The El Niño/La Niña Summer Precipitation Diversity In Eastern China In The Following Year

East China experiences positive precipitation anomalies in post-El Ni(?)o summers,mainly in the Yangtze-Huaihe River Valley.This kind of monsoonal rainfall change induced by El Ni(?)o,however,is not always the same due to El Ni(?)o diversity and mean state change.In this study,Cluster analysis is used on the post-El Ni(?)o(PE)East China summer precipitation anomalies to identify the diversity of this El Ni(?)o-induced monsoon change.For post-La Ni(?)a(PL)East China summer precipitation anomalies,Empirical Orthogonal Function(EOF)method is used to identify the main mode.The result shows that PE East China summer rainfall anomalies mainly display three different modes for all selected 20 El Ni(?)o events from 1957 to 2016.Cluster 1 shows the middle and lower reaches of the Yangtze River demonstrate strong wet anomalies,while South and North China are dominated by dry anomalies.Cluster 2 is distinguished by dry anomalies over South China and North China,and wet anomalies over Central China,exhibiting a sandwich mode.Compared with Cluster 1,the change caused by Cluster 3 is opposite.The three clusters are correlated with successive events of El Ni(?)o,a quick transfer to a strong La Ni(?)a and a quick transfer to a weak La Ni(?)a respectively.The associated anomalous anticyclone(AAC)focuses on(120°E,23°N)in Cluster 1,which expands southward for Cluster 2 and moves eastward for Cluster 3.The feedback of AAC-sea surface temperature(SST)mainly works for supporting the AAC in Cluster 1,but it is weak for Cluster 2;the strong easterly anomalies related to La Ni(?)a contribute to the AAC location change for Cluster 2.Both AAC-SST feedback and easterly anomalies support the AAC of Cluster 3.The CMIP5 output can capture these diverse responses in circulation except that their simulated AAC for Cluster 1 is significant to the east of the observed.In all selected 19 La Ni(?)a events from 1957 to 2016,the main mode of PL summer precipitation anomalies is a dipole mode in North and South China.In the main mode,positive events are characterized as anomalous negative rainfall in South China and positive rainfall in North China,while negative events are opposite.These two categories are related to slow-decaying La Ni(?)a and a quick transfer to a weak El Ni(?)o.The related anomalous cyclone(AC)is located at 125°E,20°N in positive events,and moves eastward in negative events.The AC-SST feedback mainly maintains the AC in positive events in early summer,and the North Indian Ocean cooling in the feedback mainly maintains the AC in negative events.The CMIP5 models can roughly simulate different circulation characteristics,except that the AC in positive event is more easterly than the observation.