Vienna- Austria - TU Wien · Vienna- Austria . 7th of April 2018 . Book of Abstracts . Preface. Dear Workshop Participant, It is my pleasure to welcome you to Vienna our 6th workshop

6th Workshop – Microphysics of ice clouds

Vienna- Austria 7th of April 2018

Book of Abstracts

Preface

Dear Workshop Participant, It is my pleasure to welcome you to Vienna at our 6th workshop 'Microphysics of Ice Clouds'. We will bring together three communities of atmospheric ice research: field measurements, laboratory studies and modellers. The joint topic is the ice nucleation in clouds. We will focus on recent observations, and open questions concerning ice formation and development in the atmosphere discussing experimental and theoretical methods including chemistry and microphysics. A particular focus will be heterogeneous ice nucleation. The development of a detailed understanding of ice clouds in the atmosphere relies on the combined use of field studies, modelling at a multitude of scales, and laboratory studies that provide the necessary fundamentals. Atmospheric ice is studied by remote sensing methods from the ground, from airplanes and satellites, or in situ from airborne platforms such as aircraft and balloons. While such observations are essential, the various methods often lack sufficient access to fundamental physic-chemical parameters of ice particles and the involved nucleation process. On the other hand, laboratory studies are usually aimed at understanding the fundamentals of the underlying processes such as the details of the nucleation process, because they can be performed under well controlled conditions. Hence, under these controlled conditions the impact of individual parameters on the ice formation process can be determined. Theoretical and numerical models are then required to transfer the knowledge of laboratory and field studies into small and large-scale models using sensible parameterizations. Moreover, the influence and impact of the nature of pre-existing aerosol particles on ice nucleation efficiency, ice microstructure and ice cloud dynamics are one of the least understood parameters in cloud microphysics. The knowledge of chemists, biologists and crystallographers about the aerosol composition has to be combined with the ice dynamic models of physicists, meteorologists and computational modellers to gain a better understanding of the whole process. For these reasons it seems viable for progress in this area to bring together scientists from various (sub-) disciplines and foster discussions between them. Given the importance of understanding the atmospheric ice nucleation process for various atmospheric applications, e.g. the modelling precipitation and for a representation of clouds in climate models, we believe the topic of the workshop “Microphysics of Ice Clouds” is of high scientific interest for scientists from various disciplines such as meteorology, chemistry, physics, and biology. A workshop provides an ideal platform for more detailed and, thus, deeper interaction between the different communities and provides the opportunity to bring together scientists from the different fields of ice research. Moreover, in contrast to a regular session at the EGU General Assembly with a rapid sequence of contributed talks (typically 12min + 3min of questions), the workshop will provide more time for discussion. This may help abolishing uncertainties and prejudices existing between scientists from different disciplines, in particular for PhD students and postdocs who represent the next generation of scientists. Vienna 7th April 2018 Hinrich Grothe

Local Organizer Prof. Dr. Hinrich Grothe TU Wien Institute of Materials Chemistry www.imc.tuwien.ac.at Email: [email protected] Tel.: +43-664-605886522

Location

Italian Culture Institute

The workshop is held in the "Italian Culture Institute - Istituto Italiano di Cultura" at Ungargasse 43, 1030 Vienna, which is easily accessible by public transport.

Istituto Italiano di Cultura

Map:

Rochusgasse to Ungargasse

Transportation

Sessions Saturday 7th April

12:00 - 13:00 Registration and Buffet

13:00 - 13:10 Opening of the workshop

Hinrich Grothe (Vienna University of Technology)

Ernst Kanitz (Italian Culture Institute, Vienna)

Mixed Session

13:10 - 13:25 1st Talk Philipp Baloh Spectroscopic investigations on organic compounds in desert dust particles

13:25 - 13:30 Discussion

13:30 - 13:45 2nd Talk Ruihao Zhu A Laboratory Study on Immersion Freezing Behavior of Aerosols in Beijing


13:50 - 14:05 3rd Talk Max Port Observations of ice-clouds from deep convective outflow during the Asian monsoon


14:10 - 14:25 4th Talk Jie Chen Freezing activity of droplets containing Humic-acid like substances (HULIS)

14:25 - 14:30 Discussion 14:30 - 14: 45 Break Out Discussion (Coffee &Cakes)

Laboratory Measurements I

14:45 - 15:00 1st Talk Shizuo Fu The Efficiency Spectrum of Ice-Nucleating

Particles and Its Application to the Parameterization of Ice Formation


15:05 - 15:20 2nd Talk Huan Yu Yang Towards the surface science of ice nucleation

on aqueous organic solutions and solid substrates


15:25 - 15:40 3rd Talk Willi Pose Raman investigations on several classes of ice nucleation active aerosols

