Abstract ID: 3.12293 | Accepted as Talk | Talk/Oral | TBA | TBA

Large-Eddy Simulations (LES) are an important tool in studying meteorological processes on the local scale. Periodic boundary conditions are often used in both the streamwise and spanwise direction in LES, as periodic boundaries emulate an infinitely long domain and turbulence develops over time. To study the effect of isolated terrain features on an otherwise undisturbed flow fields, the upstream boundary must be formulated differently, such as open boundaries combined with turbulence inflow generation techniques and specified inflow fields by precursor simulations and nested domains. Flow over periodically repeating hills can be investigated with periodic boundaries and such flows have been investigated in the past. Nevertheless, the boundary condition can still have an impact To investigate the impact of the boundary condition on upstream flow profiles, a set of idealized LES were conducted above a sinusoidal mountain for a shear and buoyancy driven atmospheric boundary layer with the Cloud Model 1 (CM1). While the effect of the boundary condition was limited in purely buoyancy-driven flow regimes, flow regimes associated with synoptic forcings could not be maintained with periodic boundaries in the streamwise direction. Specifically, sheltering effects decelerated the flow in the boundary layer below crest height.