Different Summer Rainfall Anomaly Patterns in Northeast China Associated with Two Kinds of El Ni駉 Events

Abstract

The relationship between summer rainfall anomalies in northeast China and two types of El Nino events is investigated by using observation data and an atmospheric general circulation model (AGCM). It is shown that, for different types of El Nino events, there is different rainfall anomaly pattern in the following summer. In the following year of a typical El Nino event, there are remarkable positive rainfall anomalies in the central-western region of northeast China, whereas the pattern of more rainfall in the south end and less rainfall in the north end of northeast China easily appears in an El Nino Modoki event. The reason for the distinct difference is that, associated with the different sea surface temperature anomalies (SSTA) along the equatorial Pacific, the large-scale circulation anomalies along east coast of East Asia shift northward in the following summer after El Nino Modoki events. Influenced by the anomalous anticyclone in Philippine Sea, southwesterly anomalies over eastern China strengthen summer monsoon and bring more water vapor to northeast China. Meanwhile, convergence and updraft is strengthened by the anomalous cyclone right in northeast China in typical El Nino events. These moisture and atmospheric circulation conditions are favorable for enhanced precipitation. However, because of the northward shift, the anomalous anticyclone in the Philippine Sea in typical El Nino cases shifts to the south of Japan in Modoki years, and the anomalous cyclone in northeast China in typical El Nino cases shifts to the north of northeast China, leading to thedipole patternof rainfall anomalies. According to the results of numerical experiments, we further confirm that the tropical SSTA in different types of El Nino event can give rise to observed rainfall anomaly patterns in northeast China.