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In order to compare these results with observations, we need to revert to
physical space and time units need to be introduced. To set the characteristic
spatial and time scales, let the layer thickness be 1.5 km and the peak Brunt
period, in inverse radians, is 25 s using data fromGarcia (1999). From Table 7.1,
corresponding to run 1, the wavelength of the longest undulation is 1
.
5km
×
18
=
27 km. The bore formation time is 25 s
×
300
2 h . The phase speed
is c
=
0
.
54
×
N 0 h
32m/s. These values are typical of what is observed for
mesospheric bores.
It is important to note that the bore formation process considered by Seyler
(2005) differs from that in Dewan and Picard (2001) who consider the bore for-
mation results from steepening of a “hydraulic jump” created by an accelerating
piston, whereas Seyler only considered ducted gravity wave initial conditions.
Nonetheless, the analysis and numerical solutions presented by Seyler show that
mesospheric bores are consistent with nonlinear internal gravity waves trapped
within a thermal inversion layer, as proposed by Dewan and Picard (1998). The
nonlinear solutions are consistent with observations of mesospheric bores with
respect to propagation speed, wavelength, number of peaks, and formation time.
The nonlinear model predicts additional properties of mesospheric bores that are
potentially testable but have yet to be observed, such as the vertical structure of
the flow and potential temperature field.
References
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Kjeller.
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