Analysis of the January 2018 Atmospheric Circulation and Weather
The main characteristics of the general atmospheric circulation in January 2018 are as follows. There were two polar vortex centers in the Northern Hemisphere. The circulation presented a four-wave pattern in middle-high latitudes. The East Asian trough behaved strongly. The monthly mean precipita-tion was 19.6 mm, 48.4% more than normal. Besides, the activities of cold air strengthened, causing the monthly mean temperature (-5.3℃) to turn from higher than normal to lower, and the mean temperature became 0.3℃ lower than normal (-5.0℃). In this month, precipitation was strengthened with more rainfall than normal, and freezing rain and snow weather occurred in southern China and Shaanxi Province, similar to the freezing disaster in southern China in 2008. Fog-haze event appeared in this month only once, from 13 to 22 January 2018, but was characterized by the widest range, the longest duration and the maximum intensity in the winter of 2017.