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 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.

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

2012 ◽  
Vol 12 (4) ◽  
pp. 8921-8977 ◽  
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 aerosols 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.

scholarly journals Secondary Ice Formation during Freezing of Levitated Droplets

2018 ◽  
Vol 75 (8) ◽  
pp. 2815-2826 ◽  
Author(s):  
Annika Lauber ◽  
Alexei Kiselev ◽  
Thomas Pander ◽  
Patricia Handmann ◽  
Thomas Leisner
Keyword(s):  
Droplet Size ◽  
Ice Formation ◽  
Cloud Droplets ◽  
Bubble Bursting ◽  
Electrodynamic Balance ◽  
Ice Particles ◽  
Levitated Droplets ◽  
Droplet Splitting ◽  
Laboratory Investigations ◽  
Homogeneous Freezing

Abstract The formation of secondary ice in clouds, that is, ice particles that are created at temperatures above the limit for homogeneous freezing without the direct involvement of a heterogeneous ice nucleus, is one of the longest-standing puzzles in cloud physics. Here, we present comprehensive laboratory investigations on the formation of small ice particles upon the freezing of drizzle-sized cloud droplets levitated in an electrodynamic balance. Four different categories of secondary ice formation (bubble bursting, jetting, cracking, and breakup) could be detected, and their respective frequencies of occurrence as a function of temperature and droplet size are given. We find that bubble bursting occurs more often than droplet splitting. While we do not observe the shattering of droplets into many large fragments, we find that the average number of small secondary ice particles released during freezing is strongly dependent on droplet size and may well exceed unity for droplets larger than 300 μm in diameter. This leaves droplet fragmentation as an important secondary ice process effective at temperatures around −10°C in clouds where large drizzle droplets are present.

scholarly journals Towards parametrising atmospheric concentrations of ice nucleating particles active at moderate supercooling

2020 ◽  
Author(s):  
Claudia Mignani ◽  
Jörg Wieder ◽  
Michael A. Sprenger ◽  
Zamin A. Kanji ◽  
Jan Henneberger ◽  
...  
Keyword(s):  
Aerosol Particle ◽  
Aerosol Particles ◽  
Swiss Alps ◽  
Saharan Dust ◽  
Ice Formation ◽  
Coarse Particles ◽  
Cloud Droplets ◽  
Air Mass ◽  
Atmospheric Concentrations ◽  
Cloud Top Temperature

Abstract. A small fraction of freezing cloud droplets probably initiates much of the precipitation above continents. Only a minute fraction of aerosol particles, so-called ice nucleating particles (INPs), can trigger initial ice formation at −15 °C, a cloud-top temperature frequently associated with snowfall. We found at a mountain top site in the Swiss Alps that concentrations of INPs active at −15 °C are different functions of coarse (> 2 μm) aerosol particle concentrations, depending on whether an air mass is precipitating, non-precipitating, or carrying Saharan dust and non-precipitating. Consequently, we suggest that a parameterisation at moderate supercooling should consider coarse particles in combination with air mass differentiation.

scholarly journals Towards parameterising atmospheric concentrations of ice-nucleating particles active at moderate supercooling

2021 ◽  
Vol 21 (2) ◽  
pp. 657-664
Author(s):  
Claudia Mignani ◽  
Jörg Wieder ◽  
Michael A. Sprenger ◽  
Zamin A. Kanji ◽  
Jan Henneberger ◽  
...  
Keyword(s):  
Aerosol Particle ◽  
Aerosol Particles ◽  
Swiss Alps ◽  
Dust Particles ◽  
Ice Formation ◽  
Coarse Particles ◽  
Substantial Fraction ◽  
Cloud Droplets ◽  
Air Mass ◽  
Atmospheric Concentrations

Abstract. A small fraction of freezing cloud droplets probably initiates much of the precipitation above continents. Only a minute fraction of aerosol particles, so-called ice-nucleating particles (INPs), can trigger initial ice formation at −15 ∘C, at which cloud-top temperatures are frequently associated with snowfall. At a mountaintop site in the Swiss Alps, we found that concentrations of INPs active at −15 ∘C can be parameterised by different functions of coarse (> 2 µm) aerosol particle concentrations, depending on whether an air mass is (a) precipitating, (b) non-precipitating, or (c) carrying a substantial fraction of dust particles while non-precipitating. Consequently, we suggest that a parameterisation at moderate supercooling should consider coarse particles in combination with air mass differentiation.

