Figure 3-8 (left panel) shows the typical horizontal structure of continuous modes for log E=-0.20, 1.80 ≤ c ≤ 2.19. A blue filled circle in right panel indicates the position of the mode. In this case, the structure of an equatorial Rossby mode (Rossby) dominates. The structure of a continuous mode (C) cannot be observed.
The critical latitude of the mode shown in figure 3-8 is y=0.03. There should exist an amplitude peak of geopotential at y=0.03 corresponding to the structure of continuous mode, but such a peak cannot be observed very well in the left panel of figure 3-8. The structure of continuous mode is considered to be masked by an equatorial Rossby wave like structure described below.
An amplitude peak of geopotential at y=1.60 is considered to be caused by equatorial Rossby mode. Since the dispersion curve of the mode shown in figure 3-8 exists between dispersion curves of equatorial Kelvin modes and westward mixed Rossby-gravity modes, equatorial Rossby modes is only candidate that produces the amplitude peak of geopotential at y=1.60. The geostrophic structure at y=1.60 shown in the left panel is also consistent with the existence of an equatorial Rossby mode.
An ageostrophic westward structure is observed at y=3.00, although the amplitude is small. There is a possibility that a north boundary Kelvin mode assimilates to the mode shown in figure 3-8.
Figure 3-8: Horizontal structure of a continuous mode for log E=-0.20, k=0.10, c=2.03 (left panel). The position of the mode in dispersion curves is indicated by a blue filled circle in the right panel. Contours and vectors in the left panel indicate &phi and velocity field, respectively. Contour intervals are 5.00 × 10-2. Other symbols in the right panel are same as table 1.