Cloud-Aerosol-Interactions in a Nitrogen-dominated Atmosphere – New particle formation, Activation, and Turbulence (CAINA-NAT)

• Applicant: Dr. Birgit Wehner
• Subject Area: Atmospheric Science
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552347513

The formation and properties of clouds in the atmosphere depend not only on water vapor saturation, but also on the availability of suitable aerosol particles. In addition, cloud edges often provide ideal conditions for the formation of new particles, so that aerosol and cloud microphysics are closely linked. Therefore, in addition to a good knowledge of the input parameters such as particle size distribution and meteorology, a thorough understanding of the underlying processes is required for the prediction of regional weather and climate scenarios. In spring 2025, an international field experiment on the influence of nitrogen on cloud properties will take place on the Dutch coast. The region has very high concentrations of agricultural nitrate near the ground in spring. TROPOS will participate with the helicopter-borne platform ACTOS and collect cloud water for chemical analysis as part of the already funded CAINA (Cloud-Aerosol-Interactions in a Nitrogen-dominated Atmosphere) project. This opens the possibility to integrate further sensors for the characterization of aerosol particles and cloud droplets on ACTOS and to operate them during the measurement flights. This will make it possible to obtain the vertical distribution of aerosol particles and to locate regions with increased concentrations of small, presumably newly formed particles. In detail, the number size distributions of aerosol particles (PNSD) and cloud droplets (DNSD) are measured, as well as the total number concentration of particles, the liquid water content and the main meteorological parameters. A major advantage of these helicopter-borne measurements is the true air speed of about 20 m/s, which allows a high spatial resolution of the measurements. The measured PNSD and DNSD will be analyzed in combination to investigate the dependence on the origin of the air mass. It is expected that marine air masses will contain fewer aerosol particles and that clouds formed within them will contain few but large droplets. ACTOS measurements such as PNSD, water vapor and temperature profiles will further be used as input parameters in the spectral cloud microphysics model SPECS to simulate cloud formation. Vertical wind speed and particle composition will be varied and compared with the corresponding measurement data. A PhD student currently working on her Master's thesis at TROPOS will perform the aerosol measurements and analysis, while a postdoc will perform the cloud microphysics measurements and analysis and operate the model. The PhD student will be responsible for the final synergy of the data. Comparable aerosol and cloud microphysics measurements have been carried out in recent years in places such as Barbados and the Azores. There, for example, the formation of new particles at cloud edges was frequently observed. Studies of cloud droplet formation have only been carried out in part and will be systematically performed for all available data in this project.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Holger Siebert