High-resolution numerical studies on the effect of turbulence on the structure of nocturnal radiation fogs

• Applicant: Professor Dr. Björn Maronga
• Subject Area: Atmospheric Science
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257223246

Fog as a meteorological phenomenon can have a strong impact on the economy but al-so on personal safety by reducing the visibility in the atmospheric boundary layer. Totaleconomic losses associated with fog on aviation, marine and land transportation are comparable to those of winter storms. Despite the fact that there is abundant literature on fog research, our knowledge about the physical processes that lead to fog formation and its microstructure remains partial. This is due to the fact that many complex processes like radiative cooling, turbulent mixing and the microphysics of fog interact non-linearly with each other. Moreover, surface heterogeneity regarding vegetation and soil characteristics further complicate the predictability of fog. Consequently, the fog forecasting capability of numerical weather prediction models is still poor. In this project, high-resolution large-eddy simulations (LES) will be used to investigate the effect of turbulence on nocturnal radiation fogs. The LES model PALM will be used at very high resolution in the order of 1 m with both an Eulerian bulk cloud physics scheme and an embedded Lagrangian particle model that allows for explicitly resolving aerosols and fog droplets will be employed. This innovative approach allows for studying fog droplet turbulence interactions for the first time with LES. The aim of this study is to study the effect of a nocturnal fog layer on the morning transition and the daytime boundarylayer. Moreover, the effect of surface heterogeneity on nocturnal radiation fog will beinvestigated by means of LES with prescribed idealized regular and observed irregular surface heterogeneities. The simulation data will be forced and validated with observational data from the super-sites at Cabauw (The Netherlands) and Lindenberg (Germany).

• DFG Programme: Research Grants
• International Connection: Netherlands
• Cooperation Partner: Dr. Fred Bosveld