Abstract:The main characteristics of the general atmospheric circulation in December 2017 are as follows. There were two polar vortex centers in the Northern Hemisphere. The circulation presented the trough-ridge-trough pattern in the middle-high latitudes of Eurasia. The south branch trough was located near 70°E, obviously more westward than that in the same period of normal years. Therefore, the location of the south branch trough was not favorable for the water vapor transport to eastern China. The subtropical high was located more westward than that in normal years. The monthly mean precipitation over China was 5.9 mm, which is 44.8% less than the normal value (10.8 mm), especially for northern China, where precipitation amount decreased by 40%-80% of the normal. The monthly mean temperature over China was -2.2℃, 1℃ higher than the normal (-3.2℃). However, the temperature over northeastern China and the mid-eastern of Inner Mongolia was lower by 1-3℃ because of the strong east major trough. There were five cold air processes, which were not as strong as the normal events but more active than the normal. These active cold airs led to less fog-haze weather, and only one fog-haze period which occurred from 28 to 30 December 2017.