Geoscience Reference
In-Depth Information
Fig. 6. The time-radius cross-section of the asymmetric vorticity amplitude (unit:
5
×
10
−
5
s
−
1
) for case T20. To obtain radial displacement in km, multiply by 1000.
Thetimeunitishour.
asymmetry shows an up-shear tilt (Fig. 7(a)) with respect to the rotation
angular velocity of the core vortex (Fig. 2(b)). Because of this up-shear tilt,
the symmetric flows transfer their energy to the asymmetric perturbations
near
1 before hour 4 (Fig. 5), resulting in the weakening of the
symmetric core vortex at hour 3 (Fig. 4). Because the symmetric angular
velocity advects the inner asymmetry at a much faster rotation rate (see
the angular velocity profile in Fig. 2(b)) than the outer asymmetry, the
asymmetric vorticity shifts its phase to a down-shear tilt in the period of
hours 4-9 (refer to Fig. 7(b)), so that the energy is transferred back to the
symmetric flows (Fig. 5) and the asymmetric vorticity amplitude decreases
during the period (Fig. 6). Thus, the symmetric tangential wind near the
radius of 0.1 grows at the expense of the weakening of the asymmetry
from hour 6 to hour 9 (Fig. 4). A new up-shear-tilting inner asymmetry is
induced again after hour 9 (Figs. 6 and 7(c)). As a result, the symmetric
flows transfer their energy to the asymmetric perturbations during hours
9-12, while the tangential wind at the inner core region weakens (Fig. 4).
In contrast, the symmetric flows always gain energy from the
asymmetric disturbances in the outer region (
r
=0
.
15) due to the steady
down-shear phase tilt of the asymmetric disturbances (Fig. 7). This causes
r>
0
.
