Large-Scale Atmospheric Circulation Patterns Associated with the Cold Surges in Yunnan Province, China

Abstract

The dominant time-space structure of cold surges affecting Yunnan Province and the whole of China are investigated by applying an empirical orthogonal function (EOF) analysis of monthly surface temperature anomalies for the winters of 28 years (1959-1986). It has been revealed that the predominant mode for Yunnan Province is part of the cold surge over the eastern periphery of the Tibetan Plateau through the coastal area of the southernmost part of China. The predominant mode for the whole of China affects most parts of China particularly to the south of 40°N centered near the Yangtze River basin, but its influence upon Yunnan Province is small. The atmospheric circulation patterns associated with these two modes are deduced by producing composite charts of 500 mb height and sea level pressure anomalies in the Northern Hemisphere. The pattern for the dominant mode of Yunnan Province shows the so-called Eurasian pattern with the anomalous trough over central Asia, and the North Atlantic Oscillation with negative polarity over Greenland. The pattern for the dominant mode over the whole of China seems, in contrast, to be more directly related to the outbreak of a cold air mass over the eastern part of the continent.