An Equatorial Oscillation Index (EOI) is defined, based on the zonal gradient of sea surface pressure between the western Pacific and eastern Pacific along the equator, to describe the distribution of wind and pressure within the equatorial Pacific. The EOI has a stronger correlation with the Niño3.4 sea surface temperature anomaly (SSTA), as well as with westerly/easterly wind bursts (WWBs/EWBs), showing a superiority over the Southern Oscillation Index (SOI). In general, the EOI is consistent with the SOI, both of which reflect large-scale sea level pressure oscillations. However, when there are inconsistent SSTAs between the equator and subtropical regions, the SOI may contrast with the EOI due to the reverse changes in sea level pressure in the subtropical regions. As a result, the SOI fails to match the pattern of El Niño, while the EOI can still match it well. Hence, the EOI can better describe the variability of the Niño3.4 SSTA and WWBs/EWBs. The correlation between the SOI and Niño3.4 SSTA falls to its minimum in May, due to the large one-month changes of sea level pressure from April to May in the subtropical southern Pacific, which may be related to the spring predictability barrier (SPB). The newly defined EOI may be helpful for monitoring El Niño-Southern Oscillation (ENSO) and predicting ENSO.

基于赤道西太平洋和东太平洋沿赤道之间的海表压力分区梯度，定义了赤道涛动指数（EOI），以描述赤道太平洋内的风和压力分布。EOI与Niño3.4海面温度异常（SSTA）以及西风/东风爆发（WWBs / EWBs）具有更强的相关性，显示出优于南方涛动指数（SOI）的优势。通常，EOI与SOI一致，两者都反映了大规模的海平面压力振荡。但是，当赤道和亚热带地区之间的SSTA不一致时，由于亚热带地区海平面压力的反向变化，SOI可能与EOI相反。结果，SOI无法匹配厄尔尼诺现象，而EOI仍然可以很好地匹配它。因此，EOI可以更好地描述Niño3.4SSTA和WWB / EWB的变异性。SOI和Niño3.4SSTA之间的相关性在5月份降至最低，这是由于南亚热带4月至5月海平面压力发生了一个月大的变化，这可能与春季可预测性壁垒（SPB）有关）。新定义的EOI可能有助于监测厄尔尼诺-南方涛动（ENSO）和预测ENSO。