The pre-summer rainy season (PSRS; April–June) is the period of most frequent strong precipitation in South China (SC). Persistent strong precipitation events (PSPEs) can cause greater loss of life and property than short-lived strong precipitation. This paper investigates extended-range signals near the tropopause preceding two persistent positive climatological intraseasonal oscillations (PPCISOs) in precipitation corresponding to two climatological PSPEs in SC during the PSRS, using the CISO analysis of isentropic potential vorticity (IPV). It is found that precursor signals can be better seen in IPV CISOs than in unfiltered IPV. The first rainfall PPCISO is caused by an eastward propagation of high-IPV CISOs along the dynamical tropopause originating from the Arctic region and west of the Tibetan Plateau. The second is the most persistent (13 days). Its high-IPV CISOs originate over the Arctic region and the tropical monsoon region, respectively, 20 or more days prior to the rainfall CISO peak. The west of the Tibetan Plateau and the northern region of the East Asian westerly jet near the tropopause are two transit points where extratropical high-IPV CISOs strengthen and then change their propagation direction. The southward high-IPV CISOs and the northward positive IPV CISO caused by the monsoon begin to interact about 10 days prior to rainfall peak. Since then, the interaction leads a narrow meridional positive PV channel on the inclined 345 K isentropic surface. A specific CISO pattern, characterized by an elongated high-IPV CISO isolated by three negative IPV CISOs (the South Asian, the Okhotsk and the western Pacific subtropical highs), is responsible for the long duration of the second rainfall PPCISO.

夏季前的雨季（PSRS； 4月至6月）是华南（SC）最频繁的强降水期。与短暂的强降水相比，持续的强降水事件（PSPEs）可能造成更大的生命和财产损失。本文使用等熵电势涡旋（IPV）的CISO分析方法，研究了PSRS期间对应于SC中两个气候PSPE的降水中两次持续的正气候季节内振荡（PPCISO）之前对流层顶附近的扩展信号。发现在IPV CISO中比在未过滤的IPV中可以更好地看到前驱信号。第一次降雨PPCISO是由高IPV CISOs沿动态对流层顶向东传播引起的，该对流层顶起源于北极地区和青藏高原以西。第二个是最持久的（13天）。其高IPV CISO分别发生在降雨CISO高峰之前20天或更长时间的北极地区和热带季风区域。青藏高原的西部和对流层顶附近的东亚西风急流的北部是温带高IPV CISO增强并改变其传播方向的两个过渡点。由季风引起的南高IPV CISO和北正IPV CISO在降雨高峰前约10天开始相互作用。从那时起，相互作用在倾斜的345 K等熵表面上导致一个狭窄的子午正PV通道。一种特定的CISO模式，其特征在于由三个负IPV CISO（南亚，鄂霍次克和西太平洋副热带高压）隔离的拉长的高IPV CISO，