2000年4月广东极端降水影响因子

Influencing Factors of Extreme Precipitation in Guangdong in April 2000

摘要: 2000年4月广东发生极端降水事件，降水量为4月气候平均值的2.5倍。本文从能量学的角度分析其影响因子。分析表明，中纬度西大西洋极端暖海温异常，其作为强热力强迫源，激发出一支横跨西大西洋至东亚的准定常罗斯贝波列(“正–负–正–负”型)。该波列的能量沿西风波导向东频散，导致下游东亚地区出现异常低压，并显著增强其南侧的西风急流。广东位于该异常急流入口区的右侧，高空辐散的动力强迫触发低层辐合与强烈上升运动。天气尺度分析进一步表明，西大西洋扰动位能信号约领先广东降水5天，能量通过“西大西洋–西亚–东亚急流–华南上升运动”的过程对降水产生影响，并通过三次典型降水过程的合成分析得到验证。

Abstract: In April 2000, an extreme precipitation event occurred in Guangdong, with the precipitation reaching 2.5 times the April climate average. From an energetics perspective, the analysis of its influencing factors reveals that the anomalously warm sea surface temperatures in the mid-latitude western Atlantic acted as a strong thermal forcing source. This condition excited a quasi-stationary Rossby wave train (with a “positive-negative-positive-negative” pattern) spanning from the western Atlantic to East Asia. The energy of this wave train dispersed eastward along the westerly waveguide, leading to an anomalous low-pressure system over downstream East Asia and significantly enhancing the westerly jet stream along its southern flank. Guangdong was situated to the right of the entrance region of this anomalous jet stream, where the dynamic forcing from upper-level divergence triggered low-level convergence and intense upward motion. Further synoptic-scale analysis indicates that the disturbance energy signal from the western Atlantic preceded the Guangdong precipitation by approximately five days. This energy influenced the precipitation through the mechanism of “western Atlantic-West Asia-East Asian jet stream-ascending motion in South China,” which was validated by composite analysis of three typical precipitation events.