Manchester Ice Nucleus Counter (MINC) measurements from the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007)

Jones, Huw; Flynn, Michael J.; DeMott, Paul J.; Möhler, Ottmar

doi:10.5194/acp-11-53-2011

Cited by 24 publications

(22 citation statements)

References 29 publications

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“…For example, during the 2007 International Workshop on Comparing Ice Nucleation Measuring Systems (ICIS-2007) in Germany Möhler et al, 2008), instruments encompassing continuous flow diffusion chambers (e.g., the CFDC of CSU), static diffusion chambers, mixing chambers, and expansion chambers were used to investigate different particle types including mineral dust and bacteria (Snomax ® , hereafter Snomax). In general, the fraction of aerosols serving as INPs as a function of temperature and RH between all instruments agreed within a factor of 4-5 (DeMott et al, 20084-5 (DeMott et al, , 20114-5 (DeMott et al, , 2015Jones et al, 2011). Similar differences were observed between the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) cloud expansion chamber (Möhler et al, 2006) and the CFDC of CSU during the Third AerosolCloud Interaction (ACI03) campaign with samples of ambient aerosols and coated and uncoated Asian dust .…”

Section: Moudi-dft and Cfdc Intercomparisonmentioning

confidence: 99%

The micro-orifice uniform deposit impactor–droplet freezing technique (MOUDI-DFT) for measuring concentrations of ice nucleating particles as a function of size: improvements and initial validation

et al. 2015

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Abstract. The micro-orifice uniform deposit impactordroplet freezing technique (MOUDI-DFT) combines particle collection by inertial impaction (via the MOUDI) and a microscope-based immersion freezing apparatus (the DFT) to measure atmospheric concentrations of ice nucleating particles (INPs) as a function of size and temperature. In the first part of this study we improved upon this recently introduced technique. Using optical microscopy, we investigated the non-uniformity of MOUDI aerosol deposits at spatial resolutions of 1, 0.25 mm, and for some stages when necessary 0.10 mm. The results from these measurements show that at a spatial resolution of 1 mm and less, the concentration of particles along the MOUDI aerosol deposits can vary by an order of magnitude or more. Since the total area of a MOUDI aerosol deposit ranges from 425 to 605 mm 2 and the area analyzed by the DFT is approximately 1.2 mm 2 , this non-uniformity needs to be taken into account when using the MOUDI-DFT to determine atmospheric concentrations of INPs. Measurements of the non-uniformity of the MOUDI aerosol deposits were used to select positions on the deposits that had relatively small variations in particle concentration and to build substrate holders for the different MOUDI stages. These substrate holders improve reproducibility by holding the substrate in the same location for each measurement and ensure that DFT analysis is only performed on substrate regions with relatively small variations in particle concentration. In addition, the deposit non-uniformity was used to determine correction factors that take the non-uniformity into account when determining atmospheric concentrations of INPs. In the second part of this study, the MOUDI-DFT utilizing the new substrate holders was compared to the continuous flow diffusion chamber (CFDC) technique of Colorado State University. The intercomparison was done using INP concentrations found by the two instruments during ambient measurements of continental aerosols. Results from two sampling periods were compared, and the INP concentrations determined by the two techniques agreed within experimental uncertainty. The agreement observed here is commensurate with the level of agreement found in other studies where CFDC results were compared to INP concentrations measured with other methods.

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Section: Moudi-dft and Cfdc Intercomparisonmentioning

confidence: 99%

The micro-orifice uniform deposit impactor–droplet freezing technique (MOUDI-DFT) for measuring concentrations of ice nucleating particles as a function of size: improvements and initial validation

et al. 2015

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“…Koehler et al (2010) observed ice nucleation at water saturation at highest temperatures of 237-243 K for 200-400 nm particles. An activated fraction of 0.1 % at water saturation at ∼ 251 K was observed by Jones et al (2011) for an aerosol containing ATD particles with diameters < 1 µm. The data point at 256 K is uncertain because it was measured at a supersaturation with respect to water of 5 %.…”

Section: Arizona Test Dust (Atd)mentioning

confidence: 99%

Deposition nucleation viewed as homogeneous or immersion freezing in pores and cavities

