Although the physical interpretations for the most unstable modes
were given by TI2006,
other unstable modes, neutral modes, and continuos modes
are not well examined.
The following problems are left unexamined:
- Equatorial Rossby modes
(Matsuno, 1966)
are not observed in
the results of TI2006,
although equatorial Kelvin modes, inertial gravity modes,
and mixed Rossby-gravity
modes were identified.
TI2006 speculated that all
equatorial Rossby modes assimilate into continuous
modes.
However, the structural change of continuous modes
with such assimilation
are not shown.
- Among symmetric unstable modes,
TI2006 considered only the lowest order modes
which correspond to so-called inertially unstable mode.
The resonating neutral modes causing
high-order symmetric unstable modes
were not clarified.
- In some dispersion curves obtained by TI2006,
nearby dispersion curves of neutral modes intersect
(an example is shown in figure (c) in table 1).
TI2006 does not discuss the nature of such
neutral modes.
- The dispersion curves of equatorial Kelvin modes and
westward mixed Rossby-gravity modes are obscure
when the two modes resonate.
Their dispersion curves are buried among dispersion curves of continuous
modes in the figures of TI2006.
In this paper,
the above mentioned problems are examined
in order to give interpretations
for all modes obtained by TI2006.
Each problem is examined in the following each section.
In section 2, governing equations are described.
In sections 3 to 6, more detailed description for each problem
and results are given.
Section 7 is a summary.
