The Relationship Between East-Asian Summer Monsoon And Rainfalls China

East Asian Monsoon affects summer Rainfalls in China to most extent. But the physical mechanism between them is still not clear. Since East Asian Monsoon consists of two types with different characters, which are South-China Sea Tropical Monsoon and East Asian Sub-tropical Monsoon. Therefore, different researchers define monsoon index from different sides because they pay attention to different keys, and the relationship between monsoon intensity and rainfalls in China. Based on the study of the existing Monsoon Indices, we advance a new idea, which is to look for the monsoon factor affecting rainfall by dynamics, accordingly to unify monsoon indices. Having induced the connection between rainfall and atmospheric circulation, we regard those subsections that behave obvious seasonal variety as monsoon factor, then forming a function. We get a new set of defining monsoon indices, including East-Asia Summer Monsoon Front Location Index (EASMFLI) and East-Asia Summer Monsoon Intensity index (EASMII). Further, we analyze the relationship between the two Indices and summer rain-belt in East-China. The results show that the Front Location Index is corresponding to summer rain-belt in East-China. When the summer monsoon抯 front is in North-China, the rain-belt is also in North-China, vice verse. When the intensity of the summer monsoon was stronger, the corresponding rail-belt was also stronger than normal. The relationship between the EASMFI and rainfall抯 location in East-China is unstable. The year of 1998 as a type shows that, monsoon抯 stronger than normal and its location in South-China are the most cause of flood in Changjiang River. We also calculate annual monsoon Intensity index and Front Location Index by averaging the indices of 18 pentads in summer. The results show that the summer rainfalls in China have tight relation not only to the intensity of Monsoon, but also to the location of Monsoon. When Monsoon is strong and in North, excessive rainfalls in North and few in South; when Monsoon is weak and in North, few in China all over; when Monsoon is strong and in South, excessive in China all over; when Monsoon is weak and in South, excessive in South and few in North. The intensity of Monsoon controls the intensity of rainfalls, while the location controls the location of the main rain-belt in summer.