2014

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Abstract. Heterogeneous ice nucleation is an important mechanism for the glaciation of mixed phase clouds and may also be relevant for cloud formation and dehydration at the cirrus cloud level. It is thought to proceed through different mechanisms, namely contact, condensation, immersion and deposition nucleation. Conceptually, deposition nucleation is the only pathway that does not involve liquid water, but occurs by direct water vapor deposition onto a surface. This study challenges this classical view by putting forward the hypothesis that what is called deposition nucleation is in fact pore condensation and freezing (PCF) occurring in voids and cavities that may form between aggregated primary particles and host water at relative humidity RH w < 100 % because of the inverse Kelvin effect. Homogeneous ice nucleation is expected to occur below 235 K when at least one pore is filled with water. Ice nucleation in pores may also happen in immersion mode but with a lower probability because it requires at least one active site in a water filled pore. Therefore a significant enhancement in ice nucleation efficiency is expected when temperature falls below 235 K. For a deposition nucleation process from water vapor no discontinuous change in ice nucleation efficiency should occur at T = 235 K because no liquid water is involved in this process. Studies on freezing in confinement carried out on mesoporous silica materials such as SBA-15, SBA-16, MCM-41, zeolites and KIT have shown that homogeneous ice nucleation occurs abruptly at T = 230-235 K in pores with diameters (D) of 3.5-4 nm or larger but only gradually at T = 210-230 K in pores with D = 2.5-3.5 nm. Pore analysis of clay minerals shows that kaolinites exhibit pore structures with pore diameters (D p ) of 20-50 nm. The mesoporosity of illites and montmorillonites is characterized by pores with D p = 2-5 nm. The number and size of pores is distinctly increased in acid treated montmorillonites like K10. Water adsorption isotherms of MCM-41 show that pores with D p = 3.5-4 nm fill with water at RH w = 56-60 % in accordance with an inverse Kelvin effect. Water in such pores should freeze homogeneously for T < 235 K even before relative humidity with respect to ice (RH i ) reaches ice saturation. Ice crystal growth by water vapor deposition from the gas phase is therefore expected to set in as soon as RH i > 100 %. Pores with D > 7.5 nm fill with water at RH i > 100 % for T < 235 K and are likely to freeze homogeneously as soon as they are filled with water. Given the pore structure of clay minerals, PCF should be highly efficient for T < 235 K and may occur at T > 235 K in particles that exhibit active sites for immersion freezing within pores. Most ice nucleation studies on clay minerals and mineral dusts indeed show a strong increase in ice nucleation efficiency when temperature is decreased below 235 K in accordance with PCF and are not explicable by the classical view of deposition nucleation. PCF is probably also the prevailing ice nucleation mechanism below...

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“…5a therefore lie on the water saturation line. Only for Snomax ™ , an artificial snow inducer consisting of freeze-dried Pseudomonas syringae bacteria cells, cell debris and dried culture medium (Lagriffoul et al, 2010), deposition nucleation has been studied extensively (Chernoff and Bertram, 2010;Jones et al, 2011;Kanji et al, 2011;DeMott et al, 2011). More results on freezing experiments with biological particles, also from other habitats, are discussed in Després et al (2012).…”

Section: Primary Biological Aerosol Particlesmentioning

confidence: 99%

“…(1) can also be applied to polydisperse The data by Kanji et al (2008) are interpolated to the same total particle surface areas. The data by Jones et al (2011) are from the CSU-CFDC instrument and for water-subsaturated conditions. particles, with A aer obtained from the total aerosol surface area concentration divided by the total aerosol number concentration.…”

Section: Surface Area Dependencementioning

confidence: 99%

Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments

2012

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Abstract.A small subset of the atmospheric aerosol population has the ability to induce ice formation at conditions under which ice would not form without them (heterogeneous ice nucleation). While no closed theoretical description of this process and the requirements for good ice nuclei is available, numerous studies have attempted to quantify the ice nucleation ability of different particles empirically in laboratory experiments. In this article, an overview of these results is provided. Ice nucleation "onset" conditions for various mineral dust, soot, biological, organic and ammonium sulfate particles are summarized. Typical temperaturesupersaturation regions can be identified for the "onset" of ice nucleation of these different particle types, but the various particle sizes and activated fractions reported in different studies have to be taken into account when comparing results obtained with different methodologies. When intercomparing only data obtained under the same conditions, it is found that dust mineralogy is not a consistent predictor of higher or lower ice nucleation ability. However, the broad majority of studies agrees on a reduction of deposition nucleation by various coatings on mineral dust. The ice nucleation active surface site (INAS) density is discussed as a simple and empirical normalized measure for ice nucleation activity. For most immersion and condensation freezing measurements on mineral dust, estimates of the temperature-dependent INAS density agree within about two orders of magnitude. For deposition nucleation on dust, the spread is significantly larger, but a general trend of increasing INAS densities with increasing supersaturation is found. For soot, the presently available results are divergent. Estimated average INAS densities are high for ice-nucleation active bacteria at high subzero temperatures. At the same time, it is shown that INAS densities of some other biological aerosols, like certain pollen grains, fungal spores and diatoms, tend to be similar to those of dust. These particles may owe their high ice nucleation onsets to their large sizes. Surface-area-dependent parameterizations of heterogeneous ice nucleation are discussed. For immersion freezing on mineral dust, fitted INAS densities are available, but should not be used outside the temperature interval of the data they were based on. Classical nucleation theory, if employed with only one fitted contact angle, does not reproduce the observed temperature dependence for immersion nucleation, the temperature and supersaturation dependence for deposition nucleation, and the time dependence of ice nucleation. Formulations of classical nucleation theory with distributions of contact angles offer possibilities to overcome these weaknesses.

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Manchester Ice Nucleus Counter (MINC) measurements from the 2007 International workshop on Comparing Ice nucleation Measuring Systems (ICIS-2007)

Cited by 24 publications

References 29 publications

The micro-orifice uniform deposit impactor–droplet freezing technique (MOUDI-DFT) for measuring concentrations of ice nucleating particles as a function of size: improvements and initial validation

The micro-orifice uniform deposit impactor–droplet freezing technique (MOUDI-DFT) for measuring concentrations of ice nucleating particles as a function of size: improvements and initial validation

Deposition nucleation viewed as homogeneous or immersion freezing in pores and cavities

Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments

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