Event-based extreme precipitation in Central-Eastern China: large-scale anomalies and teleconnections

Abstract

Event-based extreme precipitation (EEP), defined as an extreme precipitation event (no less than 1 mm for continuous days) having at least one daily precipitation exceeding the 90th percentile, are categorized into three types according to the time distribution pattern (TDP) of extreme precipitation: daily intense precipitation appearing only at the first half of event (TDP1), at both the first and second halves (TDP2), and only at the second half of event (TDP3). This study focuses on the TDP1 and TDP2 types, which occur much more frequently in the central-eastern China and investigates associated distinguishing large-scale teleconnection patterns. The TDP1 events dominantly occur in mid-to-late spring, which are associated with the Silk Road pattern (SRP) wave train manifested from western Europe to northwest Pacific along the subtropical westerly jet. The tripolar sea surface temperature (SST) anomalous pattern over the North Atlantic Ocean, i.e., low SST anomalies in the Azores Islands, two high SST anomalies over the Greenland and subtropical North Atlantic are mainly attributed to force the SRP wave. Meanwhile, the enhanced northwestward moisture transport from the South China converges with the southeastward moisture transport related to the SRP from the North China, resulting in the TDP1 extreme precipitation events over the central-eastern China. The TDP2 events are closely conjunction with the Meiyu precipitation in the Yangtze-Huai River basin in summer. During the TDP2 events, the East Asia/Pacific (EAP) teleconnection is exhibited along the East Asia coasts, which is triggered by the anomalous convection in the western North Pacific. An anomalous anticyclone related to the EAP teleconnection contributes to the westward stretch of the western Pacific subtropical high, providing significant enhanced moisture transportation toward the Yangtze-Huai River basin. Correspondingly, the meridional gradient of the equivalent potential temperature $$\theta_{e}$$ is intensified and favored of forming Meiyu front precipitation. This study highlights the definition of EEP event emphasizing the TDP of extreme precipitation and distinguished features of occurring seasons and large-scale circulations associated with the two dominant types of EEP events.