Geoscience Reference
In-Depth Information
Fig. 5. The time-radius cross-section of the asymmetry-to-symmetric kinetic energy
transfer rate (unit: 1
.
25
×
10
−
4
m
2
s
−
3
) in association with the wave-wave interactions
in case T20. To obtain radial displacement in km, multiply by 1000. The time unit is
hour.
transfer from the asymmetric perturbation to the symmetric flow, whereas
inside of this radius there is oscillatory behavior in the energy transfer,
that is, the symmetric flow gains energy from the asymmetry during hours
4-9 but loses energy into the asymmetry during hours 0-4 and 9-12. This
is consistent with the time tendency of the symmetric tangential wind
near RMW.
To understand the cause of the distinctive energy transfer behavior,
we examine the asymmetric perturbation structure and its evolution
characteristics. Figure 6 shows the time evolution of amplitude of the
asymmetric perturbation. Note that in this numerical experiment (T20)
the initial wavenumber 2 asymmetry is placed at the radius of 0.2. After
time integration, a strong asymmetry is generated within the first four hours
inside the radius of 0.1 where the absolute value of the symmetric vorticity
gradient is the largest (Fig. 2(d)). The asymmetry amplitude in the outer
region (
r>
0
.
15), however, decreases gradually.
The horizontal pattern of the asymmetric perturbation reveals that the
asymmetric vorticity field exhibits distinctive patterns during the different
development stages. For example, at hour 1, the phase line connecting
this newly generated asymmetry inside of RMW and the original outer
