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Ph. D. Ottmar Moehler is on the trail of ice-nucleating particles in the air that promote precipitation formation. Together with industry and research partners, he has developed the mobile cloud chamber PINE for long-term measurements of such particles.

When looking at the sky, cloud formations are constantly changing: Cirrus, cumulus or even nimbostratus are just some of the cloud images – fascinating and transient at the same time. But clouds are not only a spectacle of nature, they are also an important factor influencing the climate and the environment. They regulate the global water balance: Evaporated water, for example from lakes and rivers, is stored and carried over long distances in the clouds. As precipitation, for example in the form of rain or snow, the water finally returns to the earth's surface and supplies flora and fauna. Behind the formation of clouds and precipitation lie complex physical phenomena that are influenced by a wide variety of factors. Ph. D. Ottmar Moehler and his research group Aerosol-Cloud Interactions at the Institute for Meteorology and Climate Research (IMK) focus on a subgroup of atmospheric aerosols that have a central influence on precipitation: Ice Nucleating Particles, INPs by short.

Such airborne aerosol particles, mostly of mineral or organic origin, are responsible for the formation of ice crystals in clouds at temperatures below 0 degrees Celsius, triggering the formation of precipitation. "INPs are found in very low concentrations in the atmosphere, often less than one particle per liter. Systematic measurements could further characterize the chemical and physical properties of the particles or provide information about the formation and growth of the ice crystals," Moehler explains the importance of INP measurements. Until now, INPs could only be measured using very time-consuming methods and with low temporal resolution. "We wanted to build the first fully automated INP measuring device that research groups could also use without a lot of human resources and with little effort, and that would still deliver very good measurement results," Moehler continues.

After three years of intensive development in cooperation with the University of Leeds, a prototype of a mobile measuring device for long-term operation was created. Together with Bilfinger Noell, a high-tech company for special machinery and equipment, this was turned into a commercial measuring device within a year: PINE (Portable Ice Nucleation Experiment). Ph. D. Wolfgang Walter, Head of Product at Bilfinger Noell, emphasizes:

"Together, we have shown that it is possible to achieve something in a very short time in a partnership-based, goal-oriented collaboration. Based on our cryogenic experience, we have achieved the optimal integration of all components in a mobile product." In addition to a new cooling concept, modern manufacturing technologies, such as 3D printing, were also incorporated into the design and production of PINE.

Aerosol measurement with PINE works like a cyclically operating expansion chamber, similar to the large cloud simulation chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) at KIT's North Campus. "We succeeded in scaling up and automating the AIDA principle to a small, mobile device," Moehler proudly reports. The principle mimics cloud formation by air mass uplift in a mobile chamber. In an expansion process – determined by ambient air, temperature and air pressure – cloud droplets and ice particles are formed in the cloud chamber under defined process parameters, similar to real clouds. The formed ice particles in this process are counted by using an optical particle detector.

PINE was successfully brought to market by Bilfinger Noell. The partners are already working on further development. Ph. D. Ronald Hepper, Managing Director of Bilfinger Noell, stays positive: "Cooperation with research institutions offers direct and close involvement in the development and initial application of new technologies. PINE opens the door to a completely new customer base, which we are meeting with an attractive offer for the professionalization of cloud research." The mobile instrument can be used to conduct a wide variety of experiments on aerosol ice formation at any location – both in the field, e.g. at mountain stations or other atmospheric measurement stations, and for research on ice nucleation in the laboratory. "PINE offers researchers and meteorologists a unique and valuable insight into the development of ice crystals." cloud researcher Moehler is convinced.

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Images: Der Punkt GmbH · Patrick Langer / KIT


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