scholarly journals The role of organic aerosols in homogeneous ice formation

2005 ◽  
Vol 5 (3) ◽  
pp. 703-714 ◽  
Author(s):  
B. Kärcher ◽  
T. Koop
Keyword(s):  
Water Uptake ◽  
Organic Aerosols ◽  
Supercooled Liquid ◽  
Accommodation Coefficient ◽  
Model Calculations ◽  
Inorganic Particles ◽  
Ice Cloud ◽  
Organic Particles ◽  
Homogeneous Freezing ◽  
Cooling Air

Abstract. Recent field observations suggest that the fraction of organic-containing aerosol particles in ice cloud particles is diminished when compared to the background aerosol prior to freezing. In this work, we use model calculations to investigate possible causes for the observed behavior. In particular, homogeneous freezing processes in cooling air parcels containing aqueous inorganic particles and organic particles are studied with a detailed microphysical model. A disparate water uptake and resulting size differences that occur between organic and inorganic particles prior to freezing are identified as the most likely reason for the poor partitioning of organic aerosols into the ice phase. The differences in water uptake can be caused by changes in the relationship between solute mass fraction and water activity of the supercooled liquid phase, by modifications of the accommodation coefficient for water molecules, or by a combination thereof. The behavior of peak ice saturation ratios and total ice crystal number concentrations is examined, and the dependence of the results on cooling rate is investigated. Finally, processes are discussed that could possibly modify the homogeneous freezing behavior of organic particles.

scholarly journals The role of organic aerosols in homogeneous ice formation

2004 ◽  
Vol 4 (5) ◽  
pp. 6719-6745
Author(s):  
B. Kärcher ◽  
T. Koop
Keyword(s):  
Sulfuric Acid ◽  
Water Uptake ◽  
Organic Aerosols ◽  
Supercooled Liquid ◽  
Accommodation Coefficient ◽  
Model Calculations ◽  
Inorganic Particles ◽  
Organic Particles ◽  
Homogeneous Freezing ◽  
Cooling Air

Abstract. Recent field observations suggest that the fraction of organics containing aerosol particles in ice cloud particles is diminished when compared to the background aerosol prior to freezing. In this work, we use model calculations to investigate possible causes for the observed behavior. In particular, homogeneous freezing processes in cooling air parcels containing aqueous inorganic particles (represented by sulfuric acid) and organic particles (represented by pure malonic acid and mixed malonic/sulfuric acid) are studied with a detailed microphysical model. A disparate water uptake and resulting size differences that occur between organic and inorganic particles prior to freezing are identified as the most likely reason for the poor partitioning of organic aerosols into the ice phase. The differences in water uptake can be caused by changes in the relationship between solute mass fraction and water activity of the supercooled liquid phase, by modifications of the accommodation coefficient for water molecules, or by a combination thereof. The behavior of peak ice saturation ratios and total ice crystal number concentrations is examined, and the dependence of the results on cooling rate is investigated. Finally, processes are discussed that could possibly modify the homogeneous freezing behavior of organic particles.

scholarly journals Ice nucleation properties of volcanic ash from Eyjafjallajökull

2011 ◽  
Vol 11 (6) ◽  
pp. 17201-17243 ◽  
Author(s):  
C. R. Hoyle ◽  
V. Pinti ◽  
A. Welti ◽  
B. Zobrist ◽  
C. Marcolli ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Model Calculations ◽  
Airborne Measurements ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Homogeneous Freezing

Abstract. The ice nucleation ability of volcanic ash particles collected close to the Icelandic volcano Eyjafjallajökull during its eruptions in April and May 2010 is investigated experimentally, in the immersion and deposition modes, and applied to atmospheric conditions by comparison with airborne measurements and microphysical model calculations. The number of ash particles which are active as ice nuclei (IN) is strongly temperature dependent, with a very small minority being active in the immersion mode at temperatures of 250–263 K. Average ash particles show only a moderate effect on ice nucleation, by inducing freezing at temperatures between 236 K and 240 K (i.e. approximately 3–4 K higher than temperatures required for homogeneous ice nucleation, measured with the same instrument). By scaling the results to aircraft and lidar measurements of the conditions in the ash plume days down wind of the eruption and by applying a simple microphysical model, it was found that the IN active in the immersion mode in the range 250–263 K generally occurred in atmospheric number densities at the lower end of those required to have an impact on ice cloud formation. However, 3–4 K above the homogeneous freezing point, immersion mode IN number densities a few days down wind of the eruption were sufficiently high to have a moderate influence on ice cloud formation. The efficiency of IN in the deposition mode was found to be poor except at very cold conditions (< 238 K), when they reach an efficiency similar to that of mineral dust with the onset of freezing at 10 % supersaturation with respect to ice, and with the frozen fraction nearing its maximum value at a supersaturation 20 %. In summary, these investigations suggest volcanic ash particles to have only moderate effects on atmospheric ice formation.

