Reviewer comment on "Development of the drop Freezing Ice Nuclei Counter (FINC), intercomparison of droplet freezing techniques, and use of soluble lignin as an atmospheric ice nucleation standard" by Anna J. Miller et al.

AbstractIce particles in high-altitude cold clouds can obstruct aircraft functioning. Over the last 20 years, there have been more than 150 recorded cases with engine power-loss and damage caused by tiny cloud ice crystals, which are difficult to detect with aircraft radars. Herein, we examine two aircraft accidents for which icing linked to convective weather conditions has been officially reported as the most likely reason for catastrophic consequences. We analyze whether desert mineral dust, known to be very efficient ice nuclei and present along both aircraft routes, could further augment the icing process. Using numerical simulations performed by a coupled atmosphere-dust model with an included parameterization for ice nucleation triggered by dust aerosols, we show that the predicted ice particle number sharply increases at approximate locations and times of accidents where desert dust was brought by convective circulation to the upper troposphere. We propose a new icing parameter which, unlike existing icing indices, for the first time includes in its calculation the predicted dust concentration. This study opens up the opportunity to use integrated atmospheric-dust forecasts as warnings for ice formation enhanced by mineral dust presence.

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Condensed-phase biogenic–anthropogenic interactions with implications for cold cloud formation

Faraday Discussions ◽

10.1039/c7fd00010c ◽

2017 ◽

Vol 200 ◽

pp. 165-194 ◽

Cited By ~ 14

Author(s):

Joseph C. Charnawskas ◽

Peter A. Alpert ◽

Andrew T. Lambe ◽

Thomas Berkemeier ◽

Rachel E. O’Brien ◽

...

Keyword(s):

Freezing Temperature ◽

Organic Aerosol ◽

Ice Nucleation ◽

Mixed Phase ◽

Cloud Formation ◽

Fossil Fuel Combustion ◽

Soot Particles ◽

Ice Nuclei ◽

Deliquescence Relative Humidity ◽

Homogeneous Freezing

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating of SOA. We investigate SOA–soot biogenic–anthropogenic interactions and their impact on ice nucleation in relation to the particles’ organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without the presence of sulfate or soot particles. Corresponding particle glass transition (Tg) and full deliquescence relative humidity (FDRH) were estimated using a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibit a core–shell configuration (i.e.a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation, in agreement with respectiveTgand FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid, inducing ice nucleation. Naphthalene SOA coated soot particles acted as ice nuclei above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate renders this even less likely. However, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during pre-industrial times or in pristine areas.

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Ice nucleation efficiency of AgI: review and new insights

10.5194/acp-2016-142 ◽

2016 ◽

Author(s):

Claudia Marcolli ◽

Baban Nagare ◽

André Welti ◽

Ulrike Lohmann

Keyword(s):

Water Saturation ◽

Experimental Studies ◽

Freezing Temperature ◽

Nucleating Agent ◽

Companion Paper ◽

Chem Phys ◽

Ice Nucleation ◽

Lattice Match ◽

Ice Nuclei ◽

Immersion Freezing

Abstract. AgI is one of the best investigated ice nuclei. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Theoretical and experimental studies over the last sixty years provide a complex picture of silver iodide as ice nucleating agent with conflicting and inconsistent results. This review compares experimental ice nucleation studies in order to analyse the factors that influence the ice nucleation ability of AgI. We have performed experiments to compare contact and immersion freezing by AgI. This is one of three papers that describe and analyse contact and immersion freezing experiments with AgI. In Nagare et al. (Nagare, B., Marcolli, C., Stetzer, O., and Lohmann, U.: Comparison of measured and calculated collision efficiencies at low temperatures, Atmos. Chem. Phys., 15, 13759–13776, doi:10.5194/acp-15-13759-2015, 2015) collision efficiencies based on contact freezing experiments with AgI are determined and compared with theoretical formulations. In a companion paper, contact freezing experiments are compared with immersion freezing experiments conducted with AgI, kaolinite, and ATD as ice nuclei. The following picture emerges from this analysis: The ice nucleation ability of AgI seems to be enhanced when the AgI particle is on the surface of a droplet, which is indeed the position that a particle takes when it can freely move in a droplet. Ice nucleation by particles with surfaces exposed to air, depends on water adsorption. AgI surfaces seem to be most efficient as ice nuclei when they are exposed to relative humidity at or even above water saturation. For AgI particles that are totally immersed in water, the freezing temperature increases with increasing AgI surface area. Higher threshold freezing temperature seem to correlate with improved lattice matches as can be seen for AgI-AgCl solid solutions and 3AgI•NH4I•6H2O, which have slightly better lattice matches with ice than AgI and also higher threshold freezing temperatures. However, the effect of a good lattice match is annihilated when the surfaces have charges. Also, the ice nucleation ability seems to decrease during dissolution of AgI particles. This introduces an additional history and time dependence of ice nucleation in cloud chambers with short residence times.

