This study investigates the role of the interannual variation of boreal winter (December–February) snow cover over the Tibetan Plateau (TPSC) in modulating the relationship between the Madden Julian Oscillation (MJO) and tropical cyclogenesis over the western North Pacific (WNP) during the following boreal summer (June–October). During the boreal summer following a high snow cover anomaly (SCA), MJO-associated convection tends to be confined to the west of 140 °E, coinciding with more frequent tropical cyclone (TC) activity in this region. By contrast, there tends to be stronger MJO-associated convection extending farther east during years following low SCA. The MJO-associated convection extends to ~ 160 °E over the WNP basin with a peak around 140 °E. Thus, more TCs form farther east in the WNP in these years. We use composite analyses of large-scale environmental factors to demonstrate that low-level relative vorticity is one of the most important factors in controlling TCs in response to the change of MJO-associated convection between years with high SCA and low SCA. Meanwhile, eddy kinetic energy variations associated with the MJO are consistent with changes in tropical cyclogenesis over the WNP basin between years with high and low SCA. The Asian summer monsoon plays an important role in linking prior winter TPSC to MJO activity in the following summer. During high-SCA years, increased snow cover results in positive soil moisture anomalies and cooling over the Tibetan Plateau, thus weakening the following summer Asian monsoon and weakening associated water vapor advection, while the opposite chain of events occurs in low-SCA years. These changes in high-SCA years are favorable for MJO propagation and are unfavorable for MJO propagation in low-SCA years. Meanwhile, the interannual variation of SCA exerts a significant impact on the upper-tropospheric circulation and thus changes in vertical wind shear. During high-SCA years, there are anomalous upper-level easterlies in the Indian Ocean and upper-level westerlies in the Pacific Ocean, which result in anomalous easterly wind shear in the Indian Ocean and anomalous westerly shear in the Pacific Ocean. The opposite shear pattern arises in low-SCA years. In addition to changes in wind shear, the background vertical motion associated with changes in TPSC may also be partly responsible for changes in MJO activity.

这项研究调查了青藏高原（TPSC）上的冬季冬季（12月至2月）积雪的年际变化在调节北太平洋西部（WNP）期间朱利安涛动（MJO）与热带气旋作用之间的关系。接下来的夏季（六月至十月）。在高积雪异常（SCA）之后的北方夏季，与MJO相关的对流往往局限于140°E以西，这与该地区更频繁的热带气旋（TC）活动相吻合。相反，在低SCA之后的几年里，与MJO相关的对流往往会向东延伸。与MJO相关的对流在WNP盆地上延伸至〜160°E，峰值约为140°E。因此，这些年来，更多的TC形成于WNP的更东端。我们使用大型环境因素的综合分析表明，低水平相对涡度是控制TC的最重要因素之一，以响应高SCA和低SCA年份之间MJO相关对流的变化。同时，与MJO相关的涡动能变化与SCA高低年份之间WNP盆地热带回旋作用的变化是一致的。亚洲夏季风在将先前的冬季TPSC与次年夏季的MJO活动联系起来方面发挥了重要作用。在高SCA年份，积雪增加导致青藏高原土壤湿度异常并变冷，从而减弱了随后的夏季亚洲季风并减弱了相关的水汽平流，而在低SCA年份则发生了相反的事件。高SCA年的这些变化有利于MJO的传播，而不利于低SCA年的MJO的传播。同时，SCA的年际变化对对流层高层环流有很大影响，因此垂直风切变也发生了变化。在高SCA年代，印度洋上空有上东风异常，太平洋上有西风上空，这导致印度洋上的东风切变异常，而太平洋上的西风切变异常。相反的剪切模式出现在低SCA年。除了风切变的变化外，与TPSC的变化相关的背景垂直运动也可能部分负责MJO活动的变化。SCA的年际变化对对流层高层环流有重要影响，因此垂直风切变也发生了变化。在高SCA年代，印度洋上空有上东风异常，太平洋上有西风上空，这导致印度洋上的东风切变异常，而太平洋上的西风切变异常。相反的剪切模式出现在低SCA年。除了风切变的变化外，与TPSC的变化相关的背景垂直运动也可能部分负责MJO活动的变化。SCA的年际变化对对流层高层环流有重要影响，因此垂直风切变也发生了变化。在高SCA年代，印度洋上空有上东风异常，太平洋上有西风上空，这导致印度洋上的东风切变异常，而太平洋上的西风切变异常。相反的剪切模式出现在低SCA年。除了风切变的变化外，与TPSC的变化相关的背景垂直运动也可能部分负责MJO活动的变化。印度洋上空有异常的上东风，太平洋上有西风上的异常，这导致印度洋上的东风切变异常，而太平洋上的西风切变异常。相反的剪切模式出现在低SCA年。除了风切变的变化外，与TPSC的变化相关的背景垂直运动也可能部分负责MJO活动的变化。印度洋上空有异常的上东风，太平洋上有西风上的异常，这导致印度洋上的东风切变异常，而太平洋上的西风切变异常。相反的剪切模式出现在低SCA年。除了风切变的变化外，与TPSC的变化相关的背景垂直运动也可能部分负责MJO活动的变化。