15:40 - 15:45 Discussion 15:45 - 16:00 Break Out Discussion (Coffee &Cakes)

Laboratory Measurements II

16:00 - 16:15 1st Talk Dominik Heger Looking for the relevance of laboratory experiment to ice clouds


16:20 - 16:35 2nd Talk Jan Voráč Spectroscopy of electrical discharges in contact with water/ice


16:40 - 16:55 3rd Talk Jan Voráč Measurement of reactive radical species in discharges in contact with water/ice

16:55 - 17:00 Discussion 17:00 - 17:15 Break Out Discussion (Coffee &Cakes)

Field Measurements I

17:15 - 17:30 1st Talk Claudia Mignani

A case study of biological ice nucleating particles in the Arctic


17:35 - 17:50 2nd Talk Bruce Moffett Significance of Fresh Water Ice Nucleating

Particles in USA, UK and Mainland European Rivers


17:55 - 18:10 3rd Talk Jessie Creamean

Using spectra characteristics to define ice nucleating particle populations from north and

south of the Alps 18:10 - 18:15 Discussion 18:15 - 18:30 Break Out Discussion (Coffee &Cakes)

Field Measurements II

18:30 - 18:45 1st Talk Veronika Wolf Two totally different Arctic cirrus clouds in February - A case study


18:50 - 19:05 2nd Talk Vaughan Phillips

Raindrop-freezing fragmentation in natural clouds


19:10 - 19:25 3rd Talk Durgesh Nandan Piyush

Diurnal variation of cloud ice water path as observed from SAPHIR onboard Megha-

Tropiques 19:25 - 19:30 Discussion

19:30 - 19:45 4th Talk David Delene Research Aircraft Observations of the Micro-physics of Ice Clouds

19:45 - 19:50 Discussion 19:50 - 20:00 General Discussion 20:00 – 22:00 Dinner & After-Dinner Workshop (optional)

Spectroscopic investigations on organic compounds in desert dust particles

Philipp Baloh1*, Yvonne Boose2,3*, Michael Plötze4, Ulrike Lohmann2, Zamin Kanji2, and Hinrich Grothe1

1Institute of Materials Chemistry, TU Wien, Vienna, Austria;

2ETH Zürich, Institute for Atmospheric and Climate Science, Zürich, Switzerland;

3German Aerospace Center (DLR), Institute for Atmospheric Physics, Oberpfaffenhofen;

4ETH Zürich, Institute for Geotechnical Engineering, Zürich.

* Email: [email protected], [email protected] Mineral dust particles are the most abundant ice nucleating particles (INPs) found in the

atmosphere. Their mineralogical composition in part dictates if they can act as strong INPs or

not. Certain minerals such as microcline show an exceptionally strong ice nucleating

potential, yet its presence in a desert dust particle alone does not seem to be the determining

factor for ice nucleation. In a mixed phase particle, strong ice nucleating minerals may not

come to their full potential due to chemical and mechanical aging that can inactivate their

nucleation sites or due to an interference with compounds that coat the particles, yet only

contribute very little to its overall mass. Carbonic acids, for example, are well known to

hinder ice nucleation to a certain extent and other compounds may simply be able to shield, or

react with the surface in a way that antagonizes the nucleation active sites. What kind of

surface chemicals could be present on dust particles can vary highly depending on the source

of the particle but also on the atmospheric conditions it encounters during transport.

In this study, we investigate how mineralogy, crystal water, and heat labile organic

compounds on dust particles affect the ice nucleating behavior of desert dust collected from

the soil or after atmospheric transport. Before and after heating three dust samples to 573 K,

we measured their ice active surface site density (ns) in the deposition and condensation mode

and used X-ray diffraction (XRD), and Raman- and Infrared- spectroscopy to search for the

cause of observed differences in ns. Infrared spectroscopy was conducted on the bulk material

and Raman spectroscopy on single particles by means of micro-Raman mapping of impacted

dust. Indications for heat labile organic compounds were found in two samples as well as

indications for soot. However, also the inorganic composition in the form of crystal water –

and its subsequent change in mineralogic composition due to its loss – seems to play a role for

one sample. While the ns of this sample increased after heating, in a second sample the

release of heat labile organic compounds led to suppression of the ice nucleation ability. Our

study shows that apart from mineralogy, other factors such as organics and crystal water can

alter the ice nucleation behavior of desert dust during atmospheric transport in various ways.

