scholarly journals Pore condensation and freezing is responsible for ice formation below water saturation for porous particles

2019 ◽  
Vol 116 (17) ◽  
pp. 8184-8189 ◽  
Author(s):  
Robert O. David ◽  
Claudia Marcolli ◽  
Jonas Fahrni ◽  
Yuqing Qiu ◽  
Yamila A. Perez Sirkin ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Radiative Forcing ◽  
Water Saturation ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Ice Formation ◽  
Classical Nucleation Theory ◽  
Radiative Balance ◽  
Porous Particles ◽  
Pore Condensation

Ice nucleation in the atmosphere influences cloud properties, altering precipitation and the radiative balance, ultimately regulating Earth’s climate. An accepted ice nucleation pathway, known as deposition nucleation, assumes a direct transition of water from the vapor to the ice phase, without an intermediate liquid phase. However, studies have shown that nucleation occurs through a liquid phase in porous particles with narrow cracks or surface imperfections where the condensation of liquid below water saturation can occur, questioning the validity of deposition nucleation. We show that deposition nucleation cannot explain the strongly enhanced ice nucleation efficiency of porous compared with nonporous particles at temperatures below −40 °C and the absence of ice nucleation below water saturation at −35 °C. Using classical nucleation theory (CNT) and molecular dynamics simulations (MDS), we show that a network of closely spaced pores is necessary to overcome the barrier for macroscopic ice-crystal growth from narrow cylindrical pores. In the absence of pores, CNT predicts that the nucleation barrier is insurmountable, consistent with the absence of ice formation in MDS. Our results confirm that pore condensation and freezing (PCF), i.e., a mechanism of ice formation that proceeds via liquid water condensation in pores, is a dominant pathway for atmospheric ice nucleation below water saturation. We conclude that the ice nucleation activity of particles in the cirrus regime is determined by the porosity and wettability of pores. PCF represents a mechanism by which porous particles like dust could impact cloud radiative forcing and, thus, the climate via ice cloud formation.

THE ICE NUCLEATION BEHAVIOR OF AMINO-ACID PARTICLES

1966 ◽  
Vol 44 (10) ◽  
pp. 2431-2445 ◽  
Author(s):  
J. Maybank ◽  
N. Barthakur
Keyword(s):  
Amino Acid ◽  
Liquid Phase ◽  
Water Saturation ◽  
Ice Nucleation ◽  
Cloud Chamber ◽  
Airborne Particles ◽  
Ice Formation ◽  
Vapor Pressures ◽  
Nucleation Behavior ◽  
Threshold Temperatures

The problem of whether ice nucleation takes place more readily from the vapor directly to the solid, or via an intermediate liquid phase has been studied for several of the more efficient amino-acid nucleators. It has been shown that the threshold temperatures observed in cloud chamber tests are in fact those of the material acting as freezing nuclei (i.e. via the liquid phase), and any discrepancies between such tests and trials with bulk water may be accounted for satisfactorily by partial destruction of the nucleus surface by the water. Investigations on ice formation about airborne particles and on macroscopic amino-acid crystals have shown that for certain of these substances a transition in behavior takes place around −20 °C. Below this temperature, ice formation no longer requires saturation conditions with respect to supercooled water and so the particles may be considered to act by converting the vapor directly to ice, and can, therefore, be designated sublimation nuclei.The major obstacle in the way of airborne particles acting as freezing nuclei has been the requirement that they act first as condensation centers. Under the conditions prevailing in supercooled clouds with vapor pressures equal to, or barely exceeding that of water saturation, condensation is unlikely on the somewhat hydrophobic surfaces of amino-acid particles. It has been shown, however, by using a radioactive tracer in small water droplets that droplet–particle collisions can occur. While not efficient, this process would permit a few particles in a cloud chamber experiment to act as freezing nuclei, thereby establishing the potential activity of the material itself.

scholarly journals Exploring the Mechanisms of Ice Nucleation on Kaolinite: From Deposition Nucleation to Condensation Freezing

2013 ◽  
Vol 71 (1) ◽  
pp. 16-36 ◽  
Author(s):  
André Welti ◽  
Zamin A. Kanji ◽  
F. Lüönd ◽  
Olaf Stetzer ◽  
Ulrike Lohmann
Keyword(s):  
Water Saturation ◽  
Particle Surface ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Appreciable Amount ◽  
Nucleation Mechanisms ◽  
Ice Nucleation Activity

