Interaction of the Atlantic Equatorial Cold Tongue and the African Monsoon*

The seasonal cycle of equatorial Atlantic sea surface temperature (SST) is characterized by a rapid cooling from April to July, coinciding with the onset of the West African summer monsoon and followed by a slow warming that lasts 3 times longer. Two ensemble simulations are carried out with an atmospheric general circulation model to investigate the mechanisms for the wind changes that cause this rapid oceanic cooling and its feedback onto the African monsoon. In the control simulation, SST is globally prescribed in its full climatological seasonal cycle, while in the second simulation, equatorial Atlantic SST is held constant in time from 15 April onward.