资源环境科技发展态势分析平台

Summertime western Pacific subtropical high (WPSH) is closely related to remote sea surface temperature anomalies (SSTA) in the tropical oceans (TO) and local SSTA in the western North Pacific (WNP). Based on atmospheric reanalysis and multimodel ensemble products, the warming (cooling) of the tropical Indian, tropical central-eastern Pacific, and tropical Atlantic (tropical western Pacific and WNP) can lead to westward extension of the WPSH, and vice versa. A series of numerical experiments are conducted to quantify the relative importance of remote and local SSTA, including the separate impact of different TO basins. In response to warming (cooling) of the tropical Indian, tropical central-eastern (western) Pacific, and tropical Atlantic, ascending (descending) motions develop locally and subsequently excite remote baroclinic and barotropic responses. The baroclinic anticyclone west of 140 degrees E contributes to the westward extension of the WPSH. The barotropic anticyclone and descending motion over the WNP can further increase the sea level pressure and strengthen the WPSH. Based on the quasi-geostrophic omega equation, we find that the anomalous vorticity advection (thermal advection) primarily accounts for the anomalous descending motion in response to remote (local) SSTA. Compared to local SSTA, the remote SSTA can induce larger perturbations, subsequently making the zonal variability of the WPSH more significant. Furthermore, it is found that the westward extension of the WPSH is primarily induced by atmospheric baroclinic (barotropic) response to the SSTA in tropical Indian and tropical Atlantic (tropical Pacific). Overall, the tropical Indian plays the most important role on the zonal movement of the WPSH.