scholarly journals Chemical composition and mixing-state of ice residuals sampled within mixed phase clouds

2010 ◽  
Vol 10 (10) ◽  
pp. 23865-23894 ◽  
Author(s):  
M. Ebert ◽  
A. Worringen ◽  
N. Benker ◽  
S. Mertes ◽  
E. Weingartner ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Mixed Phase ◽  
Research Station ◽  
Mixing State ◽  
Transmission Electron ◽  
Anthropogenic Component ◽  
Significant Enrichment ◽  
Alpine Research ◽  
The Individual ◽  
Mixed Phase Clouds

Abstract. During an intensive campaign at the high alpine research station Jungfraujoch, Switzerland, in February/March 2006 ice particle residuals within mixed-phase clouds were sampled using the Ice-counterflow virtual impactor (Ice-CVI). Size, morphology, chemical composition, mineralogy and mixing state of the ice residual and the interstitial (i.e., non-activated) aerosol particles were analyzed by scanning and transmission electron microscopy. Ice nuclei (IN) were identified from the significant enrichment of particle groups in the ice residual (IR) samples relative to the interstitial aerosol. In terms of number lead-bearing particles are enriched by a factor of approximately 25, complex internal mixtures with silicates or metal oxides as major components by a factor of 11, and mixtures of secondary aerosol and soot (C-O-S particles) by a factor of 2. Other particle groups (sulfates, sea salt, Ca-rich particles, external silicates) observed in the ice-residual samples cannot be assigned unambiguously as IN. Between 9 and 24% of all IR are Pb-bearing particles. Pb was found as major component in around 10% of these particles (PbO, PbCl2). In the other particles, Pb was found as some 100 nm sized agglomerates consisting of 3–8 nm sized primary particles (PbS, elemental Pb). C-O-S particles are present in the IR at an abundance of 17–27%. The soot component within these particles is strongly aged. Complex internal mixtures occur in the IR at an abundance of 9–15%. Most IN identified at the Jungfraujoch station are internal mixtures containing anthropogenic components (either as main or minor constituent), and it is concluded that admixture of the anthropogenic component is responsible for the increased IN efficiency within mixed phase clouds. The mixing state appears to be a key parameter for the ice nucleation behaviour that cannot be predicted from the separate components contained within the individual particles.

scholarly journals Chemical composition and mixing-state of ice residuals sampled within mixed phase clouds

2011 ◽  
Vol 11 (6) ◽  
pp. 2805-2816 ◽  
Author(s):  
M. Ebert ◽  
A. Worringen ◽  
N. Benker ◽  
S. Mertes ◽  
E. Weingartner ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Carbonaceous Material ◽  
Mixed Phase ◽  
Research Station ◽  
Mixing State ◽  
Anthropogenic Component ◽  
Significant Enrichment ◽  
Alpine Research ◽  
Main Component ◽  
Mixed Phase Clouds

Abstract. During an intensive campaign at the high alpine research station Jungfraujoch, Switzerland, in February/March 2006 ice particle residuals within mixed-phase clouds were sampled using the Ice-counterflow virtual impactor (Ice-CVI). Size, morphology, chemical composition, mineralogy and mixing state of the ice residual and the interstitial (i.e., non-activated) aerosol particles were analyzed by scanning and transmission electron microscopy. Ice nuclei (IN) were identified from the significant enrichment of particle groups in the ice residual (IR) samples relative to the interstitial aerosol. In terms of number lead-bearing particles are enriched by a factor of approximately 25, complex internal mixtures with silicates or metal oxides as major components by a factor of 11, and mixtures of secondary aerosol and carbonaceous material (C-O-S particles) by a factor of 2. Other particle groups (sulfates, sea salt, Ca-rich particles, external silicates) observed in the ice-residual samples cannot be assigned unambiguously as IN. Between 9 and 24% of all IR are Pb-bearing particles. Pb was found as major component in around 10% of these particles (PbO, PbCl2). In the other particles, Pb was found as some 100 nm sized agglomerates consisting of 3–8 nm sized primary particles (PbS, elemental Pb). C-O-S particles are present in the IR at an abundance of 17–27%. The soot component within these particles is strongly aged. Complex internal mixtures occur in the IR at an abundance of 9–15%. Most IN identified at the Jungfraujoch station are internal mixtures containing anthropogenic components (either as main or minor constituent), and it is concluded that admixture of the anthropogenic component is responsible for the increased IN efficiency within mixed phase clouds. The mixing state appears to be a key parameter for the ice nucleation behaviour that cannot be predicted from the sole knowledge of the main component of an individual particle.

