Decadal change in factors affecting winter precipitation over eastern China

The temporal and spatial distributions of winter precipitation variability over eastern China were analyzed on the basis of the empirical orthogonal function method. The results showed that the primary mode of winter precipitation variability over this area presented a homogeneous change during the study period, with a significant decadal change around the late 1980s. The factors that influenced winter precipitation variability over eastern China changed over different interdecadal periods. Before the late 1980s, the Eurasian (EU) mode and North Pacific Oscillation (NPO) mode were the two major atmospheric factors. After the late 1980s, the influence of the EU mode remained. However, the impact of the NPO weakened significantly, and a new Rossby Wave (RW) pattern became a key factor. Further analyses of both observations and numerical simulations indicated that the convective activity over the western tropical Pacific strengthened significantly around the late 1980s; the convection encouraged the RW mode and ultimately contributed to the anomalous winter precipitation over eastern China after the late 1980s. The results imply that the prediction of winter precipitation should consider different interdecadal backgrounds; otherwise, the changing factors could result in failure of the prediction over some decadal periods.