青藏高原汛期降水的时空分布特征

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

根据1967～2008年青藏高原地区67个气象台站的月平均降水资料,利用线性趋势分析、EOF分解和Morlet小波变换等方法分析了青藏高原地区汛期(5～9月)降水的时空分布特征。结果表明:青藏高原汛期降水存在明显的区域性差异,EOF分解揭示出青藏高原汛期存在3种主要的空间分布型:南北反向型、全区一致型和东南—西北反向型。南北反向型分布存在着3～5a的年际变化周期和10～12a的年代际变化周期;而全区一致型普遍存在着5～7a的振荡周期。近42年来青藏高原北区降水主要表现为减少的趋势,而南区呈现出增加的趋势。汛期降水的南北反向型分布主要受初夏(5～6月)降水的影响,而全区一致型分布主要受盛夏(7～8月)降水的影响。

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.