Abstract:The main characteristics of atmospheric circulation in December 2025 are as follows. The polar vortex in the Northern Hemisphere exhibited a dipole pattern with a negative geopotential height anomaly. The mid-to-high latitude circulation presented a four-wave pattern, while the Eurasian Continent was governed by a meridional pattern with high pressure in the west and low pressure in the east. The national average precipitation was 8.6 mm, decreasing by 28% compared to the long-term average for the same period. Furthermore, the spatial distribution of the precipitation anomaly percentage was characterized by higher values in northern China and lower values in southern China. The monthly average temperature was -1.2℃, which is 1.8℃ above that in the same period of normal years, ranking as the second highest since 1961. The cold airs were frequent, manifesting as multiple waves of intrusion occurring in stages with relatively weak intensity. In December, China experienced four cold air processes. During mid-December, the widespread cold wave occurred with the first wide range of rain and snow in winter, accompanied by a sand-dust event. Additionally, two fog-haze episodes appeared during the intermittent periods of cold air processes in mid-to-late December.