Effects of sulfuric acid and ammonium sulfate coatings on the ice nucleation properties of kaolinite particles

Eastwood, Michael L.; Cremel, Sébastien; Wheeler, M. J.; Murray, Benjamin J.; Girard, E.; Bertram, Allan K.

doi:10.1029/2008gl035997

Cited by 116 publications

(153 citation statements)

References 31 publications

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“…The borosilicate glass cover slip was coated with a hydrophobic organosilane. This substrate had a contact angle of 100 • and ensured the surface did not interfere with ice nucleation (Dymarska et al, 2006;Knopf and Lopez, 2009;Koop et al, 1998;Eastwood et al, 2009;. The same procedure was used to examine homogeneous nucleation and the resulting nucleation rates were in good agreement with literature data, thus confirming that the surface did not initiate crystallisation .…”

Section: Methodssupporting

confidence: 67%

Heterogeneous freezing of water droplets containing kaolinite particles

et al. 2011

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Abstract. Clouds composed of both ice particles and supercooled liquid water droplets exist at temperatures above ∼236 K. These mixed phase clouds, which strongly impact climate, are very sensitive to the presence of solid particles that can catalyse freezing. In this paper we describe experiments to determine the conditions at which the clay mineral kaolinite nucleates ice when immersed within water droplets. These are the first immersion mode experiments in which the ice nucleating ability of kaolinite has been determined as a function of clay surface area, cooling rate and also at constant temperatures. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and cooled at rates of between 0.8 and 10 K min −1 or held at constant sub-zero temperatures. The time and temperature at which individual 10-50 µm diameter droplets froze were determined by optical microscopy. For a cooling rate of 10 K min −1 , the median nucleation temperature of 10-40 µm diameter droplets increased from close to the homogeneous nucleation limit (236 K) to 240.8 ± 0.6 K as the concentration of kaolinite in the droplets was increased from 0.005 wt% to 1 wt%. This data shows that the probability of freezing scales with surface area of the kaolinite inclusions. We also show that at a constant temperature the number of liquid droplets decreases exponentially as they freeze over time. The constant cooling rate experiments are consistent with the stochastic, singular and modified singular descriptions of heterogeneous nucleation; however, freezing during cooling and at constant temperature can be reconciled best with the stochastic approach. We report temperature dependent nucleation rate coefficients (nucleation events per unit Correspondence to: B. J. Murray (b.j.murray@leeds.ac.uk) time per unit area) for kaolinite and present a general parameterisation for immersion nucleation which may be suitable for cloud modelling once nucleation by other important ice nucleating species is quantified in the future.

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Section: Methodssupporting

confidence: 67%

Heterogeneous freezing of water droplets containing kaolinite particles

et al. 2011

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“…From the inorganic mass concentrations measured by the C-ToF-AMS, the ratio of the measured NH 4 to that predicted from the measured inorganic ions (NH 4MEAS :NH 4PRED ) is proximately 0.68 when the site was in the FT, suggesting that the aerosol is slightly acidic (Middlebrook et al, 2012). The extent to which aerosol sulphate is neutralized can be important for heterogeneous chemistry (Fan and Jacob, 1992) and ice cloud nucleation (Abbatt et al, 2006;Eastwood et al, 2009), and can have implications for aerosol radiative forcing (Martin et al, 2004). The organic aerosol mass is made up of 60% of LV-OOA, contributions of SV-OOA and BBOA to the total organic aerosol always remain less than 10 and 20% respectively (Fig.…”

Section: Initial Free Tropospheric Particle and Gas-phase Propertiesmentioning

confidence: 99%

Experimental Evidence of the Feeding of the Free Troposphere with Aerosol Particles from the Mixing Layer

Freney¹,

Sellegri²,

Asmi³

et al. 2016

Aerosol Air Qual. Res.

