Interactive comment on ``Classical nucleation theory of immersion freezing: Sensitivity of contact angle schemes to thermodynamic and kinetic parameters'' by L. Ickes et al.

2016 ◽  
Author(s):  
Peter Alpert
Keyword(s):  
Contact Angle ◽  
Kinetic Parameters ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Immersion Freezing ◽  
Thermodynamic And Kinetic Parameters

scholarly journals Classical nucleation theory of immersion freezing: sensitivity of contact angle schemes to thermodynamic and kinetic parameters

2017 ◽  
Vol 17 (3) ◽  
pp. 1713-1739 ◽  
Author(s):  
Luisa Ickes ◽  
André Welti ◽  
Ulrike Lohmann
Keyword(s):  
Experimental Data ◽  
Contact Angle ◽  
Kinetic Parameters ◽  
Aerosol Particles ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Kinetic And Thermodynamic Parameters ◽  
Immersion Freezing ◽  
Thermodynamic And Kinetic Parameters ◽  
Homogeneous Freezing

Abstract. Heterogeneous ice formation by immersion freezing in mixed-phase clouds can be parameterized in general circulation models (GCMs) by classical nucleation theory (CNT). CNT parameterization schemes describe immersion freezing as a stochastic process, including the properties of insoluble aerosol particles in the droplets. There are different ways to parameterize the properties of aerosol particles (i.e., contact angle schemes), which are compiled and tested in this paper. The goal of this study is to find a parameterization scheme for GCMs to describe immersion freezing with the ability to shift and adjust the slope of the freezing curve compared to homogeneous freezing to match experimental data. We showed in a previous publication that the resulting freezing curves from CNT are very sensitive to unconstrained kinetic and thermodynamic parameters in the case of homogeneous freezing. Here we investigate how sensitive the outcome of a parameter estimation for contact angle schemes from experimental data is to unconstrained kinetic and thermodynamic parameters. We demonstrate that the parameters describing the contact angle schemes can mask the uncertainty in thermodynamic and kinetic parameters. Different CNT formulations are fitted to an extensive immersion freezing dataset consisting of size-selected measurements as a function of temperature and time for different mineral dust types, namely kaolinite, illite, montmorillonite, microcline (K-feldspar), and Arizona test dust. We investigated how accurate different CNT formulations (with estimated fit parameters for different contact angle schemes) reproduce the measured freezing data, especially the time and particle size dependence of the freezing process. The results are compared to a simplified deterministic freezing scheme. In this context, we evaluated which CNT-based parameterization scheme able to represent particle properties is the best choice to describe immersion freezing in a GCM.

scholarly journals Classical nucleation theory of immersion freezing: Sensitivity of contact angle schemes to thermodynamic and kinetic parameters

2016 ◽  
Author(s):  
L. Ickes ◽  
A. Welti ◽  
U. Lohmann
Keyword(s):  
Experimental Data ◽  
Contact Angle ◽  
Kinetic Parameters ◽  
Aerosol Particles ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Kinetic And Thermodynamic Parameters ◽  
Immersion Freezing ◽  
Thermodynamic And Kinetic Parameters ◽  
Homogeneous Freezing