A Laboratory Study on Immersion Freezing Behavior of Aerosols in Beijing

Ruihao Zhu, Yangze Ren, Shizuo Fu, and Huiwen Xue

Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, China ([email protected])

This study investigates the immersion freezing behavior of aerosols in Beijing. Three types of

local aerosols are considered in the experiments: dry deposition aerosols, pollen, and soil

particles. We also investigate the immersion freezing behavior of montmorillonite, to compare

with the local aerosols. The experimental data show that there exist different onset

temperatures for different types of aerosols, above which freezing does not occur. The

average onset temperatures for dry deposition aerosols, pollen, soil particles, and

montmorillonite are respectively -13.8℃, -13.1℃, -14.3℃, and -14.5℃. We then use a θ-pdf

scheme to parameterize the freezing process. This scheme assumes that the cosine of contact

angle follows a lognormal distribution. The calculated curves fit well with the data points.

The fitting parameters show that the nucleation efficiencies of different aerosols are quite

different. There is a 5000-10000 times difference in nucleation rate between dry deposition

aerosols and soil particles. Results of this study indicate that pollen and dry deposition

aerosols are more efficient than soil particles in immersion freezing mode.

Observations of ice-clouds from deep convective outflow during the Asian monsoon

Max Port1, Oliver Schlenczek1,6, Christoph Mahnke1, Ralf Weigel2, Silvia Viciani3, Francesco D'Amato3, Gennady Belyaev4, Fred Stroh5, Stephan Borrmann1,2

1Max-Planck lnstitute for Chemistry, Mainz, Germany

2University of Mainz, Germany

3lnstituto Nazionale di Ottica, Firenze, ltaly

4Myasishchev Design Bureau, Zhukovsky, Russia

5Forschungszentrum Juelich, Juelich, Germany

6Now at Max Planck lnstitute for Dynamics and Self-Organization, Goettingen, Germany

The StratoClim field campaign was carried out using the Russian high-altitude aircraft M-55

Geophysica and took place during the monsoon season during July and August 2017 in Nepal.

A total number of 8 flights (≈ 30 flight hours) were carried out within the Asian Monsoon

Anticyclone (AMA) over Nepal, lndia and Bangladesh, reaching up to altitudes of 20

kilometers thereby. A set of 5 different underwing cloud probes (including a holographic

device) covers a particle size diameter range from 2.5µm - 6400µm (time resolution: 1Hz,

uncertainty of number concentrations ≈ 10%). We present data of size distributions and

number densities for ice particles sampled during approximately 7 hours of cloud passes in

the sub-tropical UTLS region above 200hPa.

During Flight 8 on August 10th the aircraft encountered an outflow event of a large convective

system over northern India. As shown in the figure, combining results from the ice particle

instruments and the carbon monoxide measurements from COLD (time resolution: 1Hz,

sensitivity: 2 ppb, uncertainty: 6%), we see periods where increased cloud particle number

concentrations (up to 10 particles per cm3) and elevated CO mixing ratios (up to 100 ppb)

coincide. The observation of high CO mixing ratios is indicative for low level air carried aloft

by deep convection. ln the presentation the observed ice particle size distributions, their

number densities and their shapes at the cold point tropopause are shown for pressure levels

of around 85 hPa, and in particular from the region of the Asian Monsoon anticyclone.

Freezing activity of droplets containing Humic-acid like substances (HULIS)

Jie Chen1, Zhijun Wu1, Yao Bai1, Min Hu1, and Heike Wex2

1Peking University, Beijing, China, ([email protected]).

2Leibniz Institute for Tropospheric Research, 04318, Leipzig, Germany

Currently, the ice nucleation efficiency of organic materials is not well-recognized. HULIS are important surface- active components of water soluble organic carbon, its presence may depress the surface tension of droplets, therefore, impacting the cloud droplet formation and the subsequent ice crystallization. In the present study, a recently developed and well calibrated optical droplet cooling array was used to measure the ice nucleating efficiency of droplets containing HULIS derived from ambient particulate matters, in parallel with the determination of surface tension by a drop shape analyzer (DSA-30) and chemical composition by an ESI-Orbitrap mass spectrometry. The HULIS were extracted from particles collected in the atmosphere over Beijing using a well-established method (Lin et al., 2010), and then dissolved with Milli-Q water. The HULIS carbon content of each sample was quantified by a total organic carbon analyzer. The experiments showed that 1μl droplet containing HULIS (15.8 - 96.7 mg C/L) frozen in the temperature range from -9°C to -22°C, which was above the pure water background and the typical homogenous freezing temperature (below -38°C). Droplets with higher HULIS content (96.7 mg C/L, surface tension 66.3 mN/m) frozen at a lower temperature in contrast to those with lower HULIS carbon (15.8-37.8 mg C/L, surface tension 70.2-71.5 mN/m). The freezing activities of mixture of ammonium sulfate and HULIS and related to chemical composition of HULIS will also be presented.

