Author(s): Marina Farias De Reyes; Karla Montero

Linked Author(s): Marina Farias de Reyes

Keywords: ENSO; Coastal El Nino; Global El Nino; La Nina; Nino 1+2

Abstract: The definitions of El Nino/La Nina are evolving, the international scientific community assigns this name to the El Nino-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 Nino events dissociated from ENSO recur, which is called Coastal El Nino (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 Nino 1+2 monitoring region, where El Nino 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 Nino/La Nina (ENSO), while the partial mismatch of the indicators indicated coastal El Nino/La Nina events. Thus, 5 different types of years were obtained: global El Nino (GEN), coastal El Nino (CEN), global La Nina (LNG), coastal La Nina (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.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0953-cd

Year: 2023