资源环境科技发展态势分析平台

Changes in the activity of summer high-temperature extremes (HTEs) over many regions are linked with the El Nino-Southern Oscillation. However, how the HTEs respond to different flavors of El Nino remains unclear. Using observational analyses, we show that summer HTEs in China during eastern Pacific (EP) and central Pacific (CP) types of El Nino exhibit different spatial patterns. EP (CP) El Nino is significantly correlated with summer HTEs over South China (Yangtze River valley). These relationships can be attributed to the modulation of the western North Pacific subtropical high and the East Asian jet stream. EP (CP) El Nino events are accompanied by westward (eastward) extension of the western North Pacific subtropical high and equatorward (poleward) movement of the jet stream over East Asia (Pacific). During EP (CP) El Nino episodes, the westward (eastward) and equatorward (poleward) displacements of upper-tropospheric anticyclone over the western North Pacific coincide with the subsidence anomaly over South China (Yangtze River valley).

Plain Language Summary The variations in summer heat extremes have strong impacts on human society as well as ecosystems and need to be better understood. This study conducts statistical analyses to investigate the year-to-year variations of summer high-temperature extremes (HTEs) in China associated with two types of El Nino, with prominent sea surface temperature anomalies appearing in the eastern Pacific and the central Pacific, respectively. The results suggest that the two El Nino types are associated with increased HTE activity in different locations of China, by influencing the position of the western North Pacific subtropical high and the East Asian jet stream. The eastern Pacific El Nino significantly increases the frequency of summer HTEs in South China, whereas the central Pacific El Nino mainly affects HTEs in the Yangtze River valley region of East China. The findings reported in this study advance our understanding of the temporal variability of extreme hot spells in China and have important implications for the seasonal prediction of such severe weather events.