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Laboratory and Field Studies of Ice Nucleation: Natural and Anthropogenic Effects

English title Laboratory and Field Studies of Ice Nucleation: Natural and Anthropogenic Effects
Applicant Lohmann Ulrike
Number 127275
Funding scheme Project funding (Div. I-III)
Research institution Institut für Atmosphäre und Klima ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.11.2009 - 31.10.2013
Approved amount 426'916.00
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Keywords (7)

Ice nucleation; Aerosol-cloud interaction; Laboratory and field studies; Clouds; Mineral Dust; Freezing; Aerosol-Cloud-Interactions

Lay Summary (German)

Lead
Lay summary
Neben CO2, dessen Einfluss auf das Klima inzwischen erwiesen ist, gibt es noch eine Reihe anderer Einflussgrössen auf das Klima z.B. Methan aber auch Staubpartikel (Aerosole) und deren Einfluss auf die Bildung von Wolken. Der letztgenannte zählt zu den am wenigsten verstandenen und quantifizierbaren Effekten auf das Klima und wird unter dem Oberbegriff Aerosol-Wolken-Wechselwirkung zusammengefasst.Wolken bestehen aus flüssigen Tröpfchen, die je nach Umweltbedingungen auch deutlich unter 0° C als sogenannte unterkühlte Tröpfchen existieren können, und/oder Eiskristallen. Besonders die Bildung von Eiskristallen ist ein wichtiger Prozess in Wolken, weil die Niederschlagsbildung häufig über die Eisphase initiiert wird. Zudem reflektieren Eiskristalle Licht anders als flüssige Tröpfchen. Die Bildung von Eiskristallen setzt entweder sehr tiefe Temperaturen voraus (kälter als -38° C) oder die Anwesenheit von sogenannten Eiskeimen, die die Bildung von Eis oder das Gefrieren von Tröpfchen katalysieren. Dieses Projekt befasst sich mit dem Einfluss dieser Eiskeime auf Wolken und deren Veränderung durch menschliche Aktivitäten. Es ist bekannt, dass z.B. Wüstenstaub sehr gut als Eiskeim wirkt. Die physikalischen und chemischen Eigenschaften, die dafür verantwortlich sind, sind jedoch wesentlich weniger gut bekannt und noch weniger weiss man darüber, wie diese Eigenschaften durch menschliche Emissionen, z.B. von Abgasen, beeinflusst werden können.Um diese Einflüsse zu untersuchen, werden im Labor Staubpartikel als Aerosol (d.h. luftgetragen) in einem Edelstahltank gespeichert und mit verschiedenen Spurengasen versetzt, die in der Atmosphäre als Folge menschlicher Aktivitäten anzutreffen sind (z.B. Schwefeldioxid, Stickoxide, Ozon). Während dieser künstlichen "Alterung" der Aerosole werden kontinuierlich deren Eigenschaften mit verschiedenen Methoden untersucht. Eine zentrale Rolle spielen dabei Instrumente, die in unserer Arbeitsgruppe entwickelt wurden, und mit denen man die Bildung von Eis auf Aerosolen untersuchen kann. Da es verschiedene Mechanismen gibt, die die Eisbildung initiieren können (z.B. Eisbildung direkt auf den Partikeln oder das Gefrieren von bereits existierenden unterkühlten Tröpfchen) sind verschiedene Instrumente notwendig, in denen diese Prozesse simuliert werden. Aus diesen Messungen sollen schlussendlich Parametrisierungen über die Initiierung der Eisphase für die verschiedenen Eiskeime und die verschiedenen Gefriermechanismen abgeleitet werden. Diese Parametrisierungen können dann in Klimamodellen verwendet werden um den Einfluss von anthropogenen Aerosolen auf Eiswolken zuverlässiger abzuschätzen zu können.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Laboratory studies of immersion and deposition mode ice nucleation of ozone aged mineral dust particles
Kanji Zamin, Welti André, Chou Cédric, Stetzer Olaf and Lohmann Ulrike (2013), Laboratory studies of immersion and deposition mode ice nucleation of ozone aged mineral dust particles, in Atmos. Chem. Phys., 9097.
Ice nuclei properties within a Saharan dust event at the Jungfraujoch in the Swiss Alps
Chou C., Stetzer O., Weingartner E., Juranyi Z., Kanji Z.A. and Lohmann U (2011), Ice nuclei properties within a Saharan dust event at the Jungfraujoch in the Swiss Alps, in Atmos. Chem. Phys., 4725.
Contact freezing experiments of kaolinite particles with cloud droplets
Ladino L., Stetzer O., Lüönd F., Welti A., Lohmann U., Contact freezing experiments of kaolinite particles with cloud droplets, in Journal of Geophysical Research, 116.
Experimental Study of Collection Efficiencies between Submicron Aerosols and Cloud Droplets
Ladino Luis, Stetzer Olaf, Hattendorf Bodo, Günther Detlef, Croft Betty, Lohmann Ulrike, Experimental Study of Collection Efficiencies between Submicron Aerosols and Cloud Droplets, in Journal of the Atmospheric Sciences, 68(9).
Ice nucleation properties of volcanic ash from Eyjafjallajokull
Hoyle C.R., Pinti V., Welti A., Zobrist. B., Marcolli C., Luo B., Hoeskuldsson A., Mattsson H.B., Stetzer O., Thorsteinsson T., Larsen G., Peter T., Ice nucleation properties of volcanic ash from Eyjafjallajokull, in Atmospheric Chemistry and Physics, 11(18), 9911-9926.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Goldschmidt 2011 Conference Talk given at a conference Time dependence of immersion freezing: an experimental study on size selected kaolinite particles 14.08.2011 Prague, Czech Republic Stetzer Olaf; Lohmann Ulrike; Welti André;
The XXV IUGG General Assembly Talk given at a conference Time dependence of immersion freezing: an experimental study on size selected kaolinite particles 28.06.2011 Melbourne, Australia Lohmann Ulrike; Nagare Baban Parasharam; Sierau Berko; Welti André; Ladino Moreno Luis; Stetzer Olaf;


