Temporal variations of the spring persistent rains and SCS subtropical high and their correlations to the circulation and precipitation of the East Asia summer monsoon

National Meteorological Information Center (NMIC) rainfall data and NCEP/NCAR daily circulation reanalysis data are employed to establish onset pentad index of SPR (Spring persistent rain) and the droppentad index of the South China Sea SubHigh (SCSSH). These indexes are used to study the relationship between the factors in SPR period and their relations to the circulation and precipitation of the East Asia summer monsoon (EASM). Results show that, the summer rainfall over southeastern China decreases when SPR onset is late. For then EASM strengthens and the cyclonic circulation around the Tibet Plateau (TP) strengthens, which makes abnormal anticyclonic circulation (cyclonic convergent circulation weakens) appear over southeastern China. When the drop of SCSSH delays, abnormal flood prevail on the south of the middle and lower reaches of the Yangtze river. That is mainly caused by EASM weakening while SCSSH strengthening. The anomalous southwesterly over South China and the northerlies of abnormal anti-cyclonic circulation around TP converge over the Yangtze valley. The onsetpentad index and the drop-pentad index are independent with each other, which is favorable to the prediction of the anomalies of the circulation and precipitation of EASM. The two indexes have high correlations with Multivariate ENSO Index (MEI) in March, indicating that the climate abnormity in East Asia correlates with global climate abnormity tightly. From this point of view, we must take the global climate ba ckground into account when we analyse and predict the East Asia summer circulation and precipitation.