资源环境科技发展态势分析平台

Interdecadal changes in the relationship between summer rainfall over Japan and the western edge of the North Pacific subtropical high (NPSH) were investigated for the 1901-2000 period. In this study, indices describing the zonal and meridional displacement of the western edge of the NPSH (NPSHI-Z and NPSHI-M, respectively) were used for the analysis. Consistent with the southwestward shift of the NPSH after 1950, the region with a significant correlation between summer rainfall and the NPSHI-Z has shifted southwestward, from the Pacific side of central Honshu in the pre50 (1901-1950) to around Kyushu in the post50 (1951-2000). Moreover, a significant connection between summer rainfall and the NPSHI-M was widely observed in the post50, whereas no significant relationship between these phenomena was detected in the pre50. The identified change was likely due to the change in the relationship between the Pacific-Japan (PJ) pattern and the NPSHI-M. It is found that there is a change point in 1950 for the PJ pattern and after that the relationship between the NPSHI-M and PJ pattern has become stronger.