Abstract:This study investigates the interdecadal variations of winter precipitation and associated physical mechanisms over the Three River Source (TRS) region based on gridded CN05.1 and NCEP/NCAR reanalysis datasets for the period of 1961/1962–2006/2007. Results indicate that the winter precipitation over the TRS region experienced an intensification in the late 1980s. The decadal changes are modulated by the anomalous low over the Ural Mountains and the anomalous high extending from Lake Baikal to Northeast China, which may be associated with the ocean–atmosphere interaction over the North Atlantic. Specifically, after the late 1980s, the warm SST anomalies over the mid-high latitudes of North Atlantic can contribute to the abnormal ascending motions, strengthening the convection over that region and triggering the eastward wave train, causing the anomalous low over the Ural Mountains and the anomalous high extending from Lake Baikal to Northeast China. On the one hand, the coincidence of anomalous low and high induced the enhancement and southward shift of the polar front jet, causing the upper-level divergence and development of convection over the TRS region. On the other hand, the anomalous easterly wind over the TRS caused by the anomalous high extending from Lake Baikal to Northeast China, influenced the decadal intensification of winter precipitation over the TRS via inducing the abnormal convergence of water vapor flux. In addition, the warm SST anomalies in the Indian Ocean may also have influence on the interdecadal variations of winter precipitation over the TRS region by affecting the south branch trough.