Variation Characteristics Of Winter Cold Air And Its Relationship With Sea Surface Temperature

Based on the daily surface temperature data at384stations of China from1961to2010, the NCEP/NCAR daily reanalysis data, and Hadley Center daily sea surface temperature(SST) data, this paper analyzes the characteristics of China cold air in winter and the relationship between the cold air frequency and the global sea surface temperature, and reveals the key SST areas where is closely related to cold air frequency by using the moving overlapping average, correlation analysis, and singular value decomposition methods. The conclusions are made as follows:(1) Both frequency and intensity of station cold air are higher in northern China. The average declining of temperature is lower in middle of China, and the average duration of cold air is longer in southern than that in northern. From1961to2010, both frequency and intensity of cold air are decreased in most part of China, especially in Northeast China. According to intensity, cold air is divided into general cold air, strong cold air and cold wave. General cold air dominates in25～40°N region and cold wave dominates in north to25°N and south to40°N.(2) Based on invading routes, northern China is divided into three parts in which cold air occurs more in November; Southern China is divided into two parts in which cold air occurs more in December and January, and reveals a significant decreasing about frequency and intensity on the interannual scale. On the interdecadal scale, intensity of cold air in all five parts weakens from1960s to1980s. Nationwide cold air decreases on the interdecadal scale, especially in1960s and1990s while the frequency oscillation of north cold air is weak.(3)When cold air occurs more (less) in a year, there is a negative (positive) abnormaly over Europe and Asia areas in the years in500hPa geopotential height field which represents that the Asia trough is stronger(weaker) than that in normal years. There is a uniform pattern in500hPa geopotential height abnormaly fields over Europe and Asia areas corresponding to cold air frequency over in each month: negative-east to positive-west in years when more cold air occurs and positive-east to negative-west in years when less cold air occurs. (4) The result shows that earlier SST anomalies have closely relation with the cold air frequency in winter. A exceptional higher SST ahead of a year in western Atlantic or a exceptional higher SST ahead of six months in high-latitude western Atlantic could result in a decrease of cold air frequency in Inner Mongolia and North China; A exceptional lower SST in Western and a higher SST in Eastern Pacific ahead of a half year could result in a increase of cold air frequency in northern China and a decrease in eastern Tibet, Guangdong and Guangxi; A exceptional higher SST ahead of a year in areas from Indian Ocean to Wharton Basin, Arafura and north India Ocean in40°N could result in a decrease of cold air frequency in eastern coastal area of china, eastern Tibet, Mongolia and North China.