The research and teaching activities of the laboratory and field measurements group focus on aerosol-cloud interactions and cloud microphysics with emphasis on understanding how and which types of aerosols act as cloud condensation (CCN) and ice nuclei (IN). In addition, we investigate the importance of aerosol chemical composition on CCN and IN activity. The basic research is conducted in laboratory and field experiments using instrumentation that is mainly designed and developed in-house coupled with commercially available particle sizing and detection instruments. The experimental group is subdivided into two groups – the “Ice Nucleation Group” led by Zamin Kanji and the “Aerosol Physics / Aerosol Mass Spectrometry Group” led by Berko Sierau
The self-designed and developed instrumentation, mainly for ice nucleation experiments include ice nucleation chambers for measuring deposition/condensation mode ice nucleation (ZINC/PINC/HINC), immersion freezing (IMCA/PIMCA) and contact freezing (CLINCH). We developed two ice optical detectors (IODE) that are capable of distinguishing between particles that show strong, weak or no depolarization of polarized light allowing us to distinguish ice crystals and cloud droplets. To investigate the spatial distribution of ice crystals and supercooled water droplets in mixed-phase clouds, a holographic particle-imaging device (HOLIMO) has been developed. Warm cloud properties and droplet activation can be measured in-situ using our Fog Monitor and CCN Counter, respectively.
To investigate the influence of chemical composition on the ability of particles to act as CCN or IN, our group carries out measurements using mass spectrometry. Two types of aerosol mass spectrometers are applied: The Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) capable of analysing single particles, and the Soot-Particle Aerosol Mass Spectrometer (SP-AMS), providing quantitative information on the mass of soot and associated material. Both instruments are used in the lab and in the field.
Complementary, commercial equipment is available to aerosolize and to measure physical properties of particles. We also have the rather new Centrifugal Particle Mass Analyser (CPMA) to select particles based on mass. The CPMA is an important instrument to analyse agglomerates and thus important to characterize soot particles and their sources. We have also built an aerosol-trace gas interactions tank (volume of 2780L) where we can re-suspend and process aerosols. The ice and droplet nucleation devices and the instruments for physical and chemical characterization are then able to sample from the aerosol tank to compare aged and non-aged aerosols. Our goal is to understand the role that particle composition, size and chemistry play in forming ice and water clouds.
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