The Influence Of The Spring Greenland Sea-ice On The Summer Rainfall Of North China And Its Ways

In this paper, the spatial and temporal distribution of the summer rainfall of North China and the sea-ice extent of North Arctic are firstly analyzed, by the way of SVD we also analyze the correlation distribution pattern of the spring North Arctic sea-ice and the summer rainfall of China, and find out that the key section of North Arctic Sea-ice is the Greenland Sea, then the climate characteristics of the spring Greenland sea-ice are analyzed, at last we have discussed the infection of the spring Greenland sea-ice on the summer rainfall of North China and its possible ways. Through the preliminary analysis, we get the main conclusions as following:(1) Analysis of period indicates that the summer rainfall of North China has change periods of about 2 years, 3 years, 6 years, 8 years and 18 years. There is an evident decrease of the summer rainfall of North China from 1951 to 2000. What's more, the summer rainfall clearly takes place a catastrophe around 1979, there is much more rain before 1979 and less after 1979. In the fifty years the summer rainfall of North China has seven serious flood years and eight serious drought years, of which 1956 and 1963 are the unusual flood years and 1997 is the unusual drought year. The summer climate of North China is wetter with more frequent flood from the 1950s to the 1960s and drier with more frequent drought from the 1980s to the 1990s.(2) The sec-ice extent of North Arctic is largest in March, and larger in February , April; it is smallest in September, and smaller in August, October. The change range of sea-ice extent during the periods of February-April and August-October is small, while that during the periods of April-July and October-January is large. Thereby we bring forward such a method to divide seasons: February, March and April are winter; May, June and July are spring; August, September and October are summer; November, December and the next January are autumn. The sea-ice extent of North Arctic undergoes an evident decrease during the last 42 years (from 1953 to 1994), for which the unusual changes of the spring (May-July) North Arctic sea-ice extent make the main contribution.(3) By using the method of SVD and its second spatial distribution pattern, we can find that there is an evident positive relationship between the spring Greenland sea-ice extent and summer rainfall of North China, that is to say, if the spring sea-ice extent of Greenland is larger (smaller), then there is much more (less) summer rainfall in North China.(4) Analysis of period indicates that the spring Greenland sea-ice extent has change periods of about 2-3 years, 4 years, 5 years and 11 years. There is an evident decrease of the spring Greenland sea-ice extent since the 1970s, especially from the 1980s to the 1990s. With the method of Mann-Kendall, we find that the spring Greenland sea-ice extent clearly takes place a catastrophe around 1972.( 5) The spring Greenland sea-ice extent is larger (smaller): then during the following summer the high of the Japanese Sea is stronger (weaker), and the low of the Asian Land is stronger (weaker), which make the pattern of low west and high east easily (uneasily) form; the ascending movement over North China is strengthened (weakened); the summer monsoon of East Asia is stronger (weaker), then the southeastern, warm and damp airflow towards the North China is stronger (weaker), and the cold airflow of the high level over the North China is also stronger (weaker), which make the convergence of the cold and warm air over North China easily (uneasily) form; the SST of the east Pacific Ocean is lower (higher), while the SST of west wind drift is higher (lower). Under the above circumfluence background, there is much more (less) summer rainfall in North China, which makes the flood (drought) tend to happen there.