Abstract To identify the temperature and humidity conditions at which different ice nucleation mechanisms are active, the authors conducted experiments on 200-, 400-, and 800-nm size-selected kaolinite particles, exposing them to temperatures between 218 and 258 K and relative humidities with respect to ice (RHi) between 100% and 180%, including the typical conditions for cirrus and mixed-phase-cloud formation. Measurements of the ice active particle fraction as a function of temperature and relative humidity with respect to ice are reported. The authors find enhanced activated fractions when water saturation is reached at mixed-phase-cloud temperatures between 235 and 241 K and a distinct increase in the activated fraction below 235 K at conditions below water saturation. To provide a functional description of the observed ice nucleation mechanisms, the experimental results are analyzed by two different particle-surface models within the framework of classical nucleation theory. Describing the ice nucleation activity of kaolinite particles by assuming deposition nucleation to be the governing mechanism below water saturation was found to be inadequate to represent the experimental data in the whole temperature range investigated. The observed increase in the activated fraction below water saturation and temperatures below 235 K corroborate the assumption that an appreciable amount of adsorbed or capillary condensed water is present on kaolinite particles, which favors ice nucleation.

scholarly journals Parameterization of homogeneous ice nucleation for cloud and climate models based on classical nucleation theory

2012 ◽  
Vol 12 (3) ◽  
pp. 6745-6803
Author(s):  
V. I. Khvorostyanov ◽  
J. A. Curry
Keyword(s):  
Climate Models ◽  
Water Saturation ◽  
Ice Nucleation ◽  
Small Time ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Free Energies ◽  
Elementary Functions ◽  
Analytical Functions ◽  
Semi Empirical

Abstract. A new analytical parameterization of homogeneous ice nucleation is developed based on extended classical nucleation theory including new equations for the critical radii of the ice germs, free energies and nucleation rates as the functions of the temperature and water saturation ratio simultaneously. By representing these quantities as separable products of the analytical functions of the temperature and supersaturation, analytical solutions are found for the integral-differential supersaturation equation and concentration of nucleated crystals. Parcel model simulations are used to illustrate the general behavior of various nucleation properties under various conditions, for justifications of the further key analytical simplifications, and for verification of the resulting parameterization. The final parameterization is based upon the values of the supersaturation that determines the current or maximum concentrations of the nucleated ice crystals. The crystal concentration is analytically expressed as a function of time and can be used for parameterization of homogeneous ice nucleation both in the models with small time steps and for substep parameterization in the models with large time steps. The crystal concentration is expressed analytically via the error functions or elementary functions and depends only on the fundamental atmospheric parameters and parameters of classical nucleation theory. The diffusion and kinetic limits of the new parameterization agree with previous semi-empirical parameterizations.

scholarly journals Technical note: Fundamental aspects of ice nucleation via pore condensation and freezing including Laplace pressure and growth into macroscopic ice

2020 ◽  
Vol 20 (5) ◽  
pp. 3209-3230 ◽  
Author(s):  
Claudia Marcolli
Keyword(s):  
Negative Pressure ◽  
Active Sites ◽  
Water Saturation ◽  
Particle Surface ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Ice Crystal ◽  
Spherical Cap ◽  
Pore Opening ◽  
Pore Condensation

Abstract. Pore condensation and freezing (PCF) is an ice nucleation mechanism that explains ice formation at low ice supersaturation. It assumes that liquid water condenses in pores of solid aerosol particles below water saturation, as described by the Kelvin equation, followed by homogeneous ice nucleation when temperatures are below about 235 K or immersion freezing at higher temperatures, in case the pores contain active sites that induce ice nucleation. Porewater is under tension (negative pressure) below water saturation as described by the Young–Laplace equation. This negative pressure affects the ice nucleation rates and the stability of the pore ice. Here, pressure-dependent parameterizations of classical nucleation theory are developed to quantify the increase in homogeneous ice nucleation rates as a function of tension and to assess the critical diameter of pores that is required to accommodate ice at negative pressures. Growth of ice out of the pore into a macroscopic ice crystal requires ice supersaturation. This supersaturation as a function of the pore opening width is derived, assuming that the ice phase first grows as a spherical cap on top of the pore opening before it starts to expand laterally on the particle surface into a macroscopic ice crystal.

scholarly journals Parameterization of homogeneous ice nucleation for cloud and climate models based on classical nucleation theory

2012 ◽  
Vol 12 (19) ◽  
pp. 9275-9302 ◽  
Author(s):  
V. I. Khvorostyanov ◽  
J. A. Curry
Keyword(s):  
Climate Models ◽  
Water Saturation ◽  
Ice Nucleation ◽  
Small Time ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Free Energies ◽  
Elementary Functions ◽  
Analytical Functions ◽  
Semi Empirical

