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Tiny particles akin to ice crystals or ash particles are likely to oscillate as they settle through the atmosphere. Of their experiments, the scientists were capable of track non-spherical particles of size smaller than 1 millimeter with unprecedented accuracy. Their observations gave rise to a model which may also help to refine prediction on air pollutants or weather forecasts.
The atmosphere accommodates many tiny solid particles. Scientists from the Max Planck Institute for Dynamics and Self-Organization (MPI-DS) and the University of Göttingen in collaboration with the Centre national de la recherche scientifique (CNRS) in France and the university of Gothenburg, Sweden, now studied how such non-spherical particles settle in air. For this, they used a brand new precision apparatus equipped with high-speed cameras and a novel particle injection mechanism. Using a 3D-printer, they created particles of various shapes resembling discs of thickness as little as 50 micrometer and rods of length as high as 880 micrometers. Because of this setup, they might observe that particles are likely to oscillate as they settle in quiescent air.
“To date, most studies on the behavior of such small particles were done with models in liquids since experiments in air are extremely difficult,” Mohsen Bagheri, group leader at MPI-DS, describes previous approaches. “Nonetheless, the true settling dynamics couldn’t be explored this fashion. They were now revealed in our experimental setting, directly measuring the motion of real-size particles, that are much heavier than the encircling environment,” he continues.
The observed oscillation could impact the collision of individual particles, their travelling distance within the atmosphere and their interaction with the solar radiation.
Predicting the dynamics of particles
Typically, atmospheric particles should not perfectly spherical, but reasonably flattened or elongated structures. The scientists developed and tested a model to explain and predict the movement of such particles, which very accurately captures the experimental results. The brand new model will be used to review the dynamics and formation of particles clusters and the resulting effects in on a regular basis life. “Specifically, our results may also help to higher predict how long pollutants reside within the atmosphere or how precipitation is initiated in clouds,” summarizes Alain Pumir. The CNRS researcher developed the model together together with his colleagues Bernhard Mehlig and Kristian Gustavsson.
In total, these latest insights contribute to a more accurate understanding of atmospheric particles, and the way they affect the environment and climate.
