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<p>Comprehensive understanding of sea surface temperature (SST) variability in the tropical Indian Ocean (TIO) remains a challenge for simple conceptual models. In this study, we adapt a spatiotemporal oscillator (STO) model which originally developed for Pacific ENSO dynamics to the TIO through localized parameter adjustments that account for the TIO’s distinct mean state and seasonal forcing. With these adaptations, the TIO SST anomaly (SSTA) is physically decomposed into a set of eigenspatial modes, each oscillating at its own natural frequency. The zeroth mode exhibits a basin‑wide uniform SSTA structure, corresponding to the observed Indian Ocean Basin mode (IOBM). The first eigenspatial mode captures a zonal contrast between the eastern and western TIO, closely resembling the classic Indian Ocean Dipole (IOD) pattern, with a natural period of approximately 2&#xa0;years. The second mode displays a tripolar structure, with SSTA contrasts between the central TIO and its eastern/western flanks, and a characteristic period of about 1&#xa0;year (half that of the IOD mode); this mode corresponds to the Indian Ocean Tripole (IOT). These eigenmodes provide a compact dynamical description of the dominant spatiotemporal variability of TIO SSTA, consistent with empirical orthogonal function analysis. By introducing annually varying parameters, the STO framework further reveals the phase‑locking behavior of both IOD and IOT: both modes preferentially phase‑lock in late boreal summer, peaking in August, broadly consistent with the observed characteristics of early IOD and IOT events. This late‑summer locking differs from the boreal winter preference of Pacific ENSO, highlighting a basin‑specific seasonal modulation. Overall, the adapted STO model demonstrates that a linear air‑sea interaction framework, while rooted in Pacific ENSO theory, can uncover TIO‑specific dynamics after careful regional adaptation, including distinct natural periods and a phase‑locking calendar shaped by the local annual cycle.</p>

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A spatiotemporal oscillator model for sea surface temperature variability in the tropical Indian Ocean

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Liancheng Wei,
  • Yaokun Li

摘要

Comprehensive understanding of sea surface temperature (SST) variability in the tropical Indian Ocean (TIO) remains a challenge for simple conceptual models. In this study, we adapt a spatiotemporal oscillator (STO) model which originally developed for Pacific ENSO dynamics to the TIO through localized parameter adjustments that account for the TIO’s distinct mean state and seasonal forcing. With these adaptations, the TIO SST anomaly (SSTA) is physically decomposed into a set of eigenspatial modes, each oscillating at its own natural frequency. The zeroth mode exhibits a basin‑wide uniform SSTA structure, corresponding to the observed Indian Ocean Basin mode (IOBM). The first eigenspatial mode captures a zonal contrast between the eastern and western TIO, closely resembling the classic Indian Ocean Dipole (IOD) pattern, with a natural period of approximately 2 years. The second mode displays a tripolar structure, with SSTA contrasts between the central TIO and its eastern/western flanks, and a characteristic period of about 1 year (half that of the IOD mode); this mode corresponds to the Indian Ocean Tripole (IOT). These eigenmodes provide a compact dynamical description of the dominant spatiotemporal variability of TIO SSTA, consistent with empirical orthogonal function analysis. By introducing annually varying parameters, the STO framework further reveals the phase‑locking behavior of both IOD and IOT: both modes preferentially phase‑lock in late boreal summer, peaking in August, broadly consistent with the observed characteristics of early IOD and IOT events. This late‑summer locking differs from the boreal winter preference of Pacific ENSO, highlighting a basin‑specific seasonal modulation. Overall, the adapted STO model demonstrates that a linear air‑sea interaction framework, while rooted in Pacific ENSO theory, can uncover TIO‑specific dynamics after careful regional adaptation, including distinct natural periods and a phase‑locking calendar shaped by the local annual cycle.