Esrange Sweden Simulation - December Winds
This page describes a numerical simulation of gravity waves due to wintertime
winds blowing over the Scandinavian Mountain ranges in Norway and Sweden.
Computational Domain
The layout of the of the simulation is shown in the figure below. Note that
the boundaries of the computation domain (shown by the thin white line) has
been rotated by 26 degrees with respect to lines of constant latitude.
Just the computational domain is shown in the figure below. In this plot, the surface has been interpolated to rectangular coordinates.
The mesh is uniform at 500 m spacing from the Norwegian coastline to a point 50 km east-southeast of Esrange, Sweden. Gentle stretching is used upstream and downstream of these points. The mesh is also uniformly spaced at 500 m in the lateral direction over the central regon +/- 50 km N-NE and S-SW of Esrange. Gentle stretching is once again used from this region to the outer boundaries. The mesh is uniformly spaced at 250 m for all altitudes in the z direction. In total the mesh contains 650 x 274 x 560 points and sponge layers are used on all external boundaries in order to absorb outgoing waves.
Wind and Thermodynamic Profiles
The wind and temperature profiles were based on radiosonde mesurements
taken over Esrange on December 11, 2013 at 23:30 UTC. The radiosonde
measurements were smoothed somewhat and the data was extended between
30 and 113 km using climatology. Polynomial extrapolation was used above
113 km.
Initial Wind Condition
Here the winds are initially set to zero from the surface to an altitude of
about 20 km. At this point the wind transitions to the profiles shown in the
plots above. Forcing terms then gradually introduce winds near the surface
with the
objective of achieving the profile shown above within a two hour period.
A hyperbolic tangent function is used in order to produce gentle
acceleration of the wind near the beginning and end of the forcing period.
The maximum forcing rate is equivalent to that of a linear ramp with a
duration of 30 minutes.
Computational Domain
The layout of the of the simulation is shown in the figure below. Note that
the boundaries of the computation domain (shown by the thin white line) has
been rotated by 26 degrees with respect to lines of constant latitude. Just the computational domain is shown in the figure below. In this plot, the surface has been interpolated to rectangular coordinates.
The mesh is uniform at 500 m spacing from the Norwegian coastline to a point 50 km east-southeast of Esrange, Sweden. Gentle stretching is used upstream and downstream of these points. The mesh is also uniformly spaced at 500 m in the lateral direction over the central regon +/- 50 km N-NE and S-SW of Esrange. Gentle stretching is once again used from this region to the outer boundaries. The mesh is uniformly spaced at 250 m for all altitudes in the z direction. In total the mesh contains 650 x 274 x 560 points and sponge layers are used on all external boundaries in order to absorb outgoing waves.
Wind and Thermodynamic Profiles
The wind and temperature profiles were based on radiosonde mesurements
taken over Esrange on December 11, 2013 at 23:30 UTC. The radiosonde
measurements were smoothed somewhat and the data was extended between
30 and 113 km using climatology. Polynomial extrapolation was used above
113 km.