Different Decaying Characteristics for Two Types of El Niño and Their Relationships with the Summer Rainfall in China

Different decaying characteristics for two types of El Niño and their relationships with the summer rainfall in China were investigated by using 743 stations daily precipitation data from China Meteorological Administration, NCEP circulation reanalysis datasets and the monthly mean Met Office Hadley Center sea surface temperature (SST) analyses data,. Based on the evolution of the SST anomalies (SSTA) across the equator（5°S－5°N）, two type of decaying patterns are identified for EP-El Niño: ① an evolution pattern that SSTA decaying from east to west (E－W). The positive SSTA larger than 0.5℃ first disappear in offshore of South America and the disappearance extends to the west. ② an evolution pattern that SSTA decaying from west to east (W－E). The positive SSTA larger than 0.5℃ first disappear in the central Pacific and the disappearance extends to the east. The decaying evolution of CP-El Niño is classified into three types: ① a symmetric (S)‐decaying pattern whose SSTA grow and decay symmetrically with respect to a peak phase, ② a prolonged(P)‐decaying pattern that is followed by a EP-El Niño type, ③ an abrupt(A)‐decaying pattern that is followed by a EP-La Niña type. In the following summer of EP El Niño in two different decaying patterns, there are almost completely opposite rainfall anomalies in North China, South China，the region between and the upstream area of the Yangtze River and the Yellow River Valley ( They are called the Two River for short). In the following summer for E－W pattern, suppressed rainfall appears in the region between and the upstream area of the two River , while the rainfall in North China is abundant and rainfall of the area to the south of the Yangtze River is slightly more. However, there are significantly positive anomalies in the region between and the upstream area of the Two River with the center of positive anomalies located along the Yangtze River, but the negative rainfall anomalies in most region of South China and North China for W－E pattern. As for three decaying patterns of CP-El Niño, the positive anomalies are present in the region between the Huaihe River and the Yellow River Valley for S pattern, in the Yangtze River Valley for P pattern, while in the lower reaches of the Yellow River for A pattern. Rainfall in the Northeast China , especially in the northern of Northeast China, is below normal for S and A pattern, while above normal for P pattern. In the Southwest China, wet (dry) signal appears for S (A) pattern. And in the northern of Northwest China，there is less (more) precipitation for A pattern (S and P pattern). Different distribution of summer rainfall anomalies in the decaying phase of El Niño is closely associated with their different decaying patterns. When inspecting the impacts of the two types of El Niño on the following summer rainfall, it would be better to consider their different decaying patterns in view of the larger significant area and T-inspection value of rainfall anomalies. All these will provide important reference for the short-term climate prediction of summer rainfall.