Effects of Image Charges on the Scavenging of Aerosol Particles by Cloud Droplets and on Droplet Charging and Possible Ice Nucleation Processes

2000 ◽  
Vol 57 (13) ◽  
pp. 2118-2134 ◽  
Author(s):  
B. A. Tinsley ◽  
R. P. Rohrbaugh ◽  
M. Hei ◽  
K. V. Beard
Keyword(s):  
Aerosol Particles ◽  
Ice Nucleation ◽  
Cloud Droplets

scholarly journals Competition between water uptake and ice nucleation by glassy organic aerosol particles

2014 ◽  
Vol 14 (11) ◽  
pp. 16451-16492 ◽  
Author(s):  
T. Berkemeier ◽  
M. Shiraiwa ◽  
U. Pöschl ◽  
T. Koop
Keyword(s):  
Aerosol Particles ◽  
Liquid Core ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Empirical Method ◽  
Water Diffusion ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Cloud Droplets ◽  
Organic Particles

Abstract. Organic aerosol particles play a key role in climate by serving as nuclei for clouds and precipitation. Their sources and composition are highly variable, and their phase state ranges from liquid to solid under atmospheric conditions, affecting the pathway of activation to cloud droplets and ice crystals. Due to slow diffusion of water in the particle phase, organic particles may deviate in phase and morphology from their thermodynamic equilibrium state, hampering the prediction of their influence on cloud formation. We overcome this problem by combining a novel semi-empirical method for estimation of water diffusivity with a kinetic flux model that explicitly treats water diffusion. We estimate timescales for particle deliquescence as well as various ice nucleation pathways for a wide variety of organic substances, including secondary organic aerosol (SOA) from the oxidation of isoprene, α-pinene, naphthalene, and dodecane. The simulations show that in typical atmospheric updrafts, glassy states and solid/liquid core-shell morphologies can persist for long enough that heterogeneous ice nucleation in the deposition and immersion mode can dominate over homogeneous ice nucleation. Such competition depends strongly on ambient temperature and relative humidity as well as humidification rates and particle sizes. Due to relatively high glass transition temperature and low hygroscopicity, naphthalene SOA particles have a higher potential to act as heterogeneous ice nuclei than the other investigated substances. Our findings demonstrate that kinetic limitations of water diffusion into organic aerosol particles strongly affect their ice nucleation pathways and require advanced formalisms for the description of ice cloud formation in atmospheric models.

scholarly journals Mineral and biological ice-nucleating particles above the South East of the British Isles

2021 ◽  
Author(s):  
Alberto Sanchez-Marroquin ◽  
Jonathan S. West ◽  
Ian Burke ◽  
James B McQuaid ◽  
Benjamin John Murray
Keyword(s):  
Aerosol Particles ◽  
Ice Formation ◽  
British Isles ◽  
The South ◽  
Cloud Droplets ◽  
Homogeneous Freezing

A small fraction of aerosol particles known as Ice-Nucleating Particles (INPs) have the potential to trigger ice formation in cloud droplets at higher temperatures than homogeneous freezing. INPs can strongly...

scholarly journals Simulating the influence of primary biological aerosol particles on clouds by heterogeneous ice nucleation

2018 ◽  
Vol 18 (20) ◽  
pp. 15437-15450 ◽  
Author(s):  
Matthias Hummel ◽  
Corinna Hoose ◽  
Bernhard Pummer ◽  
Caroline Schaupp ◽  
Janine Fröhlich-Nowoisky ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Aerosol Particles ◽  
Fungal Spores ◽  
Ice Nucleation ◽  
Ice Crystals ◽  
Atmospheric Measurements ◽  
Cloud Ice ◽  
Biological Aerosol Particles ◽  
Ice Phase ◽  
Heterogeneous Ice Nucleation

Abstract. Primary ice formation, which is an important process for mixed-phase clouds with an impact on their lifetime, radiative balance, and hence the climate, strongly depends on the availability of ice-nucleating particles (INPs). Supercooled droplets within these clouds remain liquid until an INP immersed in or colliding with the droplet reaches its activation temperature. Only a few aerosol particles are acting as INPs and the freezing efficiency varies among them. Thus, the fraction of supercooled water in the cloud depends on the specific properties and concentrations of the INPs. Primary biological aerosol particles (PBAPs) have been identified as very efficient INPs at high subzero temperatures, but their very low atmospheric concentrations make it difficult to quantify their impact on clouds. Here we use the regional atmospheric model COSMO–ART to simulate the heterogeneous ice nucleation by PBAPs during a 1-week case study on a domain covering Europe. We focus on three highly ice-nucleation-active PBAP species, Pseudomonas syringae bacteria cells and spores from the fungi Cladosporium sp. and Mortierella alpina. PBAP emissions are parameterized in order to represent the entirety of bacteria and fungal spores in the atmosphere. Thus, only parts of the simulated PBAPs are assumed to act as INPs. The ice nucleation parameterizations are specific for the three selected species and are based on a deterministic approach. The PBAP concentrations simulated in this study are within the range of previously reported results from other modeling studies and atmospheric measurements. Two regimes of PBAP INP concentrations are identified: a temperature-limited and a PBAP-limited regime, which occur at temperatures above and below a maximal concentration at around −10 ∘C, respectively. In an ensemble of control and disturbed simulations, the change in the average ice crystal concentration by biological INPs is not statistically significant, suggesting that PBAPs have no significant influence on the average state of the cloud ice phase. However, if the cloud top temperature is below −15 ∘C, PBAP can influence the cloud ice phase and produce ice crystals in the absence of other INPs. Nevertheless, the number of produced ice crystals is very low and it has no influence on the modeled number of cloud droplets and hence the cloud structure.

