Freezing nucleation apparatus puts new slant on study of biological ice nucleators in precipitation

Stopelli, Emiliano; Conen, Franz; Zimmermann, Lukas; Alewell, Christine; Morris, Cindy E.

doi:10.5194/amt-7-129-2014

Cited by 82 publications

(132 citation statements)

References 20 publications

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“…The heat treatment, plating, and sequencing results suggest that the warm INPs are likely biological in origin. This finding is consistent with previous studies involving heat treatment (or other methods used in destruction of proteinaceous active sites) from experimental data that underlies the gray‐shaded area shown in Figure (Christner et> al., ; Hill et al, ; Joly et al, ; Stopelli et al, ). The INP experiments of a particular precipitation sample (D3) showed the presence of both antifreeze proteins and ice‐nucleating proteins, presumably associated with Pantoea strains.…”

Section: Discussionmentioning

confidence: 99%

Characterization of Ice‐Nucleating Particles Over Northern India

et al. 2019

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The sources and concentrations of ice‐nucleating particles (INPs) over India are not well known. Here, INP concentrations in rainwater from Northern India and a dust sample from the Thar Desert are characterized. Rainwater INP concentrations ranged between 104 and 3 × 107 L−1 water, spanning temperatures between −4 and −28 °C. During the monsoon season, INP concentrations were low and approached those in remote marine air mass. During the winter season, INPs active between −4 to −10 °C were occasionally observed. An increase in INP activity sometimes occurred after the initial onset of rain. The onset freezing temperature of samples active at warmer temperatures was shifted to colder temperature after heat treatment, suggesting that the INP activity stemmed from biological influence. Plating was used to isolate and sequence INP active bacterial strains from some of the rainwater samples, specifically strains of close taxonomic affiliation with the ice nucleating genera Pantoea. The size‐resolved ice nucleation active site density for 200–600‐nm particles of Thar Desert Dust ranged between 107 and 109 m−2 at −20 °C, values similar to dusts from other regions of the world. The data reported herein may help constrain models that seek to predict the impact of INP on the properties of mixed‐phased clouds over the Indian subcontinent.

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Section: Discussionmentioning

confidence: 99%

Characterization of Ice‐Nucleating Particles Over Northern India

et al. 2019

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“…This section addresses these problems and the solutions employed. As discussed by Stopelli et al (2014), certain problems are encountered when using open droplet systems, where droplets are arranged on a hydrophobic surface, compared to closed droplet experiments, where each droplet is held in a separate container, or under inert oil. In an open droplet system, there is potential for droplets to evaporate over time, for contamination of droplets from airborne particles or for the freezing of droplets to influence neighbouring droplets by frost growth or splintering.…”

Section: Discussion Of Potential Artefacts and Uses Of Droplet-freezimentioning

confidence: 99%

“…As the µl-NIPI is an open droplet system, these issues must be overcome. Closed droplet systems avoid some of these prob- lems, but monitoring of freezing becomes more challenging as the droplets are not easily visible (Stopelli et al, 2014).…”

Section: Discussion Of Potential Artefacts and Uses Of Droplet-freezimentioning

confidence: 99%

“…Our experimental approach builds on techniques employing aliquots of water much larger than the dimensions of typical cloud droplets which have been used since the very early days of ice nucleation studies (Vali, 1971(Vali, , 1995 and continue to be used in the present day (Stopelli et al, 2014;Conen et al, 2011;Knopf and Forrester, 2011;Garcia et al, 2012;Budke and Koop, 2015). The advantage of this approach is that the surface area of nucleant per droplet scales with the volume of the droplet (for a constant mass fraction of nucleant in water).…”

Section: T F Whale Et Al: Quantifying Heterogeneous Ice Nucleationmentioning

confidence: 99%

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A technique for quantifying heterogeneous ice nucleation in microlitre supercooled water droplets

et al. 2015

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Abstract. In many clouds, the formation of ice requires the presence of particles capable of nucleating ice. Icenucleating particles (INPs) are rare in comparison to cloud condensation nuclei. However, the fact that only a small fraction of aerosol particles can nucleate ice means that detection and quantification of INPs is challenging. This is particularly true at temperatures above about − 20 • C since the population of particles capable of serving as INPs decreases dramatically with increasing temperature. In this paper, we describe an experimental technique in which droplets of microlitre volume containing ice-nucleating material are cooled down at a controlled rate and their freezing temperatures recorded. The advantage of using large droplet volumes is that the surface area per droplet is vastly larger than in experiments focused on single aerosol particles or cloud-sized droplets. This increases the probability of observing the effect of less common, but important, high-temperature INPs and therefore allows the quantification of their ice nucleation efficiency. The potential artefacts which could influence data from this experiment, and other similar experiments, are mitigated and discussed. Experimentally determined heterogeneous ice nucleation efficiencies for K-feldspar (microcline), kaolinite, chlorite, NX-illite, Snomax ® and silver iodide are presented.

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“…Immersion mode freezing was tested using a drop freezing assay (DFA) cold plate apparatus. This cold plate technique was based on previous but slightly modified apparatuses Stopelli et al, 2014;Tobo, 2016;. For brevity, we call this system the NOAA drop freezing cold plate (DFCP).…”

Section: Offline Ice Nucleation Analyses 241 Drop Freezing Assay Fomentioning

confidence: 99%

HOVERCAT: a novel aerial system for evaluation of aerosol–cloud interactions

et al. 2018

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Abstract. Aerosols have a profound impact on cloud microphysics through their ability to serve as ice nucleating particles (INPs). As a result, cloud radiative properties and precipitation processes can be modulated by such aerosolcloud interactions. However, one of the largest uncertainties associated with atmospheric processes is the indirect effect of aerosols on clouds. The need for more advanced observations of INPs in the atmospheric vertical profile is apparent, yet most ice nucleation measurements are conducted on the ground or during infrequent and intensive airborne field campaigns. Here, we describe a novel measurement platform that is less expensive and smaller (< 5 kg) when compared to traditional aircraft and tethered balloon platforms and that can be used for evaluating two modes of ice nucleation (i.e., immersion and deposition). HOVERCAT (Honing On VERtical Cloud and Aerosol properTies) flew during a pilot study in Colorado, USA, up to 2.6 km above mean sea level (1.1 km above ground level) and consists of an aerosol module that includes an optical particle counter for size distributions (0.38-17 µm in diameter) and a new sampler that collects up to 10 filter samples for offline ice nucleation and aerosol analyses on a launched balloon platform. During the May 2017 test flight, total particle concentrations were highest closest to the ground (up to 50 cm −3 at < 50 m above ground level) and up to 2 in 10 2 particles were ice nucleation active in the immersion mode (at −23 • C). The warmest temperature immersion and deposition mode INPs (observed up to −6 and −40.4 • C, respectively) were observed closest to the ground, but overall INP concentrations did not exhibit an inverse correlation with increasing altitude. HOVERCAT is a prototype that can be further modified for other airborne platforms, including tethered balloon and unmanned aircraft systems. The versatility of HOVERCAT affords future opportunities to profile the atmospheric column for more comprehensive evaluations of aerosol-cloud interactions. Based on our test flight experiences, we provide a set of recommendations for future deployments of similar measurement systems and platforms.

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Freezing nucleation apparatus puts new slant on study of biological ice nucleators in precipitation

Cited by 82 publications

References 20 publications

Characterization of Ice‐Nucleating Particles Over Northern India

Characterization of Ice‐Nucleating Particles Over Northern India

A technique for quantifying heterogeneous ice nucleation in microlitre supercooled water droplets

HOVERCAT: a novel aerial system for evaluation of aerosol–cloud interactions

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