Based on monthly rainfall data from 80 stations of China for the period of January 1951—February 1985analysed in terms of the maximum entropy spectrum and EEOF(extended empirical orthogonal function)techniques,the spatial and temporal features of quasi-biennial oscillation(QBO)in the rainfall are investigatedin a detailed manner,with some results of interest acquired.Highly evident is the QBO in rainfall over China,especially the mid and lower reaches of the ChangjiangRiver,the NE side of the Qinghai-Xizang Plateau,North China,the southern part of NE China,areas southof the Changjiang River and of the Nanling mountain region,and most of Xinjiang.The spatial wave described by the first and second eigenvectors of EEOF for eastern China is a type of wavetravelling from NE to SW,indicating the cycle of patterns(in the south to north direction):dryness(D)-wetness(W)-dryness(D)→southern W-northern slight D→W-D-W→southern D-northern slight W→D-W-D again,with the flooded region between the Changjiang and Huanghe Rivers for the D-W-D occurrenceand with the Changjiang River as the division for the southern W-northern slight D happening.The third andfourth eigenvectors show a standing wave-like feature for the same eastern part,indicating the cycle of D-W-D→transition→W-D-W→transition→D-W-D,again,where the transition means the generalweakening of drought and flooding and their subsequent reversal development.The amplitudes of the time coefficients of the first two eigenvectors are opposite in the trend of their changesto those of the next two and show a period of 10—14 years.
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