scholarly journals Cloud history can change water–ice–surface interactions of oxide mineral aerosols: a case study on silica

2020 ◽  
Vol 20 (2) ◽  
pp. 1075-1087 ◽  
Author(s):  
Ahmed Abdelmonem ◽  
Sanduni Ratnayake ◽  
Jonathan D. Toner ◽  
Johannes Lützenkirchen
Keyword(s):  
Surface Properties ◽  
Second Harmonic ◽  
Aerosol Particles ◽  
Water Structure ◽  
Cloud Droplet ◽  
Ice Nucleation ◽  
Nonlinear Spectroscopy ◽  
Atmospheric Conditions ◽  
Mineral Aerosols ◽  
Interfacial Water Structure

Abstract. Mineral aerosol particles nucleate ice, and many insights have been obtained on water freezing as a function of mineral surface properties such as charge or morphology. Previous studies have mainly focused on pristine samples despite the fact that aerosol particles age under natural atmospheric conditions. For example, an aerosol-containing cloud droplet can go through freeze–melt or evaporation–condensation cycles that change the surface structure, the ionic strength, and pH. Variations in the surface properties of ice-nucleating particles in the atmosphere have been largely overlooked. Here, we use an environmental cell in conjunction with nonlinear spectroscopy (second-harmonic generation) to study the effect of freeze–melt processes on the aqueous chemistry at silica surfaces at low pH. We found that successive freeze–melt cycles disrupt the dissolution equilibrium, substantially changing the surface properties and giving rise to marked variations in the interfacial water structure and the ice nucleation ability of the surface. The degree of order of water molecules, next to the surface, at any temperature during cooling decreases and then increases again with sample aging. Along the aging process, the water ordering–cooling dependence and ice nucleation ability improve continuously.

scholarly journals Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

2019 ◽  
Author(s):  
Nsikanabasi Silas Umo ◽  
Robert Wagner ◽  
Romy Ullrich ◽  
Alexei Kiselev ◽  
Harald Saathoff ◽  
...  
Keyword(s):  
Fly Ash ◽  
Significant Role ◽  
Coal Fly Ash ◽  
Aerosol Particles ◽  
Ice Nucleation ◽  
Temperature Cycling ◽  
Cloud Formation ◽  
Ice Formation ◽  
Nucleation Activity ◽  
Ice Nucleation Activity

Abstract. Ice-nucleating particles (INPs), which are precursors for ice formation in clouds, can alter the microphysical and optical properties of clouds, hence, impacting the cloud lifetimes and hydrological cycles. However, the mechanisms with which these INPs nucleate ice when exposed to different atmospheric conditions are still unclear for some particles. Recently, some INPs with pores or permanent surface defects of regular or irregular geometries have been reported to initiate ice formation at cirrus temperatures via the liquid phase in a two-step process, involving the condensation and freezing of supercooled water inside these pores. This mechanism has therefore been labelled as pore condensation and freezing (PCF). The PCF mechanism allows formation and stabilization of ice germs in the particle without the formation of macroscopic ice. Coal fly ash (CFA) aerosol particles are known to nucleate ice in the immersion freezing mode and may play a significant role in cloud formation. In our current ice nucleation experiments with CFA particles, which we conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) aerosol and cloud simulation chamber at the Karlsruhe Institute of Technology, Germany, we partly observed a strong increase in the ice-active fraction for experiments performed at temperatures just below the homogeneous freezing of pure water, which could be related to the PCF mechanism. To further investigate the potential of CFA particles undergoing PCF mechanism, we performed a series of temperature-cycling experiments in AIDA. The temperature-cycling experiments involve exposing CFA particles to lower temperatures (down to ~ 228 K), then warming them up to higher temperatures (238 K–273 K) before investigating their ice nucleation properties. For the first time, we report the enhancement of the ice nucleation activity of the CFA particles for temperatures up to 263 K, from which we conclude that it is most likely due to the PCF mechanism. This indicates that ice germs formed in the CFA particles’ pores during cooling remains in the pores during the warming and induces ice crystallization as soon as the pre-activated particles experience ice-supersaturated conditions at warmer temperatures; hence, showing an enhancement in their ice-nucleating ability compared to the scenario where the CFA particles are directly probed at warmer temperatures without temporary cooling. The enhancement in the ice nucleation ability showed a positive correlation with the specific surface area and porosity of the particles. On the one hand, the PCF mechanism could be the prevalent nucleation mode for intrinsic ice formation at cirrus temperatures rather than the previously acclaimed deposition mode. On the other, the PCF mechanism can also play a significant role in mixed-phase cloud formation in a case where the CFA particles are injected from higher altitudes and then transported to lower altitudes after being exposed to lower temperatures.

