Representing time-dependent freezing behaviour in immersion mode ice nucleation

Herbert, Ross; Murray, Benjamin J.; Whale, Thomas F.; Dobbie, S.; Atkinson, James

doi:10.5194/acp-14-8501-2014

Cited by 75 publications

(128 citation statements)

References 52 publications

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“…1. The finding of this exercise is consistent with previously published work on time-dependent freezing such as those reported by Barahona (2012), , and Herbert et al (2014), amongst others.…”

Section: Internal Variability and Its Impact On Time-dependent Freezingsupporting

confidence: 83%

Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

2016

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Abstract. Heterogeneous ice nucleation remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established parameterization of immersion freezing properties. Here, we formulate an ice active, surface-sitebased stochastic model of heterogeneous freezing with the unique feature of invoking a continuum assumption on the ice nucleating activity (contact angle) of an aerosol particle's surface that requires no assumptions about the size or number of active sites. The result is a particle-specific property g that defines a distribution of local ice nucleation rates. Upon integration, this yields a full freezing probability function for an ice nucleating particle.Current cold plate droplet freezing measurements provide a valuable and inexpensive resource for studying the freezing properties of many atmospheric aerosol systems. We apply our g framework to explain the observed dependence of the freezing temperature of droplets in a cold plate on the concentration of the particle species investigated. Normalizing to the total particle mass or surface area present to derive the commonly used ice nuclei active surface (INAS) density (n s ) often cannot account for the effects of particle concentration, yet concentration is typically varied to span a wider measurable freezing temperature range. A method based on determining what is denoted an ice nucleating species' specific critical surface area is presented and explains the concentration dependence as a result of increasing the variability in ice nucleating active sites between droplets. By applying this method to experimental droplet freezing data from four different systems, we demonstrate its ability to interpret immersion freezing temperature spectra of droplets containing variable particle concentrations.It is shown that general active site density functions, such as the popular n s parameterization, cannot be reliably extrapolated below this critical surface area threshold to describe freezing curves for lower particle surface area concentrations. Freezing curves obtained below this threshold translate to higher n s values, while the n s values are essentially the same from curves obtained above the critical area threshold; n s should remain the same for a system as concentration is varied. However, we can successfully predict the lower concentration freezing curves, which are more atmospherically relevant, through a process of random sampling from g distributions obtained from high particle concentration data. Our analysis is applied to cold plate freezing measurements of droplets containing variable concentrations of particles from NX illite minerals, MCC cellulose, and commercial Snomax bacterial particles. Parameterizations that can predict the temporal evolution of the frozen fraction of cloud droplets in larger atmospheric models are also derived from this new fra...

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Section: Internal Variability and Its Impact On Time-dependent Freezingsupporting

confidence: 83%

Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

2016

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“…The role of time dependence in ice nucleation has recently been extensively discussed (Vali, 2008(Vali, , 2014Vali et al, 2014Vali et al, , 2015Herbert et al, 2014;. For feldspar (at least for BCS 376 microcline) it is thought that the time dependence of nucleation is relatively weak and that the particle to particle, or active site to active site, variability is much more important (Herbert et al, 2014).…”

Section: Experimental Methods and Data Analysismentioning

confidence: 99%

“…Throughout this paper we refer to nucleation occurring on active sites, or specific sites, on the surface of feldspar. It is thought that nucleation by most ice active minerals is consistent with nucleation on active sites with a broad spectrum of activities (Marcolli et al, 2007;Lüönd et al, 2010;Niedermeier et al, 2010;Augustin-Bauditz et al, 2014;Herbert et al, 2014;Vali, 2014;Wex et al, 2014;Wheeler et al, 2015;Hiranuma et al, 2015;Hartmann et al, 2016). However, the nature of these active sites is not known.…”

