scholarly journals Measurements of ice nucleation by mineral dusts in the contact mode

2012 ◽  
Vol 12 (8) ◽  
pp. 20291-20309 ◽  
Author(s):  
K. W. Bunker ◽  
S. China ◽  
C. Mazzoleni ◽  
A. Kostinski ◽  
W. Cantrell
Keyword(s):  
High Temperatures ◽  
Laboratory Experiments ◽  
Ice Nucleation ◽  
Submicron Particles ◽  
Cloud Physics ◽  
Contact Mode ◽  
Earth’S Atmosphere ◽  
Ice Nuclei ◽  
Mineral Dusts ◽  
Earth's Atmosphere

Abstract. Formation of ice in Earth's atmosphere at temperatures above approximately −20 °C is one of the outstanding problems in cloud physics. Contact nucleation has been suggested as a possible mechanism for freezing at relatively high temperatures; some laboratory experiments have shown contact freezing activity at temperatures as high as −4 °C. We have investigated Arizona Test Dust and kaolinite as contact nuclei as a function of size and temperature and find that the fraction of submicron particles that are active as contact ice nuclei is less than 10−3 for −18 °C and greater. We also find that the different dusts are quite distinct in their effectiveness as contact nuclei; Arizona Test Dust catalyzed freezing in the contact mode at all mobility diameters we tested at −18 °C whereas kaolinite triggered freezing only for mobility diameters of 1000 and 500 nm at that temperature.

scholarly journals Feldspar minerals as efficient deposition ice nuclei

2013 ◽  
Vol 13 (22) ◽  
pp. 11175-11185 ◽  
Author(s):  
J. D. Yakobi-Hancock ◽  
L. A. Ladino ◽  
J. P. D. Abbatt
Keyword(s):  
Clay Minerals ◽  
Mojave Desert ◽  
Diffusion Chamber ◽  
Ice Nucleation ◽  
Lower Percentage ◽  
Lead Iodide ◽  
Experimental Procedure ◽  
Ice Nuclei ◽  
Mineral Dusts ◽  
Comparable Activity

Abstract. Mineral dusts are well known to be efficient ice nuclei, where the source of this efficiency has typically been attributed to the presence of clay minerals such as illite and kaolinite. However, the ice nucleating abilities of the more minor mineralogical components have not been as extensively examined. As a result, the deposition ice nucleation abilities of 24 atmospherically relevant mineral samples have been studied, using a continuous flow diffusion chamber at −40.0 ± 0.3 °C and particles size-selected at 200 nm. By focussing on using the same experimental procedure for all experiments, a relative ranking of the ice nucleating abilities of the samples was achieved. In addition, the ice nucleation behaviour of the pure minerals is compared to that of complex mixtures, such as Arizona Test Dust (ATD) and Mojave Desert Dust (MDD), and to lead iodide, which has been previously proposed for cloud seeding. Lead iodide was the most efficient ice nucleus (IN), requiring a critical relative humidity with respect to ice (RHi) of 122.0 ± 2.0% to activate 0.1% of the particles. MDD (RHi) 126.3 ± 3.4%) and ATD (RHi 129.5 ± 5.1%) have lower but comparable activity. From a set of clay minerals (kaolinite, illite, montmorillonite), non-clay minerals (e.g. hematite, magnetite, calcite, cerussite, quartz), and feldspar minerals (orthoclase, plagioclase) present in the atmospheric dusts, it was found that the feldspar minerals (particularly orthoclase) and some clays (particularly kaolinite) were the most efficient ice nuclei. Orthoclase and plagioclase were found to have critical RHi values of 127.1 ± 6.3% and 136.2 ± 1.3%, respectively. The presence of feldspars (specifically orthoclase) may play a significant role in the IN behaviour of mineral dusts despite their lower percentage in composition relative to clay minerals.

scholarly journals Influence of particle size on the ice nucleating ability of mineral dusts

2009 ◽  
Vol 9 (18) ◽  
pp. 6705-6715 ◽  
Author(s):  
A. Welti ◽  
F. Lüönd ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Particle Size ◽  
Size Dependence ◽  
Water Saturation ◽  
Mineral Dust ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Ice Nuclei ◽  
Mineral Dusts ◽  
Measured Activation ◽  
Formation Efficiency

