Observations of Kelvin waves on the African Atlantic shelf.
Top: general geography and location of observation stations.
Bottom left: Sea surface temperature (°C) at various locations along the coast. The effect of the wave on the surface temperature is seen as periodic upwelling and downwelling, which produces periodic lowering and rising of the water temperature. The period is approximately 14 days.
Bottom right: Temperature and alongshore currents at 12, 42 and 82 m depth at a mooring located about halfway along the heavy line that goes out across the shelf from Tema in the top figure. Water temperature and observed sea level in Tema harbour are also shown. All variables display the same 14 day periodicity. The current reverses for several days but shows the wave superimposed on westward mean flow.
Adapted from Houghton and Beer (1976)