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<p>This study identifies a decadal shift in the interannual variability of Southern China Spring Rainfall (SCSR) in the early 2000s. Before 2000, SCSR was mainly driven by ENSO-induced tropical sea surface temperature anomalies. After 2000, the ENSO-SCSR relationship weakened, with extratropical factors—particularly the North Pacific Oscillation (NPO)—becoming more influential. The analysis reveals that a negative NPO-related anticyclone extends southwestward from the central North Pacific to the Philippine Sea, with associated southeasterly winds influencing SCSR. The southwestward extension and tilting of the NPO-related anticyclone are associated with the Pacific Meridional Mode (PMM), which became significantly coherent with the NPO from the middle 1990s onward. Observations suggest that PMM-related variability is linked to large-scale subsidence and diabatic cooling over the central Pacific. Consistent with the observations, numerical experiments illustrate that such cooling can induce a Gill-type anticyclone in the western North Pacific, which may contribute to the southwestward-tilted NPO-related anticyclone. The results suggest an increased role of extratropical–subtropical processes in modulating SCSR variability in recent decades.</p>

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Enhanced influences from North Pacific Oscillation and Pacific Meridional Mode on Southern China Spring rainfall since 2000

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Chiung-Wen June Chang,
  • Jun Chiang,
  • Chi-Cherng Hong,
  • Wan-Ling Tseng,
  • An-Yi Huang

摘要

This study identifies a decadal shift in the interannual variability of Southern China Spring Rainfall (SCSR) in the early 2000s. Before 2000, SCSR was mainly driven by ENSO-induced tropical sea surface temperature anomalies. After 2000, the ENSO-SCSR relationship weakened, with extratropical factors—particularly the North Pacific Oscillation (NPO)—becoming more influential. The analysis reveals that a negative NPO-related anticyclone extends southwestward from the central North Pacific to the Philippine Sea, with associated southeasterly winds influencing SCSR. The southwestward extension and tilting of the NPO-related anticyclone are associated with the Pacific Meridional Mode (PMM), which became significantly coherent with the NPO from the middle 1990s onward. Observations suggest that PMM-related variability is linked to large-scale subsidence and diabatic cooling over the central Pacific. Consistent with the observations, numerical experiments illustrate that such cooling can induce a Gill-type anticyclone in the western North Pacific, which may contribute to the southwestward-tilted NPO-related anticyclone. The results suggest an increased role of extratropical–subtropical processes in modulating SCSR variability in recent decades.