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Investigating the role of dust in ice nucleation within clouds and further effects on regional weather system over East Asia – Part I: model development and validation

10.5194/acp-2017-754 ◽

2017 ◽

Author(s):

Lin Su ◽

Jimmy C.H. Fung

Keyword(s):

East Asia ◽

Source Region ◽

Model Development ◽

Ice Nucleation ◽

Dust Particles ◽

Weather System ◽

Microphysics Scheme ◽

Ice Nuclei ◽

Cloud Ice ◽

Ice Water

Abstract. The GOCART–Thompson microphysics scheme, which couples the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and aerosol-aware Thompson microphysics scheme, has been implemented in the Weather Research and Forecast model coupled with Chemistry (WRF-Chem), to quantify and evaluate the effect of dust on the ice nucleation process in the atmosphere by serving as ice nuclei. The performance of the GOCART-Thompson microphysics scheme in simulating the effect of dust in atmospheric ice nucleation is then evaluated over East Asia during spring in 2012, a typical dust-intensive season. Based upon the dust emission reasonably reproduced by WRF-Chem, the effect of dust on atmospheric cloud ice water content is well reproduced. With abundant dust particles serving as ice nuclei, the simulated ice water mixing ratio and ice crystal number concentration increases by one order of magnitude over the dust source region and downwind areas during the investigated period. The comparison with ice water path from satellite observations demonstrated that the simulation of cloud ice profile is substantially improved by applying the GOCART–Thompson microphysics scheme in the simulations. Additional sensitivity experiments are carried out to optimize the parameters in the ice nucleation parameterization in the GOCART–Thompson microphysics scheme, and the results suggest that the calibration factor in the ice nucleation scheme should be set to 3 or 4. Lowering the threshold relative humidity with respect to ice to 100 % for the ice nucleation parameterization leads to further improvement in cloud ice simulation.

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Suspendable macromolecules are responsible for ice nucleation activity of birch and conifer pollen

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-2541-2012 ◽

2012 ◽

Vol 12 (5) ◽

pp. 2541-2550 ◽

Cited By ~ 150

Author(s):

B. G. Pummer ◽

H. Bauer ◽

J. Bernardi ◽

S. Bleicher ◽

H. Grothe

Keyword(s):

Radiative Forcing ◽

Pollen Grains ◽

Ice Nucleation ◽

Cloud Formation ◽

Distribution Area ◽

Ice Cloud ◽

Ice Nuclei ◽

Nucleation Activity ◽

Ice Nucleation Activity ◽

The Impact

Abstract. The ice nucleation of bioaerosols (bacteria, pollen, spores, etc.) is a topic of growing interest, since their impact on ice cloud formation and thus on radiative forcing, an important parameter in global climate, is not yet fully understood. Here we show that pollen of different species strongly differ in their ice nucleation behaviour. The average freezing temperatures in laboratory experiments range from 240 to 255 K. As the most efficient nuclei (silver birch, Scots pine and common juniper pollen) have a distribution area up to the Northern timberline, their ice nucleation activity might be a cryoprotective mechanism. Far more intriguingly, it has turned out that water, which has been in contact with pollen and then been separated from the bodies, nucleates as good as the pollen grains themselves. The ice nuclei have to be easily-suspendable macromolecules located on the pollen. Once extracted, they can be distributed further through the atmosphere than the heavy pollen grains and so presumably augment the impact of pollen on ice cloud formation even in the upper troposphere. Our experiments lead to the conclusion that pollen ice nuclei, in contrast to bacterial and fungal ice nucleating proteins, are non-proteinaceous compounds.