Abstract. A new analytical parameterization of homogeneous ice nucleation is developed based on extended classical nucleation theory including new equations for the critical radii of the ice germs, free energies and nucleation rates as simultaneous functions of temperature and water saturation ratio. By representing these quantities as separable products of the analytical functions of temperature and supersaturation, analytical solutions are found for the integral-differential supersaturation equation and concentration of nucleated crystals. Parcel model simulations are used to illustrate the general behavior of various nucleation properties under various conditions, for justifications of the further key analytical simplifications, and for verification of the resulting parameterization. The final parameterization is based upon the values of the supersaturation that determines the current or maximum concentrations of the nucleated ice crystals. The crystal concentration is analytically expressed as a function of time and can be used for parameterization of homogeneous ice nucleation both in the models with small time steps and for substep parameterization in the models with large time steps. The crystal concentration is expressed analytically via the error functions or elementary functions and depends only on the fundamental atmospheric parameters and parameters of classical nucleation theory. The diffusion and kinetic limits of the new parameterization agree with previous semi-empirical parameterizations.

scholarly journals Technical note: Fundamental aspects of ice nucleation via pore condensation and freezing including Laplace pressure and growth into macroscopic ice

2019 ◽  
Author(s):  
Claudia Marcolli
Keyword(s):  
Negative Pressure ◽  
Active Sites ◽  
Water Saturation ◽  
Particle Surface ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Ice Crystal ◽  
Spherical Cap ◽  
Pore Opening ◽  
Pore Condensation

Abstract. Pore condensation and freezing (PCF) is an ice nucleation mechanism that explains ice formation at low ice supersaturation. It assumes that liquid water condenses in pores of solid aerosol particles below water saturation, as described by the Kelvin equation, followed by homogeneous ice nucleation when temperatures are below about 235 K or immersion freezing at higher temperatures, in case the pores contain active sites that induce ice nucleation. Pore water is under tension (negative pressure) below water saturation as described by the Young-Laplace equation. This negative pressure affects the ice nucleation rates and the stability of the pore ice. Here, pressure dependent parameterizations of classical nucleation theory are developed to quantify the increase of homogeneous ice nucleation rates as a function of tension and to assess the critical diameter of pores that is required to accommodate ice at negative pressures. For growth out of the pore into a macroscopic ice crystal, ice supersaturation is required. The required supersaturation as a function of the pore opening width is derived, assuming that the ice phase first grows as a spherical cap on top of the pore opening before it starts to expand laterally on the particle surface into a macroscopic ice crystal.

scholarly journals Brief Overview of Ice Nucleation

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 392
Author(s):  
Nobuo Maeda
Keyword(s):  
Molecular Level ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Radiation Balance ◽  
Feature Article ◽  
Aircraft Wings ◽  
Food Engineering ◽  
Research Activities ◽  
Important Field

The nucleation of ice is vital in cloud physics and impacts on a broad range of matters from the cryopreservation of food, tissues, organs, and stem cells to the prevention of icing on aircraft wings, bridge cables, wind turbines, and other structures. Ice nucleation thus has broad implications in medicine, food engineering, mineralogy, biology, and other fields. Nowadays, the growing threat of global warming has led to intense research activities on the feasibility of artificially modifying clouds to shift the Earth’s radiation balance. For these reasons, nucleation of ice has been extensively studied over many decades and rightfully so. It is thus not quite possible to cover the whole subject of ice nucleation in a single review. Rather, this feature article provides a brief overview of ice nucleation that focuses on several major outstanding fundamental issues. The author’s wish is to aid early researchers in ice nucleation and those who wish to get into the field of ice nucleation from other disciplines by concisely summarizing the outstanding issues in this important field. Two unresolved challenges stood out from the review, namely the lack of a molecular-level picture of ice nucleation at an interface and the limitations of classical nucleation theory.

scholarly journals Efficiency of immersion mode ice nucleation on surrogates of mineral dust

2007 ◽  
Vol 7 (19) ◽  
pp. 5081-5091 ◽  
Author(s):  
C. Marcolli ◽  
S. Gedamke ◽  
T. Peter ◽  
B. Zobrist
Keyword(s):  
Contact Angle ◽  
Active Sites ◽  
Quantitative Agreement ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Aqueous Suspensions ◽  
Freezing Temperatures ◽  
Good Agreement ◽  
Heterogeneous Ice Nucleation