Abstract. Heterogeneous ice formation by immersion freezing in mixed-phase clouds can be parameterized in general circulation models (GCMs) by Classical Nucleation Theory (CNT). CNT parameterization schemes describe freezing as a stochastic process including the properties of insoluble aerosol particles, so called ice nuclei, in the droplets. There are different ways how to describe the properties of aerosol particles (i.e. contact angle schemes), which are compiled and tested in this paper. The goal of this study is to find a parameterization scheme for GCMs to describe immersion freezing with the ability to shift and adjust the slope of the freezing curve compared to homogeneous freezing to match experimental data. The results of using CNT are very sensitive to unconstrained kinetic and thermodynamic parameters in the case of homogeneous freezing leading to uncertainties in calculated nucleation rates Jhom of several orders of magnitude. Here we investigate how sensitive the outcome of a parameter estimation for contact angle schemes from experimental data is to kinetic and thermodynamic parameters. We show that additional free parameter can mask the uncertainty of Jimm due to thermodynamic and kinetic parameters. Different CNT formulations are fitted to an extensive immersion freezing dataset as a function of particle diameter (d), temperature T and time t for different mineral dust types, namely kaolinite, illite, montmorillonite, microcline (K-feldspar) and Arizona test dust. It is investigated how accurate different CNT formulations (with the estimated fit parameters) reproduce the measured freezing curves, especially the time and particle size dependence of the freezing process. The results are compared to a simplified deterministic freezing scheme. It is evaluated in this context which CNT based parameterization scheme to represent particle properties is a good choice to describe immersion freezing in a GCM.

Classical nucleation theory of homogeneous freezing of water: thermodynamic and kinetic parameters

2015 ◽  
Vol 17 (8) ◽  
pp. 5514-5537 ◽  
Author(s):  
Luisa Ickes ◽  
André Welti ◽  
Corinna Hoose ◽  
Ulrike Lohmann
Keyword(s):  
Kinetic Parameters ◽  
Thermodynamic Parameters ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Kinetic And Thermodynamic Parameters ◽  
Thermodynamic And Kinetic Parameters ◽  
Homogeneous Freezing

Different formulations of the kinetic and thermodynamic parameters of CNT are evaluated against measured nucleation rates.

Relation between metastable zone width and induction time of butyl paraben in ethanol

CrystEngComm ◽  
2015 ◽  
Vol 17 (3) ◽  
pp. 577-586 ◽  
Author(s):  
Huaiyu Yang
Keyword(s):  
Kinetic Parameters ◽  
Induction Time ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Metastable Zone Width ◽  
Zone Width ◽  
Metastable Zone ◽  
Thermodynamic And Kinetic Parameters ◽  
Experimental Values

A relation between induction time and metastable zone width has been developed based on Classical Nucleation Theory, by which relation metastable zone width has been extrapolated from the induction time results and compared with experimental values. Influences of several thermodynamic and kinetic parameters on metastable zone width have been estimated.

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 CNT Parameterization Based on the Observed INP Concentration during Arctic Summer Campaigns in a Marine Environment

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 916 ◽  
Author(s):  
Ana Cirisan ◽  
Eric Girard ◽  
Jean-Pierre Blanchet ◽  
Setigui Aboubacar Keita ◽  
Wanmin Gong ◽  
...  
Keyword(s):  
Particle Concentration ◽  
Climate Models ◽  
Canadian Arctic ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Atmospheric Models ◽  
Ice Clouds ◽  
Immersion Freezing ◽  
Aerosol Cloud Interactions ◽  
The Right

Aerosol–cloud interactions present a large source of uncertainties in atmospheric and climate models. One of the main challenges to simulate ice clouds is to reproduce the right ice nucleating particle concentration. In this study, we derive a parameterization for immersion freezing according to the classical nucleation theory. Our objective was to constrain this parameterization with observations taken over the Canadian Arctic during the Amundsen summer 2014 and 2016 campaigns. We found a linear dependence of contact angle and temperature. Using this approach, we were able to reproduce the scatter in ice nucleated particle concentrations within a factor 5 of observed values with a small negative bias. This parameterization would be easy to implement in climate and atmospheric models, but its representativeness has to first be validated against other datasets.

scholarly journals Immersion freezing of water and aqueous ammonium sulfate droplets initiated by humic-like substances as a function of water activity

2013 ◽  
Vol 13 (13) ◽  
pp. 6603-6622 ◽  
Author(s):  
Y. J. Rigg ◽  
P. A. Alpert ◽  
D. A. Knopf
Keyword(s):  
Water Activity ◽  
Active Sites ◽  
Melting Curve ◽  
Contact Angles ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Surface Areas ◽  
Immersion Freezing ◽  
Freezing Temperatures

