The properties of a cloud (e.g., reflectivity or lifetime) depend on what proportion of the cloud is comprised of liquid water droplets and ice crystals. Predicting the formation of ice is thus an integral component of weather and climate models. Experimentally, microfluidics--the science of manipulating fluids at micron dimensions--has emerged as a promising tool for gaining new insight into the nucleation of ice. Recently, we developed a microfluidic ice nucleation platform that ensures long-term aqueous droplet stability (by avoiding polydimethylsiloxane that absorbs water) and high temperature accuracy (by using an ethanol bath). Then, we observed the freezing of pure water droplets with two diameters (75 and 100 µm) cooled at two different rates (0.1 and 1 K/min). The experimentally-observed fraction of droplets frozen at each temperature was used to calculate the rate at which nucleation occurs, from which a new parameterization was proposed with an estimated accuracy of ± 0.2 K. Finally, we investigated aqueous sucrose droplets and tracked their optical brightness over several freeze-thaw cycles. The observed changes in optical brightness lend insight into ice nucleation and crystal growth in organic-rich aerosols in the atmosphere. Overall, our work aims to inform weather and climate models with parameterizations for ice nucleation that are better constrained, thus permitting uncertainties in cloud optical properties and precipitation formation to be reduced.
About Dr. Shardt
Nadia Shardt is a newly appointed Associate Professor in Chemical Engineering Dept at NTNU. She will officially start her position in April and be a part of the Ugelstad Laboratory (Ugelstad Laboratory - Colloid and Polymer Chemistry - NTNU ), her group's research focus will be using microfluidics to study emulsions and colloids (applications in, e.g., water treatment and foam formation).
Nadia did her PhD at University of Alberta, then a postdoc at ETH Zurich (ETH and NSERC Postdoctoral Fellowships; 2020 - 2022). In the seminar, she will talk about the microfluidic device setup that she developed during her postdoc to probe ice nucleation (heterogeneous and homogeneous) in aqueous droplets. The precision and control provided by microfluidics approach to generate droplets is an important step towards looking at ice nucleation and growth in atmospherically relevant size aqueous droplets.