Lin, P., Huang, X.-F., He, L.-Y., and Zhen Yu, J.: Abundance and size distribution of HULIS in ambient aerosols at a rural site in South China, J. Aerosol Sci., 41, 74-87, doi:10.1016/j.jaerosci.2009.09.001, 2010.

The Efficiency Spectrum of Ice-Nucleating Particles and Its Application to the Parameterization of Ice Formation

Shizuo Fu1 and Huiwen Xue2

1Peking University, Department of Atmospheric and Oceanic Sciences, China ([email protected]);

2Peking University, Department of Atmospheric and Oceanic Sciences, China ([email protected]);

Ice-nucleating particles (INPs) can heterogeneously nucleate ice crystals above 235 K. They

hence play a very important role in the evolution of mixed-phase clouds, and subsequently

exert a significant influence on the hydrological cycle and the radiative balance of the earth

system. However, due to its complexity, heterogeneous nucleation has not been well

understood, leading to remarkable differences in the parameterizations of heterogeneous

nucleation. These differences have been found to be responsible for the differences in cloud

fraction and therefore cloud radiative forcing among the models.

Based on the measurement performed with the continuous-flow diffusion chamber (CFDC),

this study derived an efficiency spectrum of INP. The spectrum shows that INP concentration

exponentially increases with decreasing efficiency. The efficiency spectrum was then

implemented into the classical nucleation theory (CNT) to compare the ice concentration

predicted by the CNT with that predicted by the deterministic theory (DT) at different cooling

rates. Results show that when the cooling rate decreases from the typical cooling rate for

convective clouds (~1 K min-1) to the typical cooling rate of stratiform clouds (~1 K day-1),

the ice concentration predicted by the CNT becomes progressively higher than that predicted

by the DT. This is because CNT allows the INPs that are not detected by the CFDC at the

current temperature to contribute to the ice formation while the DT does not. This study

suggests that the CNT, into which the efficiency spectrum of INP is incorporated, should be

used to parameterize ice formation.

Towards the surface science of ice nucleation on aqueous organic solutions and solid substrates

Huan Yu Yang1,2, Artiglia Luca1, Fabrizio Orlando1, ShuZhen Chen1,2, XiangRui Kong1, and Markus Ammann1

1Paul Scherrer Institut, Villigen, Switzerland,

2ETH Zürich, Zürich, Switzerland,

The nucleation of ice is an important process in chemistry, physics and atmospheric science. Although ice nucleation has been studied since long, our understanding of ice nucleation is still far from complete, particularly from a molecular point of view. The hydrogen bonding structure of H2O can be significantly different between liquid water to ice. This structure is responsible for most of the difference in physical and chemical properties between the different aggregation states of water. The difference between the hydrogen bonding structure of liquid water and ice can be experimentally observed by near edge X-ray absorption fine structure (NEXAFS) spectroscopy at the oxygen K-edge, because it involves resonant transitions into unoccupied molecular orbitals, which are very sensitive to the nearest neighbors of oxygen atoms. NEXAFS spectroscopy can be performed in electron yield mode, in which Auger electrons emitted upon initial core hole excitation are detected, which provides a surface sensitive NEXAFS spectrum. Experiments reported in this work were performed at the near ambient photoelectron spectroscopy endstation (NAPP) at the SIM and NANOXAS beamline at the Swiss Light Source (PSI, SLS). Since it has been suggested that some organic compounds have the potential to modify the structure of water that influences the nucleation of ice, we have measured electron yield NEXAFS spectra from a liquid jet of aqueous solution containing tetrabutylammonium bromide (TBAB). The O K-edge spectra exhibit a clear change in the relative features. These features represent hydrogen bonding at different level, indicating that the cationic head group of TBAB induces a significant variation of the hydrogen bonding network near the surface of the aqueous solution. On the other hand, the hydrogen bonding structure of adsorbed water on a solid substrate may control deposition nucleation, which is another pathway of heterogeneous ice nucleation. The hydrogen bonding structure may be affected by short and long range interactions between the substrate and the adsorbed water molecules. As a first approach, we have measured electron yield NEXAFS spectra of adsorbed water on graphite and titanium dioxide (TiO2) under subsaturated conditions with respect to ice. Under isobaric conditions and by varying the temperature of the sample, we can change the relative humidity, which leads to varying amounts of adsorbed water in equilibrium between the substrate and water vapor. Preliminary results show that, under different relative humidity, the weakly and strongly coordinated OH bond of adsorbed water on TiO2 and graphite show different contributions to the Auger electron yield NEXAFS spectrum, that is, the resonant transitions near the oxygen K-edge vary with relative humidity and temperature. We attribute this to the modification of the organization of water molecules in response to the interactions with the solid substrate. In view of the application of the NEXAFS technique, we believe it opens up a powerful tool to address the surface science of ice nucleation in the future.

