Response of Southern China winter rainfall to El Niño diversity and its relevance to projected Southern China rainfall change

Responding to El Nino diversity, greater winter southern China (SC) rainfall is associated with an anomalous warming in the eastern tropical Pacific, but less rainfall with an anomalous warming in the central tropical Pacific. Compared with other widely used indices, the first two principal components of sea surface temperature anomalies in the tropical Pacific better represent the influences of the different El Nino anomaly patterns on winter SC rainfall. This is because these two indices can distinguish a zonal shift of the west North Pacific anticyclone, which conveys the tropical Pacific influence on SC rainfall. At a positive phase, the first principal component features a pattern similar to that of a canonical El Nino, whereas the second component is characterized by a warming in the central Pacific. Based on these two indices, performance of phase 5 of the Coupled Model Intercomparison Project models in simulating the SC rainfall response to El Nino is evaluated. About half of the models cannot reproduce the response to either principal component. The majority of the remaining models can only simulate the response to one principal component, and only five models produce a reasonable response to both principal components. Importantly, changes to SC rainfall in the future depend on the simulation of the SC rainfall response. Models that simulate the teleconnection of SC rainfall with only the first (second) principal component project an increase (decrease) in SC rainfall. Projection of a rainfall change in models that simulate the teleconnection with both principal components, that is, a moderate increase in SC winter rainfall, is more credible.