Parameterizations for ice nucleation in biological and atmospheric systems

Koop, Thomas; Zobrist, B.

doi:10.1039/b914289d

Cited by 176 publications

(349 citation statements)

References 112 publications

(193 reference statements)

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“…The uncertainty in a w is ±0.01. The ice melting curve (dashed line) and the volume corrected homogeneous freezing curve with an uncertainty in a w of ±0.01 shown as the solid black line and grey shaded area, respectively, is parameterized by Koop and Zobrist 40 .…”

Section: Ice Nucleation Experiments With Diatom Exudatesmentioning

confidence: 99%

“…First, a freezing curve as a function of a w was constructed through the median freezing points following the a w criterion where median immersion freezing temperatures can be described by a horizontal shift in the ice melting curve 40 . Then the difference between expected median freezing temperatures for pure water (i.e.…”

Section: Freezing Depression Correction For Immersion Mode Experimentsmentioning

confidence: 99%

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A marine biogenic source of atmospheric ice-nucleating particles

Wilson

Ladino

Alpert

et al. 2015

Nature

522

644

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The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties 1,2 . The formation of ice in clouds is facilitated by the presence of airborne ice nucleating particles 1,2 . Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice 3-11 . Sea spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer [12][13][14][15][16][17][18][19] . Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice nucleating material is likely biogenic and less than ~0.2 μm in size. We find that exudates separated from cells of the marine diatom T. Pseudonana nucleate ice and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol in combination with our measurements suggest that marine organic material may be an important source of ice nucleating particles in remote marine environments such as the Southern Ocean, North Pacific and North Atlantic.Atmospheric ice nucleating particles (INPs) allow ice to nucleate heterogeneously at higher temperatures or lower relative humidity than is typical for homogeneous ice nucleation. Heterogeneous ice nucleation proceeds via different pathways depending on temperature and humidity. In low altitude mixed-phase clouds, INPs are commonly immersed in supercooled liquid droplets and freezing can occur on them at temperatures between -36 and 0°C 2 . At higher altitudes and lower temperatures (<-36°C) where cirrus clouds form, nucleation occurs below water saturation, proceeding by homogeneous, deposition or immersion-in-solution nucleation 1 . Understanding the sources of atmospheric INPs is important because they affect cloud lifetime, cloud albedo and precipitation 1,2 . Recent modelling work has shown that the ocean is potentially an important source of biogenic atmospheric INPs particularly in remote, high latitude regions 9,10 . However, it has never been directly shown that there is a source of atmospheric INPs associated with organic material found in marine waters or sea-spray aerosol.Organic material makes up a substantial fraction of sub-micron sea-spray aerosol and it is estimated that 10±5 Tg yr -1 of primary organic sub-micron aerosol is emitted from marine sources globally 12 . Rising bubbles scavenge surface active organic material from the water column at their interfaces and this process facilitates the formation of the organic enriched sea-air interface known as the sea surface microlayer (SML). This organic material is ejected into the atmosphere during bubble bursting resulting in sea spray aerosol containing similar organic material to that of the microlaye...

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Section: Ice Nucleation Experiments With Diatom Exudatesmentioning

confidence: 99%

Section: Freezing Depression Correction For Immersion Mode Experimentsmentioning

confidence: 99%

A marine biogenic source of atmospheric ice-nucleating particles

Wilson

Ladino

Alpert

et al. 2015

Nature

522

644

View full text Add to dashboard Cite

show abstract

“…The specification of the thermodynamic properties of water at very low T is challenging since several combinations of parameters can lead to thermodynamically consistent solutions. Several studies (e.g., Johari et al, 1994;Koop and Zobrist, 2009) have used some form of thermodynamic continuation below T ∼ 235 K to define a w,eq and h f , which is also used in this work. This approximation is indirectly supported by experimental results (Koop and Zobrist, 2009;Murphy and Koop, 2005;Johari et al, 1994); however, it may lead to uncertainty.…”

Section: Discussionmentioning

confidence: 99%

“…(14); in both cases the empirical expression for σ iw from Barahona (2014) was used. For the model of Koop et al (2000), a w,eq was defined as in Koop and Zobrist (2009). Also presented are experimental results and empirical formulations obtained from the literature.…”

Section: Discussionmentioning

confidence: 99%

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Thermodynamic derivation of the activation energy for ice nucleation

Barahona

2015

Atmos. Chem. Phys.

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Abstract. Cirrus clouds play a key role in the radiative and hydrological balance of the upper troposphere. Their correct representation in atmospheric models requires an understanding of the microscopic processes leading to ice nucleation. A key parameter in the theoretical description of ice nucleation is the activation energy, which controls the flux of water molecules from the bulk of the liquid to the solid during the early stages of ice formation. In most studies it is estimated by direct association with the bulk properties of water, typically viscosity and self-diffusivity. As the environment in the ice-liquid interface may differ from that of the bulk, this approach may introduce bias in calculated nucleation rates. In this work a theoretical model is proposed to describe the transfer of water molecules across the ice-liquid interface. Within this framework the activation energy naturally emerges from the combination of the energy required to break hydrogen bonds in the liquid, i.e., the bulk diffusion process, and the work dissipated from the molecular rearrangement of water molecules within the ice-liquid interface. The new expression is introduced into a generalized form of classical nucleation theory. Even though no nucleation rate measurements are used to fit any of the parameters of the theory the predicted nucleation rate is in good agreement with experimental results, even at temperature as low as 190 K, where it tends to be underestimated by most models. It is shown that the activation energy has a strong dependency on temperature and a weak dependency on water activity. Such dependencies are masked by thermodynamic effects at temperatures typical of homogeneous freezing of cloud droplets; however, they may affect the formation of ice in haze aerosol particles. The new model provides an independent estimation of the activation energy and the homogeneous ice nucleation rate, and it may help to improve the interpretation of experimental results and the development of parameterizations for cloud formation.

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The unstable ice nucleation properties of Snomax® bacterial particles

2016

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Snomax® is often used as a surrogate for biological ice nucleating particles (INPs) and has recently been proposed as an INP standard for evaluating ice nucleation methods. We have found the immersion freezing properties of Snomax particles to be substantially unstable, observing a loss of ice nucleation ability over months of repeated droplet freezing measurements of the same batch of Snomax stored as dry pellets in a freezer. This reflects the fragility of the most ice active large protein aggregates and presents issues for the use of Snomax as an INP standard. The ice nucleation properties we determined using a fresh Snomax batch agreed well with the recent method intercomparison from the Ice Nucleation UnIT (UNIT) project, while an older batch did not. Using an oil immersion droplet freezing technique, repeated freezes of Snomax droplets resulted in a decrease in ice nucleation ability after successive refreezes. We attribute this to the disruption or displacement of the most ice active protein aggregates that are thought to contain the ice nucleants. Partitioning of the protein aggregates from the droplet into the immersion oil that is accelerated by droplet freezing events could explain the observed decrease in freezing ability. Droplets in mineral oil or low viscosity silicone oil experienced a smaller reduction in freezing temperature than when squalene oil was used. The effect of the immersion oil may be specific to proteinaceous biological particles, and we have not observed it in nonproteinaceous materials. Caution is warranted in the use of oil immersion droplet freezing methods to determine immersion freezing properties.

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Parameterizations for ice nucleation in biological and atmospheric systems

Cited by 176 publications

References 112 publications

A marine biogenic source of atmospheric ice-nucleating particles

A marine biogenic source of atmospheric ice-nucleating particles

Thermodynamic derivation of the activation energy for ice nucleation

The unstable ice nucleation properties of Snomax® bacterial particles

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