The internal structure and evolution of a monsoon trough (MT) and associated mesoscale convective systems (MCSs) in the western North Pacific were investigated, based mainly on radiosonde and a Doppler radar observations in Palau. The MT was observed on June 15-16, 2013, with the pre-existing disturbance of Typhoon Leepi (2013) being embedded in it. The large-scale circulation around the MT featured a pattern representing an active MT. Deep convection developed ahead and at the leading edge of the downward-sloping monsoonal flow, where intense low-level convergence was observed. Stratiform precipitation broadened rearward over the MT axis. A deep and wide layer of warm and moist air over the MT axis was undercut by a layer of cold air sloping downward from the trailing stratiform region to the leading convective region. An intense low-pressure zone formed in the interface between the warm layer above and cold layer below, with the westerly monsoonal and easterly trade flows being enhanced on its west and east sides, respectively, from the low to middle troposphere. The results suggest that a strengthening of the large-scale cyclonic circulation in response to the internal processes of the MCSs triggered by the MT is important for typhoon genesis.

主要基于帕劳的探空仪和多普勒雷达观测资料，研究了北太平洋西部季风槽（MT）和相关的中尺度对流系统（MCS）的内部结构和演化。在2013年6月15日至16日观察到了MT，并嵌入了台风Leepi（2013）的既有干扰。MT周围的大规模循环具有代表活跃MT的模式。深对流在向下倾斜的季风流的前缘和前沿形成，在那里观测到强烈的低层会聚。层状降水在MT轴上向后扩展。从尾随的层状区域向下到领先的对流区域向下倾斜的一层冷空气削弱了MT轴上深而宽的温暖和潮湿的空气层。在上层的暖层和下层的冷层之间的界面上形成了一个强烈的低压区，从低到中对流层，西风和东风的贸易流分别在其西侧和东侧得到增强。结果表明，响应由MT触发的MCS的内部过程而加强的大规模旋风循环对于台风的发生很重要。