The work in this project was performed in five work packages, three of which comprised the scientific work, one contained the training activities and one work package dealt with communication and outreach.
The scientific work packages were focusing on laboratory work using the turbulent wind tunnel LACIS-T (WP 1), and on computer simulations using models at different scales - one simulating the conditions that occurred during the measurements in the wind tunnel (WP 2) and one for simulating cases of observed clouds from a field experiment (WP 3).
LACIS-T uses two air streams which can be controlled and conditioned separately concerning temperature, humidity and flow speed (for more information on the wind tunnel see
https://www.tropos.de/en/research/projects-infrastructures-technology/technology-at-tropos/aerosol-research-facilities/lacis-t(se abrirá en una nueva ventana)). The two air streams are then turbulently mixed at the inlet of the measurement section. In the measurement setup for STEP one stream was kept at constant conditions whereas one parameter in the second stream was varied to test the influence of that parameter on entrainment and its impact on droplet size distributions. Water droplets were injected into the measurement section by a droplet generator.
The Computational Fluid Dynamics model was adapted to properly simulate the behaviour of the water droplets and simulations were run for all measurement conditions. These simulations provided the full 3 dimensional fields, where measurements were only able to provide point measurements. Large Eddy Simulations were setup to simulate two observed cloud cases from the ACORES campaign, which took place in July 2017 above the Azores.
Most interesting results were found when varying the flow speed, while the change in temperature and humidity did not lead to major differences in the observed size distributions. The results raise questions in regard to further turbulent cloud microphysical processes beyond the scope of STEP, which the fellow is planning to address in future projects.
The results have been presented at three major international conferences: A poster at the International Conference on Clouds and Precipitation in 2021, and oral presentations at the American Geophysical Union fall meeting 2021, and the 16th American Meteorological Society Conference on Cloud Physics, 2022, which led to further fruitful discussions. As the Covid-19 pandemic impeded in-person events, most public engagement activities were happening online, mainly through activities on twitter. For the researcher's training, the Fellow attended six training workshops and conferences on various topics from HPC computing, didactic, gender issues to science diplomacy, plus the seminars and workshops of the Leibniz mentoring.
The computing intensive work packages (WP2 and WP3) secured computing time on High Performance Computing clusters to pursue the simulations: 1000 node hours on Mistral and 700 node hours on Levante at DKRZ, Hamburg, Germany, and 470,000 hours CPU-time and 1200
GPU hours on taurus at ZIH Dresden, Germany.
