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Abstract:
In 2022, the dynamic cloud simulation chamber AIDAd (Aerosol Interaction and Dynamics in the Atmosphere – dynamic version) came into operation at the Karlsruhe Institute of Technology. The walls of the cloud chamber located inside a vacuum chamber can actively be cooled at constant rates up to 10 K min-1 (equivalent to an updraft velocity of about 15 m s-1 in the atmosphere) within the temperature range of +30°C to -55°C. This unique technical design enables the simulation and investigation of tropospheric cloud processes in a wide range of cooling rates and liquid condensation levels. The cloud chamber is made of five segments with independent temperature control. Therefore, the chamber can be operated at either isothermal or controlled temperature gradient conditions.
The performance of AIDAd was demonstrated in series of test runs with cooling rates between 1 and 10 K min-1, and with cloud droplet freezing experiments, which showed the homogeneous freezing of pure water droplets to occur, as expected, at temperatures between -35°C and -37°C. Results from these test runs and proof-of-concept experiments will be discussed in the first part of the presentation. The second part will focus on the ice-nucleation activity of dust aerosols in the immersion freezing mode. Series of experiments have been conducted at different temperatures and cooling rates. The results from these experiments may provide new evidence for the ice-nucleation active site (INAS) concept to be appropriate for quantifying the ice-nucleation activity of mineral dust aerosol in the immersion freezing mode.
