Abstract:
Based on the daily minimum temperatures and mean temperatures of 122 meteorological observation stations in Yunnan from 1961 to 2015, the activity rules of the cold wave in Yunnan and the corresponding atmospheric circulation are analyzed. The results indicate that: ① The winter cold wave frequency (intensity) in Yunnan shows a decreasing (weakening) trend from 1961 to 2014. The turning point from more (strong) to less (weak) took place in 1984. Besides, the winter cold wave over Yunnan displays a significant change cycle of about every 8 years. ② There is a better concurrent variation between winter cold wave, temperature and precipitation in Yunnan. When the winter cold wave frequency is more (less) than normal, the temperature is lower (higher) than normal and the precipitation is above (below) normal. ③ The interannual variation of winter cold wave frequency in Yunnan is closely related to the atmospheric circulation. In the sea level pressure field in winter, the cold wave frequency in Yunnan is more (less) than normal, when the Arctic Oscillation (AO) is in its positive (negative) phase, the Siberian High is stronger (weaker) than normal and the East Asian winter monsoon is stronger (weaker) than normal. In the 500 hPa height field in winter, the cold wave frequency in Yunnan is more (less) than normal, when the polar vortex is stronger (weaker) than normal, the Baikal high ridge is stronger (weaker) than normal and the deep East Asian trough and the southern branch trough are stronger (weaker) than normal. ④ The change of subtropical jet stream in the upper troposphere is an important factor affecting the cold wave frequency change in Yunnan. The jet stream may impact on the cold wave frequency in Yunnan by affecting the frequency of cold surges bursting southward.