Raman investigations on several classes of ice nucleation active aerosols

Willi Pose

University of Innsbruck, Institute of Physical Chemistry, Innrain 52c, A-6020 Innsbruck, Austria

Heterogeneous ice nucleation is the major cause for solid and liquid precipitation via ice

cloud and mixed phase cloud formation. Aerosol particles in suitable size and composition

trigger thereby the phase change of supercooled liquid water to hexagonal ice. Several classes

of ice active aerosols (IN) are known which nucleate ice at different temperatures.

Quantitatively, IN are well described though the heterogeneous freezing path understanding

lacks micro physical findings. The class of organic IN acts on the warmer temperature range.

Some amino acids are active for temperatures up to 267 K. With Alanine, Serine and Tyrosine

in immersion mode (respectively) is a Raman-microscopy observation performed to learn of

how those IN transform liquid water structure to ice. Therefore the changes on the Raman

shift spectra of the translational and OH vibrations within a water droplet are evaluated.

Additionally the influences by some insoluble IN are investigated. The soluble amino acids in

pure water at 268 K raise the shoulder of the OH-peak and the translational peak. This

happens in pure water at 12 K (present experiment) lower temperature, which indicates the

step before freezing. Comparing the translation peak and the OH-Peak it is a mirrored

behaviour found. The insoluble materials do not stimulate the vibrational modes of water like

the amino acids what suggests a different freezing mechanism or is a difference in freezing

mode.

Looking for the relevance of laboratory experiment to ice clouds

Dominik Heger

Department of Chemistry and RECETOX, Faculty of Science, Masaryk University, Kamenice 5/A8, 625 00 Brno, Czech Republic;

[email protected], http://hegerd.sci.muni.cz/

I wish to share our spectroscopic and microscopic observations if ice impurities and to

question their relevance to ice clouds chemistry and physics. We apply UV-Vis and

fluorescence spectroscopies to learn about the ice surface acidities1-3 and compounds

aggregation.4,5 In recent environmental scanning electron microscopy studies details of the

evaporation of water from the salty ice (frost-flowers) showed the presence of microscopic

crystals of salt.6

(1) Vetráková, Ľ.; Vykoukal, V.; Heger, D. International Journal of Pharmaceutics 2017,

530, 316.

(2) Heger, D.; Klanova, J.; Klan, P. Journal of Physical Chemistry B 2006, 110, 1277.

(3) Krausko, J.; Runštuk, J.; Neděla, V.; Klán, P.; Heger, D. Langmuir 2014, 30, 5441.

(4) Krausko, J.; Malongwe, J. K. E.; Bičanová, G.; Klán, P.; Nachtigallová, D.; Heger, D.

The Journal of Physical Chemistry A 2015, 119, 8565.

(5) Heger, D.; Jirkovsky, J.; Klan, P. Journal of Physical Chemistry A 2005, 109, 6702.

(6) Yang, X.; Neděla, V.; Runštuk, J.; Ondrušková, G.; Krausko, J.; Vetráková, Ľ.; Heger,

D. Atmos. Chem. Phys. 2017, 17, 6291.

Spectroscopy of electrical discharges in contact with water/ice

Jan Voráč, Pavel Dvořák, Martina Mrkvičková

Department of Physical Electronics, Faculty of Science, Masaryk University Kotlářská 2, Brno 611 37, Czech Republic

[email protected]

Figure 1. An overview spectrum of a streamer discharge ignited in ambient air in contact with

ice surface. Note the different axes scales.

Plasma in the form of electrical discharge is readily formed during various occasions in

everyday life, including thunderstorms or corona discharges on high-voltage conductors.

Plasma is also often a source of radiation which can be spectroscopically analysed and

provide useful information about the processes taking place. In [1] we have analysed

spectrum of microdischarges formed in contact with liquid water and observed strongly

inequilibiral distribution of quantum states, caused mainly by violent dissociation of water

molecules.

In Figure 1 a preliminary measurement of emission of microdischarges ignited in ambient air

and propagating along an ice surface is presented. The spectrum is absolutely dominated by

nitrogen second positive system, or N2 (C 3Πu → B 3Πg) electronic transition in the range 290 -

450 nm. Between 500 and 1100, much weaker emission of N2 (B 3Πg → A 3Σu+), or first positive

system, was observed. According to the first analyses, the vibrational distribution of nitrogen

molecules can be vaguely described by vibrational temperature around 4000 K, but deviations

from Boltzmann distribution were present

[1] Voráč, J., Synek, P., Procházka, V., & Hoder, T. (2017). State-by-state emission spectra

fitting for non- equilibrium plasmas: OH spectra of surface barrier discharge at argon/water

interface. Journal of Physics D: Applied Physics, 50(29), 294002.

