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 Ocea n-Global Atmosphere (TOGA) program have served to corroborate preexist ing notions concerning the seasonally dependent relationships between sea surface temperature, sea level pressure, wind stress, rainfall, up per tropospheric circulation, and ocean thermal structure anomalies in the El Nino-Southern Oscillation (ENSO) phenomenon. However, the para digm of a quasiperiodic ''ENSO cycle,'' phase locked with the annual m arch, does not capture the complexity of the evolution of the anomalie s. The inadequacy of this model was particularly apparent during the s econd half of TOGA when the variability was highly aperiodic. Also, a single modal structure or empirical orthogonal function does not appea r 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. D ata collected during TOGA serve to confirm the influence of tropical A tlantic sea surface temperature anomalies upon rainfall in northeast B razil.