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Small ice particles at slightly supercooled temperatures in tropical maritime convection

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-3895-2020 ◽

2020 ◽

Vol 20 (6) ◽

pp. 3895-3904

Author(s):

Gary Lloyd ◽

Thomas Choularton ◽

Keith Bower ◽

Jonathan Crosier ◽

Martin Gallagher ◽

...

Keyword(s):

Ice Nucleation ◽

Dust Particles ◽

Cumulus Clouds ◽

Desert Dust ◽

Ice Nuclei ◽

Production Processes ◽

Ice Particles ◽

Small Crystals ◽

Vapour Diffusion ◽

Very High

Abstract. In this paper we show that the origin of the ice phase in tropical cumulus clouds over the sea may occur by primary ice nucleation of small crystals at temperatures just between 0 and −5 ∘C. This was made possible through use of a holographic instrument able to image cloud particles at very high resolution and small size (6 µm). The environment in which the observations were conducted was notable for the presence of desert dust advected over the ocean from the Sahara. However, there is no laboratory evidence to suggest that these dust particles can act as ice nuclei at temperatures warmer than about −10 ∘C, the zone in which the first ice was observed in these clouds. The small ice particles were observed to grow rapidly by vapour diffusion, riming, and possibly through collisions with supercooled raindrops, causing these to freeze and potentially shatter. This in turn leads to the further production of secondary ice in these clouds. Hence, although the numbers of primary ice particles are small, they are very effective in initiating the rapid glaciation of the cloud, altering the dynamics and precipitation production processes.

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Ice nucleation by fertile soil dusts: relative importance of mineral and biogenic components

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-1853-2014 ◽

2014 ◽

Vol 14 (4) ◽

pp. 1853-1867 ◽

Cited By ~ 113

Author(s):

D. O'Sullivan ◽

B. J. Murray ◽

T. L. Malkin ◽

T. F. Whale ◽

N. S. Umo ◽

...

Keyword(s):

Ice Nucleation ◽

Experimental Methodology ◽

Dust Particles ◽

Soil Dust ◽

Source Regions ◽

Ice Nuclei ◽

Wide Range ◽

Mineral Components ◽

Droplet Sizes ◽

Biogenic Components

Abstract. Agricultural dust emissions have been estimated to contribute around 20% to the global dust burden. In contrast to dusts from arid source regions, the ice-nucleating abilities of which have been relatively well studied, soil dusts from fertile sources often contain a substantial fraction of organic matter. Using an experimental methodology which is sensitive to a wide range of ice nucleation efficiencies, we have characterised the immersion mode ice-nucleating activities of dusts (d < 11 μm) extracted from fertile soils collected at four locations around England. By controlling droplet sizes, which ranged in volume from 10−12 to 10−6 L (concentration = 0.02 to 0.1 wt% dust), we have been able to determine the ice nucleation behaviour of soil dust particles at temperatures ranging from 267 K (−6 °C) down to the homogeneous limit of freezing at about 237 K (−36 °C). At temperatures above 258 K (−15 °C) we find that the ice-nucleating activity of soil dusts is diminished by heat treatment or digestion with hydrogen peroxide, suggesting that a major fraction of the ice nuclei stems from biogenic components in the soil. However, below 258 K, we find that the ice active site densities tend towards those expected from the mineral components in the soils, suggesting that the inorganic fraction of soil dusts, in particular the K-feldspar fraction, becomes increasingly important in the initiation of the ice phase at lower temperatures. We conclude that dusts from agricultural activities could contribute significantly to atmospheric IN concentrations, if such dusts exhibit similar activities to those observed in the current laboratory study.

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