The Microfluidic Ice Nuclei Counter Zürich (MINCZ): a platform for homogeneous and heterogeneous ice nucleation
<p>Ice nucleation in the atmosphere is the precursor to important processes that determine cloud properties and lifetime. Computational models that are used to predict weather and project future climate changes require parameterizations of both homogeneous nucleation (i.e. in pure water) and h...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-09-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/15/5367/2022/amt-15-5367-2022.pdf |
| Summary: | <p>Ice nucleation in the atmosphere is the precursor to
important processes that determine cloud properties and lifetime.
Computational models that are used to predict weather and project future
climate changes require parameterizations of both homogeneous nucleation
(i.e. in pure water) and heterogeneous nucleation (i.e. catalysed by
ice-nucleating particles, INPs). Microfluidic systems have gained momentum
as a tool for obtaining such parameterizations and gaining insight into the
stochastic and deterministic contributions to ice nucleation. To overcome
the shortcomings of polydimethylsiloxane (PDMS) microfluidic devices with
regard to temperature uncertainty and droplet instability due to continuous
water adsorption by PDMS, we have developed a new instrument: the
Microfluidic Ice Nuclei Counter Zürich (MINCZ). In MINCZ, droplets with
a diameter of 75 <span class="inline-formula">µm</span> are generated using a PDMS chip, and hundreds of these droplets are then stored in fluoropolymer tubing that is relatively
impermeable to water and solvents. Droplets within the tubing are cooled in
an ethanol bath. We validate MINCZ by measuring the homogeneous freezing
temperatures of water droplets and the heterogeneous freezing temperatures
of aqueous suspensions containing microcline, a common and effective INP in
the atmosphere. We obtain results with a high accuracy of 0.2 K in measured droplet temperature. Pure water droplets with a diameter of 75 <span class="inline-formula">µm</span> freeze at a median temperature of 237.3 K with a standard deviation of 0.1 K. Additionally, we perform several freeze–thaw cycles. In the future, MINCZ will be used to investigate the freezing behaviour of INPs, motivated by a need for better-constrained parameterizations of ice nucleation in weather and climate models, wherein the presence or absence of ice influences cloud optical properties and precipitation formation.</p> |
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| ISSN: | 1867-1381 1867-8548 |