Different impacts of El Niño and El Niño Modoki on China rainfall in the decaying phases

Abstract In this study, we investigate the different impacts of El Niño and El Niño Modoki on China rainfall in their decaying phases. During spring, in the decaying year of El Niño events, there are positive rainfall anomalies south of the Yangtze River, whereas no obvious rainfall signals are found in the same season for the decaying El Niño Modoki. In the subsequent summer season, the wet signal south of the Yangtze River associated with El Niño continues, while suppressed rainfall now appears in the northern Yangtze–Huaihe River region. In contrast, the rainfall is above normal in the region from the Huaihe River to the Yellow River, and below normal in southern China during the summer of the decaying El Niño Modoki events. The distinct China rainfall anomaly is mainly attributed to the difference between the evolution and location of the anomalous western North Pacific (WNP) anti‐cyclone associated with El Niño and El Niño Modoki events. For the case of El Niño, the WNP anti‐cyclone brings plentiful moisture to southern China; meanwhile it shifts the ridge of sub‐tropical high westward in both spring and summer. These tend to induce positive rainfall anomalies in the southern Chinese region. In contrast, due to fast decaying of El Niño Modoki, the anomalous WNP anti‐cyclone becomes weak so that there are no significant rainfall anomalies in China. In summer, however, the WNP anti‐cyclone re‐invigorates possibly associated with a subsequent developing La Niña and extends more northwestward towards the inland region, compared to its El Niño counterpart. The anomalous moisture transport and sub‐tropical high activity associated with this WNP anti‐cyclone result in different summer rainfall anomalies in China. Copyright © 2010 Royal Meteorological Society