Section: The Stability Of Active Sitesmentioning

confidence: 99%

Not all feldspars are equal: a survey of ice nucleating properties across the feldspar group of minerals

et al. 2016

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Abstract. Mineral dust particles from wind-blown soils are known to act as effective ice nucleating particles in the atmosphere and are thought to play an important role in the glaciation of mixed phase clouds. Recent work suggests that feldspars are the most efficient nucleators of the minerals commonly present in atmospheric mineral dust. However, the feldspar group of minerals is complex, encompassing a range of chemical compositions and crystal structures. To further investigate the ice-nucleating properties of the feldspar group we measured the ice nucleation activities of 15 characterized feldspar samples. We show that alkali feldspars, in particular the potassium feldspars, generally nucleate ice more efficiently than feldspars in the plagioclase series which contain significant amounts of calcium. We also find that there is variability in ice nucleating ability within these groups. While five out of six potassium-rich feldspars have a similar ice nucleating ability, one potassium rich feldspar sample and one sodium-rich feldspar sample were significantly more active. The hyper-active Na-feldspar was found to lose activity with time suspended in water with a decrease in mean freezing temperature of about 16 • C over 16 months; the mean freezing temperature of the hyper-active K-feldspar decreased by 2 • C over 16 months, whereas the "standard" K-feldspar did not change activity within the uncertainty of the experiment. These results, in combination with a review of the available literature data, are consistent with the previous findings that potassium feldspars are important components of arid or fertile soil dusts for ice nucleation. However, we also show that there is the possibility that some alkali feldspars may have enhanced ice nucleating abilities, which could have implications for prediction of ice nucleating particle concentrations in the atmosphere.

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“…This specific approach neglects the time dependence of freezing, and assumes that a characteristic condition (e.g., temperature) must be met to nucleate ice. The semi-deterministic forms of the singular approach have a cooling rate dependence incorporated (Vali, 2008;Herbert et al, 2014). Predicting ice nucleation from a singular perspective does not require a vast knowledge of particle-specific parameters (e.g., surface composition, structures, surface tension and solubility) that are particular to each ice nucleus and, therefore, enables ice nucleation parameterization to be relatively simple and efficient compared to the CNT-based approaches (Murray et al, 2011).…”

Section: Stochastic Nature Of Freezing and Time Dependencementioning

confidence: 99%

A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques

et al. 2015

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Abstract. Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques.Within the framework of INUIT (Ice Nuclei Research Unit), we distributed an illite-rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain Published by Copernicus Publications on behalf of the European Geosciences Union. N. Hiranuma et al.: A comparison of 17 IN measurement techniquesIN data as a function of particle concentration, temperature (T ), cooling rate and nucleation time. A total of 17 measurement methods were involved in the data intercomparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while 10 other instruments employed water vapor condensation onto drydispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing data set was evaluated using the ice nucleation active surface-site density, n s , to develop a representative n s (T ) spectrum that spans a wide temperature range (−37 • C < T < −11 • C) and covers 9 orders of magnitude in n s .In general, the 17 immersion freezing measurement techniques deviate, within a range of about 8 • C in terms of temperature, by 3 orders of magnitude with respect to n s . In addition, we show evidence that the immersion freezing efficiency expressed in n s of illite NX particles is relatively independent of droplet size, particle mass in suspension, particle size and cooling rate during freezing. A strong temperature dependence and weak time and size dependence of the immersion freezing efficiency of illite-rich clay mineral particles enabled the n s parameterization solely as a function of temperature. We also characterized the n s (T ) spectra and identified a section with a steep slope between −20 and −27 • C, where a large fraction of active sites of our test dust may trigger immersion freezing. This slope was followed by a region with a gentler slope at temperatures below −27 • C. While the agreement between different instruments was reasonable below ∼ −27 • C, there seemed to be a different trend in the temperature-dependent ice nucleation activity from the suspension and dry-dispersed particle measurements for this mineral dust, in particular at higher temperatures. For instance,...

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Representing time-dependent freezing behaviour in immersion mode ice nucleation

Cited by 75 publications

References 52 publications

Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

Not all feldspars are equal: a survey of ice nucleating properties across the feldspar group of minerals

A comprehensive laboratory study on the immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques

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