Impacts of El Niño diversity on East Asian summertime precipitation extremes

Abstract

This study examines the impacts of Eastern Pacific (EP) and Central Pacific (CP) El Niño on summertime extreme precipitation over East Asia during the El Niño decay phase. The findings reveal distinct patterns of extreme precipitation for the two El Niño types. During EP El Niño, more intense extreme precipitation occurs over south of the Yangtze River (SYR), while suppressed extremes are observed over Mei-Yu rainband in China, Baiu in Japan, and Changma in South Korea (MBC). Conversely, CP El Niño leads to weaker (stronger) extreme precipitation over SYR (MBC). This study also differentiates between tropical cyclone (TC) and non-TC related precipitation, showing that TCs have minimal influence on the overall extreme precipitation compared to non-TC related events. Further investigation reveals that EP and CP El Niño distinctly influence atmospheric circulation patterns, thereby causing different distributions of non-TC extreme precipitation. Specifically, during EP El Niño, sea surface temperature (SST) warming signals in the tropical Indian Ocean induce the southward displacement of the South Asia High (SAH), westerly jet (WJ), and Western Pacific subtropical high (WPSH). This amplifies moisture flux convergence, elevating the likelihood of intense extreme precipitation over SYR. Conversely, MBC experiences moisture flux divergence, resulting in fewer precipitation extremes. During CP El Niño, SST warming signals in the Maritime Continent prompt the northward shift of SAH, WJ, and WPSH by modulating local Hadley circulations. These anomalies lead to strengthened moisture convergence (divergence) over MBC (SYR), consequently resulting in a higher (lower) likelihood of intense extreme precipitation over MBC (SYR).