中文摘要：

本文通过对1979～2005年5～10月发生在西太平洋地区的156个副热带高压双脊线过程进行统计分析，发现87．82％的双脊线过程的出现是因为南侧新生一脊线，而且有明显的“季节锁相”，即其发生频数在7月中旬至9月中旬有两个峰值．历年过程中最典型的“南生南存型”双脊线过程的合成分析表明该类双脊线过程形成、维持和消失与副高南侧外围东风波系统自东南向西北传播发展密切相关．500hPa距平环流演变显示北侧脊线的减弱消失符合气候规律，东风波槽前的异常气旋仅影响副高北侧脊线位置；而东风波槽后的异常反气旋性环流有利于南侧脊线异常发展与维持，造成该类双脊线过程结束后副高异常偏南．进一步分析发现，东风波和西太平洋副热带高压的相互作用改变了副高区域垂直运动分布．这一方面改变了经向风的分布，使500hPa副高南侧脊线区域地转涡度平流项发展；另一方面引起非绝热加热垂直分布不均匀，在两脊线之间诱生一异常气旋性环流，在南侧脊线区生成异常反气旋环流．因此，东风波与西太平洋副热带高压的相互作用可能会造成副高的不连续南退，这对副高预报有一定预示作用．

英文摘要：

Based on statistical analysis of the 156 double-ridges processes of West Pacific subtropical high from May to Oct. in 1979-2005, it is found in this paper that 87.82% of the double-ridges processes occur because a new ridge is born on the southern flank and there is distinct ＂seasonal phase-lock＂, i.e. there are two peaks in the occurring frequency during mid- Jul. and mid-Sep. The composite analysis of the most typical pattern of ＂born in south and existing in south＂ shows that the formation, maintenance and disappearance of this type of double-ridges processes have close relationship with propagation of the easterly waves from southeast to northwest on the periphery of the southern flank of subtropical high. The evolution of the anomalous circulation at 500 hPa shows weakening and disappearing of the ridge on the northern flank accords well with the climate laws. The anomalous cyclone before the trough of easterly waves affects only the position of the northern ridge, while the anomalous anticyclonic circulation behind the trough of easterly waves is favorable to the development and maintenance of the southern ridge, therefore, the subtropical high is anomalously in the south when this type of double-ridges processes come to end. It can be seen after further analysis that the interaction between the easterly waves and West Pacific subtropical high changes the distribution of vertical motion in the subtropical high regions. On one hand, it changes the distribution of meridional wind, thus the geostrophic vortivity develops in the ridge region on the south of the subtropical high at 500 hPa. On the other hand, it causes inhomogeneity of the vertical distribution of diabetic heating, triggering anomalous cyclonic circulation between two ridges and anticyclonic circulation in the ridge region on the south. Therefore, the interaction between the easterly waves and West Pacific subtropical high may result in discontinuous retreat of the subtropical high to the south, which has ominous significance for the pre