Pacific Ocean decadal forcing of long-term changes in the western Pacific subtropical high.

The western Pacific subtropical high (WPSH) has a significant effect on droughts, heat waves, and tropical cyclone tracks over East Asia and the northwest Pacific. The WPSH has intensified during the past three decades, but its causes are not yet well understood. Here we show that the Pacific Decadal Oscillation (PDO) is responsible for the long-term changes in the WPSH through the meridional shift of the subtropical jet, based on comprehensive data analysis and model results. El Niño-Southern Oscillation (ENSO) is the leading forcing of WPSH variability over interannual timescales, whereas the PDO accounts for its low-frequency variability, resulting in it being independent of ENSO with regard to WPSH variability. The PDO in summer can be interpreted as a coupling with the WPSH. Our results provide useful information for projecting long-term changes in the WPSH.