Increased Recurrence of Global and Coastal El Niño Events on the South American Coasts

de Reyes M.F.; Montero K. · Proceedings of the IAHR World Congress (2023) · DOI: 10.3850/978-90-833476-1-5_iahr40wc-p0953-cd

Resumen

The definitions of El Niño/La Niña are evolving, the international scientific community assigns this name to the El Niño-Southern Oscillation ENSO, of a global nature and which affects a large part of the Pacific Ocean, as in 1983 and 1998. However, in the extreme eastern Pacific, El Niño events dissociated from ENSO recur, which is called Coastal El Niño CEN, as in 1925, 2017 and 2023. Both types of events can have very strong impacts on the South American coasts, and are apparently associated with nonlinear convective feedbacks, but with very different dynamics. The objective of this research is to identify and classify by intensity the occurrence of active ENSO and CEN phases in Piura, at 4°S-6°S, in the Niño 1+2 monitoring region, where El Niño occurs with greater intensity. Local hydrometeorological indicators and local and global oceanic-atmospheric parameters recorded between 1950 and 2023 were used. Their coincidence was analyzed to identify warm/cold anomalies such as global El Niño/La Niña ENSO, while the partial mismatch of the indicators indicated coastal El Niño/La Niña events. Thus, 5 different types of years were obtained: global El Niño GEN, coastal El Niño CEN, global La Niña LNG, coastal La Niña LNC and neutral. This confirmed the two different sources of climate anomalies on the South American coasts. Categories 1-5 were assigned using percentiles, classifying the events as extraordinary, very strong, strong, moderate and weak. It was concluded that there was a 76% higher incidence of global anomalies than coastal ones, which is positive due to its greater predictability and 76% more cold than warm events, with cold events having fewer negative consequences. In the last century, 4 extraordinary warm events occurred, with 31 years of recurrence. When updating to the year 2023 previous identification studies from 1987, it was found that the recurrence of very strong warm events decreased from 58 to 38 years and in the study period the recurrence is only 16 years, which could denote an intensification of the events of this type, and that would be the subject of continuous evaluation.

Instituciones: Universidad Nacional Agraria La Molina; Universidad de Piura