4b: Shutting down El Niño
The warm ENSO event shuts down when Rossby waves generated by the relaxation of the trade winds in the central Pacific (red oval) travel west to the Indonesian archipelago and are reflected back as Kelvin waves. The Kelvin waves bring cold water back towards the surface (in the blue region), initiating the cooling that shuts down the warm ENSO event and restrengthens the trade winds.