The European Research Council has recently announced which researchers are awarded their prestigious ERC Consolidator Grant. A researcher from Chalmers is among the recipients, Gaetano Sardina from the Department of Mechanics and Maritime Sciences. He receives the grant for his research on complex three-phase cloud systems.
The research grants from the European Research Council, ERC, are aimed at tackling major questions across all scientific disciplines. The Consolidator Grant is given to researchers with 7–12 years of experience since completion of PhD, a scientific track record showing great promise and an excellent research proposal.
Explores the structure of complex clouds
One researcher at Chalmers has been awarded ERC's Consolidator Grant in the current call: Gaetano Sardina, Associate Professor at the Department of Mechanics and Maritime Sciences, M2. His research takes place among the clouds. More specifically among the complex mixed-phase clouds that are atmospheric three-phase systems, containing suspended ice particles, supercooled water droplets, and water vapor at temperatures between -40 °C and 0 °C.
“These clouds are responsible for most of the precipitations reaching the Earth’s surface,” he says. “In addition, these clouds play a primary role in the planet’s radiative energy budget and the water cycle. Despite their relevance, there is a lack of a basic understanding of the complex hydrodynamics, heat, and mass transfer between the different water components.”
One unsolved scientific question in mixed-phase clouds is the problem of ice formation in the atmosphere. Despite the temperature below 0°C, liquid droplets do not spontaneously freeze but remain in a special thermodynamic state that is called supercooling.
Unexplained extra ice
“Ice generation from supercooled droplets can only occur with the presence of specific aerosol solid particles, called ice nuclei, suspended in the atmosphere,” he says. “However, because ice nuclei are rare, ice concentration measured in observations exceeds the ice nuclei concentration by several orders of magnitude. Essentially, we do not know where the ‘extra’ ice comes from, a phenomenon that is called ice multiplication.”
Within the project, he aims to quantify, using numerical simulations, different possible mechanisms of ice formation called secondary ice production, an ensemble of several processes that generate new ice directly from pre-existing ice particles, including ice fragmentation after droplet freezing or after ice crystal collisions or breakup.
“Moreover, we will explore the possibility of ice nucleation triggered by turbulent fluctuations without the need for the presence of an ice nucleus. Another open question is the partitioning of ice and liquid droplets in a cloud at different environmental conditions: temperature, humidity, and turbulent fluctuations.”
Better climate predictions – and safer aviation
An improved understanding of mixed-phase clouds can help climatologists predict and understand their impact on the Earth's energy budget and the water cycle. The number, sizes, and distributions of the different water particles (ice and liquid droplets have different radiation properties) in clouds determine the amount of radiation reflected by clouds, which is still one of the most difficult challenges in weather and climate models.
“Moreover, the project will contribute to developing novel tools that can be used to investigate general industrial and environmental applications of complex multiphase turbulent flows in the presence of phase changes. Finally, the physics of the interactions between ice and supercooled water is important in aviation, where the ice formation around airplane’s wings, instruments, and probes is a dangerous condition, in refrigeration to preserve beverages or human organs and in anti-freezing and deicing systems.”
Receiving the grant comes with a feeling of a great personal satisfaction for him.
“I will have the freedom for the next five years to work on an interdisciplinary project between fluid mechanics and atmospheric science.”
Gaetano Sardina gets 2 Million Euro for his project.
- Professor, Fluid Dynamics, Mechanics and Maritime Sciences