scholarly journals Single-particle characterization of ice-nucleating particles and ice particle residuals sampled by three different techniques

2014 ◽  
Vol 14 (16) ◽  
pp. 23027-23073 ◽  
Author(s):  
A. Worringen ◽  
K. Kandler ◽  
N. Benker ◽  
T. Dirsch ◽  
S. Weinbruch ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Metal Oxides ◽  
Carbonaceous Material ◽  
Submicron Particles ◽  
Research Station ◽  
Mixing State ◽  
Potential Measurement ◽  
Virtual Impactor ◽  
Alpine Research ◽  
Mixed Phase Clouds

Abstract. In the present work, three different techniques are used to separate ice-nucleating particles (INP) and ice particle residuals (IPR) from non-ice-active particles: the Ice Selective Inlet (ISI) and the Ice Counterflow Virtual Impactor (Ice-CVI), which sample ice particles from mixed phase clouds and allow for the analysis of the residuals, as well as the combination of the Fast Ice Nucleus Chamber (FINCH) and the Ice Nuclei Pumped Virtual Impactor (IN-PCVI), which provides ice-activating conditions to aerosol particles and extracts the activated ones for analysis. The collected particles were analyzed by scanning electron microscopy and energy-dispersive X-ray microanalysis to determine their size, chemical composition and mixing state. Samples were taken during January/February 2013 at the High Alpine Research Station Jungfraujoch. All INP/IPR-separating techniques had considerable abundances (median 20–70%) of contamination artifacts (ISI: Si-O spheres, probably calibration aerosol; Ice-CVI: Al-O particles; FINCH + IN-PCVI: steel particles). Also, potential measurement artifacts (soluble material) occurred (median abundance < 20%). After removal of the contamination particles, silicates and Ca-rich particles, carbonaceous material and metal oxides were the major INP/IPR particle types separated by all three techniques. Minor types include soot and Pb-bearing particles. Sea-salt and sulfates were identified by all three methods as INP/IPR. Lead was identified in less than 10% of the INP/IPR. It was mainly present as an internal mixture with other particle types, but also external lead-rich particles were found. Most samples showed a maximum of the INP/IPR size distribution at 400 nm geometric diameter. In a few cases, a second super-micron maximum was identified. Soot/carbonaceous material and metal oxides were present mainly in the submicron range. ISI and FINCH yielded silicates and Ca-rich particles mainly with diameters above 1 μm, while the Ice-CVI also sampled many submicron particles. Probably owing to the different meteorological conditions, the INP/IPR composition was highly variable on a sample to sample basis. Thus, some part of the discrepancies between the different techniques may result from the (unavoidable) non-parallel sampling. The observed differences of the particles group abundances as well as the mixing state of INP/IPR point to the need of further studies to better understand the influence of the separating techniques on the INP/IPR chemical composition.

scholarly journals Single-particle characterization of ice-nucleating particles and ice particle residuals sampled by three different techniques

2015 ◽  
Vol 15 (8) ◽  
pp. 4161-4178 ◽  
Author(s):  
A. Worringen ◽  
K. Kandler ◽  
N. Benker ◽  
T. Dirsch ◽  
S. Mertes ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Metal Oxides ◽  
Relative Number ◽  
Carbonaceous Material ◽  
Submicron Particles ◽  
Research Station ◽  
Mixing State ◽  
Separation Techniques ◽  
Potential Measurement ◽  
Virtual Impactor

