3Drelief

Case description

The 3Drelief case simulates the interaction between atmospheric flow and a 3D bell-shaped mountain. This is a classic test case for orographic flow dynamics in 3D and validates the model ability to reproduce three-dimensional mountain waves and flow splitting.

Configuration

Parameter

Value

Category

Idealized cases

Dynamics

Non-hydrostatic

Horizontal grid spacing

2000 m (128x96 grid)

Integration length

10000 s (2.8 hours)

Time step

80 s

Coriolis effect

disabled

Turbulence

NONE

Cloud scheme

NONE

Deep convection

NONE

Radiation

NONE

Steps

Step

Script

001_prep_ideal

run_prep_ideal_case

002_mesonh

run_mesonh

Specificities

Scientific specificities

  • 3D bell-shaped mountain (Gaussian hill) with height 1000m

  • Horizontal domain: 128x96 points (10km half-width)

  • 72 vertical levels with 250m spacing

  • Open boundary conditions on all sides

  • Boussinesq enabled (LHE equations)

  • 10 m/s westerly flow

Technical specificities

  • Nested grid (9x49 inner points for mountain)

  • Horizontal relaxation at boundaries (6x3 rim)

  • Damping layer at model top

  • No radiation, cloud or turbulence schemes (DNS mode)

Validation

  • Vertical velocity field

  • Wave breaking patterns

  • Flow splitting visualization

Numerical ressources

Single CPU (1 node, 1 core)

References

  • Gallus, W.A., and R.A. Ahmadov (2021): Sensitivity of simulated 24-h forecasts to horizontal resolution in the US. Atmosphere, 12, 1686.