The structure and evolution of ENSO-related climate variability in the tropical Pacific: Lessons from TOGA

Improved observations in the tropical Pacific during the Tropical Ocean-Global Atmosphere (TOGA) program have served to corroborate preexisting notions concerning the seasonally dependent relationships between sea surface temperature, sea level pressure, wind stress, rainfall, upper tropospheric circulation, and ocean thermal structure anomalies in the El Nino-Southern Oscillation (ENSO) phenomenon. However, the paradigm of a quasiperiodic "ENSO cycle," phase locked with the annual march, does not capture the complexity of the evolution of the anomalies. The inadequacy of this model was particularly apparent during the second half of TOGA when the variability was highly aperiodic. Also, a single modal structure or empirical orthogonal function does not appear to be capable of representing the range of spatial patterns of ocean-atmosphere interaction in the tropical Pacific. These results suggest the need for a more inclusive phenomenological description of ENSO. Data collected during TOGA serve to confirm the influence of tropical Atlantic sea surface temperature anomalies upon rainfall in northeast Brazil.