The Study On Relationship Between Characteristics Of East Asian Winter/summer Monsoon Intensity Indices And The Large Scale Southern/northern Drought/flood In China From 1951 To 2003

The paper comprehensively analyzed the characteristics of southern/northern drought/flood of flood period precipitation in China, the variable features of the East Asian winter/summer and monthly (DJF/JJA) monsoon indices, and the relationship between monsoon indices and temperature and southern/northern drought/flood in China. The main contents and results are as follows.The spatial seesaw structures and climate features of April to September in east China were studied month by month and season by season in this paper, the results show that the position and intensity are different in different period. The features of southern/northern drought/flood are more obviously when time scale is more large. The index of southern/northern drought/flood was defined, and we have used the method to calculate the index from 1951 to 2003. We have analyzed the secular trend and decadal variation of the features of southern/northern drought/flood during 1951-2003.The relation between the index of southern/northern drought/flood and cold/warm events was also studied.The East Asian winter/summer and monthly monsoon indices are constructed for the period of 1873-2003/2004 and their secular trend variations are analyzed. Evidence suggests that the summer June and July monsoon was greatly enhanced from 1951 to 2003 with obviously enfeebled for the winter, January and February monsoon. The results also show that East Asian winter/summer and monthly monsoon intensity indices display obvious interannual and interdecadal variations. There are bigger different between month and season. The strong/weak winter/summer monsoon years correlate with definite circulation. Also, analysis shows that the January monsoon displayed enfeebled sudden change around 1985 concurrently with the abrupt change in general circulation of atmosphere.Studies of the relations of the EASM/EAWM and monthly intensity indices tohomochronous temperature over China by using the data for the past 53 years show that they take on distinct negative correlation. It was warm(cold) when summer(winter) monsoon was strong, and cold(warm) weather when summer(winter) monsoon was weak.The relations between the indices of East Asian winter/summer and monthly monsoon and the southern/northern drought/flood in China have noticeable time variability. There will be more drought in north and flooding in south when April monsoon was weak, and as the monsoon was strong, there will be much more flooding in north and drought in south. In contrast, there will be more drought in north and flooding in south when summer and July and August monsoon was strong, and as the monsoon was weak, there will be much more flooding in north and drought in south. The East Asian winter monsoon anomaly has biseasonal effect on the circulation and weather in the following summer. There will be more drought in north and flooding in south in the following summer when winter monsoon was strong, and as the monsoon was weak, there will be much more flooding in north and drought in south in the following summer.The northern 500hpa corresponding period circulation showed different anomalous distribution for the years of the strong and weak EASM/EAWM were examined. It is found that when the East Asian winter monsoon was strong, there exists a strong EAP teleconnection pattern at 500hpa in the following July that extends from the low latitude mainland of China to the east of Alaska.