scholarly journals Coal fly ash: linking immersion freezing behavior and physicochemical particle properties

2018 ◽  
Vol 18 (19) ◽  
pp. 13903-13923 ◽  
Author(s):  
Sarah Grawe ◽  
Stefanie Augustin-Bauditz ◽  
Hans-Christian Clemen ◽  
Martin Ebert ◽  
Stine Eriksen Hammer ◽  
...  
Keyword(s):  
Fly Ash ◽  
Single Particle ◽  
Coal Fly Ash ◽  
Ice Nucleation ◽  
Freezing Behavior ◽  
Cloud Droplets ◽  
X Ray ◽  
Particle Properties ◽  
Cold Stage ◽  
Immersion Freezing

Abstract. To date, only a few studies have investigated the potential of coal fly ash particles to trigger heterogeneous ice nucleation in cloud droplets. The presented measurements aim at expanding the sparse dataset and improving process understanding of how physicochemical particle properties can influence the freezing behavior of coal fly ash particles immersed in water. Firstly, immersion freezing measurements were performed with two single particle techniques, i.e., the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the SPectrometer for Ice Nuclei (SPIN). The effect of suspension time on the efficiency of the coal fly ash particles when immersed in a cloud droplet is analyzed based on the different residence times of the two instruments and employing both dry and wet particle generation. Secondly, two cold-stage setups, one using microliter sized droplets (Leipzig Ice Nucleation Array) and one using nanoliter sized droplets (WeIzmann Supercooled Droplets Observation on Microarray setup) were applied. We found that coal fly ash particles are comparable to mineral dust in their immersion freezing behavior when being dry generated. However, a significant decrease in immersion freezing efficiency was observed during experiments with wet-generated particles in LACIS and SPIN. The efficiency of wet-generated particles is in agreement with the cold-stage measurements. In order to understand the reason behind the deactivation, a series of chemical composition, morphology, and crystallography analyses (single particle mass spectrometry, scanning electron microscopy coupled with energy dispersive X-ray microanalysis, X-ray diffraction analysis) were performed with dry- and wet-generated particles. From these investigations, we conclude that anhydrous CaSO4 and CaO – which, if investigated in pure form, show the same qualitative immersion freezing behavior as observed for dry-generated coal fly ash particles – contribute to triggering heterogeneous ice nucleation at the particle–water interface. The observed deactivation in contact with water is related to changes in the particle surface properties which are potentially caused by hydration of CaSO4 and CaO. The contribution of coal fly ash to the ambient population of ice-nucleating particles therefore depends on whether and for how long particles are immersed in cloud droplets.

scholarly journals Photomineralization mechanism changes the ability of dissolved organic matter to activate cloud droplets and to nucleate ice crystals

2019 ◽  
Vol 19 (19) ◽  
pp. 12397-12412 ◽  
Author(s):  
Nadine Borduas-Dedekind ◽  
Rachele Ossola ◽  
Robert O. David ◽  
Lin S. Boynton ◽  
Vera Weichlinger ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Organic Acids ◽  
Liquid Water ◽  
Supercooled Liquid ◽  
Ice Nucleation ◽  
Ice Crystals ◽  
Cloud Droplets ◽  
Photochemical Processing

