Influence of the Asian-Pacific Oscillation on Spring Precipitation over Central Eastern China

The linkage between the Asian-Pacific oscillation (APO) and theprecipitation over central eastern China in spring is preliminarilyaddressed by use of the observed data. Results show that they correlate verywell, with the positive (negative) phase of APO tending to increase(decrease) the precipitation over central eastern China. Such a relationshipcan be explained by the atmospheric circulation changes over Asia and theNorth Pacific in association with the anomalous APO. A positive phase ofAPO, characterized by a positive anomaly over Asia and a negative anomalyover the North Pacific in the upper-tropospheric temperature, corresponds todecreased low-level geopotential height (H) and increased high-level H overAsia, and these effects are concurrent with increased low-level H anddecreased high-level H over the North Pacific. Meanwhile, an anticycloniccirculation anomaly in the upper troposphere and a cyclonic circulationanomaly in the lower troposphere are introduced in East Asia, and thelow-level southerly wind is strengthened over central eastern China. Thesechanges provide advantageous conditions for enhanced precipitation overcentral eastern China. The situation is reversed in the negative phase ofAPO, leading to reduced precipitation in this region.