Interdecadal variations of the western Pacific subtropical high and surface heat flux over East Asia and their relationship

The interdecadal variation of intensity of the western Pacific subtropical high (WPSH) during the period 1951-2001 is studied by using data from the National Climate Center (NCC), China Meteorological Administration. The characteristics of the circulations at 500 hPa and the surface heat flux over East Asia are also analyzed based on the NCEP/NCAR monthly reanalysis data. The results reveal that the WPSH and the circulations exhibit interdecadal variations around 1978, with enhancing intensities. The interseasonal persistence of the WPSH intensity alters correspondingly to some extent, which is more significant during 1978-2001 than during 1951-1978. The surface heat flux over East Asia also displays a remarkable interdecadal variation, which leads that of the WPSH intensity. The key variation areas of the surface sensible heat flux (SSHF) are mainly located over the eastern and western Tibetan Plateau around the late 1960s. However, the difference of the SSHF between the eastern and western Plateau exhibits a change in the mid 1970s, close to the time of the abrupt climate change of the WPSH intensity. The SSHF of the Plateau stably increases in the west and decreases in the east before the mid-late 1960s, while it stably increases in the east and decreases in the west after the mid1970s. On the other hand, the key variation area of the surface latent heat flux (SLHF) is mainly situated over the West Pacific (WP), where the SLHF anomaly in spring changes from positive to negative in the south before 1978, but from negative to positive in the north after 1978; while in summer it turns from positive to negative all over the WP after 1978. The interdecadal variation of SLHF in both spring and summer corresponds well to the interdecadal variation of the WPSH intensity in the same season. The notable correlation between the WPSH intensity and SSHF (or SLHF) maintains without any change although each of these qnantities varies on the interdecadal scale.