Different impacts of two types of El Ni?o events on precipitation in eastern China based on spatiotemporal diversity
El Nino significantly influences precipitation in eastern China,and it has been demonstrated that the diversity of El Niño characteristics leads to inconsistent impacts.Traditional identification of El Niño diversity fo-cuses only on difference in spatial distributions of anomalous features,overlooking the temporal discrepancies a-mong types.This leaves it unclear whether these time-scale differences change El Niño's influence.Therefore,utili-zing high-resolution grid data of precipitation in China from 1961 to 2022,this study revisited the El Niño influ-ence on precipitation in eastern China based on a newly proposed classification method that considers both spatial and temporal characteristics.We identified historical El Niño events into two primary spatiotemporal types:the low-frequency eastern-Pacific(LF-EP)type,characterized by a long lifecycle and located in the tropical eastern Pacific,and the quasi-biennial central-Pacific(QB-CP)type,with a shorter lifecycle and located relatively west.In the evolution of LF-EP-type events,the LF mode is dominant,while the QB mode is relatively weak.In QB-CP-type events,the LF mode is in the phase transition stage,while the QB mode is dominant.Composite analysis results indicate these two different spatiotemporal types of El Niño have distinct impacts on the evolution of pre-cipitation anomalies in eastern China.LF-EP-type events have a stable influence on precipitation in eastern China,with a nearly four-season-lasting anomaly starting from autumn of the development year to summer of the decay year,resulting in above-normal rainfall south of the Yangtze River.Moreover,the center of the anomalous rain belt migrates northward starting in the spring of development year.In contrast,QB-CP-type events exhibit more frequent changes in precipitation anomaly characteristics.During summer and autumn of the development year,rainfall is generally less south of the Yangtze River,contrary to LF-EP-type events.Positive precipitation anomalies begin to emerge south of the Yangtze River in winter and show a gradual southward retreat,culminating in a"positive-negative-positive"distribution across North China,the Yangtze River basin,and South China by the decay year's summer.This study also compared large-scale moisture transport differences between the two spatiotemporal types of El Niño to investigate the potential mechanisms behind their differing impacts.The results show that the difference in the zonal positioning of SST anomalies is a key factor leading to distinct atmospheric circulation responses.Due to the shift in the latitudinal position of SST and convective anomalies,the positions of anticyclonic circulation a-nomalies in the Northwest Pacific Ocean vary among different types of El Niño in summer and autumn,resulting in different moisture transports towards eastern China.In winter,the different types of El Niño induce a similar a-nomalous Walker circulation,whose sinking branch in the maritime continent region leads to relatively consistent anticyclonic water vapor transport towards eastern China.However,the related circulation anomaly dominated by the LF ENSO mode persists significantly longer due to its longer lifecycle.That is to say,the differences in per-sistence and phase transition timing between the two types of spatiotemporal events result in changes in the times-cale of their impact on precipitation in eastern China.Additionally,during the spring and summer of the decay year,LF-EP El Niño can also indirectly develop anticyclonic water vapor transport in the Northwest Pacific to maintain its influence on precipitation in eastern China through the Indo-western Pacific Ocean"capacitor"effect and through the nonlinear interaction with the tropical Pacific annual cycle.
El Niñospatiotemporal typeprecipitation anomaly in eastern Chinarain belt evolutionENSO-annual cycle combination mode
国家科技期刊平台
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