By utilizing the meteorological observational data over the mainland of China and surrounding oceans from 1951 to 1990, the characteristics of the climatic trend of East Asian Monsoon and the interannual variation of monsoon overlapped on the general trend have been studied. The results show that during the past 40 years, especially in the 1980s, China has generally been drying and the areas south of 35°N in China are getting cooler. This may be attributed to the weakening of the winter and summer monsoon in China. Mei-Yu in middle and lower reaches of Yangtze River and the precipitation in other areas of China are affected by the climatic change trend.
It has long been believed that the Indian Monsoon is correlative to the summer precipitation of China. But in our studies, it can be concluded that there is a significant correlation only between the summer precipitation over India and that over the western part of North China, and for other areas of China the correlation is not obvious.
The interannual anomaly of the summer monsoon in China is mainly attributed to the variation of each member of the circulation system of the East Asian summer monsoon. The interactions of air-sea and air-land have also been discussed. Although a significant correlation can not be found between the SST of equatorial eastern Pacific/Polar ice and the winter/summer monsoon of China, they all have similar significant interannual oscillations and the correlation between these interannual oscillation components of the same frequency is very high.