scholarly journals Ice nucleation properties of volcanic ash from Eyjafjallajökull

2011 ◽  
Vol 11 (18) ◽  
pp. 9911-9926 ◽  
Author(s):  
C. R. Hoyle ◽  
V. Pinti ◽  
A. Welti ◽  
B. Zobrist ◽  
C. Marcolli ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Model Calculations ◽  
Airborne Measurements ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Homogeneous Freezing

Abstract. The ice nucleation ability of volcanic ash particles collected close to the Icelandic volcano Eyjafjallajökull during its eruptions in April and May 2010 is investigated experimentally, in the immersion and deposition modes, and applied to atmospheric conditions by comparison with airborne measurements and microphysical model calculations. The number of ash particles which are active as ice nuclei (IN) is strongly temperature dependent, with a very small minority being active in the immersion mode at temperatures of 250–263 K. Average ash particles show only a moderate effect on ice nucleation, by inducing freezing at temperatures between 236 K and 240 K (i.e. approximately 3–4 K higher than temperatures required for homogeneous ice nucleation, measured with the same instrument). By scaling the results to aircraft and lidar measurements of the conditions in the ash plume days down wind of the eruption, and by applying a simple microphysical model, it was found that the IN active in the immersion mode in the range 250–263 K generally occurred in atmospheric number densities at the lower end of those required to have an impact on ice cloud formation. However, 3–4 K above the homogeneous freezing point, immersion mode IN number densities a few days down wind of the eruption were sufficiently high to have a moderate influence on ice cloud formation. The efficiency of IN in the deposition mode was found to be poor except at very cold conditions (<238 K), when they reach an efficiency similar to that of mineral dust with the onset of freezing at 10 % supersaturation with respect to ice, and with the frozen fraction nearing its maximum value at a supersaturation 20 %. In summary, these investigations suggest volcanic ash particles to have only moderate effects on atmospheric ice formation.

Water Uptake and Optical Properties of Mixed Organic-Inorganic Particles

2021 ◽  
pp. 1-19
Author(s):  
Lucy Nandy ◽  
Yu Yao ◽  
Zhonghua Zheng ◽  
Nicole Riemer
Keyword(s):  
Optical Properties ◽  
Water Uptake ◽  
Inorganic Particles

Characterization of the temperature and humidity-dependent phase diagram of amorphous nanoscale organic aerosols

2017 ◽  
Vol 19 (9) ◽  
pp. 6532-6545 ◽  
Author(s):  
Nicholas E. Rothfuss ◽  
Markus D. Petters
Keyword(s):  
Phase Diagram ◽  
Amorphous Phase ◽  
Phase State ◽  
Organic Aerosols ◽  
State Diagram ◽  
Model Calculations ◽  
Temperature And Humidity

The amorphous phase state diagram for sucrose aerosol is obtained from a mix of measurements and model calculations.

scholarly journals Studying volatility from composition, dilution, and heating measurements of secondary organic aerosols formed during <i>α</i>-pinene ozonolysis

2018 ◽  
Vol 18 (8) ◽  
pp. 5455-5466 ◽  
Author(s):  
Kei Sato ◽  
Yuji Fujitani ◽  
Satoshi Inomata ◽  
Yu Morino ◽  
Kiyoshi Tanabe ◽  
...  
Keyword(s):  
Secondary Organic Aerosols ◽  
Yield Curve ◽  
Volume Fraction ◽  
Organic Aerosols ◽  
Accommodation Coefficient ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Mass Accommodation Coefficient ◽  
Kinetic Inhibition ◽  
Photochemical Aging

Abstract. Traditional yield curve analysis shows that semi-volatile organic compounds are a major component of secondary organic aerosols (SOAs). We investigated the volatility distribution of SOAs from α-pinene ozonolysis using positive electrospray ionization mass analysis and dilution- and heat-induced evaporation measurements. Laboratory chamber experiments were conducted on α-pinene ozonolysis, in the presence and absence of OH scavengers. Among these, we identified not only semi-volatile products, but also less volatile highly oxygenated molecules (HOMs) and dimers. Ozonolysis products were further exposed to OH radicals to check the effects of photochemical aging. HOMs were also formed during OH-initiated photochemical aging. Most HOMs that formed from ozonolysis and photochemical aging had 10 or fewer carbons. SOA particle evaporation after instantaneous dilution was measured at  < 1 and  ∼ 40 % relative humidity. The volume fraction remaining of SOAs decreased with time and the equilibration timescale was determined to be 24–46 min for SOA evaporation. The experimental results of the equilibration timescale can be explained when the mass accommodation coefficient is assumed to be 0.1, suggesting that the existence of low-volatility materials in SOAs, kinetic inhibition, or some combined effect may affect the equilibration timescale measured in this study.