Abstract. The recently developed Zurich Ice Nucleation Chamber (ZINC) was used to explore ice nucleation of size-selected mineral dust particles at temperatures between −20°C and −55°C. Four different mineral dust species have been tested: montmorillonite, kaolinite, illite and Arizona test dust (ATD). The selected particle diameters are 100 nm, 200 nm, 400 nm and 800 nm. Relative humidities with respect to ice (RHi) required to activate 1% of the dust particles as ice nuclei (IN) are reported as a function of temperature. An explicit size dependence of the ice formation efficiency has been observed for all dust types. 800 nm particles required the lowest RHi to activate. Deposition nucleation below water saturation was found only below −30°C or −35°C dependent on particle size. Minimum RHi for 1% activation were 105% for illite, kaolinite and montmorillonite at −40°C, respectively 110% for ATD at −45°C. In addition, a possible parameterisation for the measured activation spectra is proposed, which could be used in modeling studies.

scholarly journals Ice nucleation properties of fine ash particles from the Eyjafjallajökull eruption in April 2010

2011 ◽  
Vol 11 (6) ◽  
pp. 17665-17698 ◽  
Author(s):  
I. Steinke ◽  
O. Möhler ◽  
A. Kiselev ◽  
M. Niemand ◽  
H. Saathoff ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Active Surface ◽  
Ice Nucleation ◽  
Saharan Dust ◽  
Surface Site ◽  
Ice Nuclei ◽  
Active Surface Site ◽  
Mineral Dusts ◽  
Immersion Freezing ◽  
Ice Fraction

Abstract. During the eruption of the Eyjafjallajökull volcano in the south of Iceland in April/May 2010, about 40 Tg of ash mass were emitted into the atmosphere. However, it was unclear whether volcanic ash particles with d < 10 μm facilitate the glaciation of clouds. Thus, ice nucleation properties of volcanic ash particles were investigated in AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber experiments simulating atmospherically relevant conditions. The ash sample that was used for our experiments had been collected at a distance of 58 km from the Eyjafjallajökull during the eruption period in April 2010. The temperature range covered by our ice nucleation experiments extended from 219 to 264 K, and both ice nucleation via immersion freezing and deposition nucleation could be observed. Immersion freezing was first observed at 252 K, whereas the deposition nucleation onset lay at 242 K and RHice = 126 %. About 0.1 % of the volcanic ash particles were active as immersion freezing nuclei at a temperature of 249 K. For deposition nucleation, an ice fraction of 0.1 % was observed at around 233 K and RHice = 116 %. Taking ice-active surface site densities as a measure for the ice nucleation efficiency, volcanic ash particles are similarly efficient ice nuclei in immersion freezing mode (ns, imm ~ 109 m−2 at 247 K) compared to certain mineral dusts. For deposition nucleation, the observed ice-active surface site densities ns, dep were found to be 1011 m−2 at 224 K and RHice = 116 %. Thus, volcanic ash particles initiate deposition nucleation more efficiently than Asian and Saharan dust but appear to be poorer ice nuclei than ATD particles. Based on the experimental data, we have derived ice-active surface site densities as a function of temperature for immersion freezing and of relative humidity over ice and temperature for deposition nucleation.

scholarly journals A Technique to Measure Ice Nuclei in the Contact Mode

2014 ◽  
Vol 31 (4) ◽  
pp. 913-922 ◽  
Author(s):  
Joseph Niehaus ◽  
Kristopher W. Bunker ◽  
Swarup China ◽  
Alexander Kostinski ◽  
Claudio Mazzoleni ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Ice Nucleation ◽  
Contact Mode ◽  
Droplet Collision ◽  
Ice Nuclei ◽  
Air Water Interface ◽  
Temperature Controlled ◽  
The Difference ◽  
A New Technique ◽  
Number Of Particles

Abstract This study presents a new technique to study ice nucleation by aerosols in the contact mode. Contact freezing depends upon the interaction of a supercooled droplet of water and an aerosol particle, with the caveat that the particle must be at the air–water interface. To measure nucleation catalyzed in this mode, the technique employs water droplets that are supercooled via a temperature-controlled copper stage, then pulls aerosol-laden air past them. Particles deposit out of the airstream and come into contact with the surface of the droplet. The probability that a particle–droplet collision initiates a freezing event, necessitating knowledge of the total number of particles that collide with the droplet, is reported. In tests of the technique, ice nucleation by the bacteria Pseudomonas syringae is found to be more efficient in the contact mode than in the immersion mode by two orders of magnitude at −3°C with the difference diminishing by −8°C.