Notes of a Geologist in Ireland during August and September, 1857

The Geologist ◽  
1858 ◽  
Vol 1 (7) ◽  
pp. 292-296
Author(s):  
W. S. Symonds
Keyword(s):  
British Association ◽  
British Isles ◽  
The South

As the summer approaches, many of the readers of the Geologist will be preparing for their vacation-rambles; and should any think of visiting our Sister Isle—“Old Erin”—the following notes may be of service.We started on a bright August morning of last year for the meeting of the British Association for the Advancement of Science, held in Dublin, and with the intention of travelling over as much country, breaking as many stones, gathering as many plants, and catching as many salmon as time and circumstances would permit. We were fortunate in our combination of naturalist and sportsman, but as these notes are intended solely for the naturalist, we leave our “salmon struggles” unrecorded—at least in the pages of the Geologist.We travelled by Conway and Bangor to Holyhead, and as it was blowing a gale of wind when we arrived, we determined to wait until the sea was calmer, and, in the meanwhile, to visit the Cambrian rocks of Anglesea.We never saw a more instructive example of contortion and twisting of rocks than is displayed at the South Stack Lighthouse, of which a good sketch is given in Sir R. Murchison's “Siluria.” It is indeed a rugged coast; and the terrible Bay of Caernarvon to the south has been the locale of more shipwrecks than any other in the British Isles. We visited the grand quarries of quartzite, worked on a gigantic scale for the great breakwater. Here, as the geologist approaches the quarry from Holyhead, is a greenstone-dyke traversing the quartzite with a singular vein of pink decomposing felspathic rock.

scholarly journals Measurements of Ice Nucleating Particles and Ice Residuals

2017 ◽  
Vol 58 ◽  
pp. 8.1-8.13 ◽  
Author(s):  
Daniel J. Cziczo ◽  
Luis Ladino ◽  
Yvonne Boose ◽  
Zamin A. Kanji ◽  
Piotr Kupiszewski ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Condensed Phase ◽  
Atmospheric Aerosols ◽  
Aerosol Particles ◽  
Ice Crystals ◽  
Ice Formation ◽  
Similar Amount ◽  
Residual Material ◽  
History Of ◽  
Phase Water

Abstract It has been known that aerosol particles act as nuclei for ice formation for over a century and a half (see Dufour). Initial attempts to understand the nature of these ice nucleating particles were optical and electron microscope inspection of inclusions at the center of a crystal (see Isono; Kumai). Only within the last few decades has instrumentation to extract ice crystals from clouds and analyze the residual material after sublimation of condensed-phase water been available (see Cziczo and Froyd). Techniques to ascertain the ice nucleating potential of atmospheric aerosols have only been in place for a similar amount of time (see DeMott et al.). In this chapter the history of measurements of ice nucleating particles, both in the field and complementary studies in the laboratory, are reviewed. Remaining uncertainties and artifacts associated with measurements are described and suggestions for future areas of improvement are made.

scholarly journals Distribution of Atmospheric Aerosol over the South China Sea

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Shih-Jen Huang ◽  
Chen-Chih Lin
Keyword(s):  
South China Sea ◽  
South China ◽  
Aerosol Particles ◽  
Correlation Coefficients ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Fine Aerosol ◽  
Coarse Aerosol

The satellite-derived aerosol optical depth (AOD) data is used to investigate the distribution of aerosol over the South China Sea (SCS). High correlation coefficients are found between in situ AERONET data and satellite AOD measurements around the SCS with the highest coefficient of 0.9 on the Dongsha Island (i.e., Pratas Island). The empirical orthogonal function (EOF) analysis of AOD over the SCS shows that high AOD is always found around offshore areas of China, Indochina, Sumatra, and Borneo. Besides, spring is the major season of occurring coarse aerosol particles (AOT_C) but fine aerosol particles (AOT_F) occur yearly. The biomass burning is found in Indochina during March and April, and so it is in Sumatra and Borneo from August to October. The results also show that the AOT_F are higher during El Niño events, but higher AOT_C are found in La Niña years.

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.

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