Spatial And Temporal Variations Of Spring/Summer Extreme Low Temperature In North-east China And Its Relationship With SST Anomaly

By using the data set of the mean monthly global sea surface temperature and geopotential height fields from 1958 to 2007, and the surface air temperature of 64 stations in North-east China during the same period, the spatial/temporal variations of spring and summer extreme low temperature in North-east China, as well as their relationship with atmospheric circulation and the sea surface temperature anomalies are analyzed. The results obtained here suggests the following several standpoint.(1)Over the past 50 years the frequency of spring extreme low temperature in North-east China tends to decrease, and spring and summer extreme low temperature all have such two models as large-scale consistent and north being contrary to south.(2)There is a significant negative correlation between the frequency of spring extreme low temperature and the AO index. At the same time there are strong tendencies for weak polar vortex, strong blocking highs in the Ural and strong northeast cold vortex associated during frequently extreme low temperature year, and vice versa.(3)The frequency of summer extreme low temperature in North-east China has important relationship with the blocking highs in the Ural, the East Asia major trough, the Aleutian low and northeast cold vortex.(4)The middle-north Atlantic Ocean is the key area that affects the spring extreme low temperature in North-east China, with negative SST anomalies for frequently extreme low temperature and positive anomalies for rarely extreme low temperature, which implies important significance for extreme low temperature prediction, In addition, the result of numerical simulation also shows that there will be higher air temperature over North-east China when the SST anomalies in middle-north Atlantic motivated Eurasian wave trains. (5)The SST in the east equatorial pacific is related with summer extreme low temperature in North-east China. Before the early 90s, the occurrence of summer extreme low temperature is well consistent with the appearance of the El Nino in the east equatorial pacific, but after early 1990s, their relations damaged.(6)The Western Pacific Warm Pool is the key area that affects the summer extreme low temperature in North-east China.Further research shows that the Western Pacific Warm Pool will affects the circulation in North-east China.