Abstract:Based on the typical case analysis, the linkage between the anomalous cold vortex activity in Northeast China during the early summer and the Northern Hemisphere low-frequency variability and the possible underlying mechanism are investigated. It is shown that: (1) The anomalous cold vortex activity in Northeast China in the early summer is quite in concert with persistent circulation anomalies near the Ural Mountains and Japan. During the strong cold vortex year, the persistent blocking-type circulation around the Ural Mountains is maintained both by the Rossby wave energy dispersion and anomalous transient eddy forcing. It, on the one hand, drives the polar cold air to move toward Northeast China and, on the other hand, amplifies the cold vortex through the Rossby wave energy dispersion. For the weak cold vortex year, the situation is basically reversed.(2) It is shown in Harmonic analysis and low-frequency oscillation analysis that while the cold vortex activity is strong (weak) from May to June, positive (negative) vorticity phase prevails over Northeast China, which corresponds well to the westward shift (eastward advance) of the ultra-long wave trough over the North Pacific. The persistent anomaly circulation around the Ural Mountains is maintained by the standing waves across the North Pacific-North America-the North Atlantic, through dispersion of the Rossby wave energy.(3) The anomalous circulation around the Ural Mountains in May constitutes a precursory signal to the cold vortex activity in Northeast China in the early summer.