The interdecadal variation of the summer western Pacific subtropical high (WPSH) during 1948–2009 is investigated in this study. Compared with most previous works, which focused on the 500 hPa geopotential height, the interdecadal variation of the horizontal winds, relative vorticity, and eddy geopotential height over the western Pacific are all analyzed. The weakened anticyclone and decreased negative relative vorticity at middle-low levels over the western Pacific suggest that the WPSH weakened during 1979–2009 relative to 1948–78. After subtracting the zonal belt mean height between 0° and 40°N, the 500 hPa eddy geopotential height with significant negative anomalies over the western Pacific can correctly depict this weakened interdecadal variation of the WPSH. The illusory westward extension signal reflected by the 500 hPa geopotential height may derive from the significant increment of the geopotential height at middle and lower latitudes in the late 1970s under global warming.
本文主要研究1948-2008年夏季西太平洋副热带高压（副高）的年代际变化。相比与前人主要关注500 hPa位势高度场，本文对位势高度场、扰动位势高度场、水平风场和相对涡度场上的年代际信号进行了对比分析。在中低层西太洋地区反气旋环流的减弱和相对负涡度场的减弱说明副高在1970s后期减弱。扣除0-40°N平均的纬向平均后，500 hPa扰动位势高度场可以正确反映副高减弱的年代际信号。500 hPa位势高度场上诱导性的西伸信号可能来自于1970s后期全球变暖引起的中低纬位势高度的增加。