Abstract:Previous literatures suggest that El Ni〖AKn~D〗o is a dominant factor causing spring drought in Yunnan Province. Under the background of super-strong El Ni〖AKn~D〗o event during 2015, the spring (March-May) precipitation in most parts of western Yunnan Province was below normal, and the rainy season started late or even very late. However, the precipitation in eastern part was more than normal generally, and the rainy seasons in some regions started early or even very early, presenting a sharp contrast between the east and west. By using daily rain gauge precipitation of Yunnan Province, the CPC (Climate Prediction Center, USA) global unified gauge-based analysis of daily precipitation and NCEP/NCAR (National Centers for Environmental Prediction/ National Center for Atmospheric Research) reanalysis data, the influence of 10-30 d atmospheric oscillation on the spring abnormal precipitation over eastern Yunnan was studied by statistical and dynamical diagnosis methods. The analysis shows that the 10-30 d oscillation was active in the areas to the east of 100°E from mid-March to late-April, which is a major reason for the abnormal abundant precipitation over eastern Yunnan. 〖JP2〗Three distinct precipitation processes in eastern Yunnan happened associated closely with the southward approaching of the low-frequency cold phase embedded in the Eurasian pattern (EU) wave train from the mid- and high-latitudes of East Asia. Namely, when the upward branch of the secondary circulation around the subtropical westerly jet entrance interacted with the reflux vapor on the southwestern fringe of the cold high, the rainfall process was formed.