2Drelief

Case description

The 2Drelief case simulates the interaction between atmospheric flow and a 2D bell-shaped mountain. This is a classic test case for orographic flow dynamics and validates the model ability to reproduce mountain waves and gravity wave drag.

Configuration

Parameter

Value

Category

Idealized cases

Dynamics

Non-hydrostatic

Horizontal grid spacing

5000 m (256x1 grid)

Integration length

10800 s (3 hours)

Time step

60 s

Coriolis effect

disabled

Turbulence

TKEL (3D)

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

  • 2D bell-shaped mountain (Gaussian hill) with height 500m

  • Horizontal domain: 256 points (10km half-width bell)

  • 48 vertical levels from 0 to 5000m

  • Open western boundary, cyclic eastern boundary

  • 10m/s westerly flow

Technical specificities

  • Stretched vertical grid (10m near surface, 500m near model top)

  • Boussinesq disabled for full compressible dynamics

  • Damping layer at model top (XALKTOP=0.005)

  • Horizontal relaxation at boundaries

Validation

  • Vertical velocity perturbation

  • Pressure perturbation

  • Mountain wave 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.