Tropical easterly waves are common features in the trade wind zones and they are important sources of tropical cyclogenesis. Despite numerous studies have analyzed the genesis and maintenance of easterly waves in the Western North Pacific, few had examined their dissipation processes. Focusing on tropical easterly waves during May-September of 1979–2017, this study shows that most of the easterly waves (∼70 %) eventually dissipate when encountering the monsoon trough and associated westerlies, while 22 % were carried northward by the monsoonal southwesterly flows and became recurving disturbances. Less than 10 % of easterly waves propagate across the South China Sea against the prevailing monsoon westerlies and into the Indochina peninsula. The vorticity budget analysis illustrates that total vortex stretching in the lower troposphere is the key factor in propelling the small number of easterly waves westward, suggesting that stronger and more convectively active easterly waves tend to move further into the developed monsoon trough. This echoes the previous observation that tropical disturbances alone have a limited probability in developing into a typhoon, for those disturbances or easterly waves almost always need to interact with the monsoon trough or a monsoon gyre, as well as other intraseasonal features to sustain the organized convection and rotation.

热带东风浪是贸易风带的共同特征，它们是热带气旋作用的重要来源。尽管有大量研究分析了北太平洋西部东风浪的发生和维持，但很少有研究者研究了它们的消散过程。这项研究着眼于1979-2017年5月至9月的热带东风浪，大部分东风浪（约70％）在遇到季风槽和相关的西风时最终消散，而22％由季风西南风带向北成为反曲风。不到10％的东风波在南海与盛行的季风西风一起传播并进入印度支那半岛。涡度预算分析表明，对流层低层的总涡旋伸展是推动少量东风向西推进的关键因素，这表明较强和对流活跃的东风趋向于进一步向发达的季风槽移动。这与以前的观察结果相呼应，因为仅热带干扰就有可能发展为台风，因为这些干扰或东风浪几乎总是需要与季风槽或季风回旋以及其他季节内特征相互作用以维持有组织的对流和旋转。