AN ABRUPT CHANGE IN THE INTENSITY OF THE EAST-ASIAN SUMMER MONSOON INDEX AND ITS RELATIONSHIP WITH TEMPERATURE AND PRECIPITATION OVER EAST CHINA

In this study, an East Asian summer monsoon intensity index is defined and the summer monthly indices of the East Asian monsoon are calculat ed for the period 1873-1989. Studies of the climate change of the inde x indicate that around 1918 the East Asian monsoon experienced an abru pt change, from weak to strong. This abrupt change occurred synchronou sly with that of the Northern Hemisphere air temperature. Studies of t he relation of this East Asian summer monsoon index to the rainfall an d temperature over China by using the data for the recent 40 years sho ws that when a strong monsoon occurs, China will experience an extensi ve high temperature in summer. The relationship between the East Asian summer monsoon and China's summer rainfall manifests itself on the no rth-south position of the rain belt. The position of the summer belt i s northward when the monsoon is strong and southward when the monsoon is weak. Wet years over the middle and lower reaches of Chingjiang Riv er are related to a weak monsoon whereas with a strong summer monsoon, dry years are often observed.