Spatiotemporal Variations and Characteristics of the El Niño–Southern Oscillation (ENSO) Phenomenon from 1950 to 2023

The El Niño–Southern Oscillation (ENSO) is one of the most important climate phenomena on Earth due to its impacts on the global atmospheric circulation. This paper conducts a comprehensive analysis of the spatiotemporal variations and characteristics of ENSO from 1950 to 2023. A number of indices, including the Oceanic Niño index, Modoki index, and the modified El Niño Modoki Index, were used to differentiate between various ENSO types and assess their respective impacts on the global climate. The analysis reveals notable changes in the frequency and intensity of ENSO events over the past seven decades. Notably, since 1990, the sea surface temperature anomalies (SSTAs) in the tropical Western Pacific regions have shifted westward by approximately 18 degrees longitude, potentially a result of global warming. During the same time period, the frequency and intensity of ENSO events have also changed, with an increase in the frequency of Central Pacific El Niño events and a decline in the frequency of Eastern Pacific El Niño events. The occurrence frequency of both Central and Eastern Pacific La Niña events has remained relatively stable but shows some variability. Based on the analysis results, this article also suggests potential improvement in data collection, which is critical to further understanding and verification of the spatiotemporal variations of ENSO events.