scholarly journals The H<sub>2</sub>O–O<sub>2</sub> water vapour complex in the Earth's atmosphere

2011 ◽  
Vol 11 (3) ◽  
pp. 10069-10086 ◽  
Author(s):  
Y. Kasai ◽  
E. Dupuy ◽  
R. Saito ◽  
K. Hashimoto ◽  
A. Sabu ◽  
...  
Keyword(s):  
Equilibrium Constant ◽  
Water Vapour ◽  
Laboratory Experiments ◽  
Lower Stratosphere ◽  
Molecular Complexes ◽  
Abundant Species ◽  
Statistical Thermodynamic ◽  
Earth’S Atmosphere ◽  
Abundance Estimates ◽  
Earth's Atmosphere

Abstract. Until recently, abundance estimates for bound molecular complexes have been affected by uncertainties of a factor 10–100. This is due to the difficulty of accurately obtaining the equilibrium constant, either from laboratory experiments or by statistical thermodynamic calculations. In this paper, we firstly present laboratory experiments that we performed in order to determine the molecular structure of H2O-O2. We also derive global abundance estimates for H2O-O2 in the Earth's atmosphere. The equilibrium constant Kp evaluated using the "anharmonic oscillator approach" (AHOA) (Sabu et al., 2005) was employed: the AHOA explains well the structure of the complex obtained by the present experiment. The Kp calculated by this method shows a realistic temperature dependence. We used this Kp to derive global abundance estimates for H2O-O2 in the Earth's atmosphere. The distribution of H2O-O2 follows that of water vapour in the troposphere and seems inversely proportional to temperature in the lower stratosphere. Preliminary estimates at the surface show amount of H2O-O2 is comparable to CO or N2O, ranking water vapour complexes among the ten most abundant species in the boundary layer.

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

2012 ◽  
Vol 12 (5) ◽  
pp. 12531-12621 ◽  
Author(s):  
C. Hoose ◽  
O. Möhler
Keyword(s):  
Laboratory Experiments ◽  
Mineral Dust ◽  
Fungal Spores ◽  
Pollen Grains ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Small Subset ◽  
Ice Nuclei ◽  
Heterogeneous Ice Nucleation

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 sulphate particles are summarized. Typical temperature-supersaturation 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 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 some other biological aerosols, like certain pollen grains and fungal spores, are not intrinsically better ice nuclei than dust, but 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 one fitted contact angle, does not reproduce the observed temperature dependence for immersion nucleation, temperature and supersaturation dependence for deposition nucleation, and time dependence.

scholarly journals Ice nucleation properties of fine ash particles from the Eyjafjallajökull eruption in April 2010

2011 ◽  
Vol 11 (24) ◽  
pp. 12945-12958 ◽  
Author(s):  
I. Steinke ◽  
O. Möhler ◽  
A. Kiselev ◽  
M. Niemand ◽  
H. Saathoff ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Active Surface ◽  
Ice Nucleation ◽  
Saharan Dust ◽  
Surface Site ◽  
Ice Nuclei ◽  
Active Surface Site ◽  
Mineral Dusts ◽  
Immersion Freezing ◽  
Ice Fraction

Abstract. During the eruption of the Eyjafjallajökull volcano in the south of Iceland in April/May 2010, about 40 Tg of ash mass were emitted into the atmosphere. It was unclear whether volcanic ash particles with d < 10 μm facilitate the glaciation of clouds. Thus, ice nucleation properties of volcanic ash particles were investigated in AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber experiments simulating atmospherically relevant conditions. The ash sample that was used for our experiments had been collected at a distance of 58 km from the Eyjafjallajökull during the eruption period in April 2010. The temperature range covered by our ice nucleation experiments extended from 219 to 264 K, and both ice nucleation via immersion freezing and deposition nucleation could be observed. Immersion freezing was first observed at 252 K, whereas the deposition nucleation onset lay at 242 K and RHice =126%. About 0.1% of the volcanic ash particles were active as immersion freezing nuclei at a temperature of 249 K. For deposition nucleation, an ice fraction of 0.1% was observed at around 233 K and RHice =116%. Taking ice-active surface site densities as a measure for the ice nucleation efficiency, volcanic ash particles are similarly efficient ice nuclei in immersion freezing mode (ns,imm ~ 109 m−2 at 247 K) compared to certain mineral dusts. For deposition nucleation, the observed ice-active surface site densities ns,dep were found to be 1011 m−2 at 224 K and RHice =116%. Thus, volcanic ash particles initiate deposition nucleation more efficiently than Asian and Saharan dust but appear to be poorer ice nuclei than ATD particles. Based on the experimental data, we have derived ice-active surface site densities as a function of temperature for immersion freezing and of relative humidity over ice and temperature for deposition nucleation.

