Analysis of the December 2013 Atmospheric Circulation and Weather
The following are the main characteristics of the general circulation of atmosphere in December 2013: There are two polar vortex centers in the Northern Hemisphere with the weaker strength than normal years. The circulation presents the troughridgetrough pattern in middlehigh latitudes. The south branch trough behaves actively, and is located near 90°E averagely. The subtropical high is stronger than normal years. Besides, it is located more westward and northward than normal years. The monthly mean precipitation is 15.4 mm, 46.7% more than normal (10.5 mm). In addition, significant difference is found in different areas: The precipitation in the major part of southern China is 20%-40% more than normal. The precipitation in the northern part to Huaihe River is less than normal, and especially, there is almost no any effective rainfall in the North of China and Huanghuai Region. The monthly mean temperature is -2.8℃, 0.4℃ higher than normal (-3.2℃) which presents a regional characteristic, i.e., the weather is warm in North China and cold in South China. There are three cold air processes nationwide and one major rainfall process in this month. There is a largescale obvious rainfall event and persisting low temperature weather in the southern China. Meanwhile, the fog and the haze appear in the central and eastern part of China.