A comprehensive laboratory study on the immersion freezing behavior of illite NX particles : a comparison of seventeen ice nucleation measurement techniques

Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a vari
Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice nucleating particles (INPs). However, an inter-comparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques.
Within the framework of INUIT (Ice Nucleation research UnIT), we distributed an illite rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain IN data as a function of particle concentration, temperature (T), cooling rate and nucleation time. Seventeen measurement methods were involved in the data inter-comparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while ten other instruments employed water vapor condensation onto dry-dispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing dataset was evaluated using the ice nucleation active surface-site density (ns) to develop a representative ns(T) spectrum that spans a wide temperature range (−37 °C < T < −11 °C) and covers nine orders of magnitude in ns.
Our inter-comparison results revealed a discrepancy between suspension and dry-dispersed particle measurements for this mineral dust. While the agreement was good below ~ −26 °C, the ice nucleation activity, expressed in ns, was smaller for the wet suspended samples and higher for the dry-dispersed aerosol samples between about −26 and −18 °C. Only instruments making measurement techniques with wet suspended samples were able to measure ice nucleation above −18 °C. A possible explanation for the deviation between −26 and −18 °C is discussed. In general, the seventeen immersion freezing measurement techniques deviate, within the range of about 7 °C in terms of temperature, by three orders of magnitude with respect to ns. In addition, we show evidence that the immersion freezing efficiency (i.e., ns) of illite NX particles is relatively independent on droplet size, particle mass in suspension, particle size and cooling rate during freezing. A strong temperature-dependence and weak time- and size-dependence of immersion freezing efficiency of illite-rich clay mineral particles enabled the ns parameterization solely as a function of temperature. We also characterized the ns (T) spectra, and identified a section with a steep slope between −20 and −27 °C, where a large fraction of active sites of our test dust may trigger immersion freezing. This slope was followed by a region with a gentler slope at temperatures below −27 °C. A multiple exponential distribution fit is expressed as ns(T) = exp(23.82 × exp(−exp(0.16 × (T + 17.49))) + 1.39) based on the specific surface area and ns(T) = exp(25.75 × exp(−exp(0.13 × (T + 17.17))) + 3.34) based on the geometric area (ns and T in m−2 and °C, respectively). These new fits, constrained by using an identical reference samples, will help to compare IN measurement methods that are not included in the present study and, thereby, IN data from future IN instruments.
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Author:Naruki Hiranuma, Stefanie Augustin-Bauditz, Heinz Bingemer, Carsten Budke, Joachim Curtius, Anja Danielczok, Karoline Diehl, Katharina Dreischmeier, Martin Ebert, Fabian Frank, Nadine Hoffmann, Konrad Kandler, Alexei Kiselev, Thomas Koop, Thomas Leisner, Ottmar Möhler, Björn Nillius, Andreas Peckhaus, Diana Rose, Stephan Weinbruch, Heike Wex, Yvonne Boose, Paul J. DeMott, John D. Hader, Thomas C. Hill, Zamin A. Kanji, Gargi Kulkarni, Ezra J. T. Levin, Christina S. McCluskey, Masataka Murakami, Benjamin J. Murray, Dennis Niedermeier, Markus D. Petters, Daniel O'Sullivan, Atsushi Saito, Gregory P. Schill, Takuya Tajiri, Margret A. Tolbert, André Welti, Thomas F. Whale, Timothy P. Wright, Katsuya Yamashita
Parent Title (English):Atmospheric chemistry and physics / Discussions
Publisher:European Geosciences Union
Place of publication:Katlenburg-Lindau
Document Type:Article
Date of Publication (online):2014/08/28
Date of first Publication:2014/08/28
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2015/04/22
First Page:22045
Last Page:22116
© Author(s) 2014. This work is distributed under the Creative Commons Attribution 3.0 License.
HeBIS PPN:369072820
Dewey Decimal Classification:550 Geowissenschaften
Licence (German):License LogoCreative Commons - Namensnennung 4.0

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