The Pacific El Niño Phenomenon and the Atlantic Circulation

Abstract

Abstract Atmospheric–oceanic departure patterns in the tropical Atlantic and eastern Pacific associated with the Ecuador/Peru El Ninno and its antithesis are studied on the basis of long-term ship observations during 1911–71. Departure maps of sea level pressure (SLP), wind speed and sea surface temperature (SST) in March/April are presented for composite of ten extreme years of either regime. The evolution of SLP anomalies from the preceding to the event year is traced for large ocean areas. Gaussian and binomial probabilities are calculated as a measure of the importance of SLP departures. El Nino years are characterized by abnormally low SLP over the eastern South Pacific and positive SLP anomalies over the Atlantic; winds are weaker than normal over the Pacific, and stronger over the Atlantic; SST anomalies are positive in the Pacific, but negative in a band of the Atlantic extending from West Africa toward the South American coast. During counter-El Nino years, departure patterns am approximately inv...