Abstract. In the present work, three different techniques to separate ice-nucleating particles (INPs) as well as ice particle residuals (IPRs) from non-ice-active particles are compared. The Ice Selective Inlet (ISI) and the Ice Counterflow Virtual Impactor (Ice-CVI) sample ice particles from mixed-phase clouds and allow after evaporation in the instrument for the analysis of the residuals. The Fast Ice Nucleus Chamber (FINCH) coupled with the Ice Nuclei Pumped Counterflow Virtual Impactor (IN-PCVI) provides ice-activating conditions to aerosol particles and extracts the activated particles for analysis. The instruments were run during a joint field campaign which took place in January and February 2013 at the High Alpine Research Station Jungfraujoch (Switzerland). INPs and IPRs were analyzed offline by scanning electron microscopy and energy-dispersive X-ray microanalysis to determine their size, chemical composition and mixing state. Online analysis of the size and chemical composition of INP activated in FINCH was performed by laser ablation mass spectrometry. With all three INP/IPR separation techniques high abundances (median 20–70%) of instrumental contamination artifacts were observed (ISI: Si-O spheres, probably calibration aerosol; Ice-CVI: Al-O particles; FINCH + IN-PCVI: steel particles). After removal of the instrumental contamination particles, silicates, Ca-rich particles, carbonaceous material and metal oxides were the major INP/IPR particle types obtained by all three techniques. In addition, considerable amounts (median abundance mostly a few percent) of soluble material (e.g., sea salt, sulfates) were observed. As these soluble particles are often not expected to act as INP/IPR, we consider them as potential measurement artifacts. Minor types of INP/IPR include soot and Pb-bearing particles. The Pb-bearing particles are mainly present as an internal mixture with other particle types. Most samples showed a maximum of the INP/IPR size distribution at 200–400 nm in geometric diameter. In a few cases, a second supermicron maximum was identified. Soot/carbonaceous material and metal oxides were present mainly in the sub-micrometer range. Silicates and Ca-rich particles were mainly found with diameters above 1 μm (using ISI and FINCH), in contrast to the Ice-CVI which also sampled many submicron particles of both groups. Due to changing meteorological conditions, the INP/IPR composition was highly variable if different samples were compared. Thus, the observed discrepancies between the different separation techniques may partly result from the non-parallel sampling. The differences of the particle group relative number abundance as well as the mixing state of INP/IPR clearly demonstrate the need of further studies to better understand the influence of the separation techniques on the INP/IPR chemical composition. Also, it must be concluded that the abundance of contamination artifacts in the separated INP and IPR is generally large and should be corrected for, emphasizing the need for the accompanying chemical measurements. Thus, further work is needed to allow for routine operation of the three separation techniques investigated.

scholarly journals The Horizontal Ice Nucleation Chamber (HINC): INP measurements at conditions relevant for mixed-phase clouds at the High Altitude Research Station Jungfraujoch

2017 ◽  
Vol 17 (24) ◽  
pp. 15199-15224 ◽  
Author(s):  
Larissa Lacher ◽  
Ulrike Lohmann ◽  
Yvonne Boose ◽  
Assaf Zipori ◽  
Erik Herrmann ◽  
...  
Keyword(s):  
High Altitude ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Saharan Dust ◽  
Research Station ◽  
Minimum Detectable Concentration ◽  
The North ◽  
New Instrument ◽  
Marine Air ◽  
Mixed Phase Clouds

