The western North Pacific monsoon in the Northern Hemisphere (NH) and the local Hadley circulation in the Southern Hemisphere (SH) are important components of the vertical meridional circulation over the western Pacific Ocean. Here, we define the SH meridional circulation (SHMC) and NH meridional circulation (NHMC) and investigate their relationship over the western Pacific Ocean. Although they are consistent integrally in the climatological circulation, the NHMC and SHMC do not have a positive change relationship but a significantly negative relationship. In addition, this negative correlation experiences an interdecadal change, with one closely related period during 1989–2003 (Period 2, P2) and two weakened related periods during 1979–1988 (Period 1, P1) and 2004–2017 (Period 3, P3). Through the analysis of the meridional wind field at lower and upper levels, we found that the SHMC moves northward during P2, which can result in a close relationship with the NHMC. The possible mechanism is as follows: The Walker circulation strengthened in P2, which strengthened the ascending motion over the western Pacific Ocean, thus inducing the SHMC to strengthen and move northward, resulting in a significantly stronger relationship with the NHMC.

中文翻译：

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西太平洋南北半球经向环流关系的年代际变化

北半球（NH）的北太平洋西部季风和南半球（SH）的局部哈德利环流是西太平洋垂直子午环流的重要组成部分。在这里，我们定义了SH子午环流（SHMC）和NH子午​​环流（NHMC），并研究了它们在西太平洋上的关系。尽管它们在气候循环中整体上是一致的，但NHMC和SHMC并不具有正变化关系，而具有明显的负关系。此外，这种负相关经历了年代际变化，其中一个密切相关的时期在1989-2003年（期间2，P2），两个弱相关时期在1979-1988年（期间1，P1）和2004-2017年（期间3，P3） ）。通过分析上下两层的子午风场，我们发现SHMC在P2期间向北移动，这可能与NHMC有密切的关系。可能的机制如下：P2中的沃克环流增强，这增强了西太平洋上空的上升运动，从而促使SHMC加强并向北移动，从而与NHMC的关系明显增强。