Self-assembly of strawberry-like organic–inorganic hybrid particle clusters with directionally distributed bimetal and facile transformation of the core and corona

2020 ◽  
Vol 11 (18) ◽  
pp. 3136-3151 ◽  
Author(s):  
Shuxing Mei ◽  
Mingwang Pan ◽  
Juan Wang ◽  
Xiaopeng Zhang ◽  
Shaofeng Song ◽  
...  
Keyword(s):  
Strong Interaction ◽  
Self Assembly ◽  
Carboxyl Groups ◽  
Amino Groups ◽  
Inorganic Hybrid ◽  
Inorganic Particles ◽  
Hybrid Particle ◽  
The Core ◽  
Organic Particles ◽  
Facile Transformation

Controllable structure of organic–inorganic hybrid particle clusters were successfully fabricated by self-assembly which derived from the strong interaction between carboxyl groups of the organic particles and amino groups of the inorganic particles.

scholarly journals Pre-activation of ice-nucleating particles by the pore condensation and freezing mechanism

2016 ◽  
Vol 16 (4) ◽  
pp. 2025-2042 ◽  
Author(s):  
Robert Wagner ◽  
Alexei Kiselev ◽  
Ottmar Möhler ◽  
Harald Saathoff ◽  
Isabelle Steinke
Keyword(s):  
Capillary Condensation ◽  
Ice Nucleation ◽  
Temperature Cycling ◽  
Activation Mechanism ◽  
Crystal Formation ◽  
Model Calculations ◽  
Surface Samples ◽  
Activation Efficiency ◽  
Kelvin Effect ◽  
Homogeneous Freezing

Abstract. In spite of the resurgence in ice nucleation research a comparatively small number of studies deal with the phenomenon of pre-activation in heterogeneous ice nucleation. Fifty years ago, it was shown that various mineral dust and volcanic ash particles can be pre-activated to become nuclei for ice crystal formation even at temperatures as high as 270–271 K. Pre-activation was achieved under ice-subsaturated conditions without any preceding macroscopic ice growth by just temporarily cooling the particles to temperatures below 228 K. A two-step mechanism involving capillary condensation of supercooled water and subsequent homogeneous freezing was proposed to account for the particles' enhanced ice nucleation ability at high temperatures. This work reinvestigates the efficiency of the proposed pre-activation mechanism in temperature-cycling experiments performed in a large cloud chamber with suspended particles. We find the efficiency to be highest for the clay mineral illite as well as for highly porous materials like zeolite and diatomaceous earth, whereas most aerosols generated from desert dust surface samples did not reveal a measurable pre-activation ability. The pre-activation efficiency is linked to particle pores in a certain size range. As estimated by model calculations, only pores with diameters between about 5 and 8 nm contribute to pre-activation under ice-subsaturated conditions. This range is set by a combination of requirements from the negative Kelvin effect for condensation and a critical size of ice embryos for ice nucleation and melting. In contrast to the early study, pre-activation is only observed for temperatures below 260 K. Above that threshold, the particles' improved ice nucleation ability disappears due to the melting of ice in the pores.

scholarly journals Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

2012 ◽  
Vol 12 (18) ◽  
pp. 8589-8610 ◽  
Author(s):  
R. Wagner ◽  
O. Möhler ◽  
H. Saathoff ◽  
M. Schnaiter ◽  
J. Skrotzki ◽  
...  
Keyword(s):  
Glass Transition ◽  
Aerosol Particles ◽  
Ice Nucleation ◽  
Ice Formation ◽  
Transition Temperatures ◽  
Glass Transition Temperatures ◽  
Ice Cloud ◽  
Ice Nuclei ◽  
Freezing Cycle ◽  
Homogeneous Freezing

Abstract. The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosol particles that have re-vitrified in contact with the ice crystals during the preceding homogeneous freezing cycle exhibit pre-activation: they may retain small ice embryos in pores, have footprints on their surface which match the ice lattice, or simply have a much greater surface area or different surface microstructure compared to the unprocessed glassy aerosol particles. Pre-activation must be considered for the correct interpretation of experimental results on the heterogeneous ice nucleation ability of glassy aerosol particles and may provide a mechanism of producing a population of extremely efficient ice nuclei in the upper troposphere.

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