EGU22-8818
https://doi.org/10.5194/egusphere-egu22-8818
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Analysis of the impacts of small-scale orography on the atmospheric boundary layer.Developing ICON-LES for the Perdigão field experiment.

Julian Quimbayo-Duarte1, Juerg Schmidli2, Martin Köhler3, and Linda Schlemmer4
Julian Quimbayo-Duarte et al.
  • 1Institute for Atmosphere and Environment, Goethe University, Frankfurt am Main, Germany (quimbayo-duarte@iau.uni-frankfurt.de)2
  • 2Institute for Atmosphere and Environment, Goethe University, Frankfurt am Main, Germany (schmidli@iau.uni-frankfurt.de)
  • 3Deutscher Wetterdienst (DWD), Offenbach am Main, Germany (Martin.Koehler@dwd.de)
  • 4Deutscher Wetterdienst (DWD), Offenbach am Main, Germany (linda.schlemmer@dwd.de)

The response of the boundary layer flow to resolved versus parametrized orographic drag over moderately complex terrain is investigated. The larger terrain scales may trigger propagating gravity waves and generate flow blocking, while the smaller scales (smaller than 5 km) may modify the turbulent boundary layer leading to turbulent orographic form drag (TOFD). We perform high-resolution numerical simulations to evaluate the ability of a TOFD parametrization to reproduce the impact of small-scale orographic features on the flow over complex terrain. The tool selected to perform the simulations is the Icosahedral Nonhydrostatic (ICON) numerical model, a unified modelling system for global numerical weather prediction (NWP) and climate studies. In the present study, the model is used in its limited-area mode. In the TOFD parametrization used for the present simulations, the surface stress and its vertical distribution are formulated in terms of the spectrum of the orography, meaning that it only depends on the orography characteristics in the domain. As a first step simulations using different grid spacings, from the km scale to the 100 m scale, are carried out to reproduce the intensive observational period (IOP) of the Perdigão field experiment. The km-scale simulations in NWP mode are run continuously for the complete 49-day IOP using ERA5 data for initial and boundary conditions. The large-eddy simulations, at O(100 m) grid spacing, are run for selected periods nested into the NWP runs. The initial results of the NWP control simulation show good performance when compared to the tower wind observations for selected periods, but not for the entire IOP. The reasons for the variable performance is investigated.

How to cite: Quimbayo-Duarte, J., Schmidli, J., Köhler, M., and Schlemmer, L.: Analysis of the impacts of small-scale orography on the atmospheric boundary layer.Developing ICON-LES for the Perdigão field experiment., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8818, https://doi.org/10.5194/egusphere-egu22-8818, 2022.

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