Wave movement with and without rotational effects.

Left: Wave movement around a node. The node is seen half-way along the basin, where the colour is always greenish-yellow regardless of the phase of the wave.
Wave movement around nodes is observed in situations where the rotation of the earth cannot influence the wave to any large extent. This is usually the case in long narrow basins such as channels or narrow lakes, where the water can move along the axis of the basin but not much across it.

Right: Water movement around an amphidromic point. The only place where the water level never changes (where the colour is always yellow) is in the centre of the basin; this is the amphidromic point. You can see the wave rotate around this point by following its highest elevation (the red region).
If the basin is of comparable dimensions in all directions the wave travels along the basin perimeter, in circular fashion around an amphidromic point.

© 1999 M.Tomczak

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