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<p>The North China August precipitation (NCAP) exhibits pronounced interannual variability superimposed on interdecadal fluctuation. Building upon previous work examining its decadal-scale variations, this study investigates the interannual variability of NCAP and its underlying mechanisms. Our analysis reveals that the east–west dipole sea surface temperature (SST) pattern in the equatorial Pacific (EPD) serves as the primary regulator of NCAP interannual variability, with positive (negative) EPD phases enhancing (suppressing) precipitation. Diagnostic analyses and Linear Baroclinic Model (LBM) experiment demonstrate the physical pathway through which EPD influences NCAP. Positive EPD-type SST anomalies generate anomalous subsidence in the eastern equatorial Pacific and ascent in the western Pacific, modifying the Walker circulation. The resultant upper-level convergence over the western Pacific triggers northward atmospheric transport, establishing an anomalous meridional circulation that strengthens the western North Pacific anticyclone. This anticyclone anomaly enhances moisture transport to North China, thereby increasing precipitation. The reverse mechanism operates during negative EPD phases. Notably, the north-east North Atlantic Tripole (NAT) modulates this EPD-NCAP relationship through interdecadal variability. During negative NCAP interdecadal phases, the north-east NAT pattern amplifies the EPD’s impact via the Eurasian teleconnection (EAT), altering regional&#xa0;atmospheric circulation and moisture transport pathways.</p>

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Interannual variability of North China August precipitation: forcing by equatorial Pacific SST and interdecadal modulation from the North Atlantic

  • 期刊论文

  • 发表日期：

    2026年1月20日

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  • Tiejun Xie,
  • Lijuan Chen,
  • Yingjuan Zhang,
  • Ji Wang,
  • Daquan Zhang

摘要

The North China August precipitation (NCAP) exhibits pronounced interannual variability superimposed on interdecadal fluctuation. Building upon previous work examining its decadal-scale variations, this study investigates the interannual variability of NCAP and its underlying mechanisms. Our analysis reveals that the east–west dipole sea surface temperature (SST) pattern in the equatorial Pacific (EPD) serves as the primary regulator of NCAP interannual variability, with positive (negative) EPD phases enhancing (suppressing) precipitation. Diagnostic analyses and Linear Baroclinic Model (LBM) experiment demonstrate the physical pathway through which EPD influences NCAP. Positive EPD-type SST anomalies generate anomalous subsidence in the eastern equatorial Pacific and ascent in the western Pacific, modifying the Walker circulation. The resultant upper-level convergence over the western Pacific triggers northward atmospheric transport, establishing an anomalous meridional circulation that strengthens the western North Pacific anticyclone. This anticyclone anomaly enhances moisture transport to North China, thereby increasing precipitation. The reverse mechanism operates during negative EPD phases. Notably, the north-east North Atlantic Tripole (NAT) modulates this EPD-NCAP relationship through interdecadal variability. During negative NCAP interdecadal phases, the north-east NAT pattern amplifies the EPD’s impact via the Eurasian teleconnection (EAT), altering regional atmospheric circulation and moisture transport pathways.