Chamber Simulations of Cloud Chemistry: The AIDA Chamber

Wagner, Robert; Bunz, H.; Linke, Christian; Möhler, Ottmar; Naumann, K.‐H.; Saathoff, H.; Schnaiter, Martin; Schurath, U.

doi:10.1007/1-4020-4232-9_5

Cited by 36 publications

(39 citation statements)

References 28 publications

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“…Figs. 6 in Möhler et al (2003) and Wagner et al (2006). As already indicated in the introduction, data analysis of current AIDA ice nucleation studies is progressing towards a quantitative evaluation of the freezing processes, i.e., towards the determination of nucleation rates and ice activation spectra, meaning the fraction of ice activated aerosol particles as function of the ice saturation ratio; see e.g.…”

Section: Aida Expansion Cooling Experimentsmentioning

confidence: 98%

“…The technical equipment of the AIDA chamber as well as its operation as an expansion cloud chamber for ice nucleation studies has been described in detail in our recent publications (Möhler et al, 2005Wagner et al, 2006) and will only briefly be summarised here. Being insulated in a large thermostated housing, the cylindrical AIDA aerosol vessel (4 m diameter, 84.3 m 3 volume) can be cooled to any temperature between ambient and 183 K (Fig.…”

Section: Aida Expansion Cooling Experimentsmentioning

confidence: 99%

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Probing ice clouds by broadband mid-infrared extinction spectroscopy: case studies from ice nucleation experiments in the AIDA aerosol and cloud chamber

Wagner¹,

Benz²,

Möhler³

et al. 2006

Atmos. Chem. Phys.

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Abstract. Series of infrared extinction spectra of ice crystals were recorded in the 6000-800 cm −1 wavenumber regime during expansion cooling experiments in the large aerosol and cloud chamber AIDA of Forschungszentrum Karlsruhe. Either supercooled sulphuric acid solution droplets or dry mineral dust particles were added as seed aerosols to initiate ice formation after having established ice supersaturated conditions inside the chamber. The various ice nucleation runs were conducted at temperatures between 237 and 195 K, leading to median sizes of the nucleated ice particles of 1-15 µm. The measured infrared spectra were fitted with reference spectra from T-matrix calculations to retrieve the number concentration as well as the number size distribution of the generated ice clouds. The precise evaluation of the time-dependent ice particle number concentrations, i.e., the rates of new ice particle formation, is of particular importance to quantitatively analyse the ice nucleation experiments in terms of nucleation rates and ice activation spectra. The ice particles were modelled as finite circular cylinders with aspect ratios ranging from 0.5 to 3.0. Benefiting from the comprehensive diagnostic tools for the characterisation of ice clouds which are available at the AIDA facility, the infrared retrieval results with regard to the ice particle number concentration could be compared to independent measurements with various optical particle counters. This provided a unique chance to quantitatively assess potential errors or solution ambiguities in the retrieval procedure which mainly originate from the difficulty to find an appropriate shape representation for the aspherical particle habits of the ice crystals. Based on these inter-comparisons, we demonstrate that there is no standard retrieval approach which can be routinely applied to all different experimental scenarios. In particular, the concept to account for the asphericity of the ice crystals, the a priori constraints which might be imposed Correspondence to: R. Wagner (robert.wagner@imk.fzk.de) on the unknown number size distribution of the ice crystals (like employing an analytical distribution function), and the wavenumber range which is included in the fitting algorithm should be carefully adjusted to each single retrieval problem.

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Section: Aida Expansion Cooling Experimentsmentioning

confidence: 98%

Section: Aida Expansion Cooling Experimentsmentioning

confidence: 99%

Probing ice clouds by broadband mid-infrared extinction spectroscopy: case studies from ice nucleation experiments in the AIDA aerosol and cloud chamber

Wagner¹,

Benz²,

Möhler³

et al. 2006

Atmos. Chem. Phys.

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“…The AIDA facility consists of a 84.3 m 3 sized aluminium chamber that is housed in an isolating containment whose temperature can be controlled between 333 and 183 K (Möh-ler et al, 2003;Wagner et al, 2006). A powerful mixing fan placed at the bottom of the chamber was continuously in operation, providing homogeneous conditions in terms of temperature, relative humidity, as well as aerosol and cloud particle number concentrations throughout the chamber volume.…”

Section: Instrumentationmentioning

confidence: 99%

Pre-activation of ice-nucleating particles by the pore condensation and freezing mechanism

et al. 2016

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Abstract. In spite of the resurgence in ice nucleation research a comparatively small number of studies deal with the phenomenon of pre-activation in heterogeneous ice nucleation. Fifty years ago, it was shown that various mineral dust and volcanic ash particles can be pre-activated to become nuclei for ice crystal formation even at temperatures as high as 270-271 K. Pre-activation was achieved under ice-subsaturated conditions without any preceding macroscopic ice growth by just temporarily cooling the particles to temperatures below 228 K. A two-step mechanism involving capillary condensation of supercooled water and subsequent homogeneous freezing was proposed to account for the particles' enhanced ice nucleation ability at high temperatures. This work reinvestigates the efficiency of the proposed preactivation mechanism in temperature-cycling experiments performed in a large cloud chamber with suspended particles. We find the efficiency to be highest for the clay mineral illite as well as for highly porous materials like zeolite and diatomaceous earth, whereas most aerosols generated from desert dust surface samples did not reveal a measurable preactivation ability. The pre-activation efficiency is linked to particle pores in a certain size range. As estimated by model calculations, only pores with diameters between about 5 and 8 nm contribute to pre-activation under ice-subsaturated conditions. This range is set by a combination of requirements from the negative Kelvin effect for condensation and a critical size of ice embryos for ice nucleation and melting. In contrast to the early study, pre-activation is only observed for temperatures below 260 K. Above that threshold, the particles' improved ice nucleation ability disappears due to the melting of ice in the pores.

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“…2) (Wagner et al, 2006b). The temperature is controlled by ventilating air around the aerosol vessel and a mixing fan is continuously operating inside the vessel to ensure for homogeneous conditions in terms of temperature, relative humidity, as well as aerosol and ice particle number concentration throughout the chamber volume.…”

Section: Ice Nucleation Studies In the Aida Expansion Cloud Chambermentioning

confidence: 99%

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

et al. 2012

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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.

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Chamber Simulations of Cloud Chemistry: The AIDA Chamber

Cited by 36 publications

References 28 publications

Probing ice clouds by broadband mid-infrared extinction spectroscopy: case studies from ice nucleation experiments in the AIDA aerosol and cloud chamber

Probing ice clouds by broadband mid-infrared extinction spectroscopy: case studies from ice nucleation experiments in the AIDA aerosol and cloud chamber

Pre-activation of ice-nucleating particles by the pore condensation and freezing mechanism

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

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