Statistical Diagnosis of the Relationship between NAO and Dipole Oscillation of Summer Precipitation over Qinghai-Xizang Plateau in Multi-time Scales
LIU Huancai;LI Man;SHI Peihong;LIU Li;SUN Jianyong;State Key Laboratory of Cryospheric Science,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences;University of Chinese Academy of Sciences;Department of Geographical Science,Shanxi Normal University;Key Laboratory of Ecodrolody of Inland River Basin,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences;
The spatiotemporal characteristics of summer precipitation over the Qinghai-Xizang Plateau( QXP)during 1961 2010 are investigated based on a developed daily precipitation dataset at 66 meteorological stations. According to the empirical orthogonal functions( EOF) analyses,it is confirmed that the reverse relationship between the northeastern and southeastern QXP is the main and stable spatial pattern of summer precipitation over the QXP in modern times which is defined as the Dipole Oscillation. And such Dipole Oscillation is mainly impacted by the summer North Atlantic Oscillation( NAO). The results showthat ensemble empirical mode decomposition( EEM D) can extract the potential signals of multi-time scales effectively from the NAO index and time series of the Dipole Oscillation according to their own typical features. The correlation analysis reveals the most important correlation between NAO and Dipole Oscillation occurs at the interannual time scale with a spectral peak in 3 ~ 4 years. Further analysis implies the atmosphere activity represented by NAO rather than sea surface temperature over Atlantic should be considered as the main possible driver of the Dipole Oscillation.