Evolution of ENSO-Related Rainfall Anomalies in East Asia

The present study documents seasonal rainfall anomalies in East Asia during different phases of El Niño–Southern Oscillation (ENSO) using station rainfall and the NCEP–NCAR reanalysis for the period of 1951–2000 through lag–lead correlation/regression and extended singular value decomposition analyses. The ENSO-related rainfall anomalies consist of two major evolving centers of action: one positive and the other negative. The positive center of action affects southern China, eastern central China, and southern Japan during the fall of an ENSO developing year through the following spring. The negative center of action is over northern China during the summer and fall of an ENSO developing year. Seasonal rainfall variance explained by ENSO is about 20%–30% in southern China in fall and winter, about 20% in eastern central China in spring after the mature phase of ENSO, and around 15%–20% in western north China in summer and fall of an ENSO developing year. The two main rainfall anomalies are induced by different anomalous circulation systems. The positive center of action is closely related to an anomalous low-level anticyclone over the western North Pacific. The anomalous anticyclone develops over the South China Sea in fall and extends eastward in winter and moves northeastward in spring and summer. The evolution of this anticyclone is determined by large-scale equatorial heating anomalies and local air–sea interactions. The negative center of action in northern China is associated with an anomalous barotropic cyclone displacing southwestward along the East Asian coast during the developing stage of ENSO. Evolution of this cyclone is affected by anomalous heating over south Asia and the western North Pacific.