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Using the data of the number of autumn precipitation days from 104 stations in the eastern Northwest China from 1960 to 2000,by means of principal component and rotated principal component analysis methods,the abnormal temporal-spatial characteristics of autumn precipitation days are analyzed.The results show that the number of autumn precipitation days(above 0.1 mm) decreases from south to north,and there are two more-than-normal precipitation centers: one in the Qilian Mountain region and the other over the southern Qinghai Province and the northern Sichuan Province.Its abnormal distribution has two patterns: consistent(abnor-)(mity) and northwest-southeast reverse abnormity.The climate region can be divided into several sections: the east sub-tropic monsoon zone,northeast Qinghai and central Gansu,Hexi and Hetao of Gansu,southern Qinghai Plateau and western Sichuan Plateau.The inter-annual changes of the number of precipitation days at representative stations show a decreasing trend,and the year of 1978 is the turning point.