Investigating local topographic effects on the stable boundary layer structure in mountainous terrain using large eddy simulations

Our understanding of the atmospheric boundary layer has improved a lot with the recent advances in the state-of-the-art remote sensing instruments and also computational resources. The atmospheric boundary layer (ABL) is the lowest part of the atmosphere, which is influenced by the presence of earth’s surface and its interaction with the surface forcings. The turbulent exchange of momentum, heat, and moisture between the earth surface and the atmosphere needs to be well understood for proper simulation of the ABL processes in weather and climate models. In addition to observations, large eddy simulation tools are used for the testing and development of boundary layer turbulence parameterization schemes used in the atmospheric numerical weather prediction (NWP) models. While the daytime convective boundary layers are well represented in the NWP models, night-time stable boundary layers are not, due to the presence of the smaller-sized eddies. Stable boundary layer (SBL)s are governed by processes such as intermittent turbulence, gravity waves, radiative cooling, katabatic flows, and fog formation. These processes have a direct impact on the society for example, fog modeling for road safety, aviation, frost for agricultural sector and also air quality modeling. We discuss the evolution of the SBL over a valley in the Fichtelgebirge mountains from observations and model simulations. Further we highlight current challenges and advancements in the SBL modeling over complex terrain using LES.

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