Will the western Pacific subtropical high constantly intensify in the future?

Abstract

The western Pacific subtropical high (WPSH) features lower-level southerlies or southwesterlies at its western and southern edges that transport amount of water vapor into East Asia, and it exerts a large influence on the East Asian summer climate. This paper evaluates the historical (1950–2005) spatial distribution and variability in the summer WPSH at 850 hPa using 28 general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) relative to the NCEP–NCAR reanalysis data. To avoid the artificial influence caused by global warming, this study primarily investigates the 850-hPa eddy geopotential height and the horizontal winds. The results show that most of the CMIP5 models reliably reproduce the geographical distribution and spatial variability in the WPSH. Four models (bcc-csm1-1, CESM1–CAM5, GFDL–ESM2G and inmcm4) generally perform well in simulating the eastward-recessed interdecadal variation in the WPSH during 1979–2005 relative to 1950–1978, with a significant cyclone anomaly appearing over the western Pacific and a decreasing trend in the WPSH index. Based on these four models, a multi-model ensemble projects a weaker WPSH during 2026–2070 relative to 2010–2025 and 2071–2100 under the representative concentration pathway 8.5 scenario.