Here we simulate a medium-frequency gravity wave interacting with an
inertial gravity wave. The medium-frequency wave has a horizontal wavelength
of 6,000 m, a vertical wavelength of 300 m, an intrinsic frequency of
N/20.03, and a non-dimensional amplitude of 0.525. The inertial gravity
wave has a vertical wavelength of 100 m, an intrinsic frequency of 2*f
(f being the Coriolis parameter), and a non-dimensional amplitude of 0.50.
Although the horizontal wavelength for this wave would be 10.2 km, it is
approximated as being infinite so that the IGW does not vary in the
x-direction. Its temporal variation is also neglected. Thus the IGW
appears as a mean flow component to the medium-frequency GW. The IGW
would have its energy flux propagating downward and to the right
(if the temporal and zonal depencence were allowed) whereas the
medium-frequency has its energy flux propagating upward and to the left.
A mean wind from left to right is used to achieve a ground-based frequency of
zero for the GW. The Reynolds number based on the medium-frequency
GW vertical wavelength and the buoyancy period is 50,000.
The simulation is 2D with computational domain 6,000 x 300 m and 5760 x 288
mesh points. The resolution is marginal, but is adequate to resolve the
primary instability structures.

Case 2 GW frequency ~N/10

This case is similar to Case 1 with the exception that the medium-frequency
GW horizontal wavelength is a factor of two smaller, or 3,000 m. This gives
it an intrinsic frequency of N/10.05. The IGW parameters are unchanged. The
computational domain was reduced to 6,000 x 300 m and the number of mesh
points reduced to 2880 x 288.

Case 3: Two GWs with frequencies ~N/10 and ~N/5

This case is similar to Case 2 with the exception that a second
GW with horizontal wavelength 1500 m and intrinsic frequency ~N/5 is
also superimposed. The non-dimensional wave amplitudes for the N/10
and N/5 components are 0.3, whereas the amplitude for the IGW is 0.5.
The IGW continues to have its energy flux downward and to the right
whereas the N/10 and N/5 waves are propagating upward and to the left.
The N/10 wave has a ground-based frequency of zero, but the N/5 wave
has a ground-based frequency of N/5-N/10=N/10.

Case 4: Two GWs with frequencies ~N/10 and ~N/3.5

This case is identical to Case 3 with the exception that the shorter GW
wavelength was reduced to 100 m, giving it an intrinsic frequency of ~N/3.5.

Case 5: Two GWs with frequencies ~N/10 propagating
upward-left and ~N/5 propagating upward-right

This case is identical to Case 3 with the exception that the N/5 GW is
propagating upward and to the right (instead of upward and to the left).

Case 6: Two GWs with frequencies ~N/10 propagating
upward-left and ~N/5 propagating downward-left

This case is identical to Case 3 with the exception that the N/5 GW is
propagating downward and to the left (instead of upward and to the left).

Case 7: Two GWs with frequencies ~N/10 propagating
upward-left and ~N/5 propagating downward-right

This case is identical to Case 3 with the exception that the N/5 GW is
propagating downward and to the right (instead of upward and to the left).