The Study on Asian Atmospheric Circulation in the Middle-High Latitude and Association with the Snowfall in Southern China during La Niña Years

The moderate-strength La Niña was throughout in boreal winter 2007-2008 year, and the anomalous snowfall and extreme low temperature occurred in Southern China during January 2008. In this paper, the Asian atmospheric circulation in middle-high latitude and association with the aspect of snowfall in southern china during La Niña years were studied based on NCAR/NCEP reanalyzed dataset. It had been found out that there was a blocking high pattern in Asian atmospheric circulation of middle-high latitude at 500hPa during La Niña years. When the intensity of blocking high over Ural Mountains was stronger than over Ochotsk Sea in January during La Niña years, the temperature was lower than normal and association with much snowfall in Southern China due to the northerly wind in Southern China was connected with the circulation in Ural Mountains. When the intensity of blocking high over Ochotsk Sea was stronger than over Ural Mountain in January during La Niña years, the temperature was above normal and association with a little snowfall in Southern China due to the northerly wind in Southern China was connected with the circulation in Ochotsk Sea. In January 2008, the intensity of blocking high in Ural Mountain looked more strengthened (positive anomalous 120gpm), The air temperature in Southern China looked extreme low is due to northerly wind of two ways effected on Southern China which were connected with the anticyclone circulation in Ural Mountain. It has been pointed out that in winter during La Niña years there was the blocking high in Ural Mountain area which was related to the positive SSTA over the regions around North Atlantic (45oN, 30oW).

Key words: La Niña events, colder air temperature, blocking high pattern of Asian atmospheric circulation in middle-high latitude.