Development of new turbulence length scale formulations

• Applicant: Professor Juerg Schmidli, Ph.D., since 6/2022
• Subject Area: Atmospheric Science
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454477837

The parametrization of turbulence processes in the Atmospheric Boundary Layer (ABL) is an essential component of numerical weather prediction (NWP) and global circulation (GC) models. Nowdays, most turbulence parameterizations in NWP/GC models use a turbulence kinetic energy (TKE) closure, which has relatively low numerical cost and is tractable. However, these parametrizations suffer from a major weakness, namely, the strong dependence on a single quantity, the so-called turbulence length scale. This is especially problematic in the gray zone of turbulence, where it is expected that the turbulence length scale is scale-dependent.The goal of this project is to develop new scale-dependent turbulence length scale formulations that would improve the turbulence parameterization in NWP/GC models.As a first step, a novel estimation of the turbulence length scale, based on the budget analyses of TKE and scalar variances, will be implemented using LES data. Subsequently, this new diagnostic will be used to assess the quality of several existing length scale parametrizations. Based on these results, the existing formulations will be adjusted and a new algebraic and a new prognostic length scale will be developed.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Ivan Bastak Duran, until 6/2022