near the tropopause, which may cause changes in troposphere and stratosphere water vapour activity, with important influences on global climate change. However, the effects of TCs on tropopause and the lower stratosphere water vapour remain unclear. Here, we use satellite data from year 2012 to 2016 to assess the effect of TCs on water vapour at the tropopause and in the lower stratosphere over the Northwest tropical Pacific Ocean. It is found that TCs could decrease the tropopause temperature and increase the process of water vapour deposition on cloud ice to a certain extent. This process can increase cloud ice mixing ratio and then dehydrate the tropopause. Part of the small cloud ice particles will be injected into the lower stratosphere, where they would be sublimated, hydrating the lower stratosphere. Compared to non‐TC area, the average water vapours in TC area decrease about 1.04 ppmv near the tropopause, but increase by 0.75 ppmv in the lower stratosphere.

Transmittance of Electromagnetic Radiation of the Visible Range by a Thin Film of Ice 0 Condensed on a Dielectric Substrate

The transmittance of electromagnetic radiation of the visible range through transparent dielectric samples with an ice nanolayer on their surface has been measured. Ice has been obtained by deposition of water vapor at a temperature of −170°C to 0°C. A decrease in the intensity of transmitted radiation at a wavelength of 0.52 μm by a factor of at least 2 depending on the material of the substrate and the temperature with a minimum near −23°C has been revealed. This effect is assumingly due to the formation of ferroelectric ice 0 and surface plasmons in a highly conducting thin layer at the ice 0–insulator interface.

Solar-to-Steam Generation via Porous Black Membranes with Tailored Pore Structures.

Solar-to-steam generation is a powerful, intense, and efficient method to harvest solar energy. Many efforts have been devoted to the development of a durable, affordable, and easy-to-manufacture solar steam device. In this study, we use a versatile polydimethylsiloxane material to fabricate an open porous black membrane with different pore structures using a simple salt water etching process and vapor deposition polymerization of pyrrole into a matrix. The porous black membrane absorbed radiation from a broad section of the light spectrum from near-infrared to ultraviolet and retained its initial pore structures and floating ability. We found that our black membrane with a tailored pore structure and surface exhibits excellent solar-to-steam generation efficiency of up to 72% at five sun irradiation. Also, a series of analyses including density functional theory calculation was used to prove the outstanding efficiency of solar-to-steam generation.

Convective hydration in the tropical tropopause layer during the StratoClim aircraft campaign: pathway of an observed hydration patch

Abstract. The source and pathway of the hydration patch in the TTL (tropical tropopause layer) that was measured during the Stratospheric and upper tropospheric processes for better climate predictions (StratoClim) field campaign during the Asian summer monsoon in 2017 and its connection to convective overshoots are investigated. During flight no. 7, two remarkable layers are measured in the TTL, namely (1) the moist layer (ML) with a water vapour content of 4.8–5.7 ppmv in altitudes of 18–19 km in the lower stratosphere and (2) the ice layer (IL) with ice content up to 1.9 eq. ppmv (equivalent parts per million by volume) in altitudes of 17–18 km in the upper troposphere at around 06:30 UTC on 8 August to the south of Kathmandu (Nepal). A Meso-NH convection-permitting simulation succeeds in reproducing the characteristics of the ML and IL. Through analysis, we show that the ML and IL are generated by convective overshoots that occurred over the Sichuan Basin about 1.5 d before. Overshooting clouds develop at altitudes up to 19 km, hydrating the lower stratosphere of up to 20 km with 6401 t of water vapour by a strong-to-moderate mixing of the updraughts with the stratospheric air. A few hours after the initial overshooting phase, a hydration patch is generated, and a large amount of water vapour (above 18 ppmv) remains at even higher altitudes up to 20.5 km while the anvil cloud top descends to 18.5 km. At the same time, a great part of the hydrometeors falls shortly, and the water vapour concentration in the ML and IL decreases due to turbulent diffusion by mixing with the tropospheric air, ice nucleation, and water vapour deposition. As the hydration patch continues to travel toward the south of Kathmandu, tropospheric tracer concentration increases up to ∼30 % and 70 % in the ML and IL, respectively. The air mass in the layers becomes gradually diffused, and it has less and less water vapour and ice content by mixing with the dry tropospheric air.

Effect of nucleation on icy pebble growth in protoplanetary discs

Solid particles in protoplanetary discs can grow by direct vapour deposition outside of ice lines. The presence of microscopic silicate particles may nevertheless hinder growth into large pebbles, since the available vapour is deposited predominantly on the small grains that dominate the total surface area. Experiments on heterogeneous ice nucleation, performed to understand ice clouds in the Martian atmosphere, show that the formation of a new ice layer on a silicate surface requires a substantially higher water vapour pressure than the deposition of water vapour on an existing ice surface. In this paper, we investigate how the difference in partial vapour pressure needed for deposition of vapour on water ice versus heterogeneous ice nucleation on silicate grains influences particle growth close to the water ice line. We developed and tested a dynamical 1D deposition and sublimation model, where we include radial drift, sedimentation, and diffusion in a turbulent protoplanetary disc. We find that vapour is deposited predominantly on already ice-covered particles, since the vapour pressure exterior of the ice line is too low for heterogeneous nucleation on bare silicate grains. Icy particles can thus grow to centimetre-sized pebbles in a narrow region around the ice line, whereas silicate particles stay dust-sized and diffuse out over the disc. The inhibition of heterogeneous ice nucleation results in a preferential region for growth into planetesimals close to the ice line where we find large icy pebbles. The suppression of heterogeneous ice nucleation on silicate grains may also be the mechanism behind some of the observed dark rings around ice lines in protoplanetary discs, as the presence of large ice pebbles outside ice lines leads to a decrease in the opacity there.

Nucleation and growth of water ice on Ru(0001): Influences of oxygen and carbon-monoxide adspecies

Abstract Crystallization kinetics of water on Ru(0001) with and without adspecies was investigated using reflection high energy electron diffraction (RHEED). Amorphous solid water is formed on the bare Ru(0001) substrate during water vapor deposition at 135 K; randomly oriented ice Ic crystallites grow after some incubation time. The nucleation and epitaxial growth tend to be aborted on the oxygenated Ru(0001) substrate, whereas ice Ih crystallites having considerable stacking disorders grow epitaxially on the CO-adsorbed Ru(0001) substrate immediately after water deposition at 135 K. Results indicate that epitaxy is controlled by the interfacial ice nucleation time and the water deposition rate.