This study utilizes an ocean model (the Coastal and Regional Ocean Community Model) to investigate the delayed outbreak of the autumn Wyrtki Jet (aWJ) during the 2023 positive Indian Ocean Dipole (PIOD) event. Two sensitivity experiments are designed to isolate the roles of wind forcing and pressure gradient force (PGF), combined with zonal momentum equation diagnosis. EXP1 eliminates PIOD-induced sea surface temperature (SST) anomalies (retaining wind forcing), showing the PGF’s easterly acceleration (0.17 × 10 −6 m s −2 ) is 30% lower than the CTRL group (0.24 × 10 −6 m s −2 ), leading to a 2–3 day aWJ delay and weakened velocity within 68°–75°E, confirming PIOD-induced SST anomalies enhance the PGF and contribute to an aWJ delay. EXP2 removes PIOD-induced wind anomalies (retaining the PGF from SST anomalies), demonstrating the PGF alone provides stable easterly acceleration (0.16 × 10 −6 m s −2 ) to drive initial aWJ formation in mid-October (57°–75°E) with a velocity of 0.3–0.4 m s −1 in December. Unlike previous studies in which PGF was regarded as a background condition, this study reveals the PGF to have been an active driver during the 2023 extreme PIOD (contribution ratio >50%), being both the fundamental driver of aWJ formation and the key regulator of its delayed outbreak. This study clarifies the critical contribution of PIOD to aWJ delay, providing new insights into the formation and evolutionary mechanisms of aWJs. 本研究利用CROCO海洋模式,通过两组敏感性试验并结合纬向动量方程诊断,探究了2023年强正印度洋偶极子(PIOD)背景下秋季Wyrtki急流(aWJ)爆发延迟的动力机制.结果表明,移除PIOD海温异常后, 压强梯度力(PGF)较对照组明显减弱并导致aWJ爆发延迟;而在无风异常情况下, PGF仍可独立驱动aWJ形成.定量分析显示, 2023年极端PIOD下PGF的动力贡献超过50%, 揭示其是aWJ形成及延迟爆发的关键调控因子.因此, 研究阐明了气候事件背景下斜压异常与风强迫在延缓aWJ爆发的动力影响.
Han et al. (Sun,) studied this question.