Coastal El Niño is an extreme situation of El Niño-Southern Oscillation (ENSO) with sea surface temperature warming confined in the far-eastern equatorial Pacific. Some coastal El Niños evolve into a basin scale El Niño, and some don't, implying a diversity in ENSO evolutions after a coastal El Niño event. In this study, the coastal El Niños in 2017 and 2023 are selected to examine their subsequent evolution. Both coastal El Niños developed after a La Niña, with the former followed by a La Niña and the latter by a basin-scale El Niño. The cold (warm) subsurface temperatures in 2017 (2023) were key factors leading to the divergent ENSO evolution. Convection over the western tropical Pacific and the atmospheric circulation anomalies across the equatorial Pacific also contributed to the differences. Model predictions suggest that differences in ENSO evolution after a coastal El Niño are associated with differences in ENSO predictability.

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2017年和2023年沿海厄尔尼诺事件后ENSO的分歧演化

沿海厄尔尼诺现象是厄尔尼诺南方涛动（ENSO）的一种极端情况，其海面温度升高仅限于赤道太平洋远东地区。一些沿海厄尔尼诺现象演变成盆地规模的厄尔尼诺现象，有些则没有，这意味着沿海厄尔尼诺事件后ENSO演变存在多样性。本研究选取2017年和2023年沿海厄尔尼诺现象来考察其后续演变。两次沿海厄尔尼诺现象都是在拉尼娜事件之后发展起来的，前者随后发生拉尼娜现象，后者发生盆地规模的厄尔尼诺现象。 2017年（2023年）次表层冷（暖）温度是导致ENSO演化出现分歧的关键因素。热带西部太平洋的对流和赤道太平洋的大气环流异常也造成了这种差异。模型预测表明，沿海厄尔尼诺现象后 ENSO 演化的差异与 ENSO 可预测性的差异相关。