关键词: 西北地区, 降水异常, 经验正交函数, 旋转经验正交函数, 小波分析, 突变分析

Abstract:

With EOF, REOF,Wavelet analysis and catastrophe analysis methods, we studied the spatial anomaly features and time evolution rule of precipitation in northwest China using the precipitation data collected in 128 observational stations during in 1971-2009. The results showed that, the first three loading vector field could reveal the most anomaly structures of precipitation in northwest China; the anomaly pattern could be summered as even in the whole area, varying from south to north, and vaarying from east to west; the first seven rotated loading vector fields could repersent six principal precipitation anomaly areas, northeast Qinghai-Tibet Plateau, Weihe River basin, Qinghai plateau, northern Xinjiang, southern Xinjiang and Hexi corridor; the northwest China saw a fluctuations in precipitation in recent 40 years, and no obvious long-term trend was found although some short-term dryer-wetter conversions existed; different anomaly regions showed different trends; the precipitation in northwest China had about 3-5 years, 10 years, and 20 years periodic variations; there existed different prevailing periods among different areas and different prevailing times within one area.

Key words: northwest china, precipitation anomaly, empirical orthogonal function, rotated empirical orthogonal function, wavelet analysis, catastrophe analysis