Abstract. An organic aerosol particle has a lifetime of approximately 1 week in the atmosphere during which it will be exposed to sunlight. However, the effect of photochemistry on the propensity of organic matter to participate in the initial cloud-forming steps is difficult to predict. In this study, we quantify on a molecular scale the effect of photochemical exposure of naturally occurring dissolved organic matter (DOM) and of a fulvic acid standard on its cloud condensation nuclei (CCN) and ice nucleation (IN) activity. We find that photochemical processing, equivalent to 4.6 d in the atmosphere, of DOM increases its ability to form cloud droplets by up to a factor of 2.5 but decreases its ability to form ice crystals at a loss rate of −0.04 ∘CT50 h−1 of sunlight at ground level. In other words, the ice nucleation activity of photooxidized DOM can require up to 4 ∘C colder temperatures for 50 % of the droplets to activate as ice crystals under immersion freezing conditions. This temperature change could impact the ratio of ice to water droplets within a mixed-phase cloud by delaying the onset of glaciation and by increasing the supercooled liquid fraction of the cloud, thereby modifying the radiative properties and the lifetime of the cloud. Concurrently, a photomineralization mechanism was quantified by monitoring the loss of organic carbon and the simultaneous production of organic acids, such as formic, acetic, oxalic and pyruvic acids, CO and CO2. This mechanism explains and predicts the observed increase in CCN and decrease in IN efficiencies. Indeed, we show that photochemical processing can be a dominant atmospheric ageing process, impacting CCN and IN efficiencies and concentrations. Photomineralization can thus alter the aerosol–cloud radiative effects of organic matter by modifying the supercooled-liquid-water-to-ice-crystal ratio in mixed-phase clouds with implications for cloud lifetime, precipitation patterns and the hydrological cycle.Highlights. During atmospheric transport, dissolved organic matter (DOM) within aqueous aerosols undergoes photochemistry. We find that photochemical processing of DOM increases its ability to form cloud droplets but decreases its ability to form ice crystals over a simulated 4.6 d in the atmosphere. A photomineralization mechanism involving the loss of organic carbon and the production of organic acids, CO and CO2 explains the observed changes and affects the liquid-water-to-ice ratio in clouds.

scholarly journals Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater

2020 ◽  
Vol 20 (3) ◽  
pp. 1451-1468 ◽  
Author(s):  
Xianda Gong ◽  
Heike Wex ◽  
Manuela van Pinxteren ◽  
Nadja Triesch ◽  
Khanneh Wadinga Fomba ◽  
...  
Keyword(s):  
Sea Level ◽  
Cloud Water ◽  
Ice Nucleation ◽  
Cape Verde ◽  
Nucleation Temperature ◽  
Sea Spray ◽  
Cloud Droplets ◽  
Cabo Verde ◽  
Active Particles ◽  
Sea Surface Microlayer

Abstract. Ice-nucleating particles (INPs) in the troposphere can form ice in clouds via heterogeneous ice nucleation. Yet, atmospheric number concentrations of INPs (NINP) are not well characterized, and, although there is some understanding of their sources, it is still unclear to what extend different sources contribute or if all sources are known. In this work, we examined properties of INPs at Cabo Verde (a.k.a. Cape Verde) from different environmental compartments: the oceanic sea surface microlayer (SML), underlying water (ULW), cloud water and the atmosphere close to both sea level and cloud level. Both enrichment and depletion of NINP in SML compared to ULW were observed. The enrichment factor (EF) varied from roughly 0.4 to 11, and there was no clear trend in EF with ice-nucleation temperature. NINP values in PM10 sampled at Cape Verde Atmospheric Observatory (CVAO) at any particular ice-nucleation temperature spanned around 1 order of magnitude below −15 ∘C, and about 2 orders of magnitude at warmer temperatures (>-12 ∘C). Among the 17 PM10 samples at CVAO, three PM10 filters showed elevated NINP at warm temperatures, e.g., above 0.01 L−1 at −10 ∘C. After heating samples at 95 ∘C for 1 h, the elevated NINP at the warm temperatures disappeared, indicating that these highly ice active INPs were most likely biological particles. INP number concentrations in PM1 were generally lower than those in PM10 at CVAO. About 83±22 %, 67±18 % and 77±14 % (median±standard deviation) of INPs had a diameter >1 µm at ice-nucleation temperatures of −12, −15 and −18 ∘C, respectively. PM1 at CVAO did not show such elevated NINP at warm temperatures. Consequently, the difference in NINP between PM1 and PM10 at CVAO suggests that biological ice-active particles were present in the supermicron size range. NINP in PM10 at CVAO was found to be similar to that on Monte Verde (MV, at 744 m a.s.l.) during noncloud events. During cloud events, most INPs on MV were activated to cloud droplets. When highly ice active particles were present in PM10 filters at CVAO, they were not observed in PM10 filters on MV but in cloud water samples instead. This is direct evidence that these INPs, which are likely biological, are activated to cloud droplets during cloud events. For the observed air masses, atmospheric NINP values in air fit well to the concentrations observed in cloud water. When comparing concentrations of both sea salt and INPs in both seawater and PM10 filters, it can be concluded that sea spray aerosol (SSA) only contributed a minor fraction to the atmospheric NINP. This latter conclusion still holds when accounting for an enrichment of organic carbon in supermicron particles during sea spray generation as reported in literature.

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