This page describes a numerical simulation of waves generated by winds
blowing over a section of the Southern Andes. The mean winds and temperature
profile are taken from one of Han Li's runs for wintertime at 50 S. These
profiles only extent to an altitude of 140 km so the winds were held fixed
at their values at 140 km for higher altitudes. The temperature profile was
smoothly extended to a maximum temperature of 800 degrees K. The wind,
temperature, and N^2 profiles are shown below.
The simulation makes use of a terrain map for the Southern Andes covering a latitude range of 44 S to 54 S and a longitude of 64.5 W to 76.5 W. This map is shown below.
A window function is then used to flatten the terrain away from the Andes mountain range. This operation results in the following modified terrain map.
The domain is then extended to cover 2500 km in the zonal direction and 1600 km in the meridional direction. The grid is clustered in the region of terrain, having 500 m resolution in the zonal direction and 2000 m in the meridional direction.
The mesh is stretched in the vertical direction, having a minimum spacing of 100 m at the surface. A total of 580 X 480 X 320 mesh points are used in the zonal, meridional, and vertical directions respectively.
The lower boundary is treated as a slip wall whereas radiation conditions in concert with a sponge is used at all other boundaries. The sponge/radiation condition produces solutions where little or no wave energy reflects (or enters) at the boundaries.
The simulation is started from rest and the wind is increased according to a hyperbolic tangent function over a period of 2 hours.
br> Click on the images below to see animations of the vorticity magnitude, zonal, and vertical velocity perturbations in the zonal-vertical plane. The color map in each of these animations is changed several times during the animation in order to accommodate the large increase in wave amplitude with time. These rescalings result in somewhat annoying jumps, but at least it is possible to visualize the entire evolution.
Click on the images below to see animations of the vorticity magnitude, zonal, and vertical velocity perturbations in the zonal-meridional plane at an altitude of 80 km. Once again the color maps are changed several times during the animation in order to accommodate the large increase in wave amplitude with time.
Click on the images below to see animations of the vorticity magnitude, zonal, and vertical velocity perturbations in the zonal-meridional plane at an altitude of 175 km. Once again the color maps are changed several times during the animation in order to accommodate the large increase in wave amplitude with time.
Compressed directories of images from the animations
xz1_u.zip
xz1_w.zip
xz1_vm.zip
xy2_u.zip
xy2_w.zip
xy2_vm.zip
xy5_u.zip
xy5_w.zip
Surface Grid
surface.vtk
The simulation makes use of a terrain map for the Southern Andes covering a latitude range of 44 S to 54 S and a longitude of 64.5 W to 76.5 W. This map is shown below.
A window function is then used to flatten the terrain away from the Andes mountain range. This operation results in the following modified terrain map.
The domain is then extended to cover 2500 km in the zonal direction and 1600 km in the meridional direction. The grid is clustered in the region of terrain, having 500 m resolution in the zonal direction and 2000 m in the meridional direction.
The mesh is stretched in the vertical direction, having a minimum spacing of 100 m at the surface. A total of 580 X 480 X 320 mesh points are used in the zonal, meridional, and vertical directions respectively.
The lower boundary is treated as a slip wall whereas radiation conditions in concert with a sponge is used at all other boundaries. The sponge/radiation condition produces solutions where little or no wave energy reflects (or enters) at the boundaries.
The simulation is started from rest and the wind is increased according to a hyperbolic tangent function over a period of 2 hours.
br> Click on the images below to see animations of the vorticity magnitude, zonal, and vertical velocity perturbations in the zonal-vertical plane. The color map in each of these animations is changed several times during the animation in order to accommodate the large increase in wave amplitude with time. These rescalings result in somewhat annoying jumps, but at least it is possible to visualize the entire evolution.
Click on the images below to see animations of the vorticity magnitude, zonal, and vertical velocity perturbations in the zonal-meridional plane at an altitude of 80 km. Once again the color maps are changed several times during the animation in order to accommodate the large increase in wave amplitude with time.
Click on the images below to see animations of the vorticity magnitude, zonal, and vertical velocity perturbations in the zonal-meridional plane at an altitude of 175 km. Once again the color maps are changed several times during the animation in order to accommodate the large increase in wave amplitude with time.
Compressed directories of images from the animations
xz1_u.zipxz1_w.zip
xz1_vm.zip
xy2_u.zip
xy2_w.zip
xy2_vm.zip
xy5_u.zip
xy5_w.zip