Characteristics of Spatial and Temporal Distribution of Precipitation in Flood Season over the Tibetan Plateau

Using the monthly mean precipitation data at 67 stations over the Tibetan Plateau during 1967 to 2008, the spatial and temporal distribution characteristics of rainfall in flood season (from May to September) are analyzed through linear trend analysis, EOF, and Morlet wavelet transformation. The results indicate that there are distinct spatial variations of rainfall in the flood season in the Tibetan Plateau, which are concluded as three main patterns based on the EOF decomposition: The north-south reverse type, the whole region consistent type, and the southeast-northwest reverse type. Otherwise, the north-south reverse type has an interannual oscillation cycle of quasi-four years and a decadal oscillation cycle of quasi-11 years, while the whole region consistent type has a cycle of 5-6 years. The precipitation in the northern part of the Tibetan Plateau shows a decreasing trend, but the precipitation in the southern part of the plateau shows an increasing trend.