Intrinsic Ocean–Atmosphere Variability of the Tropical Atlantic Ocean

The tropical Atlantic variability is composed of three major patterns of significant importance for variability and predictability of climate in the Atlantic sector. They are the southern tropical Atlantic (STA) pattern with anomalous sea surface temperature (SST) fluctuations expanding from the Angolan coast to the central equatorial ocean, the northern tropical Atlantic (NTA) pattern centered near the northern African coast, and the southern subtropical Atlantic (SSA) pattern in the open subtropical ocean. Previous studies have suggested that both the regional air–sea coupling and remote forcing from outside the basin may affect the formation of these patterns and their variability. A specially designed global coupled ocean– atmosphere general circulation model, which eliminates air–sea feedback outside the Atlantic, reproduces the major features of these observed patterns realistically. This suggests that these patterns originate from air–sea coupling within the Atlantic Ocean or by the oceanic responses to atmospheric internal forcing, in which there is no anomalous forcing external to the Atlantic Ocean. The effect of the Pacific El Niño–Southern Oscillation (ENSO) seems to modulate their temporal evolution through influencing atmospheric planetary waves propagating