Abstract. A differential scanning calorimeter (DSC) was used to explore heterogeneous ice nucleation of emulsified aqueous suspensions of two Arizona test dust (ATD) samples with particle diameters of nominally 0–3 and 0–7 μm, respectively. Aqueous suspensions with ATD concentrations of 0.01–20 wt% have been investigated. The DSC thermograms exhibit a homogeneous and a heterogeneous freezing peak whose intensity ratios vary with the ATD concentration in the aqueous suspensions. Homogeneous freezing temperatures are in good agreement with recent measurements by other techniques. Depending on ATD concentration, heterogeneous ice nucleation occurred at temperatures as high as 256 K or down to the onset of homogeneous ice nucleation (237 K). For ATD-induced ice formation Classical Nucleation Theory (CNT) offers a suitable framework to parameterize nucleation rates as a function of temperature, experimentally determined ATD size, and emulsion droplet volume distributions. The latter two quantities serve to estimate the total heterogeneous surface area present in a droplet, whereas the suitability of an individual heterogeneous site to trigger nucleation is described by the compatibility function (or contact angle) in CNT. The intensity ratio of homogeneous to heterogeneous freezing peaks is in good agreement with the assumption that the ATD particles are randomly distributed amongst the emulsion droplets. The observed dependence of the heterogeneous freezing temperatures on ATD concentrations cannot be described by assuming a constant contact angle for all ATD particles, but requires the ice nucleation efficiency of ATD particles to be (log)normally distributed amongst the particles. Best quantitative agreement is reached when explicitly assuming that high-compatibility sites are rare and that therefore larger particles have on average more and better active sites than smaller ones. This analysis suggests that a particle has to have a diameter of at least 0.1 μm to exhibit on average one active site.

scholarly journals A new temperature- and humidity-dependent surface site density approach for deposition ice nucleation

2015 ◽  
Vol 15 (7) ◽  
pp. 3703-3717 ◽  
Author(s):  
I. Steinke ◽  
C. Hoose ◽  
O. Möhler ◽  
P. Connolly ◽  
T. Leisner
Keyword(s):  
Contact Angle ◽  
Relative Humidity ◽  
Active Surface ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Aerosol Size Distribution ◽  
Surface Site ◽  
Linear Behavior ◽  
Temperature And Humidity

Abstract. Deposition nucleation experiments with Arizona Test Dust (ATD) as a surrogate for mineral dusts were conducted at the AIDA cloud chamber at temperatures between 220 and 250 K. The influence of the aerosol size distribution and the cooling rate on the ice nucleation efficiencies was investigated. Ice nucleation active surface site (INAS) densities were calculated to quantify the ice nucleation efficiency as a function of temperature, humidity and the aerosol surface area concentration. Additionally, a contact angle parameterization according to classical nucleation theory was fitted to the experimental data in order to relate the ice nucleation efficiencies to contact angle distributions. From this study it can be concluded that the INAS density formulation is a very useful tool to describe the temperature- and humidity-dependent ice nucleation efficiency of ATD particles. Deposition nucleation on ATD particles can be described by a temperature- and relative-humidity-dependent INAS density function ns(T, Sice) with ns(xtherm) = 1.88 ×105 · exp(0.2659 · xtherm) [m−2] , (1) where the temperature- and saturation-dependent function xtherm is defined as xtherm = −(T−273.2)+(Sice−1) ×100, (2) with the saturation ratio with respect to ice Sice >1 and within a temperature range between 226 and 250 K. For lower temperatures, xtherm deviates from a linear behavior with temperature and relative humidity over ice. Also, two different approaches for describing the time dependence of deposition nucleation initiated by ATD particles are proposed. Box model estimates suggest that the time-dependent contribution is only relevant for small cooling rates and low number fractions of ice-active particles.

scholarly journals Analysis of the effect of water activity on ice formation using a new thermodynamic framework

2014 ◽  
Vol 14 (14) ◽  
pp. 7665-7680 ◽  
Author(s):  
D. Barahona
Keyword(s):  
Water Activity ◽  
Nucleation Rate ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Cloud Formation ◽  
Classical Nucleation Theory ◽  
Solid Matrix ◽  
Effect Of Water ◽  
Thermodynamic Framework ◽  
New Framework

Abstract. In this work a new thermodynamic framework is developed and used to investigate the effect of water activity on the formation of ice within supercooled droplets. The new framework is based on a novel concept where the interface is assumed to be made of liquid molecules "trapped" by the solid matrix. It also accounts for the change in the composition of the liquid phase upon nucleation. Using this framework, new expressions are developed for the critical ice germ size and the nucleation work with explicit dependencies on temperature and water activity. However unlike previous approaches, the new model does not depend on the interfacial tension between liquid and ice. The thermodynamic framework is introduced within classical nucleation theory to study the effect of water activity on the ice nucleation rate. Comparison against experimental results shows that the new approach is able to reproduce the observed effect of water activity on the nucleation rate and the freezing temperature. It allows for the first time a phenomenological derivation of the constant shift in water activity between melting and nucleation. The new framework offers a consistent thermodynamic view of ice nucleation, simple enough to be applied in atmospheric models of cloud formation.

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