Measurement of reactive radical species in discharges in contact with water/ice

Pavel Dvořák, Jan Voráč, Vojtěch Procházka, Martina Mrkvičková

Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářská 2, Brno 611 37, Czech Republic

[email protected]

Plasma generated by means of electric discharges produces number of reactive radical species

that can interact with surfaces of solid or liquid objects that are in contact with plasma and

initiate number of chemical and physical reactions at the surfaces or inside liquid

environments. Plasma ignited in air with contact with aqueous solutions presents an actual

topic of research that is motivated by research in the field of plasma medicine and by

questions related to the processes occurring in the plasma at the gas-liquid interface. Logical

extension of this field is the research of plasma that is in contact with ice, i.e. research of field

that is connected with problematics of both hydrometeors in thunderstorms and removal of

toxic agents from water solutions.

Since radical species usually play the key-role in plasma-surface interactions, we apply the

fluorescence method for their detection. Whereas single-photon excitation is used for

detection of most molecular species (including the OH radical), two-photon excitation is

required for detection of most atomic species (including atomic radicals H, N and O).

Actually, we deal with fluorescence measurements in plasma that is in contact with liquid

water or with high concentration of water vapour and our plan is to continue with

measurements in plasma ignited at ice surface. The interaction of the excitation laser beam

with the ice surface produces number of parasitic signals. Fortunately, we have solved this

problematic in analogical discharges that were in contact with various solid or liquid surfaces

[1]. We observed e.g. generation of both OH and H radicals in plasma above water surface.

Concentration of atomic H radicals in plasma with water vapour decreased strongly with an

increase of water vapour content due to the reaction H + H2O <-> OH + H2 [2].

[1] M. Mrkvičková, J. Ráheľ, P. Dvořák, D. Trunec, T. Morávek: Plasma Sources, Science

and Technology, 25 (2016), 055015.

[2] V. Procházka, Z. Tučeková, P. Dvořák, D. Kováčik, P. Slavíček, A. Zahoranová, J. Voráč:

Plasma Sources, Science and Technology, 27 (2018), 015001.

A case study of biological ice nucleating particles in the Arctic

Claudia Mignani1, Daniel Weber2, Jann Schrod2, Lukas Zimmermann1, Heinz Bingemer2, Franz Conen1, Christine Alewell1

1 Department of Environmental Sciences, University of Basel, 4056 Basel, Switzerland ([email protected])

2 Institute for Atmospheric and Environmental Sciences, Goethe University, 60438 Frankfurt/Main, Germany

The formation of ice in clouds impacts Earth’s water and energy budget1. A prerequisite for initial

phase transition from liquid water to ice in mixed-phase clouds is the presence of ice nucleating

particles (INPs)2. At temperatures above - 15°C, biological INPs are likely the dominant particles

initiating the liquid-ice phase transition in clouds3. However, the sensitivity of cloud glaciation to

biological INPs is still not fully understood. Here, we present preliminary results of INP

concentrations and characteristics derived from atmospheric aerosols sampled during a 7-day field

campaign at two different sites in northern Norway (approx. 70°N and 23°E) in September 2017.

We combine offline ice nucleation experiments using the isostatic diffusion chamber FRankfurt

Ice Deposition FreezinG Experiment (FRIDGE) with offline single-particle electron microscopy

analysis for INP composition. We focus on INPs active at moderate subzero temperatures (>-

20°C) and differentiate between characteristics of INPs active above and below - 15°C. Most

particles that were analysed were of biological origin including particles lying in areas on the

sampling surface where ice was formed at - 20°C. This study can provide insight into typical

characteristics of biological INPs and helps to attribute sources of INPs active at relatively warm

temperatures.

REFERENCES 1 Pruppacher and Klett (1997), Microphysics of Clouds and Precipitation, 2nd ed., Kluwer Acad.,

Dordrecht, Netherlands. 2 Field et al. (2017), Chapter 7. Secondary Ice Production: Current state of the science and

recommendations for the future. Meteorol. Monogr., AMS MONOGRAPHS-D-16-0014.1. 3 Murray et al. (2012) Ice nucleation by particles immersed in supercooled cloud droplets.

Chemical Society Reviews 41, 6519-6554.

