| Based on the daily precipitation data of 61 meteorological stations in Gansu Province during the period of 1965～2001, the grades of flood-drought in summer (June-August) were evaluated with Z index, the methods of EOF, REOF and Maxican hat wavelet analysis were used, and the characteristics of the spatial anomaly and temporal evolution rule of summer flood-drought in Gansu Province were analyzed.The results showed as follows: firstly, as a whole system, the probability of occurrence of drought in summer was greater than that of flood;for a single month, the frequency of flood was equal to that of drought in June and July, while the frequency of relative severe drought was higher than that of flood in July and August;secondly, there were three models representing the spatial distribution of flood-drought in Gansu, and the province could be divided into five regions of flood-drought sensitivity;finally, the jumping points of flood-drought varied in different temporal scales, there was a increasingly dry trend in the long period of 26 years and a distinct 4-year cycle in very 10-year period. |