On the role of surface charges for homogeneous freezing of supercooled water microdroplets

Rzesanke, Daniel; Nadolny, Jens; Duft, Denis; Müller, R.; Kiselev, Alexei; Leisner, Thomas

doi:10.1039/c2cp23653b

Cited by 36 publications

(51 citation statements)

References 17 publications

(25 reference statements)

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“…Each J hom data set was weighted equally by representing it with three data points, at the maximum, minimum, and average temperature, determined from a straight line fit to ln(J hom ) versus T. In addition, we grouped measurements from separate papers, but made with the same instrument and methodology, into single data sets (i.e., we grouped data from Duft and Leisner 58 with Rzesanke et al, 59 Stöckel et al 61 with Kabath et al, 62 as well as Hoyle et al 64 with Lüönd et al 65 ). The resulting CNT fits are shown in Figure 3, with different lines originating from employing different parameterizations of D(T).…”

Section: Fitting the Cnt-based Model To Experimental Datamentioning

confidence: 99%

“…1,56 In this study, we have selected a subset [56][57][58][59][60][61][62][63][64][65][66][67][68] of the available data sets for the purposes of constraining the new parameterization. The criteria for selection were (i) minimal and well defined uncertainties, (ii) good reproducibility within the data set, and (iii) an internal droplet pressure of about 1 bar.…”

Section: Fitting the Cnt-based Model To Experimental Datamentioning

confidence: 99%

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A physically constrained classical description of the homogeneous nucleation of ice in water

Koop

Murray

2016

The Journal of Chemical Physics

117

155

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Liquid water can persist in a supercooled state to below 238 K in the Earth's atmosphere, a temperature range where homogeneous nucleation becomes increasingly probable. However, the rate of homogeneous ice nucleation in supercooled water is poorly constrained, in part, because supercooled water eludes experimental scrutiny in the region of the homogeneous nucleation regime where it can exist only fleetingly. Here we present a new parameterization of the rate of homogeneous ice nucleation based on classical nucleation theory. In our approach, we constrain the key terms in classical theory, i.e., the diffusion activation energy and the ice-liquid interfacial energy, with physically consistent parameterizations of the pertinent quantities. The diffusion activation energy is related to the translational self-diffusion coefficient of water for which we assess a range of descriptions and conclude that the most physically consistent fit is provided by a power law. The other key term is the interfacial energy between the ice embryo and supercooled water whose temperature dependence we constrain using the Turnbull correlation, which relates the interfacial energy to the difference in enthalpy between the solid and liquid phases. The only adjustable parameter in our model is the absolute value of the interfacial energy at one reference temperature. That value is determined by fitting this classical model to a selection of laboratory homogeneous ice nucleation data sets between 233.6 K and 238.5 K. On extrapolation to temperatures below 233 K, into a range not accessible to standard techniques, we predict that the homogeneous nucleation rate peaks between about 227 and 231 K at a maximum nucleation rate many orders of magnitude lower than previous parameterizations suggest. This extrapolation to temperatures below 233 K is consistent with the most recent measurement of the ice nucleation rate in micrometer-sized droplets at temperatures of 227-232 K on very short time scales using an X-ray laser technique. In summary, we present a new physically constrained parameterization for homogeneous ice nucleation which is consistent with the latest literature nucleation data and our physical understanding of the properties of supercooled water. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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Section: Fitting the Cnt-based Model To Experimental Datamentioning

confidence: 99%

Section: Fitting the Cnt-based Model To Experimental Datamentioning

confidence: 99%

A physically constrained classical description of the homogeneous nucleation of ice in water

Koop

Murray

2016

The Journal of Chemical Physics

117

155

View full text Add to dashboard Cite

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“…Uncertainties could arise in the case of levitation through an electrostatic field, but no direct influence of the droplet surface charge on the nucleation rate was found [19] [33]. In the case of acoustic levitation, a dynamic nucleation of ice can be favoured due to the presence of gas bubbles in the supercooled water.…”

Section: Reported Datamentioning

confidence: 99%

“…where N 0 is the total number of investigated supercooled droplets, each having the same volume V, N is the number of unfrozen droplets after a time t. By plotting ln (N/N 0 ) vs. time, it is possible to calculate directly the rate of homogeneous nucleation once the volume of the droplets is known [19] [33].…”

Section: Theoretical Approachmentioning

confidence: 99%

“…Deviations from these assumptions (e.g. preferred nucleation close to the surface) should be detectable as a change in the temporal evolution of the decay curve [33]. Assuming that the nucleation is attributed either solely to volume-or surface-initiated nucleation, Equation (4) can be rearranged by using the droplet radius, as follows:…”

Section: Theoretical Approachmentioning

confidence: 99%

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Does the Homogeneous Ice Nucleation Initiate in the Bulk Volume or at the Surface of Super-Cooled Water Droplets? A Review

Santachiara¹,

Belosi²

2014

ACS

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The formation of ice in clouds can occur through primary processes, either homogeneously or heterogeneously triggered by aerosol particles called ice nuclei, as well as through secondary processes. The homogeneous ice nucleation process involves only pure water or solution droplets. Homogeneous freezing is crucial for the microphysics in the formation of high-altitude cirrus and polar stratospheric clouds, and also in the glaciation of thunderclouds, at temperatures below about 235 K. Nucleation rates in supercooled water have been measured using different experimental techniques: expansion cloud chambers, water-in-oil emulsions, levitation methods, free falling droplets, supersonic nozzles, field measurements, and molecular dynamics simulations. An important question concerns the possibility that the nucleation process in supercooled water can occur not only in the interior volume of the droplet, but even at or close to its surface. Even if there is no conclusive evidence, the majority of experimental and theoretical results suggest that the contribution of surface nucleation increases with decreasing radius of the supercooled droplets, and the surface (or sub-surface) nucleation rate is prevalent for droplets with radius lower than about 5 μm. If homogeneous freezing initiates at the droplet surface, the freezing rate should depend on the droplet size, and even a slight contamination by molecules within the surface layer could hamper the rate of the nucleation process.

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Sensitivity of liquid clouds to homogenous freezing parameterizations

Herbert

Murray

Dobbie

et al. 2015

Geophysical Research Letters

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Water droplets in some clouds can supercool to temperatures where homogeneous ice nucleation becomes the dominant freezing mechanism. In many cloud resolving and mesoscale models, it is assumed that homogeneous ice nucleation in water droplets only occurs below some threshold temperature typically set at −40°C. However, laboratory measurements show that there is a finite rate of nucleation at warmer temperatures. In this study we use a parcel model with detailed microphysics to show that cloud properties can be sensitive to homogeneous ice nucleation as warm as −30°C. Thus, homogeneous ice nucleation may be more important for cloud development, precipitation rates, and key cloud radiative parameters than is often assumed. Furthermore, we show that cloud development is particularly sensitive to the temperature dependence of the nucleation rate. In order to better constrain the parameterization of homogeneous ice nucleation laboratory measurements are needed at both high (>−35°C) and low (<−38°C) temperatures.Key PointsHomogeneous freezing may be significant as warm as −30°CHomogeneous freezing should not be represented by a threshold approximationThere is a need for an improved parameterization of homogeneous ice nucleation

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On the role of surface charges for homogeneous freezing of supercooled water microdroplets

Cited by 36 publications

References 17 publications

A physically constrained classical description of the homogeneous nucleation of ice in water

A physically constrained classical description of the homogeneous nucleation of ice in water

Does the Homogeneous Ice Nucleation Initiate in the Bulk Volume or at the Surface of Super-Cooled Water Droplets? A Review

Sensitivity of liquid clouds to homogenous freezing parameterizations

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