Abstract. Immersion freezing of water and aqueous (NH4)2SO4 droplets containing leonardite (LEO) and Pahokee peat (PP) serving as surrogates for humic-like substances (HULIS) has been investigated. Organic aerosol containing HULIS are ubiquitous in the atmosphere; however, their potential for ice cloud formation is uncertain. Immersion freezing has been studied for temperatures as low as 215 K and solution water activity, aw, from 0.85 to 1.0. The freezing temperatures of water and aqueous solution droplets containing LEO and PP are 5–15 K warmer than homogeneous ice nucleation temperatures. Heterogeneous freezing temperatures can be represented by a horizontal shift of the ice melting curve as a function of solution aw by Δaw = 0.2703 and 0.2466, respectively. Corresponding hetrogeneous ice nucleation rate coefficients, Jhet, are (9.6 ± 2.5)×104 and (5.4 ± 1.4)×104 cm−2 s−1 for LEO and PP containing droplets, respectively, and remain constant along freezing curves characterized by Δaw. Consequently predictions of freezing temperatures and kinetics can be made without knowledge of the solute type when relative humidity and ice nuclei (IN) surface areas are known. The acquired ice nucleation data are applied to evaluate different approaches to fit and reproduce experimentally derived frozen fractions. In addition, we apply a basic formulation of classical nucleation theory (α(T)-model) to calculate contact angles and frozen fractions. Contact angles calculated for each ice nucleus as a function of temperature, α(T)-model, reproduce exactly experimentally derived frozen fractions without involving free-fit parameters. However, assigning the IN a single contact angle for the entire population (single-α model) is not suited to represent the frozen fractions. Application of α-PDF, active sites, and deterministic model approaches to measured frozen fractions yield similar good representations. Furthermore, when using a single parameterization of α-PDF or active sites distribution to fit all individual aw immersion freezing data simultaneously, frozen fraction curves are not reproduced. This implies that these fitting formulations cannot be applied to immersion freezing of aqueous solutions, and suggests that derived fit parameters do not represent independent particle properties. Thus, from fitting frozen fractions only, the underlying ice nucleation mechanism and nature of the ice nucleating sites cannot be inferred. In contrast to using fitted functions obtained to represent experimental conditions only, we suggest to use experimentally derived Jhet as a function of temperature and aw that can be applied to conditions outside of those probed in laboratory. This is because Jhet(T) is independent of time and IN surface areas in contrast to the fit parameters obtained by representation of experimentally derived frozen fractions.

scholarly journals Bacteria as Cloud Condensation Nuclei (CCN) in the Atmosphere

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 786
Author(s):  
Mihalis Lazaridis
Keyword(s):  
Contact Angle ◽  
Sulfuric Acid ◽  
Cloud Condensation Nuclei ◽  
Sulfuric Acid Concentration ◽  
Contact Angles ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Condensation Nuclei ◽  
Critical Cluster ◽  
Model Simulations

Bacteria activation and cloud condensation nuclei (CCN) formation have been studied in the atmosphere using the classical theory of heterogeneous nucleation. Simulations were performed for the binary system of sulfuric acid/water using laboratory-determined contact angles. Realistic model simulations were performed at different atmospheric heights for a set of 140 different bacteria. Model simulations showed that bacteria activation is a potentially favorable process in the atmosphere which may be enhanced at lower temperatures. CCN formation from bacteria nuclei is dependent on ambient atmospheric conditions (temperature, relative humidity), bacteria size, and sulfuric acid concentration. Furthermore, a critical parameter for the determination of bacteria activation is the value of the intermolecular potential between the bacteria’s surface and the critical cluster formed at their surface. In the classical nucleation theory, this is parameterized with the contact angle between substrate and critical cluster. Therefore, the dataset of laboratory values for the contact angle of water on different bacteria substrates needs to be enriched for realistic simulations of bacteria activation in the atmosphere.

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