scholarly journals Feldspar minerals as efficient deposition ice nuclei

2013 ◽  
Vol 13 (6) ◽  
pp. 17299-17326 ◽  
Author(s):  
J. D. Yakobi-Hancock ◽  
L. A. Ladino ◽  
J. P. D. Abbatt
Keyword(s):  
Clay Minerals ◽  
Mojave Desert ◽  
Diffusion Chamber ◽  
Ice Nucleation ◽  
Lower Percentage ◽  
Lead Iodide ◽  
Ice Nuclei ◽  
Mineral Dusts ◽  
Comparable Activity ◽  
Particle Preparation

Abstract. Mineral dusts are well known to be efficient ice nuclei, where the source of this efficiency has typically been attributed to the presence of clay minerals such as illite and kaolinite. However, the ice nucleating abilities of the more minor mineralogical components have not been as extensively examined. As a result, the deposition ice nucleation abilities of 24 atmospherically-relevant mineral samples have been studied, using a continuous flow diffusion chamber at −40.0 ± 0.3 °C. The same particle size (200 nm) and particle preparation procedure were used throughout. The ice nucleation behaviour of the pure minerals is compared to that of complex mixtures, such as Arizona Test Dust (ATD) and Mojave Desert Dust (MDD), and to lead iodide, which has been previously proposed for cloud seeding. Lead iodide was the most efficient ice nucleus (IN), requiring a critical relative humidity with respect to ice (RHi) of 122.0 ± 2.0% to activate 0.1% of the particles. MDD (RHi 126.3 ± 3.4%) and ATD (RHi 129.5 ± 5.1%) have lower but comparable activity. From a set of clay minerals (kaolinite, illite, montmorillonite), non-clay minerals (e.g. hematite, magnetite, calcite, cerussite, quartz), and feldspar minerals (orthoclase, plagioclase) present in the atmospheric dusts it was found that the feldspar minerals (particularly orthoclase), and not the clays, were the most efficient ice nuclei. Orthoclase and plagioclase were found to have critical RHi values of 127.1 ± 6.3% and 136.2 ± 1.3%, respectively. The presence of feldspars (specifically orthoclase) may play a significant role in the IN behaviour of mineral dusts despite their lower percentage in composition relative to clay minerals.

scholarly journals The H<sub>2</sub>O-O<sub>2</sub> water vapour complex in the Earth's atmosphere

2011 ◽  
Vol 11 (16) ◽  
pp. 8607-8612 ◽  
Author(s):  
Y. Kasai ◽  
E. Dupuy ◽  
R. Saito ◽  
K. Hashimoto ◽  
A. Sabu ◽  
...  
Keyword(s):  
Equilibrium Constant ◽  
Water Vapour ◽  
Laboratory Experiments ◽  
Lower Stratosphere ◽  
Molecular Complexes ◽  
Abundant Species ◽  
Statistical Thermodynamic ◽  
Earth’S Atmosphere ◽  
Abundance Estimates ◽  
Earth's Atmosphere

Abstract. Until recently, abundance estimates for bound molecular complexes have been affected by uncertainties of a factor 10–100. This is due to the difficulty of accurately obtaining the equilibrium constant, either from laboratory experiments or by statistical thermodynamic calculations. In this paper, we firstly present laboratory experiments that we performed in order to determine the molecular structure of H2O-O2. We also derive global abundance estimates for H2O-O2 in the Earth's atmosphere. The equilibrium constant Kp evaluated using the "anharmonic oscillator approach" (AHOA) (Sabu et al., 2005) was employed: the AHOA explains well the structure of the complex obtained by the present experiment. The Kp calculated by this method shows a realistic temperature dependence. We used this Kp to derive global abundance estimates for H2O-O2 in the Earth's atmosphere. The distribution of H2-O2 follows that of water vapour in the troposphere and seems inversely proportional to temperature in the lower stratosphere. Preliminary estimates at the surface show amount of H2O-O2 is comparable to CO or N2O, ranking water vapour complexes among the ten most abundant species in the boundary layer.

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