Analysis of the January 2015 Atmospheric Circulation and Weather
The main characteristics of general atmospheric circulation in January 2015 are as follows: There were two polar vortex centers in the Northern Hemisphere with weaker strength than normal years. The circulation in Eurasian mid high latitudes showed a three wave pattern and mainly performed in zonal circulation. The strength of Western Pacific subtropical high and the south branch trough were near climatological normal. The monthly mean temperature was (-3.1℃) higher than normal (-5.0℃) by 1.9℃, which is the highest in record since 1961. The monthly mean precipitation was up to 14.4 mm, 9.1% more than normal (13.2 mm). However, the distribution of precipitation was quite uneven during the study period. The amount was more than normal in Southwest China, Northwest China and the south of South China. In contrast, it was significantly less than normal from North China to Jiangnan Region and there was almost no precipitation in Beijing and some other places. There was only one cold air process nationwide in this month which occurred in the first dekad, while five rainfall processes happened during the same time. At the late stage of first dekad, record breaking heavy rain and snow event occurred in Yunnan Province and the meteorological drought was significantly alleviated. At the end of this month, large scale cryogenic rain and snow weather dominated the central and eastern part of China, which was the first time since this winter, and freezing rain was seen in Guizhou Province. Meanwhile, three wide range fog and haze processes occurred in the central and eastern part of China.