Abstract

The zonal wind stress ( \({\tau }^{x}\) ) over the equatorial Pacific plays a vital role in the air-sea interaction associated with the El Niño-Southern Oscillation (ENSO). The equatorial westerly wind stress (w \({\tau }^{x}\) ) anomalies during the El Niño (EN) decay phase propagate eastward and decrease rapidly, while the equatorial easterly wind stress (e \({\tau }^{x}\) ) anomalies during the La Niña (LN) decay phase do not display obvious zonal movement and remain near the dateline. The cause of the asymmetry in \({\tau }_{x}\) anomalies and its contribution to ENSO asymmetric decays are investigated in this study. The difference in \({\tau }^{x}\) anomalies is due to the interaction between the atmospheric response to sea surface temperature anomalies (SSTAs) and the forcing of the wind field on subsurface temperature. The results of numerical experiments demonstrate that the e \({\tau }^{x}\) anomalies during the LN decay phase have a strong and prolonged suppressive effect on the zonal advective feedback and thermocline feedback, resulting in the weakness of the delayed negative feedback. However, due to the eastward propagation and rapid decay of w \({\tau }^{x}\) anomalies, the suppressive effect during the EN decay phase is weak and favors its rapid decay. Previous studies have extensively analyzed the asymmetric response of the atmosphere to SSTAs. The difference in zonal displacement of air-sea couplings during ENSO decay phases leads to the decay asymmetry between EN and LN through weakening the negative air-sea feedback during LN, in which our results highlight that the zonal propagation asymmetry of \({\tau }^{x}\) anomalies plays a crucial role.

中文翻译：

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不对称海气反馈对 ENSO 衰减的影响：风应力异常纬向传播的作用

摘要

赤道太平洋上空的纬向风应力 ( \({\tau }^{x}\) ) 在与厄尔尼诺南方涛动 (ENSO) 相关的海气相互作用中起着至关重要的作用。厄尔尼诺（EN）衰变阶段赤道西风应力（w \({\tau }^{x}\)）异常向东传播并迅速减小，而赤道东风应力（e \({\tau } ^{x}\) ) 拉尼娜 (LN) 衰变阶段的异常没有表现出明显的纬向运动，并保持在日期变更线附近。本研究研究了\({\tau }_{x}\)异常不对称的原因及其对 ENSO 不对称衰变的贡献。 \({\tau }^{x}\)异常的差异是由于大气对海面温度异常 (SSTA) 的响应与风场对地下温度的强迫之间的相互作用造成的。数值实验结果表明， LN衰变阶段的e \({\tau }^{x}\)异常对纬向平流反馈和温跃层反馈具有强烈且持久的抑制作用，导致延迟的影响较弱。负面反馈。但由于w \({\tau }^{x}\)异常向东传播且快速衰变，EN衰变阶段的抑制作用较弱，有利于其快速衰变。先前的研究广泛分析了大气对海温异常的不对称响应。 ENSO 衰变阶段海气耦合的纬向位移差异通过削弱 LN 期间的海气负反馈而导致 EN 和 LN 之间的衰变不对称性，其中我们的结果强调了\({\tau }^{x}\)异常起着至关重要的作用。