Significance of Fresh Water Ice Nucleating Particles in USA, UK and Mainland European Rivers

Moffett, B.F.1, DeMott2, P.J., Schmale3, D.G., Scheel4, J.F., Fröhlich-Nowoisky, J.4, McKay, R.M.5 and Hill,T.C.J.6

1Ocean Lab, Fishguard Harbour, Goodwick, Pembrokeshire SA64 0DE, United Kingdom 2Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-

1371 3VirginiaTech, Department of Plant Pathology, Physiology, and Weed Science, 413 Price

Hall (0331), 170 Drillfield Drive, Blacksburg VA 24061-0331 4Max-Planck-Institut für Chemie, Hahn-Meitner-Weg 1, D-55128 Mainz, Germany

5Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403

6Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371

The nature of the ice nucleating particles (INP), which initiate precipitation, is still a matter of

debate. Most work on INPs has concentrated on bacteria such as Pseudomonas syringae and

other microbes including the fungus Mortierella alpine. Fresh water INP are now beginning

to be assessed as a potential source of atmospheric ice nuclei. Currently there are few

publications in this area. In this presentation I will demonstrate that INP are a ubiquitous

feature of all rivers analysed in Europe, UK and North America. The INP occur at numbers at

least 1000 times greater than in ocean water and the great majority are biogenic. As in the

oceans these INP are likely to be aerosolized by bubble bursting. Taking into account the

relative surface area of rivers compared to that of the oceans, the high numbers of INP in

fresh water may be more important to atmospheric processes than previously thought.

Using spectra characteristics to define ice nucleating particle populations from north and south of the Alps

Jessie M. Creamean1,2, Claudia Mignani3, Franz Conen3

1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA

2Physical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA

3Department of Environmental Sciences, University of Basel, Switzerland One of the least understood cloud processes is modulation of their microphysics by aerosols,

specifically of cloud ice by ice nucleating particles (INPs). To directly assess INP impacts on

cloud ice and subsequent precipitation formation, measurements in cloud environments are

necessary but difficult given the logistical challenges associated with airborne measurements

and separating interstitial aerosol from cloud residues. One solution is measurements at

mountaintop research stations which are commonly exposed to cloudy conditions. Here, we

present preliminary results from a comparison of INP spectral characteristics in air, cloud

rime, and fresh fallen snow for two winter storm cases at the High Altitude Research Station

Jungfraujoch. The goal of the study was two-fold: (1) to assess variability in wintertime INPs

based on storm direction and magnitude and (2) to evaluate INPs between different sampling

substances using normalized differential INP spectra. Both storms days were subject to strong

winds (average of 9 and up to 18 m s-1), in-cloud conditions, and snowfall. However,

temperatures were much warmer (−8 °C on average) as winds originated from the north

during the first storm day (15 Feb 2018) as compared to the southerly winds and colder

temperatures (−15°C on average) of the second storm day (23 Feb 2018). Such contrasting

meteorological conditions and aerosol sources led to disparate INP spectra from north to south

of Jungfraujoch and when comparing aerosol to cloud rime and snow samples. Evaluating

normalized differential INP spectra exhibited variable modality and shape—depending on the

types of INPs present—and may serve as a benchmark for comparing different sampling

substances.

Two totally different Arctic cirrus clouds in February - A case study

Veronika Wolf

Department of Computer Science, Electrical and Space Engineering, Lulea University of Technology, Kiruna, Sweden

[email protected] Cirrus clouds consist of ice crystals, which can have different shapes and sizes and vary in

number concentration. These diverse characteristics can lead to varying net cloud radiation.

For better weather and climate models and remote sensing retrieval, precise knowledge of

particle properties is required. For this purpose, balloon-borne in-situ measurements are

carried out in Kiruna, Sweden. The images obtained from the in-situ imager can be used to

determine particle properties such as size, shape, and number concentration.

Here two measurements are presented which reveal very different properties. On 20.2.2013 a

cirrus with many and very small particles has been measured. But on 12.2.2016 there was a

cirrus with very large and rather few particles. The shapes of the particles on the two days

were also totally different. On 20.2.2013 almost all particles were compact, but on 12.2.2016

most particles were irregular, rosettes or columns. That the particle properties of the two

clouds were so diverse was due to their origin. The particles on 20.2.2013 were formed

directly from the gas phase to the ice phase. By contrast, the particles have been generated via

the liquid phase on 12.2.2016.

Raindrop-freezing fragmentation in natural clouds

Vaughan Phillips

Lund University, Dept of Physical Geography and Ecosystem Science, Sölvegatan 12, S-223 62 Lund, Sweden

[email protected]

A numerical formulation is provided for secondary ice production during fragmentation of

freezing drops. This is obtained by pooling laboratory observations from past published

studies and by theoretically considering energy conservation of collisions. There are two

modes of the scheme: fragmentation of spherical freezing of raindrops, and that caused by

freezing in collisions with larger ice particles.

Microphysical simulations with a parcel model of fast ascent (8 m/sec) between -10° and -

20°C are validated against aircraft observations of tropical maritime deep convection. Ice

enhancement by an order of magnitude is predicted from inclusion of raindrop-freezing

fragmentation, as observed. The Hallett-Mossop (H-M) process was active too. Both

secondary ice mechanisms (H-M and raindrop-freezing) are accelerated by a positive

feedback with collisional raindrop-freezing.

