| Precipitation data at 56 observational stations from 1961 to 2000 are used to divide up the climate regions with REOF method, and to analyze the spatial and temporal features with the MHF wavelet analysis and EOF method. It is indicated that there exit remarkbly differences of spring precipitation among different regions on the Loess Plateau, and the wet years alternate with the drought years. The Loess Plateau can be divided into 8 climate regions in line with the spring precipitation, and there exit the periods of quasi-7 a, 19 a and 22 a for the variation of spring precipitation at the representative stations. |