What is El Nino/Southern Oscillation (ENSO)?
“ENSO” stands for “El Nino / Southern Oscillation”. The acronym arose in the climate research community, and reflects an attention bias toward the warm phase of the entire cycle. El Nino is just one phase of an irregular fluctuation between warmer than usual and colder than usual ocean temperatures in the Eastern Pacific. The cold phase has recently come to be known as “La Nina”. The El Nino/La Nina “cycle” does not occur with strict periodicity. Historically, an El Nino usually recurs every 3-7 years, as does its (cold) La Nina counterpart. The overlying atmosphere is tightly coupled to ocean temperatures and circulation patterns. An atmospheric pressure signal is seen throughout the tropics that is strongly linked to El Nino and La Nina. When barometric pressure is higher than usual in the western Pacific near Indonesia, pressure is lower than usual in the subtropical Pacific near Easter Island and Tahiti. This global-scale pressure signal, identified 70 years ago, is known as the “S