An energy-based theory of the processes in a single drop is proposed explaining the lab

observations of fragment numbers depending on size and freezing temperature. To illustrate

the behaviour of the scheme, the glaciation of idealised monodisperse populations of drops is

elucidated with an analytical 0D theory treating the freezing in drop-ice collisions by a

positive feedback of fragmentation. When drops are too few or too small, especially at

temperatures far from -15°C, there is little ice multiplication on realistic time-scales of natural

clouds, but otherwise high ice enhancement (IE) ratios of up to 100-1000 are possible.

Theoretical formulae for glaciation times and growth rates and maximum IE ratios are

proposed.

Diurnal variation of cloud ice water path as observed from SAPHIR onboard Megha-Tropiques

Durgesh Piyush and Jayaraman Srinivasan

Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, 560012, India [email protected]

Ice Water Path (IWP) plays a crucial role in determining the earth’s radiation budget. The

accurate measurement of ice water path is important in evaluating climate models. The

diurnal variations of ice water path are not known well due to inadequate temporal resolution

in polar orbiting satellites. SAPHIR (Sondeur Atmosphérique du Profil d’Humidité

Intertropicale par Radiométrie) onboard Megha-Tropiques (MT) with an inclination of 20

degree and swath of around 1700 km, provides observations 4 to 5 times a day for a given

location. In this study SAPHIR observations were used to find the diurnal variation of IWP. A

neural network based IWP retrieval algorithm was used to get the IWP from brightness

temperatures of SAPHIR. The diurnal amplitude, peak and mean of IWP for different regions

were calculated. Diurnal amplitude was found to be larger over land than over ocean. The

diurnal peak was observed in the evening over land, whereas it was in the morning over the

ocean. We have also used GPM-GMI derived IWP and SAPHIR derived deep convective

pixels to compare the diurnal variations. One year data of SAPHIR and GMI was used to

highlight the advantage to SAPHIR sampling in the diurnal variation study, the result shows

that average SAPHIR pixels per hour at any location is 5 to 7 times more than that of GMI.

Research Aircraft Observations of the Micro-physics of Ice Clouds

David J. Delene1, Nicholas J. Gapp1, Kurt Hibert2, and Dennis Afseth2

1University of North Dakota, Grand Forks, North Dakota, United States of America,

2Weather Modification International, Fargo, North Dakota, United States of America Research aircraft provide unique observations of the micro-physics of ice clouds. The

University of North Dakota (UND) has conducted airborne micro-physics research since the

1970’s using the Cessna Citation II twin-engine fanjet aircraft. The North Dakota Citation

Research Aircraft is now operated by Weather Modification International (WMI) of Fargo,

North Dakota. WMI and UND working together provide a platform capable of conducting a

wide range of field projects in a cost-effective manner, while providing a unique educational

experience for students. The Citation Research Aircraft has a number of design and

performance characteristics that make it an ideal platform for a wide range of atmospheric

studies, including sampling at high altitude (40,000 ft) which is critical for ice cloud

observations. WMI has the experience to install the custom scientific instrumentation required

for conducting in-situ observations of ice clouds, while UND provides the scientific

knowledge to obtain measurements that achieve the scientific objectives. Recent Citation

projects include the measurements of cirrus cloud particles in Florida thunderstorm anvils

during 2015 (CAPE2015 field project). During the CAPE2015 field project, ice particles were

sampled between an altitude of 29,000 ft and 40,000 ft on eight research flights. In-situ

observations were made using a Two-Dimensional Stereographic probe (2D-S) and a

Nevzorov Water Content Probe (Nevzorov). Remote sensing observations were made by the

United States Navy’s Mid-Course Radar (MCR). The MCR tracked the aircraft to obtain high

resolution radar reflectivity concurrent with in-situ probes. The concurrency of the

observations allows for examination of the variation of radar reflectivity that links cloud

micro-physics to the large-scale cloud structure and enables the understanding of cloud

evolution over time. A critical component to understanding cirrus clouds is robust software

that automates the processing of in-situ probe data. Correctly understanding and processing

two-dimensional cloud probe images to generate particle spectra is critical for comparison of

in-situ and remotely sensed data.

Sponsors & Partners

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Vienna- Austria - TU Wien · Vienna- Austria . 7th of April 2018 . Book of Abstracts . Preface. Dear Workshop Participant, It is my pleasure to welcome you to Vienna our 6th workshop

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Vienna- Austria - TU Wien · Vienna- Austria . 7th of April 2018 . Book of Abstracts . Preface. Dear Workshop Participant, It is my pleasure to welcome you to Vienna our 6th workshop