Spatio-temporal Characteristics Of Precipitation Over The Qinghai-Xizang (Tibetan) Plateau During The Modern Instrumental Observation Period

The research on precipitation variation is highlighted under the global warming. The Qinghai-Xizang (Tibetan) Plateau is characterized by unique alpine climate, which is rather sensitive and vulnerable to the global change. So it is urgent and indispensable to probe the spatio-temporal characteristics of precipitation over the Plateau. Basing on the analysis of monthly precipitation during 1961.1-2003.2 for 71 meteorological stations by using the methods of EOF, REOF, and spectral analysis, the spatio-temporal characteristics of precipitation over the Plateau are studied. Moreover, the teleconnections are also discussed between the precipitation of the Plateau and the eastern area of China, and ENSO. The main conclusions are as follows:(1) According to the contribution of the principal components, the precipitation distribution of the Qinghai-Xizang (Tibetan) Plateau can be categorized into three patterns: southwest-northeast I pattern, southwest-northeast II pattern, south-north pattern.(2) There are five kinds of patterns for the distribution of precipitation anomaly field over the Plateau: double rainy season in the southeast (Xinlong), little rain in the southwest (Jiangzi), spring and autumn rain in the northeastern boundary (Geermu), rainy season in the middle and east (Qingshuihe), and yearly dry pattern in the northwest (Xi'ning). Thereinto, double rainy season in the southeast of the Plateau is the most important component with biggest coverage for the distribution of precipitation anomaly over the Plateau.(3) Spectral analysis indicates that there exists significant periodicity of 12- and 13-yr over the southern Plateau. While for the whole Plateau, the 3-yr periodicity is obvious.(4) Wavelet analysis shows that in the coming 3-5 years there maybe much moreprecipitation for the southeastern, northwestern , and southwestern areas of the Plateau with less precipitation for the rest of the Plateau. For the future 10-20 years, the precipitation is expected to increase for the whole Plateau but the northwestern part.(5) The annual precipitation is characterized by apparent 30-yr variation for the southeastern Plateau and the North China where precipitation has decreased since the 1960s. Seen from the long-term changes, the variation of precipitation are similar for the southeastern Plateau and the Northeast China. The precipitation of the two regions increased before the mid-1960s and since the 1980s.(6) There exist sharp contrasts for the precipitation variation of the Plateau between the El Nino and the La Nifta events. Analysis discloses that the rainfall in southeastern Plateau decreases by 6%~8% than normal years in El Nino years, and decreases by 4%~6% in the next year of El Nino event. While when La Nina occurred, the precipitation would increase by 6%~8% with 7%~9% increasing of the following year.In a word, this thesis outlines one vivid picture about the spatio-temporal characteristics of precipitation variation over the Tibetan Plateau, one unique alpine region. Then the teleconnections between the precipitation of the Plateau and the eastern regions of China and ENSO events as well are discussed. These results are expected to provide scientific guidance to the socio-economic development of the Plateau.