Abstract:

Using ERA5 reanalysis data from 1979 to 2019, the characteristics of the northeast cold vortex with a lifetime of > 3 days during the forty years were analyzed using statistical methods including the Morlet wavelet and Mann-Kendall test.The results show that the continuous northeast cold vortex occurred 32.8 times on average, with a maximum of 41 times and a minimum of 22 times per year.The continuous northeast cold vortex process mostly happened in May and June and the cycles of annual times were 17 years, 9 years, 5 years and 3 years, respectively.The longer the duration of northeast cold vortex processes were, the less frequent they may occur.The longest duration could reach 13 days and those lasted 3 or 4 days appeared most frequently.The durations reaching 9 or 10 days occurred once per ten years and those lasted more than ten days appeared most significantly in June.The frequencies from high to low were the central vortex, north vortex and south vortex, with little monthly differences for the north vortex and much more during May and June for the center and south vortex.The cold vortex centers were most located in the region of 120°-130°E, 45°-55°N, and the pattern of two troughs and one ridge was the unique circulation background in the northeast cold vortex extreme months during both summer and winter half years over East Asia.

Key words: Northeast cold vortex, Continuity, Periodicity, Abrupt change