Abstract. In this work we describe the Horizontal Ice Nucleation Chamber (HINC) as a new instrument to measure ambient ice-nucleating particle (INP) concentrations for conditions relevant to mixed-phase clouds. Laboratory verification and validation experiments confirm the accuracy of the thermodynamic conditions of temperature (T) and relative humidity (RH) in HINC with uncertainties in T of ±0.4 K and in RH with respect to water (RHw) of ±1.5 %, which translates into an uncertainty in RH with respect to ice (RHi) of ±3.0 % at T > 235 K. For further validation of HINC as a field instrument, two measurement campaigns were conducted in winters 2015 and 2016 at the High Altitude Research Station Jungfraujoch (JFJ; Switzerland, 3580 m a. s. l. ) to sample ambient INPs. During winters 2015 and 2016 the site encountered free-tropospheric conditions 92 and 79 % of the time, respectively. We measured INP concentrations at 242 K at water-subsaturated conditions (RHw = 94 %), relevant for the formation of ice clouds, and in the water-supersaturated regime (RHw = 104 %) to represent ice formation occurring under mixed-phase cloud conditions. In winters 2015 and 2016 the median INP concentrations at RHw = 94 % was below the minimum detectable concentration. At RHw = 104 %, INP concentrations were an order of magnitude higher, with median concentrations in winter 2015 of 2.8 per standard liter (std L−1; normalized to standard T of 273 K and pressure, p, of 1013 hPa) and 4.7 std L−1 in winter 2016. The measurements are in agreement with previous winter measurements obtained with the Portable Ice Nucleation Chamber (PINC) of 2.2 std L−1 at the same location. During winter 2015, two events caused the INP concentrations at RHw = 104 % to significantly increase above the campaign average. First, an increase to 72.1 std L−1 was measured during an event influenced by marine air, arriving at the JFJ from the North Sea and the Norwegian Sea. The contribution from anthropogenic or other sources can thereby not be ruled out. Second, INP concentrations up to 146.2 std L−1 were observed during a Saharan dust event. To our knowledge this is the first time that a clear enrichment in ambient INP concentration in remote regions of the atmosphere is observed during a time of marine air mass influence, suggesting the importance of marine particles on ice nucleation in the free troposphere.

scholarly journals HOLIMO II: a digital holographic instrument for ground-based in-situ observations of microphysical properties of mixed-phase clouds

2013 ◽  
Vol 6 (3) ◽  
pp. 4183-4221 ◽  
Author(s):  
J. Henneberger ◽  
J. P. Fugal ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Mixed Phase ◽  
Size Spectrum ◽  
Research Station ◽  
Resolution Limit ◽  
Microphysical Properties ◽  
Cloud Particles ◽  
Mixed Phase Clouds

Abstract. Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in-situ image cloud particles in a well defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener–Bergeron–Findeisen (WBF) process.

scholarly journals Direct evidence for secondary ice formation at around −15 °C in mixed-phase clouds

2018 ◽  
Author(s):  
Claudia Mignani ◽  
Jessie M. Creamean ◽  
Lukas Zimmermann ◽  
Christine Alewell ◽  
Franz Conen
Keyword(s):  
Direct Evidence ◽  
Mixed Phase ◽  
Ice Formation ◽  
Research Station ◽  
Multiplication Factor ◽  
Ice Crystal ◽  
Narrow Temperature Range ◽  
Snow Crystals ◽  
Ice Multiplication ◽  
Mixed Phase Clouds

Abstract. Ice crystal numbers can exceed the numbers of ice-nucleating particles (INP) observed in mixed-phase clouds by several orders of magnitude also at temperatures that are colder than required for the Hallett-Mossop process (−3 °C to −8 °C). These observations provide circumstantial evidence of secondary ice formation. Attempting a more direct observational approach we made use of the fact that planar, branched snow crystals (e.g. dendrites) grow within a relatively narrow temperature range (about −12 °C to −17 °C) and can be analysed individually for INP using a field-suitable drop freezing assay technique. During February and March 2018, we analysed 190 dendritic crystals (an average of ∼3 mm in size and between 1.3 to 7.6 mm) deposited within mixed-phase clouds at the High Altitude Research Station Jungfraujoch (3580 m a.s.l.), Switzerland. Overall, one in eight of these crystals contained an INP active at −17 °C or warmer, while the remaining seven of eight most likely resulted from secondary ice formation within the clouds. The ice multiplication factor we observed was small (8), but relatively stable throughout the course of the experiment. These measurements show that secondary ice can be observed at temperatures around −15 °C in the atmosphere and thus advance our understanding of the extent of secondary ice formation in mixed-phase clouds, even where the multiplication factor is smaller than 10.