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Aerosol particles emitted by both natural and anthropogenic sources have direct and indirect radiative impacts. Within the planetary mixing layer (ML), these particles are subjected to a large number of removal processes, e.g., rain, sedimentation, coagulation, and thus have a relatively short lifetime. Once aerosols are transported into the free troposphere (FT), their atmospheric lifetime increases significantly and they tend to be representative of large spatial areas. The work presented here shows evidence of anthropogenic emissions being transported from the ML to the FT during a cold period in February 2012. Using a wide range of in-situ measurements of aerosol chemical and physical properties at the Puy de Dome (PUY) station, as well as LIDAR measurements (at the Cezeaux site) of atmospheric back scattering we studied the exchange between the ML and the FT. Criteria used to identify when the PUY station was sampling in the ML or in the FT included mixing layer height estimates from LIDAR measurements, trace gas measurements, and air mass trajectories. Within the FT, we observed a gradual change in aerosol physical properties with increases in aerosol mass concentrations of up to 2 times the starting concentration, as well as increases in the number of larger particles (particle diameter >150 nm). Aerosol chemical properties showed increases in organic and nitrate particles. A series of linear fits were made through the data providing information on how different parameters change as a function of time. The impact of these changing aerosol properties are discussed in relation to the potential influence on aerosol direct and indirect effects. This work presents a unique combination of observations, and provide valuable data for future model validation.

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“…In the CNT, the nucleation rate depends on the contact angle between the ice embryo and the IN. The contact angle is derived based on the laboratory experiments of Eastwood et al (2008Eastwood et al ( , 2009 on uncoated (h = 12 o ) and sulphuric acid-coated (h = 27 o ) kaolinite particles. The concentration of ice crystals (N i ) nucleated in a given time step (Dt) is given by:…”

Section: Model Descriptionmentioning

confidence: 99%

“…For instance, Eastwood et al (2009) have shown that the onset relative humidity with respect to ice at which ice nucleation occurs on sulphuric acid-coated kaolinite particles is substantially increased when compared with uncoated kaolinite particles. Ice nucleation on sulphuric acid-coated kaolinite particles is therefore energetically much more difficult.…”

Section: Introductionmentioning

confidence: 99%

Relative importance of acid coating on ice nuclei in the deposition and contact modes for wintertime Arctic clouds and radiation

Girard

Asl

2013

Meteorol Atmos Phys

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Aerosols emitted from volcanic activities and polluted mid-latitudes regions are efficiently transported over the Arctic during winter by the large-scale atmospheric circulation. These aerosols are highly acidic. The acid coating on ice nuclei, which are present among these aerosols, alters their ability to nucleate ice crystals. In this research, the effect of acid coating on deposition and contact ice nuclei on the Arctic cloud and radiation is evaluated for January 2007 using a regional climate model. Results show that the suppression of contact freezing by acid coating on ice nuclei leads to small changes of the cloud microstructure and has no significant effect on the cloud radiative forcing (CRF) at the top of the atmosphere when compared with the effect of the alteration of deposition ice nucleation by acid coating on deposition ice nuclei. There is a negative feedback by which the suppression of contact freezing leads to an increase of the ice crystal nucleation rate by deposition ice nucleation. As a result, the suppression of contact freezing leads to an increase of the cloud ice crystal concentration. Changes in the cloud liquid and ice water contents remain small and the CRF is not significantly modified. The alteration of deposition ice nucleation by acid coating on ice nuclei is dominant over the alteration of contact freezing.

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Effects of sulfuric acid and ammonium sulfate coatings on the ice nucleation properties of kaolinite particles

Cited by 116 publications

References 31 publications

Heterogeneous freezing of water droplets containing kaolinite particles

Heterogeneous freezing of water droplets containing kaolinite particles

Experimental Evidence of the Feeding of the Free Troposphere with Aerosol Particles from the Mixing Layer

Relative importance of acid coating on ice nuclei in the deposition and contact modes for wintertime Arctic clouds and radiation

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