Awards

Title Year
ETH Medal for PhD thesis 2013

Associated projects

Number Title Start Funding scheme
150169 Laboratory studies on the ice nucleation properties of fresh and aged mineral dust aerosols 01.11.2013 Project funding (Div. I-III)
111898 Laboratory and Field Studies of Ice Nucleation: Natural and Anthropogenic Effects 01.07.2006 Project funding (Div. I-III)
132199 Field and laboratory studies of the chemical composition and mixing state of black carbon particles and their ability to act as cloud condensation and ice nuclei 01.11.2010 Project funding (Div. I-III)
150169 Laboratory studies on the ice nucleation properties of fresh and aged mineral dust aerosols 01.11.2013 Project funding (Div. I-III)
107663 Ice Nucleation in Mixed-Phase Clouds 01.07.2005 Project funding (Div. I-III)
152813 Measurements of water uptake by fresh and aged wood-burning soot particles in the subsaturated regime 01.12.2014 Project funding (Div. I-III)

Abstract

The formation of ice is an important factor, which determines the microphysical and radiative properties of clouds. As a consequence, the lifetime of clouds and precipitation patterns are influenced and ultimately the climate. Ice can form by homogeneous freezing or by heterogeneous nucleation on pre-existing airborne particles. Heterogeneous nucleation may be sub-divided into three mechanisms. Some aerosol particles like mineral dusts from desert regions are known to be good ice nuclei. The radiative forcing of greenhouse gases is generally well understood but there is still a lack of knowledge about the influence of anthropogenic aerosol emissions on clouds and their respective radiative forcings through the so-called aerosol indirect effect. The formation of ice is one of the largest uncertainties in this context. For example, anthropogenic emissions can lead to an increase in ice nuclei and accelerate precipitation by enhancing the formation of precipitation-sized particles through the Bergeron-Findeisen process. On the other hand, emissions of soluble aerosols or trace gases can reduce the efficiency of natural ice nuclei to initiate freezing with an opposite effect on climate. A greater understanding of the ice nucleation mechanism and the effect of anthropogenic emissions on it is required in order to improve our ability to simulate these processes. With an improved knowledge it will be possible to assess if the net effect of the anthropogenic aerosol enhances or reduces its ability to form ice in clouds and to estimate the respective radiative forcings. In this proposal, we will address the following questions:1.Which aerosol is most active in which heterogeneous freezing mechanism?2.In which direction and to which degree is their ice nucleation activity influenced by atmospheric trace gases and organic components?3.Can these ageing processes be linked to certain chemical signatures in these aerosols?4.Can we use the chemical signatures of ice nuclei found in the laboratory to understand ice nuclei measurements obtained in the field?The complex nature of the nucleation mechanism, for which there is still no comprehensive theoretical model available yet, suggests a step-wise approach under idealized and well controlled conditions in a laboratory setting. Hence, we propose a set of ice nucleation experiments with surrogates for well-known atmospheric ice nuclei like kaolinite, montmorillonite, illite in the laboratory, where different ice nucleation mechanisms will be studied simultaneously. The effects of anthropogenic emissions will then be studied by the controlled exposure of these aerosols to various reactive gases like NH3, O3, SO2, NO, and NO2. These aged aerosols will then again be measured with our ice nucleation instruments. In parallel, the aerosols will be physically and chemically characterized. The conditions for ageing will then be modified stepwise towards more complex scenarios including organic substances and colder temperatures, which are more realistic to the real atmosphere. Time permitting, other aerosols will also be studied such as mineral dusts sampled from different deserts or combustion related particles like soot. Parallel to these measurements, our ice-nucleus counter PINC will be coupled to an aerosol mass spectrometer (ATOFMS) with a counterflow virtual impactor. This combination will allow us to measure the chemical signature of those particles, which had formed ice in the PINC instrument. This combination will first be tested and characterized in the laboratory using the aerosols from the above-mentioned ageing experiments. In a final step, the coupled PINC-ATOFMS system and other instruments will be deployed in a field campaign to study ice nucleation with ambient aerosols. The data taken here will be compared with our laboratory data to identify chemical signatures and to understand the dominant ice nuclei population in the real atmosphere.
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