scholarly journals Infrared photo-induced force microscopy unveils nanoscale features of Norway spruce fibre wall

Cellulose ◽  
2021 ◽  
Author(s):  
Kavindra Kumar Kesari ◽  
Padraic O’Reilly ◽  
Jani Seitsonen ◽  
Janne Ruokolainen ◽  
Tapani Vuorinen
Keyword(s):  
Cell Wall ◽  
Chemical Composition ◽  
Norway Spruce ◽  
Spatial Resolution ◽  
Lignin Content ◽  
Force Microscopy ◽  
Transmission Electron ◽  
High Resolution Images ◽  
The Individual ◽  
20 Nm

AbstractInfrared photo-induced force microscopy (IR PiFM) was applied for imaging ultrathin sections of Norway spruce (Picea abies) at 800–1885 cm−1 with varying scanning steps from 0.6 to 30 nm. Cell wall sublayers were visualized in the low-resolution mode based on differences in their chemical composition. The spectra from the individual sublayers demonstrated differences in the orientation of cellulose elementary fibrils (EFs) and in the content and structure of lignin. The high-resolution images revealed 5–20 nm wide lignin-free areas in the S1 layer. Full spectra collected from a non-lignified spot and at a short distance apart from it verified an abrupt change in the lignin content and the presence of tangentially oriented EFs. Line scans across the lignin-free areas corresponded to a spatial resolution of ≤ 5 nm. The ability of IR PiFM to resolve structures based on their chemical composition differentiates it from transmission electron microscopy that can reach a similar spatial resolution in imaging ultrathin wood sections. In comparison with Raman imaging, IR PiFM can acquire chemical images with ≥ 50 times higher spatial resolution. IR PiFM is also a surface-sensitive technique that is important for reaching the high spatial resolution in anisotropic samples like the cell wall. All these features make IR PiFM a highly promising technique for analyzing the recalcitrant nature of lignocellulosic biomass for its conversion into various materials and chemicals. Graphic abstract

scholarly journals Modelling mixed-phase clouds with large-eddy model UCLALES-SALSA

2020 ◽  
Author(s):  
Jaakko Ahola ◽  
Hannele Korhonen ◽  
Juha Tonttila ◽  
Sami Romakkaniemi ◽  
Harri Kokkola ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Liquid Layer ◽  
Cloud Model ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Model Intercomparison ◽  
Large Eddy ◽  
Ice Microphysics ◽  
Intercomparison Study ◽  
Mixed Phase Clouds

Abstract. The large-eddy model UCLALES-SALSA, with exceptionally detailed aerosol description for both aerosol number and chemical composition, has been extended for ice and mixed-phase clouds. Comparison to a previous mixed-phase cloud model intercomparison study confirmed the accuracy of newly implemented ice microphysics. Further simulation with a heterogeneous ice nucleation scheme, where also ice nucleating particles (INP) are a prognostic variable, captured the typical layered structure of Arctic mid-altitude mixed-phase cloud: a liquid layer near cloud top and ice within and below the liquid layer. In addition, the simulation showed realistic freezing rate of droplets within the vertical cloud structure. The represented detailed sectional ice microphysics with prognostic aerosols is crucially important in reproducing mixed-phase clouds.

scholarly journals Chemical composition of free tropospheric aerosol for PM1 and coarse mode at the high alpine site Jungfraujoch

