Effect of El Niño on summer extreme ocean waves over East Asian regions

Abstract Extreme wave events have had devastating impacts on East Asian (EA) coastal regions. However, despite being a prominent region for extreme waves due to the influence of anomalous seasonal atmospheric and remote climate variability, the investigation of EA extreme wave characteristics, such as duration and intensity, and their relation to the climate variability remains unclear. By applying the peaks-over-threshold (POT) method with a fixed threshold set at the 99th percentile, this study aims to quantify the duration and intensity of EA extreme wave events in boreal summer from 1980–2021 and investigates the influence of warm phase of El Niño-Southern Oscillation (ENSO, El Niño) and Pacific Decadal Oscillation (PDO) as the main climate mode in the Pacific Ocean. Spatially, the findings demonstrate that extreme waves have occurred with an intensity (the wave height above threshold) of up to 1.5 m, persisting for 8 to 35 h across the study area and revealing the significant area in the southern part of the region, impacting the southern coast of Korea. The area-averaged, calculated specifically for this significant area, indicate that the occurrence of El Niño induces longer (averaging 85 h) and more intense summer extreme waves, with a maximum intensity of 2 m. Furthermore, a positive PDO tends to strengthen the El Niño effect, with the almost doubled in duration, through strong anomalous anticyclonic formation in the Philippine Sea. The study findings enhance our understanding of the link between ENSO and TS activity with respect to extreme wave duration and intensity; these factors can be relevant in formulating plans for mitigating the impact of extreme wave events on coastal environments.