2008 ◽  
Vol 8 (2) ◽  
pp. 407-423 ◽  
Author(s):  
J. Cozic ◽  
B. Verheggen ◽  
E. Weingartner ◽  
J. Crosier ◽  
K. N. Bower ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Monitoring Program ◽  
Saharan Dust ◽  
Research Station ◽  
Aerosol Mass ◽  
Coarse Mode ◽  
Tropospheric Aerosol ◽  
Dust Events ◽  
Alpine Research ◽  
Mass Concentrations

Abstract. The chemical composition of submicron (fine mode) and supermicron (coarse mode) aerosol particles has been investigated at the Jungfraujoch high alpine research station (3580 m a.s.l., Switzerland) as part of the GAW aerosol monitoring program since 1999. A clear seasonality was observed for all major components throughout the period with low concentrations in winter (predominantly free tropospheric aerosol) and higher concentrations in summer (enhanced vertical transport of boundary layer pollutants). In addition, mass closure was attempted during intensive campaigns in March 2004, February–March 2005 and August 2005. Ionic, carbonaceous and non-refractory components of the aerosol were quantified as well as the PM1 and coarse mode total aerosol mass concentrations. A relatively low conversion factor of 1.8 for organic carbon (OC) to particulate organic matter (OM) was found in winter (February–March 2005). Organics, sulfate, ammonium, and nitrate were the major components of the fine aerosol fraction that were identified, while calcium and nitrate were the only two measured components contributing to the coarse mode. The aerosol mass concentrations for fine and coarse mode aerosol measured during the intensive campaigns were not typical of the long-term seasonality due largely to dynamical differences. Average fine and coarse mode concentrations during the intensive field campaigns were 1.7 μg m−3 and 2.4 μg m−3 in winter and 2.5 μg m−3 and 2.0 μg m−3 in summer, respectively. The mass balance of aerosols showed higher contributions of calcium and nitrate in the coarse mode during Saharan dust events (SDE) than without SDE.

scholarly journals New type of evidence for secondary ice formation at around −15 °C in mixed-phase clouds

2019 ◽  
Vol 19 (2) ◽  
pp. 877-886 ◽  
Author(s):  
Claudia Mignani ◽  
Jessie M. Creamean ◽  
Lukas Zimmermann ◽  
Christine Alewell ◽  
Franz Conen
Keyword(s):  
Mixed Phase ◽  
Ice Formation ◽  
Research Station ◽  
Multiplication Factor ◽  
Ice Crystal ◽  
Activation Temperature ◽  
Individual Crystal ◽  
New Type ◽  
Ice Multiplication ◽  
Mixed Phase Clouds

Abstract. Ice crystal numbers can exceed the numbers of ice-nucleating particles (INPs) observed in mixed-phase clouds (MPCs) by several orders of magnitude, also at temperatures that are colder than −8 ∘C. This disparity provides circumstantial evidence of secondary ice formation, also other than via the Hallett–Mossop process. In a new approach, we made use of the fact that planar, branched ice crystals (e.g. dendrites) grow within a relatively narrow temperature range (i.e. −12 to −17 ∘C) and can be analysed individually for INPs using a field-deployable drop-freezing assay. The novelty of our approach lies in comparing the growth temperature encoded in the habit of an individual crystal with the activation temperature of the most efficient INP contained within the same crystal to tell whether it may be the result of primary ice formation. In February and March 2018, we analysed a total of 190 dendritic crystals (∼3 mm median size) deposited within MPCs at the high-altitude research station Jungfraujoch (3580 m a.s.l.). Overall, one in eight of the analysed crystals contained an INP active at −17 ∘C or warmer, while the remaining seven most likely resulted from secondary ice formation within the clouds. The ice multiplication factor we observed was small (8), but relatively stable throughout the course of documentation. These measurements show that secondary ice can be observed at temperatures around −15 ∘C and thus advance our understanding of the extent of secondary ice formation in MPCs, even where the multiplication factor is smaller than 10.

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